It’s pretty common for Go developers to mix slice length and capacity or not understand them thoroughly. Assimilating these two concepts is essential for efficiently handling core operations such as slice initialization and adding elements with append, copying, or slicing. This misunderstanding can lead to using slices suboptimally or even to memory leaks.
+
In Go, a slice is backed by an array. That means the slice’s data is stored contiguously in an array data structure. A slice also handles the logic of adding an element if the backing array is full or shrinking the backing array if it’s almost empty.
+
Internally, a slice holds a pointer to the backing array plus a length and a capacity. The length is the number of elements the slice contains, whereas the capacity is the number of elements in the backing array, counting from the first element in the slice. Let’s go through a few examples to make things clearer. First, let’s initialize a slice with a given length and capacity:
The first argument, representing the length, is mandatory. However, the second argument representing the capacity is optional. Figure 1 shows the result of this code in memory.
+
+
In this case, make creates an array of six elements (the capacity). But because the length was set to 3, Go initializes only the first three elements. Also, because the slice is an []int type, the first three elements are initialized to the zeroed value of an int: 0. The grayed elements are allocated but not yet used.
+
If we print this slice, we get the elements within the range of the length, [0 0 0]. If we set s[1] to 1, the second element of the slice updates without impacting its length or capacity. Figure 2 illustrates this.
+
+
However, accessing an element outside the length range is forbidden, even though it’s already allocated in memory. For example, s[4] = 0 would lead to the following panic:
+
panic: runtime error: index out of range [4] with length 3
+
+
How can we use the remaining space of the slice? By using the append built-in function:
+
s=append(s,2)
+
+
This code appends to the existing s slice a new element. It uses the first grayed element (which was allocated but not yet used) to store element 2, as figure 3 shows.
+
+
The length of the slice is updated from 3 to 4 because the slice now contains four elements. Now, what happens if we add three more elements so that the backing array isn’t large enough?
+
s=append(s,3,4,5)
+fmt.Println(s)
+
+
If we run this code, we see that the slice was able to cope with our request:
+
[0 1 0 2 3 4 5]
+
+
Because an array is a fixed-size structure, it can store the new elements until element 4. When we want to insert element 5, the array is already full: Go internally creates another array by doubling the capacity, copying all the elements, and then inserting element 5. Figure 4 shows this process.
+
+
The slice now references the new backing array. What will happen to the previous backing array? If it’s no longer referenced, it’s eventually freed by the garbage collector (GC) if allocated on the heap. (We discuss heap memory in mistake #95, “Not understanding stack vs. heap,” and we look at how the GC works in mistake #99, “Not understanding how the GC works.”)
+
What happens with slicing? Slicing is an operation done on an array or a slice, providing a half-open range; the first index is included, whereas the second is excluded. The following example shows the impact, and figure 5 displays the result in memory:
+
s1:=make([]int,3,6)// Three-length, six-capacity slice
+s2:=s1[1:3]// Slicing from indices 1 to 3
+
+
+
First, s1 is created as a three-length, six-capacity slice. When s2 is created by slicing s1, both slices reference the same backing array. However, s2 starts from a different index, 1. Therefore, its length and capacity (a two-length, five-capacity slice) differ from s1. If we update s1[1] or s2[0], the change is made to the same array, hence, visible in both slices, as figure 6 shows.
+
+
Now, what happens if we append an element to s2? Does the following code change s1 as well?
+
s2=append(s2,2)
+
+
The shared backing array is modified, but only the length of s2 changes. Figure 7 shows the result of appending an element to s2.
+
+
s1 remains a three-length, six-capacity slice. Therefore, if we print s1 and s2, the added element is only visible for s2:
+
s1=[010],s2=[102]
+
+
It’s important to understand this behavior so that we don’t make wrong assumptions while using append.
+
+Note
+
In these examples, the backing array is internal and not available directly to the Go developer. The only exception is when a slice is created from slicing an existing array.
+
+
One last thing to note: what if we keep appending elements to s2 until the backing array is full? What will the state be, memory-wise? Let’s add three more elements so that the backing array will not have enough capacity:
+
s2=append(s2,3)
+s2=append(s2,4)// At this stage, the backing is already full
+s2=append(s2,5)
+
+
This code leads to creating another backing array. Figure 8 displays the results in memory.
+
+
s1 and s2 now reference two different arrays. As s1 is still a three-length, six-capacity slice, it still has some available buffer, so it keeps referencing the initial array. Also, the new backing array was made by copying the initial one from the first index of s2. That’s why the new array starts with element 1, not 0.
+
To summarize, the slice length is the number of available elements in the slice, whereas the slice capacity is the number of elements in the backing array. Adding an element to a full slice (length == capacity) leads to creating a new backing array with a new capacity, copying all the elements from the previous array, and updating the slice pointer to the new array.
When working with maps in Go, we need to understand some important characteristics of how a map grows and shrinks. Let’s delve into this to prevent issues that can cause memory leaks.
+
First, to view a concrete example of this problem, let’s design a scenario where we will work with the following map:
+
m:=make(map[int][128]byte)
+
+
Each value of m is an array of 128 bytes. We will do the following:
+
+
Allocate an empty map.
+
Add 1 million elements.
+
Remove all the elements, and run a Garbage Collection (GC).
+
+
After each step, we want to print the size of the heap (using a printAlloc utility function). This shows us how this example behaves memory-wise:
+
funcmain(){
+n:=1_000_000
+m:=make(map[int][128]byte)
+printAlloc()
+
+fori:=0;i<n;i++{// Adds 1 million elements
+m[i]=[128]byte{}
+}
+printAlloc()
+
+fori:=0;i<n;i++{// Deletes 1 million elements
+delete(m,i)
+}
+
+runtime.GC()// Triggers a manual GC
+printAlloc()
+runtime.KeepAlive(m)// Keeps a reference to m so that the map isn’t collected
+}
+
+funcprintAlloc(){
+varmruntime.MemStats
+runtime.ReadMemStats(&m)
+fmt.Printf("%d MB\n",m.Alloc/(1024*1024))
+}
+
+
We allocate an empty map, add 1 million elements, remove 1 million elements, and then run a GC. We also make sure to keep a reference to the map using runtime.KeepAlive so that the map isn’t collected as well. Let’s run this example:
+
0 MB <-- After m is allocated
+461 MB <-- After we add 1 million elements
+293 MB <-- After we remove 1 million elements
+
+
What can we observe? At first, the heap size is minimal. Then it grows significantly after having added 1 million elements to the map. But if we expected the heap size to decrease after removing all the elements, this isn’t how maps work in Go. In the end, even though the GC has collected all the elements, the heap size is still 293 MB. So the memory shrunk, but not as we might have expected. What’s the rationale? We need to delve into how a map works in Go.
+
A map provides an unordered collection of key-value pairs in which all the keys are distinct. In Go, a map is based on the hash table data structure: an array where each element is a pointer to a bucket of key-value pairs, as shown in figure 1.
+
+
Each bucket is a fixed-size array of eight elements. In the case of an insertion into a bucket that is already full (a bucket overflow), Go creates another bucket of eight elements and links the previous one to it. Figure 2 shows an example:
+
+
Under the hood, a Go map is a pointer to a runtime.hmap struct. This struct contains multiple fields, including a B field, giving the number of buckets in the map:
+
typehmapstruct{
+Buint8// log_2 of # of buckets
+// (can hold up to loadFactor * 2^B items)
+// ...
+}
+
+
After adding 1 million elements, the value of B equals 18, which means 2¹⁸ = 262,144 buckets. When we remove 1 million elements, what’s the value of B? Still 18. Hence, the map still contains the same number of buckets.
+
The reason is that the number of buckets in a map cannot shrink. Therefore, removing elements from a map doesn’t impact the number of existing buckets; it just zeroes the slots in the buckets. A map can only grow and have more buckets; it never shrinks.
+
In the previous example, we went from 461 MB to 293 MB because the elements were collected, but running the GC didn’t impact the map itself. Even the number of extra buckets (the buckets created because of overflows) remains the same.
+
Let’s take a step back and discuss when the fact that a map cannot shrink can be a problem. Imagine building a cache using a map[int][128]byte. This map holds per customer ID (the int), a sequence of 128 bytes. Now, suppose we want to save the last 1,000 customers. The map size will remain constant, so we shouldn’t worry about the fact that a map cannot shrink.
+
However, let’s say we want to store one hour of data. Meanwhile, our company has decided to have a big promotion for Black Friday: in one hour, we may have millions of customers connected to our system. But a few days after Black Friday, our map will contain the same number of buckets as during the peak time. This explains why we can experience high memory consumption that doesn’t significantly decrease in such a scenario.
+
What are the solutions if we don’t want to manually restart our service to clean the amount of memory consumed by the map? One solution could be to re-create a copy of the current map at a regular pace. For example, every hour, we can build a new map, copy all the elements, and release the previous one. The main drawback of this option is that following the copy and until the next garbage collection, we may consume twice the current memory for a short period.
+
Another solution would be to change the map type to store an array pointer: map[int]*[128]byte. It doesn’t solve the fact that we will have a significant number of buckets; however, each bucket entry will reserve the size of a pointer for the value instead of 128 bytes (8 bytes on 64-bit systems and 4 bytes on 32-bit systems).
+
Coming back to the original scenario, let’s compare the memory consumption for each map type following each step. The following table shows the comparison.
+
+
+
+
Step
+
map[int][128]byte
+
map[int]*[128]byte
+
+
+
+
+
Allocate an empty map
+
0 MB
+
0 MB
+
+
+
Add 1 million elements
+
461 MB
+
182 MB
+
+
+
Remove all the elements and run a GC
+
293 MB
+
38 MB
+
+
+
+
+Note
+
If a key or a value is over 128 bytes, Go won’t store it directly in the map bucket. Instead, Go stores a pointer to reference the key or the value.
+
+
As we have seen, adding n elements to a map and then deleting all the elements means keeping the same number of buckets in memory. So, we must remember that because a Go map can only grow in size, so does its memory consumption. There is no automated strategy to shrink it. If this leads to high memory consumption, we can try different options such as forcing Go to re-create the map or using pointers to check if it can be optimized.
Interfaces are one of the cornerstones of the Go language when designing and structuring our code. However, like many tools or concepts, abusing them is generally not a good idea. Interface pollution is about overwhelming our code with unnecessary abstractions, making it harder to understand. It’s a common mistake made by developers coming from another language with different habits. Before delving into the topic, let’s refresh our minds about Go’s interfaces. Then, we will see when it’s appropriate to use interfaces and when it may be considered pollution.
+
Concepts
+
An interface provides a way to specify the behavior of an object. We use interfaces to create common abstractions that multiple objects can implement. What makes Go interfaces so different is that they are satisfied implicitly. There is no explicit keyword like implements to mark that an object X implements interface Y.
+
To understand what makes interfaces so powerful, we will dig into two popular ones from the standard library: io.Reader and io.Writer. The io package provides abstractions for I/O primitives. Among these abstractions, io.Reader relates to reading data from a data source and io.Writer to writing data to a target, as represented in the next figure:
Custom implementations of the io.Reader interface should accept a slice of bytes, filling it with its data and returning either the number of bytes read or an error.
+
On the other hand, io.Writer defines a single method, Write:
Custom implementations of io.Writer should write the data coming from a slice to a target and return either the number of bytes written or an error. Therefore, both interfaces provide fundamental abstractions:
+
+
io.Reader reads data from a source
+
io.Writer writes data to a target
+
+
What is the rationale for having these two interfaces in the language? What is the point of creating these abstractions?
+
Let’s assume we need to implement a function that should copy the content of one file to another. We could create a specific function that would take as input two *os.Files. Or, we can choose to create a more generic function using io.Reader and io.Writer abstractions:
This function would work with *os.File parameters (as *os.File implements both io.Reader and io.Writer) and any other type that would implement these interfaces. For example, we could create our own io.Writer that writes to a database, and the code would remain the same. It increases the genericity of the function; hence, its reusability.
+
Furthermore, writing a unit test for this function is easier because, instead of having to handle files, we can use the strings and bytes packages that provide helpful implementations:
+
funcTestCopySourceToDest(t*testing.T){
+constinput="foo"
+source:=strings.NewReader(input)// Creates an io.Reader
+dest:=bytes.NewBuffer(make([]byte,0))// Creates an io.Writer
+
+err:=copySourceToDest(source,dest)// Calls copySourceToDest from a *strings.Reader and a *bytes.Buffer
+iferr!=nil{
+t.FailNow()
+}
+
+got:=dest.String()
+ifgot!=input{
+t.Errorf("expected: %s, got: %s",input,got)
+}
+}
+
+
In the example, source is a *strings.Reader, whereas dest is a *bytes.Buffer. Here, we test the behavior of copySourceToDest without creating any files.
+
While designing interfaces, the granularity (how many methods the interface contains) is also something to keep in mind. A known proverb in Go relates to how big an interface should be:
+
+
Rob Pike
+
The bigger the interface, the weaker the abstraction.
+
+
Indeed, adding methods to an interface can decrease its level of reusability. io.Reader and io.Writer are powerful abstractions because they cannot get any simpler. Furthermore, we can also combine fine-grained interfaces to create higher-level abstractions. This is the case with io.ReadWriter, which combines the reader and writer behaviors:
+
typeReadWriterinterface{
+Reader
+Writer
+}
+
+
+Note
+
As Einstein said, “Everything should be made as simple as possible, but no simpler.” Applied to interfaces, this denotes that finding the perfect granularity for an interface isn’t necessarily a straightforward process.
+
+
Let’s now discuss common cases where interfaces are recommended.
+
When to use interfaces
+
When should we create interfaces in Go? Let’s look at three concrete use cases where interfaces are usually considered to bring value. Note that the goal isn’t to be exhaustive because the more cases we add, the more they would depend on the context. However, these three cases should give us a general idea:
+
+
Common behavior
+
Decoupling
+
Restricting behavior
+
+
Common behavior
+
The first option we will discuss is to use interfaces when multiple types implement a common behavior. In such a case, we can factor out the behavior inside an interface. If we look at the standard library, we can find many examples of such a use case. For example, sorting a collection can be factored out via three methods:
+
+
Retrieving the number of elements in the collection
+
Reporting whether one element must be sorted before another
+
Swapping two elements
+
+
Hence, the following interface was added to the sort package:
+
typeInterfaceinterface{
+Len()int// Number of elements
+Less(i,jint)bool// Checks two elements
+Swap(i,jint)// Swaps two elements
+}
+
+
This interface has a strong potential for reusability because it encompasses the common behavior to sort any collection that is index-based.
+
Throughout the sort package, we can find dozens of implementations. If at some point we compute a collection of integers, for example, and we want to sort it, are we necessarily interested in the implementation type? Is it important whether the sorting algorithm is a merge sort or a quicksort? In many cases, we don’t care. Hence, the sorting behavior can be abstracted, and we can depend on the sort.Interface.
+
Finding the right abstraction to factor out a behavior can also bring many benefits. For example, the sort package provides utility functions that also rely on sort.Interface, such as checking whether a collection is already sorted. For instance:
Because sort.Interface is the right level of abstraction, it makes it highly valuable.
+
Let’s now see another main use case when using interfaces.
+
Decoupling
+
Another important use case is about decoupling our code from an implementation. If we rely on an abstraction instead of a concrete implementation, the implementation itself can be replaced with another without even having to change our code. This is the Liskov Substitution Principle (the L in Robert C. Martin’s SOLID design principles).
+
One benefit of decoupling can be related to unit testing. Let’s assume we want to implement a CreateNewCustomer method that creates a new customer and stores it. We decide to rely on the concrete implementation directly (let’s say a mysql.Store struct):
+
typeCustomerServicestruct{
+storemysql.Store// Depends on the concrete implementation
+}
+
+func(csCustomerService)CreateNewCustomer(idstring)error{
+customer:=Customer{id:id}
+returncs.store.StoreCustomer(customer)
+}
+
+
Now, what if we want to test this method? Because customerService relies on the actual implementation to store a Customer, we are obliged to test it through integration tests, which requires spinning up a MySQL instance (unless we use an alternative technique such as go-sqlmock, but this isn’t the scope of this section). Although integration tests are helpful, that’s not always what we want to do. To give us more flexibility, we should decouple CustomerService from the actual implementation, which can be done via an interface like so:
+
typecustomerStorerinterface{// Creates a storage abstraction
+StoreCustomer(Customer)error
+}
+
+typeCustomerServicestruct{
+storercustomerStorer// Decouples CustomerService from the actual implementation
+}
+
+func(csCustomerService)CreateNewCustomer(idstring)error{
+customer:=Customer{id:id}
+returncs.storer.StoreCustomer(customer)
+}
+
+
Because storing a customer is now done via an interface, this gives us more flexibility in how we want to test the method. For instance, we can:
+
+
Use the concrete implementation via integration tests
+
Use a mock (or any kind of test double) via unit tests
+
Or both
+
+
Let’s now discuss another use case: to restrict a behavior.
+
Restricting behavior
+
The last use case we will discuss can be pretty counterintuitive at first sight. It’s about restricting a type to a specific behavior. Let’s imagine we implement a custom configuration package to deal with dynamic configuration. We create a specific container for int configurations via an IntConfig struct that also exposes two methods: Get and Set. Here’s how that code would look:
Now, suppose we receive an IntConfig that holds some specific configuration, such as a threshold. Yet, in our code, we are only interested in retrieving the configuration value, and we want to prevent updating it. How can we enforce that, semantically, this configuration is read-only, if we don’t want to change our configuration package? By creating an abstraction that restricts the behavior to retrieving only a config value:
+
typeintConfigGetterinterface{
+Get()int
+}
+
+
Then, in our code, we can rely on intConfigGetter instead of the concrete implementation:
In this example, the configuration getter is injected into the NewFoo factory method. It doesn’t impact a client of this function because it can still pass an IntConfig struct as it implements intConfigGetter. Then, we can only read the configuration in the Bar method, not modify it. Therefore, we can also use interfaces to restrict a type to a specific behavior for various reasons, such as semantics enforcement.
+
In this section, we saw three potential use cases where interfaces are generally considered as bringing value: factoring out a common behavior, creating some decoupling, and restricting a type to a certain behavior. Again, this list isn’t exhaustive, but it should give us a general understanding of when interfaces are helpful in Go.
+
Now, let’s finish this section and discuss the problems with interface pollution.
+
Interface pollution
+
It’s fairly common to see interfaces being overused in Go projects. Perhaps the developer’s background was C# or Java, and they found it natural to create interfaces before concrete types. However, this isn’t how things should work in Go.
+
As we discussed, interfaces are made to create abstractions. And the main caveat when programming meets abstractions is remembering that abstractions should be discovered, not created. What does this mean? It means we shouldn’t start creating abstractions in our code if there is no immediate reason to do so. We shouldn’t design with interfaces but wait for a concrete need. Said differently, we should create an interface when we need it, not when we foresee that we could need it.
+
What’s the main problem if we overuse interfaces? The answer is that they make the code flow more complex. Adding a useless level of indirection doesn’t bring any value; it creates a worthless abstraction making the code more difficult to read, understand, and reason about. If we don’t have a strong reason for adding an interface and it’s unclear how an interface makes a code better, we should challenge this interface’s purpose. Why not call the implementation directly?
+
+Note
+
We may also experience performance overhead when calling a method through an interface. It requires a lookup in a hash table’s data structure to find the concrete type an interface points to. But this isn’t an issue in many contexts as the overhead is minimal.
+
+
In summary, we should be cautious when creating abstractions in our code—abstractions should be discovered, not created. It’s common for us, software developers, to overengineer our code by trying to guess what the perfect level of abstraction is, based on what we think we might need later. This process should be avoided because, in most cases, it pollutes our code with unnecessary abstractions, making it more complex to read.
+
+
Rob Pike
+
Don’t design with interfaces, discover them.
+
+
Let’s not try to solve a problem abstractly but solve what has to be solved now. Last, but not least, if it’s unclear how an interface makes the code better, we should probably consider removing it to make our code simpler.
A misconception among many developers is believing that a concurrent solution is always faster than a sequential one. This couldn’t be more wrong. The overall performance of a solution depends on many factors, such as the efficiency of our code structure (concurrency), which parts can be tackled in parallel, and the level of contention among the computation units. This post reminds us about some fundamental knowledge of concurrency in Go; then we will see a concrete example where a concurrent solution isn’t necessarily faster.
+
Go Scheduling
+
A thread is the smallest unit of processing that an OS can perform. If a process wants to execute multiple actions simultaneously, it spins up multiple threads. These threads can be:
+
+
Concurrent — Two or more threads can start, run, and complete in overlapping time periods.
+
Parallel — The same task can be executed multiple times at once.
+
+
The OS is responsible for scheduling the thread’s processes optimally so that:
+
+
All the threads can consume CPU cycles without being starved for too much time.
+
The workload is distributed as evenly as possible among the different CPU cores.
+
+
+Note
+
The word thread can also have a different meaning at a CPU level. Each physical core can be composed of multiple logical cores (the concept of hyper-threading), and a logical core is also called a thread. In this post, when we use the word thread, we mean the unit of processing, not a logical core.
+
+
A CPU core executes different threads. When it switches from one thread to another, it executes an operation called context switching. The active thread consuming CPU cycles was in an executing state and moves to a runnable state, meaning it’s ready to be executed pending an available core. Context switching is considered an expensive operation because the OS needs to save the current execution state of a thread before the switch (such as the current register values).
+
As Go developers, we can’t create threads directly, but we can create goroutines, which can be thought of as application-level threads. However, whereas an OS thread is context-switched on and off a CPU core by the OS, a goroutine is context-switched on and off an OS thread by the Go runtime. Also, compared to an OS thread, a goroutine has a smaller memory footprint: 2 KB for goroutines from Go 1.4. An OS thread depends on the OS, but, for example, on Linux/x86–32, the default size is 2 MB (see https://man7.org/linux/man-pages/man3/pthread_create.3.html). Having a smaller size makes context switching faster.
+
+Note
+
Context switching a goroutine versus a thread is about 80% to 90% faster, depending on the architecture.
+
+
Let’s now discuss how the Go scheduler works to overview how goroutines are handled. Internally, the Go scheduler uses the following terminology (see proc.go):
+
+
G — Goroutine
+
M — OS thread (stands for machine)
+
P — CPU core (stands for processor)
+
+
Each OS thread (M) is assigned to a CPU core (P) by the OS scheduler. Then, each goroutine (G) runs on an M. The GOMAXPROCS variable defines the limit of Ms in charge of executing user-level code simultaneously. But if a thread is blocked in a system call (for example, I/O), the scheduler can spin up more Ms. As of Go 1.5, GOMAXPROCS is by default equal to the number of available CPU cores.
+
A goroutine has a simpler lifecycle than an OS thread. It can be doing one of the following:
+
+
Executing — The goroutine is scheduled on an M and executing its instructions.
+
Runnable — The goroutine is waiting to be in an executing state.
+
Waiting — The goroutine is stopped and pending something completing, such as a system call or a synchronization operation (such as acquiring a mutex).
+
+
There’s one last stage to understand about the implementation of Go scheduling: when a goroutine is created but cannot be executed yet; for example, all the other Ms are already executing a G. In this scenario, what will the Go runtime do about it? The answer is queuing. The Go runtime handles two kinds of queues: one local queue per P and a global queue shared among all the Ps.
+
Figure 1 shows a given scheduling situation on a four-core machine with GOMAXPROCS equal to 4. The parts are the logical cores (Ps), goroutines (Gs), OS threads (Ms), local queues, and global queue:
+
+
First, we can see five Ms, whereas GOMAXPROCS is set to 4. But as we mentioned, if needed, the Go runtime can create more OS threads than the GOMAXPROCS value.
+
P0, P1, and P3 are currently busy executing Go runtime threads. But P2 is presently idle as M3 is switched off P2, and there’s no goroutine to be executed. This isn’t a good situation because six runnable goroutines are pending being executed, some in the global queue and some in other local queues. How will the Go runtime handle this situation? Here’s the scheduling implementation in pseudocode (see proc.go):
+
runtime.schedule() {
+ // Only 1/61 of the time, check the global runnable queue for a G.
+ // If not found, check the local queue.
+ // If not found,
+ // Try to steal from other Ps.
+ // If not, check the global runnable queue.
+ // If not found, poll network.
+}
+
+
Every sixty-first execution, the Go scheduler will check whether goroutines from the global queue are available. If not, it will check its local queue. Meanwhile, if both the global and local queues are empty, the Go scheduler can pick up goroutines from other local queues. This principle in scheduling is called work stealing, and it allows an underutilized processor to actively look for another processor’s goroutines and steal some.
+
One last important thing to mention: prior to Go 1.14, the scheduler was cooperative, which meant a goroutine could be context-switched off a thread only in specific blocking cases (for example, channel send or receive, I/O, waiting to acquire a mutex). Since Go 1.14, the Go scheduler is now preemptive: when a goroutine is running for a specific amount of time (10 ms), it will be marked preemptible and can be context-switched off to be replaced by another goroutine. This allows a long-running job to be forced to share CPU time.
+
Now that we understand the fundamentals of scheduling in Go, let’s look at a concrete example: implementing a merge sort in a parallel manner.
+
Parallel Merge Sort
+
First, let’s briefly review how the merge sort algorithm works. Then we will implement a parallel version. Note that the objective isn’t to implement the most efficient version but to support a concrete example showing why concurrency isn’t always faster.
+
The merge sort algorithm works by breaking a list repeatedly into two sublists until each sublist consists of a single element and then merging these sublists so that the result is a sorted list (see figure 2). Each split operation splits the list into two sublists, whereas the merge operation merges two sublists into a sorted list.
+
+
Here is the sequential implementation of this algorithm. We don’t include all of the code as it’s not the main point of this section:
+
funcsequentialMergesort(s[]int){
+iflen(s)<=1{
+return
+}
+
+middle:=len(s)/2
+sequentialMergesort(s[:middle])// First half
+sequentialMergesort(s[middle:])// Second half
+merge(s,middle)// Merges the two halves
+}
+
+funcmerge(s[]int,middleint){
+// ...
+}
+
+
This algorithm has a structure that makes it open to concurrency. Indeed, as each sequentialMergesort operation works on an independent set of data that doesn’t need to be fully copied (here, an independent view of the underlying array using slicing), we could distribute this workload among the CPU cores by spinning up each sequentialMergesort operation in a different goroutine. Let’s write a first parallel implementation:
+
funcparallelMergesortV1(s[]int){
+iflen(s)<=1{
+return
+}
+
+middle:=len(s)/2
+
+varwgsync.WaitGroup
+wg.Add(2)
+
+gofunc(){// Spins up the first half of the work in a goroutine
+deferwg.Done()
+parallelMergesortV1(s[:middle])
+}()
+
+gofunc(){// Spins up the second half of the work in a goroutine
+deferwg.Done()
+parallelMergesortV1(s[middle:])
+}()
+
+wg.Wait()
+merge(s,middle)// Merges the halves
+}
+
+
In this version, each half of the workload is handled in a separate goroutine. The parent goroutine waits for both parts by using sync.WaitGroup. Hence, we call the Wait method before the merge operation.
+
We now have a parallel version of the merge sort algorithm. Therefore, if we run a benchmark to compare this version against the sequential one, the parallel version should be faster, correct? Let’s run it on a four-core machine with 10,000 elements:
Surprisingly, the parallel version is almost an order of magnitude slower. How can we explain this result? How is it possible that a parallel version that distributes a workload across four cores is slower than a sequential version running on a single machine? Let’s analyze the problem.
+
If we have a slice of, say, 1,024 elements, the parent goroutine will spin up two goroutines, each in charge of handling a half consisting of 512 elements. Each of these goroutines will spin up two new goroutines in charge of handling 256 elements, then 128, and so on, until we spin up a goroutine to compute a single element.
+
If the workload that we want to parallelize is too small, meaning we’re going to compute it too fast, the benefit of distributing a job across cores is destroyed: the time it takes to create a goroutine and have the scheduler execute it is much too high compared to directly merging a tiny number of items in the current goroutine. Although goroutines are lightweight and faster to start than threads, we can still face cases where a workload is too small.
+
So what can we conclude from this result? Does it mean the merge sort algorithm cannot be parallelized? Wait, not so fast.
+
Let’s try another approach. Because merging a tiny number of elements within a new goroutine isn’t efficient, let’s define a threshold. This threshold will represent how many elements a half should contain in order to be handled in a parallel manner. If the number of elements in the half is fewer than this value, we will handle it sequentially. Here’s a new version:
+
constmax=2048// Defines the threshold
+
+funcparallelMergesortV2(s[]int){
+iflen(s)<=1{
+return
+}
+
+iflen(s)<=max{
+sequentialMergesort(s)// Calls our initial sequential version
+}else{// If bigger than the threshold, keeps the parallel version
+middle:=len(s)/2
+
+varwgsync.WaitGroup
+wg.Add(2)
+
+gofunc(){
+deferwg.Done()
+parallelMergesortV2(s[:middle])
+}()
+
+gofunc(){
+deferwg.Done()
+parallelMergesortV2(s[middle:])
+}()
+
+wg.Wait()
+merge(s,middle)
+}
+}
+
+
If the number of elements in the s slice is smaller than max, we call the sequential version. Otherwise, we keep calling our parallel implementation. Does this approach impact the result? Yes, it does:
Our v2 parallel implementation is more than 40% faster than the sequential one, thanks to this idea of defining a threshold to indicate when parallel should be more efficient than sequential.
+
+Note
+
Why did I set the threshold to 2,048? Because it was the optimal value for this specific workload on my machine. In general, such magic values should be defined carefully with benchmarks (running on an execution environment similar to production). It’s also pretty interesting to note that running the same algorithm in a programming language that doesn’t implement the concept of goroutines has an impact on the value. For example, running the same example in Java using threads means an optimal value closer to 8,192. This tends to illustrate how goroutines are more efficient than threads.
+
+
Conclusion
+
We have seen throughout this post the fundamental concepts of scheduling in Go: the differences between a thread and a goroutine and how the Go runtime schedules goroutines. Meanwhile, using the parallel merge sort example, we illustrated that concurrency isn’t always necessarily faster. As we have seen, spinning up goroutines to handle minimal workloads (merging only a small set of elements) demolishes the benefit we could get from parallelism.
+
So, where should we go from here? We must keep in mind that concurrency isn’t always faster and shouldn’t be considered the default way to go for all problems. First, it makes things more complex. Also, modern CPUs have become incredibly efficient at executing sequential code and predictable code. For example, a superscalar processor can parallelize instruction execution over a single core with high efficiency.
+
Does this mean we shouldn’t use concurrency? Of course not. However, it’s essential to keep these conclusions in mind. If we’re not sure that a parallel version will be faster, the right approach may be to start with a simple sequential version and build from there using profiling (mistake #98, “Not using Go diagnostics tooling”) and benchmarks (mistake #89, “Writing inaccurate benchmarks”), for example. It can be the only way to ensure that a concurrent implementation is worth it.
In general, we should never guess about performance. When writing optimizations, so many factors may come into play that even if we have a strong opinion about the results, it’s rarely a bad idea to test them. However, writing benchmarks isn’t straightforward. It can be pretty simple to write inaccurate benchmarks and make wrong assumptions based on them. The goal of this post is to examine four common and concrete traps leading to inaccuracy:
+
+
Not resetting or pausing the timer
+
Making wrong assumptions about micro-benchmarks
+
Not being careful about compiler optimizations
+
Being fooled by the observer effect
+
+
General concepts
+
Before discussing these traps, let’s briefly review how benchmarks work in Go. The skeleton of a benchmark is as follows:
The function name starts with the Benchmark prefix. The function under test (foo) is called within the for loop. b.N represents a variable number of iterations. When running a benchmark, Go tries to make it match the requested benchmark time. The benchmark time is set by default to 1 second and can be changed with the -benchtime flag. b.N starts at 1; if the benchmark completes in under 1 second, b.N is increased, and the benchmark runs again until b.N roughly matches benchtime:
+
$ go test -bench=.
+cpu: Intel(R) Core(TM) i5-7360U CPU @ 2.30GHz
+BenchmarkFoo-4 73 16511228 ns/op
+
+
Here, the benchmark took about 1 second, and foo was executed 73 times, for an average execution time of 16,511,228 nanoseconds. We can change the benchmark time using -benchtime:
+
$ go test -bench=. -benchtime=2s
+BenchmarkFoo-4 150 15832169 ns/op
+
+
foo was executed roughly twice more than during the previous benchmark.
+
Next, let’s look at some common traps.
+
Not resetting or pausing the timer
+
In some cases, we need to perform operations before the benchmark loop. These operations may take quite a while (for example, generating a large slice of data) and may significantly impact the benchmark results:
Calling ResetTimer zeroes the elapsed benchmark time and memory allocation counters since the beginning of the test. This way, an expensive setup can be discarded from the test results.
+
What if we have to perform an expensive setup not just once but within each loop iteration?
We can’t reset the timer, because that would be executed during each loop iteration. But we can stop and resume the benchmark timer, surrounding the call to expensiveSetup:
+
funcBenchmarkFoo(b*testing.B){
+fori:=0;i<b.N;i++{
+b.StopTimer()// Pause the benchmark timer
+expensiveSetup()
+b.StartTimer()// Resume the benchmark timer
+functionUnderTest()
+}
+}
+
+
Here, we pause the benchmark timer to perform the expensive setup and then resume the timer.
+
+Note
+
There’s one catch to remember about this approach: if the function under test is too fast to execute compared to the setup function, the benchmark may take too long to complete. The reason is that it would take much longer than 1 second to reach benchtime. Calculating the benchmark time is based solely on the execution time of functionUnderTest. So, if we wait a significant time in each loop iteration, the benchmark will be much slower than 1 second. If we want to keep the benchmark, one possible mitigation is to decrease benchtime.
+
+
We must be sure to use the timer methods to preserve the accuracy of a benchmark.
+
Making wrong assumptions about micro-benchmarks
+
A micro-benchmark measures a tiny computation unit, and it can be extremely easy to make wrong assumptions about it. Let’s say, for example, that we aren’t sure whether to use atomic.StoreInt32 or atomic.StoreInt64 (assuming that the values we handle will always fit in 32 bits). We want to write a benchmark to compare both functions:
We could easily take this benchmark for granted and decide to use atomic.StoreInt64 because it appears to be faster. Now, for the sake of doing a fair benchmark, we reverse the order and test atomic.StoreInt64 first, followed by atomic.StoreInt32. Here is some example output:
This time, atomic.StoreInt32 has better results. What happened?
+
In the case of micro-benchmarks, many factors can impact the results, such as machine activity while running the benchmarks, power management, thermal scaling, and better cache alignment of a sequence of instructions. We must remember that many factors, even outside the scope of our Go project, can impact the results.
+
+Note
+
We should make sure the machine executing the benchmark is idle. However, external processes may run in the background, which may affect benchmark results. For that reason, tools such as perflock can limit how much CPU a benchmark can consume. For example, we can run a benchmark with 70% of the total available CPU, giving 30% to the OS and other processes and reducing the impact of the machine activity factor on the results.
+
+
One option is to increase the benchmark time using the -benchtime option. Similar to the law of large numbers in probability theory, if we run a benchmark a large number of times, it should tend to approach its expected value (assuming we omit the benefits of instructions caching and similar mechanics).
+
Another option is to use external tools on top of the classic benchmark tooling. For instance, the benchstat tool, which is part of the golang.org/x repository, allows us to compute and compare statistics about benchmark executions.
+
Let’s run the benchmark 10 times using the -count option and pipe the output to a specific file:
+
$ go test -bench=. -count=10 | tee stats.txt
+cpu: Intel(R) Core(TM) i5-7360U CPU @ 2.30GHz
+BenchmarkAtomicStoreInt32-4 234935682 5.124 ns/op
+BenchmarkAtomicStoreInt32-4 235307204 5.112 ns/op
+// ...
+BenchmarkAtomicStoreInt64-4 235548591 5.107 ns/op
+BenchmarkAtomicStoreInt64-4 235210292 5.090 ns/op
+// ...
+
The results are the same: both functions take on average 5.10 nanoseconds to complete. We also see the percent variation between the executions of a given benchmark: ± 1%. This metric tells us that both benchmarks are stable, giving us more confidence in the computed average results. Therefore, instead of concluding that atomic.StoreInt32 is faster or slower, we can conclude that its execution time is similar to that of atomic.StoreInt64 for the usage we tested (in a specific Go version on a particular machine).
+
In general, we should be cautious about micro-benchmarks. Many factors can significantly impact the results and potentially lead to wrong assumptions. Increasing the benchmark time or repeating the benchmark executions and computing stats with tools such as benchstat can be an efficient way to limit external factors and get more accurate results, leading to better conclusions.
+
Let’s also highlight that we should be careful about using the results of a micro-benchmark executed on a given machine if another system ends up running the application. The production system may act quite differently from the one on which we ran the micro-benchmark.
+
Not being careful about compiler optimizations
+
Another common mistake related to writing benchmarks is being fooled by compiler optimizations, which can also lead to wrong benchmark assumptions. In this section, we look at Go issue 14813 (https://github.com/golang/go/issues/14813, also discussed by Go project member Dave Cheney) with a population count function (a function that counts the number of bits set to 1):
A duration of 0.28 nanoseconds is roughly one clock cycle, so this number is unreasonably low. The problem is that the developer wasn’t careful enough about compiler optimizations. In this case, the function under test is simple enough to be a candidate for inlining: an optimization that replaces a function call with the body of the called function and lets us prevent a function call, which has a small footprint. Once the function is inlined, the compiler notices that the call has no side effects and replaces it with the following benchmark:
The benchmark is now empty — which is why we got a result close to one clock cycle. To prevent this from happening, a best practice is to follow this pattern:
+
+
During each loop iteration, assign the result to a local variable (local in the context of the benchmark function).
+
Assign the latest result to a global variable.
+
+
In our case, we write the following benchmark:
+
varglobaluint64// Define a global variable
+
+funcBenchmarkPopcnt2(b*testing.B){
+varvuint64// Define a local variable
+fori:=0;i<b.N;i++{
+v=popcnt(uint64(i))// Assign the result to the local variable
+}
+global=v// Assign the result to the global variable
+}
+
+
global is a global variable, whereas v is a local variable whose scope is the benchmark function. During each loop iteration, we assign the result of popcnt to the local variable. Then we assign the latest result to the global variable.
+
+Note
+
Why not assign the result of the popcnt call directly to global to simplify the test? Writing to a global variable is slower than writing to a local variable (these concepts are discussed in 100 Go Mistakes, mistake #95: “Not understanding stack vs. heap”). Therefore, we should write each result to a local variable to limit the footprint during each loop iteration.
+
+
If we run these two benchmarks, we now get a significant difference in the results:
BenchmarkPopcnt2 is the accurate version of the benchmark. It guarantees that we avoid the inlining optimizations, which can artificially lower the execution time or even remove the call to the function under test. Relying on the results of BenchmarkPopcnt1 could have led to wrong assumptions.
+
Let’s remember the pattern to avoid compiler optimizations fooling benchmark results: assign the result of the function under test to a local variable, and then assign the latest result to a global variable. This best practice also prevents us from making incorrect assumptions.
+
Being fooled by the observer effect
+
In physics, the observer effect is the disturbance of an observed system by the act of observation. This effect can also be seen in benchmarks and can lead to wrong assumptions about results. Let’s look at a concrete example and then try to mitigate it.
+
We want to implement a function receiving a matrix of int64 elements. This matrix has a fixed number of 512 columns, and we want to compute the total sum of the first eight columns, as shown in figure 1.
+
+
For the sake of optimizations, we also want to determine whether varying the number of columns has an impact, so we also implement a second function with 513 columns. The implementation is the following:
+
funccalculateSum512(s[][512]int64)int64{
+varsumint64
+fori:=0;i<len(s);i++{// Iterate over each row
+forj:=0;j<8;j++{// Iterate over the first eight columns
+sum+=s[i][j]// Increment sum
+}
+}
+returnsum
+}
+
+funccalculateSum513(s[][513]int64)int64{
+// Same implementation as calculateSum512
+}
+
+
We iterate over each row and then over the first eight columns, and we increment a sum variable that we return. The implementation in calculateSum513 remains the same.
+
We want to benchmark these functions to decide which one is the most performant given a fixed number of rows:
+
constrows=1000
+
+varresint64
+
+funcBenchmarkCalculateSum512(b*testing.B){
+varsumint64
+s:=createMatrix512(rows)// Create a matrix of 512 columns
+b.ResetTimer()
+fori:=0;i<b.N;i++{
+sum=calculateSum512(s)// Create a matrix of 512 columns
+}
+res=sum
+}
+
+funcBenchmarkCalculateSum513(b*testing.B){
+varsumint64
+s:=createMatrix513(rows)// Create a matrix of 513 columns
+b.ResetTimer()
+fori:=0;i<b.N;i++{
+sum=calculateSum513(s)// Calculate the sum
+}
+res=sum
+}
+
+
We want to create the matrix only once, to limit the footprint on the results. Therefore, we call createMatrix512 and createMatrix513 outside of the loop. We may expect the results to be similar as again we only want to iterate on the first eight columns, but this isn’t the case (on my machine):
The second benchmark with 513 columns is about 50% faster. Again, because we iterate only over the first eight columns, this result is quite surprising.
+
To understand this difference, we need to understand the basics of CPU caches. In a nutshell, a CPU is composed of different caches (usually L1, L2, and L3). These caches reduce the average cost of accessing data from the main memory. In some conditions, the CPU can fetch data from the main memory and copy it to L1. In this case, the CPU tries to fetch into L1 the matrix’s subset that calculateSum is interested in (the first eight columns of each row). However, the matrix fits in memory in one case (513 columns) but not in the other case (512 columns).
+
+Note
+
This isn’t in the scope of this post to explain why, but we look at this problem in 100 Go Mistakes, mistake #91: “Not understanding CPU caches.”
+
+
Coming back to the benchmark, the main issue is that we keep reusing the same matrix in both cases. Because the function is repeated thousands of times, we don’t measure the function’s execution when it receives a plain new matrix. Instead, we measure a function that gets a matrix that already has a subset of the cells present in the cache. Therefore, because calculateSum513 leads to fewer cache misses, it has a better execution time.
+
This is an example of the observer effect. Because we keep observing a repeatedly called CPU-bound function, CPU caching may come into play and significantly affect the results. In this example, to prevent this effect, we should create a matrix during each test instead of reusing one:
+
funcBenchmarkCalculateSum512(b*testing.B){
+varsumint64
+fori:=0;i<b.N;i++{
+b.StopTimer()
+s:=createMatrix512(rows)// Create a new matrix during each loop iteration
+b.StartTimer()
+sum=calculateSum512(s)
+}
+res=sum
+}
+
+
A new matrix is now created during each loop iteration. If we run the benchmark again (and adjust benchtime — otherwise, it takes too long to execute), the results are closer to each other:
Instead of making the incorrect assumption that calculateSum513 is faster, we see that both benchmarks lead to similar results when receiving a new matrix.
+
As we have seen in this post, because we were reusing the same matrix, CPU caches significantly impacted the results. To prevent this, we had to create a new matrix during each loop iteration. In general, we should remember that observing a function under test may lead to significant differences in results, especially in the context of micro-benchmarks of CPU-bound functions where low-level optimizations matter. Forcing a benchmark to re-create data during each iteration can be a good way to prevent this effect.
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+ Being confused about when to use generics (#9) - 100 Go Mistakes and How to Avoid Them
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Generics is a fresh addition to the language. In a nutshell, it allows writing code with types that can be specified later and instantiated when needed. However, it can be pretty easy to be confused about when to use generics and when not to. Throughout this post, we will describe the concept of generics in Go and then delve into common use and misuses.
+
Concepts
+
Consider the following function that extracts all the keys from a map[string]int type:
What if we would like to use a similar feature for another map type such as a map[int]string? Before generics, Go developers had a couple of options: using code generation, reflection, or duplicating code.
+
For example, we could write two functions, one for each map type, or even try to extend getKeys to accept different map types:
First, it increases boilerplate code. Indeed, whenever we want to add a case, it will require duplicating the range loop.
+
Meanwhile, the function now accepts an empty interface, which means we are losing some of the benefits of Go being a typed language. Indeed, checking whether a type is supported is done at runtime instead of compile-time. Hence, we also need to return an error if the provided type is unknown.
+
Last but not least, as the key type can be either int or string, we are obliged to return a slice of empty interfaces to factor out key types. This approach increases the effort on the caller-side as the client may also have to perform a type check of the keys or extra conversion.
+
+
Thanks to generics, we can now refactor this code using type parameters.
+
Type parameters are generic types we can use with functions and types. For example, the following function accepts a type parameter:
+
funcfoo[Tany](tT){
+// ...
+}
+
+
When calling foo, we will pass a type argument of any type. Passing a type argument is called instantiation because the work is done at compile time which keeps type safety as part of the core language features and avoids runtime overheads.
+
Let’s get back to the getKeys function and use type parameters to write a generic version that would accept any kind of map:
To handle the map, we defined two kinds of type parameters. First, the values can be of any type: V any. However, in Go, the map keys can’t be of any type. For example, we cannot use slices:
+
varmmap[[]byte]int
+
+
This code leads to a compilation error: invalid map key type []byte. Therefore, instead of accepting any key type, we are obliged to restrict type arguments so that the key type meets specific requirements. Here, being comparable (we can use == or !=). Hence, we defined K as comparable instead of any.
+
Restricting type arguments to match specific requirements is called a constraint. A constraint is an interface type that can contain:
+
+
A set of behaviors (methods)
+
But also arbitrary type
+
+
Let’s see a concrete example for the latter. Imagine we don’t want to accept any comparable type for map key type. For instance, we would like to restrict it to either int or string types. We can define a custom constraint this way:
+
typecustomConstraintinterface{
+~int|~string// Define a custom type that will restrict types to int and string
+}
+
+// Change the type parameter K to be custom
+funcgetKeys[KcustomConstraint,Vany](mmap[K]V)[]K{
+// Same implementation
+}
+
+
First, we define a customConstraint interface to restrict the types to be either int or string using the union operator | (we will discuss the use of ~ a bit later). Then, K is now a customConstraint instead of a comparable as before.
+
Now, the signature of getKeys enforces that we can call it with a map of any value type, but the key type has to be an int or a string. For example, on the caller-side:
Note that Go can infer that getKeys is called with a string type argument. The previous call was similar to this:
+
keys:=getKeys[string](m)
+
+
+Note
+
What’s the difference between a constraint using ~int or int? Using int restricts it to that type, whereas ~int restricts all the types whose underlying type is an int.
+
To illustrate it, let’s imagine a constraint where we would like to restrict a type to any int type implementing the String() string method:
As customInt is an int and implements the String() string method, the customInt type satisfies the constraint defined.
+
However, if we change the constraint to contain an int instead of an ~int, using customInt would lead to a compilation error because the int type doesn’t implement String() string.
+
+
Let’s also note the constraints package contains a set of common constraints such as Signed that includes all the signed integer types. Let’s ensure that a constraint doesn’t already exist in this package before creating a new one.
+
So far, we have discussed examples using generics for functions. However, we can also use generics with data structures.
+
For example, we will create a linked list containing values of any type. Meanwhile, we will write an Add method to append a node:
+
typeNode[Tany]struct{// Use type parameter
+ValT
+next*Node[T]
+}
+
+func(n*Node[T])Add(next*Node[T]){// Instantiate type receiver
+n.next=next
+}
+
+
We use type parameters to define T and use both fields in Node. Regarding the method, the receiver is instantiated. Indeed, because Node is generic, it has to follow also the type parameter defined.
+
One last thing to note about type parameters: they can’t be used on methods, only on functions. For example, the following method wouldn’t compile:
+
typeFoostruct{}
+
+func(Foo)bar[Tany](tT){}
+
+
./main.go:29:15: methods cannot have type parameters
+
+
Now, let’s delve into concrete cases where we should and shouldn’t use generics.
+
Common uses and misuses
+
So when are generics useful? Let’s discuss a couple of common uses where generics are recommended:
+
+
Data structures. For example, we can use generics to factor out the element type if we implement a binary tree, a linked list, or a heap.
+
Functions working with slices, maps, and channels of any type. For example, a function to merge two channels would work with any channel type. Hence, we could use type parameters to factor out the channel type:
Meanwhile, instead of factoring out a type, we can factor out behaviors. For example, the sort package contains functions to sort different slice types such as sort.Ints or sort.Float64s. Using type parameters, we can factor out the sorting behaviors that rely on three methods, Len, Less, and Swap:
+
+
typesliceFn[Tany]struct{// Use type parameter
+s[]T
+comparefunc(T,T)bool// Compare two T elements
+}
+
+func(ssliceFn[T])Len()int{returnlen(s.s)}
+func(ssliceFn[T])Less(i,jint)bool{returns.compare(s.s[i],s.s[j])}
+func(ssliceFn[T])Swap(i,jint){s.s[i],s.s[j]=s.s[j],s.s[i]}
+
+
Conversely, when is it recommended not to use generics?
+
+
When just calling a method of the type argument. For example, consider a function that receives an io.Writer and call the Write method:
When it makes our code more complex. Generics are never mandatory, and as Go developers, we have been able to live without them for more than a decade. If writing generic functions or structures we figure out that it doesn’t make our code clearer, we should probably reconsider our decision for this particular use case.
+
+
Conclusion
+
Though generics can be very helpful in particular conditions, we should be cautious about when to use them and not use them.
+
In general, when we want to answer when not to use generics, we can find similarities with when not to use interfaces. Indeed, generics introduce a form of abstraction, and we have to remember that unnecessary abstractions introduce complexity.
+
Let’s not pollute our code with needless abstractions, and let’s focus on solving concrete problems for now. It means that we shouldn’t use type parameters prematurely. Let’s wait until we are about to write boilerplate code to consider using generics.
Writing concurrent code that leads to false sharing
+
+
In previous sections, we have discussed the fundamental concepts of CPU caching. We have seen that some specific caches (typically, L1 and L2) aren’t shared among all the logical cores but are specific to a physical core. This specificity has some concrete impacts such as concurrency and the concept of false sharing, which can lead to a significant performance decrease. Let’s look at what false sharing is via an example and then see how to prevent it.
+
In this example, we use two structs, Input and Result:
We spin up two goroutines: one that iterates over each a field and another that iterates over each b field. This example is fine from a concurrency perspective. For instance, it doesn’t lead to a data race, because each goroutine increments its own variable. But this example illustrates the false sharing concept that degrades expected performance.
+
Let’s look at the main memory. Because sumA and sumB are allocated contiguously, in most cases (seven out of eight), both variables are allocated to the same memory block:
+
+
Now, let’s assume that the machine contains two cores. In most cases, we should eventually have two threads scheduled on different cores. So if the CPU decides to copy this memory block to a cache line, it is copied twice:
+
+
Both cache lines are replicated because L1D (L1 data) is per core. Recall that in our example, each goroutine updates its own variable: sumA on one side, and sumB on the other side:
+
+
Because these cache lines are replicated, one of the goals of the CPU is to guarantee cache coherency. For example, if one goroutine updates sumA and another reads sumA (after some synchronization), we expect our application to get the latest value.
+
However, our example doesn’t do exactly this. Both goroutines access their own variables, not a shared one. We might expect the CPU to know about this and understand that it isn’t a conflict, but this isn’t the case. When we write a variable that’s in a cache, the granularity tracked by the CPU isn’t the variable: it’s the cache line.
+
When a cache line is shared across multiple cores and at least one goroutine is a writer, the entire cache line is invalidated. This happens even if the updates are logically independent (for example, sumA and sumB). This is the problem of false sharing, and it degrades performance.
+
+Note
+
Internally, a CPU uses the MESI protocol to guarantee cache coherency. It tracks each cache line, marking it modified, exclusive, shared, or invalid (MESI).
+
+
One of the most important aspects to understand about memory and caching is that sharing memory across cores isn’t real—it’s an illusion. This understanding comes from the fact that we don’t consider a machine a black box; instead, we try to have mechanical sympathy with underlying levels.
+
So how do we solve false sharing? There are two main solutions.
+
The first solution is to use the same approach we’ve shown but ensure that sumA and sumB aren’t part of the same cache line. For example, we can update the Result struct to add padding between the fields. Padding is a technique to allocate extra memory. Because an int64 requires an 8-byte allocation and a cache line 64 bytes long, we need 64 – 8 = 56 bytes of padding:
The next figure shows a possible memory allocation. Using padding, sumA and sumB will always be part of different memory blocks and hence different cache lines.
+
+
If we benchmark both solutions (with and without padding), we see that the padding solution is significantly faster (about 40% on my machine). This is an important improvement that results from the addition of padding between the two fields to prevent false sharing.
+
The second solution is to rework the structure of the algorithm. For example, instead of having both goroutines share the same struct, we can make them communicate their local result via channels. The result benchmark is roughly the same as with padding.
+
In summary, we must remember that sharing memory across goroutines is an illusion at the lowest memory levels. False sharing occurs when a cache line is shared across two cores when at least one goroutine is a writer. If we need to optimize an application that relies on concurrency, we should check whether false sharing applies, because this pattern is known to degrade application performance. We can prevent false sharing with either padding or communication.
Go offers a few excellent diagnostics tools to help us get insights into how an application performs. This post focuses on the most important ones: profiling and the execution tracer. Both tools are so important that they should be part of the core toolset of any Go developer who is interested in optimization. First, let’s discuss profiling.
+
Profiling
+
Profiling provides insights into the execution of an application. It allows us to resolve performance issues, detect contention, locate memory leaks, and more. These insights can be collected via several profiles:
+
+
CPU— Determines where an application spends its time
+
Goroutine— Reports the stack traces of the ongoing goroutines
+
Heap— Reports heap memory allocation to monitor current memory usage and check for possible memory leaks
+
Mutex— Reports lock contentions to see the behaviors of the mutexes used in our code and whether an application spends too much time in locking calls
+
Block— Shows where goroutines block waiting on synchronization primitives
+
+
Profiling is achieved via instrumentation using a tool called a profiler, in Go: pprof. First, let’s understand how and when to enable pprof; then, we discuss the most critical profile types.
+
Enabling pprof
+
There are several ways to enable pprof. For example, we can use the net/http/pprof package to serve the profiling data via HTTP:
Importing net/http/pprof leads to a side effect that allows us to reach the pprof URL: http://host/debug/pprof. Note that enabling pprof is safe even in production (https://go.dev/doc/diagnostics#profiling). The profiles that impact performance, such as CPU profiling, aren’t enabled by default, nor do they run continuously: they are activated only for a specific period.
+
Now that we have seen how to expose a pprof endpoint, let’s discuss the most common profiles.
+
CPU Profiling
+
The CPU profiler relies on the OS and signaling. When it is activated, the application asks the OS to interrupt it every 10 ms by default via a SIGPROF signal. When the application receives a SIGPROF, it suspends the current activity and transfers the execution to the profiler. The profiler collects data such as the current goroutine activity and aggregates execution statistics that we can retrieve. Then it stops, and the execution resumes until the next SIGPROF.
+
We can access the /debug/pprof/profile endpoint to activate CPU profiling. Accessing this endpoint executes CPU profiling for 30 seconds by default. For 30 seconds, our application is interrupted every 10 ms. Note that we can change these two default values: we can use the seconds parameter to pass to the endpoint how long the profiling should last (for example, /debug/pprof/profile?seconds=15), and we can change the interruption rate (even to less than 10 ms). But in most cases, 10 ms should be enough, and in decreasing this value (meaning increasing the rate), we should be careful not to harm performance. After 30 seconds, we download the results of the CPU profiler.
+
+Note
+
We can also enable the CPU profiler using the -cpuprofile flag, such as when running a benchmark. For example, the following command produces the same type of file that can be downloaded via /debug/ pprof/profile.
+
$ go test -bench=. -cpuprofile profile.out
+
+
+
From this file, we can navigate to the results using go tool:
+
$ go tool pprof -http=:8080 <file>
+
+
This command opens a web UI showing the call graph. The next figure shows an example taken from an application. The larger the arrow, the more it was a hot path. We can then navigate into this graph and get execution insights.
+
+
For example, the graph in the next figure tells us that during 30 seconds, 0.06 seconds were spent in the decode method (*FetchResponse receiver). Of these 0.06 seconds, 0.02 were spent in RecordBatch.decode and 0.01 in makemap (creating a map).
+
+
We can also access this kind of information from the web UI with different representations. For example, the Top view sorts the functions per execution time, and Flame Graph visualizes the execution time hierarchy. The UI can even display the expensive parts of the source code line by line.
+
+Note
+
We can also delve into profiling data via a command line. However, we focus on the web UI in this post.
+
+
Thanks to this data, we can get a general idea of how an application behaves:
+
+
Too many calls to runtime.mallogc can mean an excessive number of small heap allocations that we can try to minimize.
+
Too much time spent in channel operations or mutex locks can indicate excessive contention that is harming the application’s performance.
+
Too much time spent on syscall.Read or syscall.Write means the application spends a significant amount of time in Kernel mode. Working on I/O buffering may be an avenue for improvement.
+
+
These are the kinds of insights we can get from the CPU profiler. It’s valuable to understand the hottest code path and identify bottlenecks. But it won’t determine more than the configured rate because the CPU profiler is executed at a fixed pace (by default, 10 ms). To get finer-grained insights, we should use tracing, which we discuss later in this post.
+
+Note
+
We can also attach labels to the different functions. For example, imagine a common function called from different clients. To track the time spent for both clients, we can use pprof.Labels.
+
+
Heap Profiling
+
Heap profiling allows us to get statistics about the current heap usage. Like CPU profiling, heap profiling is sample-based. We can change this rate, but we shouldn’t be too granular because the more we decrease the rate, the more effort heap profiling will require to collect data. By default, samples are profiled at one allocation for every 512 KB of heap allocation.
+
If we reach /debug/pprof/heap/, we get raw data that can be hard to read. However, we can download a heap profile using /debug/pprof/heap/?debug=0 and then open it with go tool (the same command as in the previous section) to navigate into the data using the web UI.
+
The next figure shows an example of a heap graph. Calling the MetadataResponse.decode method leads to allocating 1536 KB of heap data (which represents 6.32% of the total heap). However, 0 out of these 1536 KB were allocated by this function directly, so we need to inspect the second call. The TopicMetadata.decode method allocated 512 KB out of the 1536 KB; the rest — 1024 KB — were allocated in another method.
+
+
This is how we can navigate the call chain to understand what part of an application is responsible for most of the heap allocations. We can also look at different sample types:
+
+
alloc_objects— Total number of objects allocated
+
alloc_space— Total amount of memory allocated
+
inuse_objects — Number of objects allocated and not yet released
+
inuse_space— Amount of memory allocated and not yet released
+
+
Another very helpful capability with heap profiling is tracking memory leaks. With a GC-based language, the usual procedure is the following:
+
+
Trigger a GC.
+
Download heap data.
+
Wait for a few seconds/minutes.
+
Trigger another GC.
+
Download another heap data.
+
Compare.
+
+
Forcing a GC before downloading data is a way to prevent false assumptions. For example, if we see a peak of retained objects without running a GC first, we cannot be sure whether it’s a leak or objects that the next GC will collect.
+
Using pprof, we can download a heap profile and force a GC in the meantime. The procedure in Go is the following:
+
+
Go to /debug/pprof/heap?gc=1 (trigger the GC and download the heap profile).
+
Wait for a few seconds/minutes.
+
Go to /debug/pprof/heap?gc=1 again.
+
Use go tool to compare both heap profiles:
+
+
$ go tool pprof -http=:8080 -diff_base <file2> <file1>
+
+
The next figure shows the kind of data we can access. For example, the amount of heap memory held by the newTopicProducer method (top left) has decreased (–513 KB). In contrast, the amount held by updateMetadata (bottom right) has increased (+512 KB). Slow increases are normal. The second heap profile may have been calculated in the middle of a service call, for example. We can repeat this process or wait longer; the important part is to track steady increases in allocations of a specific object.
+
+
+Note
+
Another type of profiling related to the heap is allocs, which reports allocations. Heap profiling shows the current state of the heap memory. To get insights about past memory allocations since the application started, we can use allocations profiling. As discussed, because stack allocations are cheap, they aren’t part of this profiling, which only focuses on the heap.
+
+
Goroutine Profiling
+
The goroutine profile reports the stack trace of all the current goroutines in an application. We can download a file using /debug/pprof/goroutine/?debug=0 and use go tool again. The next figure shows the kind of information we can get.
+
+
We can see the current state of the application and how many goroutines were created per function. In this case, withRecover has created 296 ongoing goroutines (63%), and 29 were related to a call to responseFeeder.
+
This kind of information is also beneficial if we suspect goroutine leaks. We can look at goroutine profiler data to know which part of a system is the suspect.
+
Block Profiling
+
The block profile reports where ongoing goroutines block waiting on synchronization primitives. Possibilities include
+
+
Sending or receiving on an unbuffered channel
+
Sending to a full channel
+
Receiving from an empty channel
+
Mutex contention
+
Network or filesystem waits
+
+
Block profiling also records the amount of time a goroutine has been waiting and is accessible via /debug/pprof/block. This profile can be extremely helpful if we suspect that performance is being harmed by blocking calls.
+
The block profile isn’t enabled by default: we have to call runtime.SetBlockProfileRate to enable it. This function controls the fraction of goroutine blocking events that are reported. Once enabled, the profiler will keep collecting data in the background even if we don’t call the /debug/pprof/block endpoint. Let’s be cautious if we want to set a high rate so we don’t harm performance.
+
+Note
+
If we face a deadlock or suspect that goroutines are in a blocked state, the full goroutine stack dump (/debug/pprof/goroutine/?debug=2) creates a dump of all the current goroutine stack traces. This can be helpful as a first analysis step. For example, the following dump shows a Sarama goroutine blocked for 1,420 minutes on a channel-receive operation:
The last profile type is related to blocking but only regarding mutexes. If we suspect that our application spends significant time waiting for locking mutexes, thus harming execution, we can use mutex profiling. It’s accessible via /debug/pprof/mutex.
+
This profile works in a manner similar to that for blocking. It’s disabled by default: we have to enable it using runtime.SetMutexProfileFraction, which controls the fraction of mutex contention events reported.
+
Following are a few additional notes about profiling:
Be sure to enable only one profiler at a time: for example, do not enable CPU and heap profiling simultaneously. Doing so can lead to erroneous observations.
+
pprof is extensible, and we can create our own custom profiles using pprof.Profile.
+
+
We have seen the most important profiles that we can enable to help us understand how an application performs and possible avenues for optimization. In general, enabling pprof is recommended, even in production, because in most cases it offers an excellent balance between its footprint and the amount of insight we can get from it. Some profiles, such as the CPU profile, lead to performance penalties but only during the time they are enabled.
+
Let’s now look at the execution tracer.
+
Execution Tracer
+
The execution tracer is a tool that captures a wide range of runtime events with go tool to make them available for visualization. It is helpful for the following:
+
+
Understanding runtime events such as how the GC performs
+
Understanding how goroutines execute
+
Identifying poorly parallelized execution
+
+
Let’s try it with an example given the Concurrency isn’t Always Faster in Go section. We discussed two parallel versions of the merge sort algorithm. The issue with the first version was poor parallelization, leading to the creation of too many goroutines. Let’s see how the tracer can help us in validating this statement.
+
We will write a benchmark for the first version and execute it with the -trace flag to enable the execution tracer:
+
$ go test -bench=. -v -trace=trace.out
+
+
+Note
+
We can also download a remote trace file using the /debug/pprof/ trace?debug=0 pprof endpoint.
+
+
This command creates a trace.out file that we can open using go tool:
+
$ go tool trace trace.out
+2021/11/26 21:36:03 Parsing trace...
+2021/11/26 21:36:31 Splitting trace...
+2021/11/26 21:37:00 Opening browser. Trace viewer is listening on
+ http://127.0.0.1:54518
+
+
The web browser opens, and we can click View Trace to see all the traces during a specific timeframe, as shown in the next figure. This figure represents about 150 ms. We can see multiple helpful metrics, such as the goroutine count and the heap size. The heap size grows steadily until a GC is triggered. We can also observe the activity of the Go application per CPU core. The timeframe starts with user-level code; then a “stop the
+world” is executed, which occupies the four CPU cores for approximately 40 ms.
+
+
Regarding concurrency, we can see that this version uses all the available CPU cores on the machine. However, the next figure zooms in on a portion of 1 ms. Each bar corresponds to a single goroutine execution. Having too many small bars doesn’t look right: it means execution that is poorly parallelized.
+
+
The next figure zooms even closer to see how these goroutines are orchestrated. Roughly 50% of the CPU time isn’t spent executing application code. The white spaces represent the time the Go runtime takes to spin up and orchestrate new goroutines.
+
+
Let’s compare this with the second parallel implementation, which was about an order of magnitude faster. The next figure again zooms to a 1 ms timeframe.
+
+
Each goroutine takes more time to execute, and the number of white spaces has been significantly reduced. Hence, the CPU is much more occupied executing application code than it was in the first version. Each millisecond of CPU time is spent more efficiently, explaining the benchmark differences.
+
Note that the granularity of the traces is per goroutine, not per function like CPU profiling. However, it’s possible to define user-level tasks to get insights per function or group of functions using the runtime/trace package.
+
For example, imagine a function that computes a Fibonacci number and then writes it to a global variable using atomic. We can define two different tasks:
+
varvint64
+// Creates a fibonacci task
+ctx,fibTask:=trace.NewTask(context.Background(),"fibonacci")
+trace.WithRegion(ctx,"main",func(){
+v=fibonacci(10)
+})
+fibTask.End()
+
+// Creates a store task
+ctx,fibStore:=trace.NewTask(ctx,"store")
+trace.WithRegion(ctx,"main",func(){
+atomic.StoreInt64(&result,v)
+})
+fibStore.End()
+
+
Using go tool, we can get more precise information about how these two tasks perform. In the previous trace UI, we can see the boundaries for each task per goroutine. In User-Defined Tasks, we can follow the duration distribution:
+
+
We see that in most cases, the fibonacci task is executed in less than 15 microseconds, whereas the store task takes less than 6309 nanoseconds.
+
In the previous section, we discussed the kinds of information we can get from CPU profiling. What are the main differences compared to the data we can get from user-level traces?
+
+
CPU profiling:
+
Sample-based
+
Per function
+
Doesn’t go below the sampling rate (10 ms by default)
+
+
+
User-level traces:
+
Not sample-based
+
Per-goroutine execution (unless we use the runtime/trace package)
+
Time executions aren’t bound by any rate
+
+
+
+
In summary, the execution tracer is a powerful tool for understanding how an application performs. As we have seen with the merge sort example, we can identify poorly parallelized execution. However, the tracer’s granularity remains per goroutine unless we manually use runtime/trace compared to a CPU profile, for example. We can use both profiling and the execution tracer to get the most out of the standard Go diagnostics tools when optimizing an application.
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circle{fill:var(--md-mermaid-label-bg-color)}.actor{fill:var(--md-mermaid-sequence-actor-bg-color);stroke:var(--md-mermaid-sequence-actor-border-color)}text.actor>tspan{fill:var(--md-mermaid-sequence-actor-fg-color);font-family:var(--md-mermaid-font-family)}line{stroke:var(--md-mermaid-sequence-actor-line-color)}.actor-man circle,.actor-man line{fill:var(--md-mermaid-sequence-actorman-bg-color);stroke:var(--md-mermaid-sequence-actorman-line-color)}.messageLine0,.messageLine1{stroke:var(--md-mermaid-sequence-message-line-color)}.note{fill:var(--md-mermaid-sequence-note-bg-color);stroke:var(--md-mermaid-sequence-note-border-color)}.loopText,.loopText>tspan,.messageText,.noteText>tspan{stroke:none;font-family:var(--md-mermaid-font-family)!important}.messageText{fill:var(--md-mermaid-sequence-message-fg-color)}.loopText,.loopText>tspan{fill:var(--md-mermaid-sequence-loop-fg-color)}.noteText>tspan{fill:var(--md-mermaid-sequence-note-fg-color)}#arrowhead 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Hn(e,{viewport$:t,target$:r,print$:o}){return T(...R(".annotate:not(.highlight)",e).map(n=>wn(n,{target$:r,print$:o})),...R("pre:not(.mermaid) > code",e).map(n=>On(n,{target$:r,print$:o})),...R("pre.mermaid",e).map(n=>_n(n)),...R("table:not([class])",e).map(n=>Cn(n)),...R("details",e).map(n=>Mn(n,{target$:r,print$:o})),...R("[data-tabs]",e).map(n=>kn(n,{viewport$:t,target$:r})),...R("[title]",e).filter(()=>G("content.tooltips")).map(n=>Ge(n)))}function Ra(e,{alert$:t}){return t.pipe(b(r=>T($(!0),$(!1).pipe(Ye(2e3))).pipe(m(o=>({message:r,active:o})))))}function $n(e,t){let r=P(".md-typeset",e);return H(()=>{let o=new v;return o.subscribe(({message:n,active:i})=>{e.classList.toggle("md-dialog--active",i),r.textContent=n}),Ra(e,t).pipe(y(n=>o.next(n)),_(()=>o.complete()),m(n=>F({ref:e},n)))})}function Pa({viewport$:e}){if(!G("header.autohide"))return $(!1);let t=e.pipe(m(({offset:{y:n}})=>n),Ke(2,1),m(([n,i])=>[nMath.abs(i-n.y)>100),m(([,[n]])=>n),Y()),o=We("search");return 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t=R("input",e),r=E("meta",{name:"theme-color"});document.head.appendChild(r);let o=E("meta",{name:"color-scheme"});document.head.appendChild(o);let n=At("(prefers-color-scheme: light)");return H(()=>{let i=new v;return i.subscribe(s=>{if(document.body.setAttribute("data-md-color-switching",""),s.color.media==="(prefers-color-scheme)"){let a=matchMedia("(prefers-color-scheme: light)"),c=document.querySelector(a.matches?"[data-md-color-media='(prefers-color-scheme: light)']":"[data-md-color-media='(prefers-color-scheme: dark)']");s.color.scheme=c.getAttribute("data-md-color-scheme"),s.color.primary=c.getAttribute("data-md-color-primary"),s.color.accent=c.getAttribute("data-md-color-accent")}for(let[a,c]of Object.entries(s.color))document.body.setAttribute(`data-md-color-${a}`,c);for(let a=0;a{let s=Te("header"),a=window.getComputedStyle(s);return 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r=`https://api.github.com/users/${e}`;return De(r).pipe(m(o=>({repositories:o.public_repos})),Qe({}))}}function ni(e,t){let r=`https://${e}/api/v4/projects/${encodeURIComponent(t)}`;return De(r).pipe(he(()=>L),m(({star_count:o,forks_count:n})=>({stars:o,forks:n})),Qe({}))}function ii(e){let t=e.match(/^.+github\.com\/([^/]+)\/?([^/]+)?/i);if(t){let[,r,o]=t;return oi(r,o)}if(t=e.match(/^.+?([^/]*gitlab[^/]+)\/(.+?)\/?$/i),t){let[,r,o]=t;return ni(r,o)}return L}var Ba;function Ga(e){return Ba||(Ba=H(()=>{let t=__md_get("__source",sessionStorage);if(t)return $(t);if(ne("consent").length){let o=__md_get("__consent");if(!(o&&o.github))return L}return ii(e.href).pipe(y(o=>__md_set("__source",o,sessionStorage)))}).pipe(he(()=>L),g(t=>Object.keys(t).length>0),m(t=>({facts:t})),B(1)))}function ai(e){let t=P(":scope > :last-child",e);return H(()=>{let r=new v;return 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n=t.pipe(m(({offset:{y:s}})=>s),Ke(2,1),m(([s,a])=>s>a&&a>0),Y()),i=r.pipe(m(({active:s})=>s));return Q([i,n]).pipe(m(([s,a])=>!(s&&a)),Y(),U(o.pipe(Le(1))),oe(!0),at({delay:250}),m(s=>({hidden:s})))}function pi(e,{viewport$:t,header$:r,main$:o,target$:n}){let i=new v,s=i.pipe(ee(),oe(!0));return i.subscribe({next({hidden:a}){e.hidden=a,a?(e.setAttribute("tabindex","-1"),e.blur()):e.removeAttribute("tabindex")},complete(){e.style.top="",e.hidden=!0,e.removeAttribute("tabindex")}}),r.pipe(U(s),X("height")).subscribe(({height:a})=>{e.style.top=`${a+16}px`}),d(e,"click").subscribe(a=>{a.preventDefault(),window.scrollTo({top:0})}),Za(e,{viewport$:t,main$:o,target$:n}).pipe(y(a=>i.next(a)),_(()=>i.complete()),m(a=>F({ref:e},a)))}function li({document$:e}){e.pipe(b(()=>R(".md-ellipsis")),re(t=>yt(t).pipe(U(e.pipe(Le(1))),g(r=>r),m(()=>t),ye(1))),g(t=>t.offsetWidth{let r=t.innerText,o=t.closest("a")||t;return o.title=r,Ge(o).pipe(U(e.pipe(Le(1))),_(()=>o.removeAttribute("title")))})).subscribe(),e.pipe(b(()=>R(".md-status")),re(t=>Ge(t))).subscribe()}function mi({document$:e,tablet$:t}){e.pipe(b(()=>R(".md-toggle--indeterminate")),y(r=>{r.indeterminate=!0,r.checked=!1}),re(r=>d(r,"change").pipe(Fr(()=>r.classList.contains("md-toggle--indeterminate")),m(()=>r))),ae(t)).subscribe(([r,o])=>{r.classList.remove("md-toggle--indeterminate"),o&&(r.checked=!1)})}function es(){return/(iPad|iPhone|iPod)/.test(navigator.userAgent)}function fi({document$:e}){e.pipe(b(()=>R("[data-md-scrollfix]")),y(t=>t.removeAttribute("data-md-scrollfix")),g(es),re(t=>d(t,"touchstart").pipe(m(()=>t)))).subscribe(t=>{let r=t.scrollTop;r===0?t.scrollTop=1:r+t.offsetHeight===t.scrollHeight&&(t.scrollTop=r-1)})}function ui({viewport$:e,tablet$:t}){Q([We("search"),t]).pipe(m(([r,o])=>r&&!o),b(r=>$(r).pipe(Ye(r?400:100))),ae(e)).subscribe(([r,{offset:{y:o}}])=>{if(r)document.body.setAttribute("data-md-scrolllock",""),document.body.style.top=`-${o}px`;else{let n=-1*parseInt(document.body.style.top,10);document.body.removeAttribute("data-md-scrolllock"),document.body.style.top="",n&&window.scrollTo(0,n)}})}Object.entries||(Object.entries=function(e){let t=[];for(let r of Object.keys(e))t.push([r,e[r]]);return t});Object.values||(Object.values=function(e){let t=[];for(let r of Object.keys(e))t.push(e[r]);return t});typeof Element!="undefined"&&(Element.prototype.scrollTo||(Element.prototype.scrollTo=function(e,t){typeof e=="object"?(this.scrollLeft=e.left,this.scrollTop=e.top):(this.scrollLeft=e,this.scrollTop=t)}),Element.prototype.replaceWith||(Element.prototype.replaceWith=function(...e){let t=this.parentNode;if(t){e.length===0&&t.removeChild(this);for(let r=e.length-1;r>=0;r--){let o=e[r];typeof o=="string"?o=document.createTextNode(o):o.parentNode&&o.parentNode.removeChild(o),r?t.insertBefore(this.previousSibling,o):t.replaceChild(o,this)}}}));function ts(){return location.protocol==="file:"?gt(`${new URL("search/search_index.js",Yr.base)}`).pipe(m(()=>__index),B(1)):De(new URL("search/search_index.json",Yr.base))}document.documentElement.classList.remove("no-js");document.documentElement.classList.add("js");var rt=No(),Rt=Jo(),wt=en(Rt),Br=Go(),_e=pn(),ur=At("(min-width: 960px)"),hi=At("(min-width: 1220px)"),bi=tn(),Yr=we(),vi=document.forms.namedItem("search")?ts():qe,Gr=new v;Wn({alert$:Gr});var Jr=new v;G("navigation.instant")&&zn({location$:Rt,viewport$:_e,progress$:Jr}).subscribe(rt);var di;((di=Yr.version)==null?void 0:di.provider)==="mike"&&Gn({document$:rt});T(Rt,wt).pipe(Ye(125)).subscribe(()=>{Be("drawer",!1),Be("search",!1)});Br.pipe(g(({mode:e})=>e==="global")).subscribe(e=>{switch(e.type){case"p":case",":let t=me("link[rel=prev]");typeof t!="undefined"&&st(t);break;case"n":case".":let r=me("link[rel=next]");typeof r!="undefined"&&st(r);break;case"Enter":let o=Re();o instanceof HTMLLabelElement&&o.click()}});li({document$:rt});mi({document$:rt,tablet$:ur});fi({document$:rt});ui({viewport$:_e,tablet$:ur});var tt=Rn(Te("header"),{viewport$:_e}),$t=rt.pipe(m(()=>Te("main")),b(e=>Fn(e,{viewport$:_e,header$:tt})),B(1)),rs=T(...ne("consent").map(e=>fn(e,{target$:wt})),...ne("dialog").map(e=>$n(e,{alert$:Gr})),...ne("header").map(e=>Pn(e,{viewport$:_e,header$:tt,main$:$t})),...ne("palette").map(e=>jn(e)),...ne("progress").map(e=>Un(e,{progress$:Jr})),...ne("search").map(e=>ti(e,{index$:vi,keyboard$:Br})),...ne("source").map(e=>ai(e))),os=H(()=>T(...ne("announce").map(e=>mn(e)),...ne("content").map(e=>Hn(e,{viewport$:_e,target$:wt,print$:bi})),...ne("content").map(e=>G("search.highlight")?ri(e,{index$:vi,location$:Rt}):L),...ne("header-title").map(e=>In(e,{viewport$:_e,header$:tt})),...ne("sidebar").map(e=>e.getAttribute("data-md-type")==="navigation"?Ur(hi,()=>Qr(e,{viewport$:_e,header$:tt,main$:$t})):Ur(ur,()=>Qr(e,{viewport$:_e,header$:tt,main$:$t}))),...ne("tabs").map(e=>si(e,{viewport$:_e,header$:tt})),...ne("toc").map(e=>ci(e,{viewport$:_e,header$:tt,main$:$t,target$:wt})),...ne("top").map(e=>pi(e,{viewport$:_e,header$:tt,main$:$t,target$:wt})))),gi=rt.pipe(b(()=>os),$e(rs),B(1));gi.subscribe();window.document$=rt;window.location$=Rt;window.target$=wt;window.keyboard$=Br;window.viewport$=_e;window.tablet$=ur;window.screen$=hi;window.print$=bi;window.alert$=Gr;window.progress$=Jr;window.component$=gi;})();
+//# sourceMappingURL=bundle.c8d2eff1.min.js.map
+
diff --git a/assets/javascripts/bundle.c8d2eff1.min.js.map b/assets/javascripts/bundle.c8d2eff1.min.js.map
new file mode 100644
index 00000000..fc522dba
--- /dev/null
+++ b/assets/javascripts/bundle.c8d2eff1.min.js.map
@@ -0,0 +1,7 @@
+{
+ "version": 3,
+ "sources": ["node_modules/focus-visible/dist/focus-visible.js", "node_modules/clipboard/dist/clipboard.js", "node_modules/escape-html/index.js", "src/templates/assets/javascripts/bundle.ts", "node_modules/rxjs/node_modules/tslib/tslib.es6.js", "node_modules/rxjs/src/internal/util/isFunction.ts", "node_modules/rxjs/src/internal/util/createErrorClass.ts", "node_modules/rxjs/src/internal/util/UnsubscriptionError.ts", "node_modules/rxjs/src/internal/util/arrRemove.ts", "node_modules/rxjs/src/internal/Subscription.ts", "node_modules/rxjs/src/internal/config.ts", "node_modules/rxjs/src/internal/scheduler/timeoutProvider.ts", "node_modules/rxjs/src/internal/util/reportUnhandledError.ts", "node_modules/rxjs/src/internal/util/noop.ts", "node_modules/rxjs/src/internal/NotificationFactories.ts", "node_modules/rxjs/src/internal/util/errorContext.ts", "node_modules/rxjs/src/internal/Subscriber.ts", "node_modules/rxjs/src/internal/symbol/observable.ts", "node_modules/rxjs/src/internal/util/identity.ts", "node_modules/rxjs/src/internal/util/pipe.ts", "node_modules/rxjs/src/internal/Observable.ts", "node_modules/rxjs/src/internal/util/lift.ts", "node_modules/rxjs/src/internal/operators/OperatorSubscriber.ts", "node_modules/rxjs/src/internal/scheduler/animationFrameProvider.ts", "node_modules/rxjs/src/internal/util/ObjectUnsubscribedError.ts", "node_modules/rxjs/src/internal/Subject.ts", "node_modules/rxjs/src/internal/scheduler/dateTimestampProvider.ts", "node_modules/rxjs/src/internal/ReplaySubject.ts", "node_modules/rxjs/src/internal/scheduler/Action.ts", "node_modules/rxjs/src/internal/scheduler/intervalProvider.ts", "node_modules/rxjs/src/internal/scheduler/AsyncAction.ts", "node_modules/rxjs/src/internal/Scheduler.ts", "node_modules/rxjs/src/internal/scheduler/AsyncScheduler.ts", "node_modules/rxjs/src/internal/scheduler/async.ts", "node_modules/rxjs/src/internal/scheduler/AnimationFrameAction.ts", "node_modules/rxjs/src/internal/scheduler/AnimationFrameScheduler.ts", "node_modules/rxjs/src/internal/scheduler/animationFrame.ts", "node_modules/rxjs/src/internal/observable/empty.ts", "node_modules/rxjs/src/internal/util/isScheduler.ts", "node_modules/rxjs/src/internal/util/args.ts", "node_modules/rxjs/src/internal/util/isArrayLike.ts", "node_modules/rxjs/src/internal/util/isPromise.ts", "node_modules/rxjs/src/internal/util/isInteropObservable.ts", "node_modules/rxjs/src/internal/util/isAsyncIterable.ts", "node_modules/rxjs/src/internal/util/throwUnobservableError.ts", "node_modules/rxjs/src/internal/symbol/iterator.ts", "node_modules/rxjs/src/internal/util/isIterable.ts", "node_modules/rxjs/src/internal/util/isReadableStreamLike.ts", "node_modules/rxjs/src/internal/observable/innerFrom.ts", "node_modules/rxjs/src/internal/util/executeSchedule.ts", "node_modules/rxjs/src/internal/operators/observeOn.ts", "node_modules/rxjs/src/internal/operators/subscribeOn.ts", "node_modules/rxjs/src/internal/scheduled/scheduleObservable.ts", "node_modules/rxjs/src/internal/scheduled/schedulePromise.ts", "node_modules/rxjs/src/internal/scheduled/scheduleArray.ts", "node_modules/rxjs/src/internal/scheduled/scheduleIterable.ts", "node_modules/rxjs/src/internal/scheduled/scheduleAsyncIterable.ts", "node_modules/rxjs/src/internal/scheduled/scheduleReadableStreamLike.ts", "node_modules/rxjs/src/internal/scheduled/scheduled.ts", "node_modules/rxjs/src/internal/observable/from.ts", "node_modules/rxjs/src/internal/observable/of.ts", "node_modules/rxjs/src/internal/observable/throwError.ts", "node_modules/rxjs/src/internal/util/EmptyError.ts", "node_modules/rxjs/src/internal/util/isDate.ts", "node_modules/rxjs/src/internal/operators/map.ts", "node_modules/rxjs/src/internal/util/mapOneOrManyArgs.ts", "node_modules/rxjs/src/internal/util/argsArgArrayOrObject.ts", "node_modules/rxjs/src/internal/util/createObject.ts", "node_modules/rxjs/src/internal/observable/combineLatest.ts", "node_modules/rxjs/src/internal/operators/mergeInternals.ts", "node_modules/rxjs/src/internal/operators/mergeMap.ts", "node_modules/rxjs/src/internal/operators/mergeAll.ts", "node_modules/rxjs/src/internal/operators/concatAll.ts", "node_modules/rxjs/src/internal/observable/concat.ts", "node_modules/rxjs/src/internal/observable/defer.ts", "node_modules/rxjs/src/internal/observable/fromEvent.ts", "node_modules/rxjs/src/internal/observable/fromEventPattern.ts", "node_modules/rxjs/src/internal/observable/timer.ts", "node_modules/rxjs/src/internal/observable/merge.ts", "node_modules/rxjs/src/internal/observable/never.ts", "node_modules/rxjs/src/internal/util/argsOrArgArray.ts", "node_modules/rxjs/src/internal/operators/filter.ts", "node_modules/rxjs/src/internal/observable/zip.ts", "node_modules/rxjs/src/internal/operators/audit.ts", "node_modules/rxjs/src/internal/operators/auditTime.ts", "node_modules/rxjs/src/internal/operators/bufferCount.ts", "node_modules/rxjs/src/internal/operators/catchError.ts", "node_modules/rxjs/src/internal/operators/scanInternals.ts", "node_modules/rxjs/src/internal/operators/combineLatest.ts", "node_modules/rxjs/src/internal/operators/combineLatestWith.ts", "node_modules/rxjs/src/internal/operators/debounceTime.ts", "node_modules/rxjs/src/internal/operators/defaultIfEmpty.ts", "node_modules/rxjs/src/internal/operators/take.ts", "node_modules/rxjs/src/internal/operators/ignoreElements.ts", "node_modules/rxjs/src/internal/operators/mapTo.ts", "node_modules/rxjs/src/internal/operators/delayWhen.ts", "node_modules/rxjs/src/internal/operators/delay.ts", "node_modules/rxjs/src/internal/operators/distinctUntilChanged.ts", "node_modules/rxjs/src/internal/operators/distinctUntilKeyChanged.ts", "node_modules/rxjs/src/internal/operators/throwIfEmpty.ts", "node_modules/rxjs/src/internal/operators/endWith.ts", "node_modules/rxjs/src/internal/operators/finalize.ts", "node_modules/rxjs/src/internal/operators/first.ts", "node_modules/rxjs/src/internal/operators/takeLast.ts", "node_modules/rxjs/src/internal/operators/merge.ts", "node_modules/rxjs/src/internal/operators/mergeWith.ts", "node_modules/rxjs/src/internal/operators/repeat.ts", "node_modules/rxjs/src/internal/operators/scan.ts", "node_modules/rxjs/src/internal/operators/share.ts", "node_modules/rxjs/src/internal/operators/shareReplay.ts", "node_modules/rxjs/src/internal/operators/skip.ts", "node_modules/rxjs/src/internal/operators/skipUntil.ts", "node_modules/rxjs/src/internal/operators/startWith.ts", "node_modules/rxjs/src/internal/operators/switchMap.ts", "node_modules/rxjs/src/internal/operators/takeUntil.ts", "node_modules/rxjs/src/internal/operators/takeWhile.ts", "node_modules/rxjs/src/internal/operators/tap.ts", "node_modules/rxjs/src/internal/operators/throttle.ts", "node_modules/rxjs/src/internal/operators/throttleTime.ts", "node_modules/rxjs/src/internal/operators/withLatestFrom.ts", "node_modules/rxjs/src/internal/operators/zip.ts", "node_modules/rxjs/src/internal/operators/zipWith.ts", "src/templates/assets/javascripts/browser/document/index.ts", "src/templates/assets/javascripts/browser/element/_/index.ts", "src/templates/assets/javascripts/browser/element/focus/index.ts", "src/templates/assets/javascripts/browser/element/hover/index.ts", "src/templates/assets/javascripts/browser/element/offset/_/index.ts", "src/templates/assets/javascripts/browser/element/offset/content/index.ts", "src/templates/assets/javascripts/utilities/h/index.ts", "src/templates/assets/javascripts/utilities/round/index.ts", "src/templates/assets/javascripts/browser/script/index.ts", "src/templates/assets/javascripts/browser/element/size/_/index.ts", "src/templates/assets/javascripts/browser/element/size/content/index.ts", "src/templates/assets/javascripts/browser/element/visibility/index.ts", "src/templates/assets/javascripts/browser/toggle/index.ts", "src/templates/assets/javascripts/browser/keyboard/index.ts", "src/templates/assets/javascripts/browser/location/_/index.ts", "src/templates/assets/javascripts/browser/location/hash/index.ts", "src/templates/assets/javascripts/browser/media/index.ts", "src/templates/assets/javascripts/browser/request/index.ts", "src/templates/assets/javascripts/browser/viewport/offset/index.ts", "src/templates/assets/javascripts/browser/viewport/size/index.ts", "src/templates/assets/javascripts/browser/viewport/_/index.ts", "src/templates/assets/javascripts/browser/viewport/at/index.ts", "src/templates/assets/javascripts/browser/worker/index.ts", "src/templates/assets/javascripts/_/index.ts", "src/templates/assets/javascripts/components/_/index.ts", "src/templates/assets/javascripts/components/announce/index.ts", "src/templates/assets/javascripts/components/consent/index.ts", "src/templates/assets/javascripts/templates/tooltip/index.tsx", "src/templates/assets/javascripts/templates/annotation/index.tsx", "src/templates/assets/javascripts/templates/clipboard/index.tsx", "src/templates/assets/javascripts/templates/search/index.tsx", "src/templates/assets/javascripts/templates/source/index.tsx", "src/templates/assets/javascripts/templates/tabbed/index.tsx", "src/templates/assets/javascripts/templates/table/index.tsx", "src/templates/assets/javascripts/templates/version/index.tsx", "src/templates/assets/javascripts/components/tooltip/index.ts", "src/templates/assets/javascripts/components/content/annotation/_/index.ts", "src/templates/assets/javascripts/components/content/annotation/list/index.ts", "src/templates/assets/javascripts/components/content/annotation/block/index.ts", "src/templates/assets/javascripts/components/content/code/_/index.ts", "src/templates/assets/javascripts/components/content/details/index.ts", "src/templates/assets/javascripts/components/content/mermaid/index.css", "src/templates/assets/javascripts/components/content/mermaid/index.ts", "src/templates/assets/javascripts/components/content/table/index.ts", "src/templates/assets/javascripts/components/content/tabs/index.ts", "src/templates/assets/javascripts/components/content/_/index.ts", "src/templates/assets/javascripts/components/dialog/index.ts", "src/templates/assets/javascripts/components/header/_/index.ts", "src/templates/assets/javascripts/components/header/title/index.ts", "src/templates/assets/javascripts/components/main/index.ts", "src/templates/assets/javascripts/components/palette/index.ts", "src/templates/assets/javascripts/components/progress/index.ts", "src/templates/assets/javascripts/integrations/clipboard/index.ts", "src/templates/assets/javascripts/integrations/sitemap/index.ts", "src/templates/assets/javascripts/integrations/instant/index.ts", "src/templates/assets/javascripts/integrations/search/highlighter/index.ts", "src/templates/assets/javascripts/integrations/search/worker/message/index.ts", "src/templates/assets/javascripts/integrations/search/worker/_/index.ts", "src/templates/assets/javascripts/integrations/version/index.ts", "src/templates/assets/javascripts/components/search/query/index.ts", "src/templates/assets/javascripts/components/search/result/index.ts", "src/templates/assets/javascripts/components/search/share/index.ts", "src/templates/assets/javascripts/components/search/suggest/index.ts", "src/templates/assets/javascripts/components/search/_/index.ts", "src/templates/assets/javascripts/components/search/highlight/index.ts", "src/templates/assets/javascripts/components/sidebar/index.ts", "src/templates/assets/javascripts/components/source/facts/github/index.ts", "src/templates/assets/javascripts/components/source/facts/gitlab/index.ts", "src/templates/assets/javascripts/components/source/facts/_/index.ts", "src/templates/assets/javascripts/components/source/_/index.ts", "src/templates/assets/javascripts/components/tabs/index.ts", "src/templates/assets/javascripts/components/toc/index.ts", "src/templates/assets/javascripts/components/top/index.ts", "src/templates/assets/javascripts/patches/ellipsis/index.ts", "src/templates/assets/javascripts/patches/indeterminate/index.ts", "src/templates/assets/javascripts/patches/scrollfix/index.ts", "src/templates/assets/javascripts/patches/scrolllock/index.ts", "src/templates/assets/javascripts/polyfills/index.ts"],
+ "sourcesContent": ["(function (global, factory) {\n typeof exports === 'object' && typeof module !== 'undefined' ? factory() :\n typeof define === 'function' && define.amd ? define(factory) :\n (factory());\n}(this, (function () { 'use strict';\n\n /**\n * Applies the :focus-visible polyfill at the given scope.\n * A scope in this case is either the top-level Document or a Shadow Root.\n *\n * @param {(Document|ShadowRoot)} scope\n * @see https://github.com/WICG/focus-visible\n */\n function applyFocusVisiblePolyfill(scope) {\n var hadKeyboardEvent = true;\n var hadFocusVisibleRecently = false;\n var hadFocusVisibleRecentlyTimeout = null;\n\n var inputTypesAllowlist = {\n text: true,\n search: true,\n url: true,\n tel: true,\n email: true,\n password: true,\n number: true,\n date: true,\n month: true,\n week: true,\n time: true,\n datetime: true,\n 'datetime-local': true\n };\n\n /**\n * Helper function for legacy browsers and iframes which sometimes focus\n * elements like document, body, and non-interactive SVG.\n * @param {Element} el\n */\n function isValidFocusTarget(el) {\n if (\n el &&\n el !== document &&\n el.nodeName !== 'HTML' &&\n el.nodeName !== 'BODY' &&\n 'classList' in el &&\n 'contains' in el.classList\n ) {\n return true;\n }\n return false;\n }\n\n /**\n * Computes whether the given element should automatically trigger the\n * `focus-visible` class being added, i.e. whether it should always match\n * `:focus-visible` when focused.\n * @param {Element} el\n * @return {boolean}\n */\n function focusTriggersKeyboardModality(el) {\n var type = el.type;\n var tagName = el.tagName;\n\n if (tagName === 'INPUT' && inputTypesAllowlist[type] && !el.readOnly) {\n return true;\n }\n\n if (tagName === 'TEXTAREA' && !el.readOnly) {\n return true;\n }\n\n if (el.isContentEditable) {\n return true;\n }\n\n return false;\n }\n\n /**\n * Add the `focus-visible` class to the given element if it was not added by\n * the author.\n * @param {Element} el\n */\n function addFocusVisibleClass(el) {\n if (el.classList.contains('focus-visible')) {\n return;\n }\n el.classList.add('focus-visible');\n el.setAttribute('data-focus-visible-added', '');\n }\n\n /**\n * Remove the `focus-visible` class from the given element if it was not\n * originally added by the author.\n * @param {Element} el\n */\n function removeFocusVisibleClass(el) {\n if (!el.hasAttribute('data-focus-visible-added')) {\n return;\n }\n el.classList.remove('focus-visible');\n el.removeAttribute('data-focus-visible-added');\n }\n\n /**\n * If the most recent user interaction was via the keyboard;\n * and the key press did not include a meta, alt/option, or control key;\n * then the modality is keyboard. Otherwise, the modality is not keyboard.\n * Apply `focus-visible` to any current active element and keep track\n * of our keyboard modality state with `hadKeyboardEvent`.\n * @param {KeyboardEvent} e\n */\n function onKeyDown(e) {\n if (e.metaKey || e.altKey || e.ctrlKey) {\n return;\n }\n\n if (isValidFocusTarget(scope.activeElement)) {\n addFocusVisibleClass(scope.activeElement);\n }\n\n hadKeyboardEvent = true;\n }\n\n /**\n * If at any point a user clicks with a pointing device, ensure that we change\n * the modality away from keyboard.\n * This avoids the situation where a user presses a key on an already focused\n * element, and then clicks on a different element, focusing it with a\n * pointing device, while we still think we're in keyboard modality.\n * @param {Event} e\n */\n function onPointerDown(e) {\n hadKeyboardEvent = false;\n }\n\n /**\n * On `focus`, add the `focus-visible` class to the target if:\n * - the target received focus as a result of keyboard navigation, or\n * - the event target is an element that will likely require interaction\n * via the keyboard (e.g. a text box)\n * @param {Event} e\n */\n function onFocus(e) {\n // Prevent IE from focusing the document or HTML element.\n if (!isValidFocusTarget(e.target)) {\n return;\n }\n\n if (hadKeyboardEvent || focusTriggersKeyboardModality(e.target)) {\n addFocusVisibleClass(e.target);\n }\n }\n\n /**\n * On `blur`, remove the `focus-visible` class from the target.\n * @param {Event} e\n */\n function onBlur(e) {\n if (!isValidFocusTarget(e.target)) {\n return;\n }\n\n if (\n e.target.classList.contains('focus-visible') ||\n e.target.hasAttribute('data-focus-visible-added')\n ) {\n // To detect a tab/window switch, we look for a blur event followed\n // rapidly by a visibility change.\n // If we don't see a visibility change within 100ms, it's probably a\n // regular focus change.\n hadFocusVisibleRecently = true;\n window.clearTimeout(hadFocusVisibleRecentlyTimeout);\n hadFocusVisibleRecentlyTimeout = window.setTimeout(function() {\n hadFocusVisibleRecently = false;\n }, 100);\n removeFocusVisibleClass(e.target);\n }\n }\n\n /**\n * If the user changes tabs, keep track of whether or not the previously\n * focused element had .focus-visible.\n * @param {Event} e\n */\n function onVisibilityChange(e) {\n if (document.visibilityState === 'hidden') {\n // If the tab becomes active again, the browser will handle calling focus\n // on the element (Safari actually calls it twice).\n // If this tab change caused a blur on an element with focus-visible,\n // re-apply the class when the user switches back to the tab.\n if (hadFocusVisibleRecently) {\n hadKeyboardEvent = true;\n }\n addInitialPointerMoveListeners();\n }\n }\n\n /**\n * Add a group of listeners to detect usage of any pointing devices.\n * These listeners will be added when the polyfill first loads, and anytime\n * the window is blurred, so that they are active when the window regains\n * focus.\n */\n function addInitialPointerMoveListeners() {\n document.addEventListener('mousemove', onInitialPointerMove);\n document.addEventListener('mousedown', onInitialPointerMove);\n document.addEventListener('mouseup', onInitialPointerMove);\n document.addEventListener('pointermove', onInitialPointerMove);\n document.addEventListener('pointerdown', onInitialPointerMove);\n document.addEventListener('pointerup', onInitialPointerMove);\n document.addEventListener('touchmove', onInitialPointerMove);\n document.addEventListener('touchstart', onInitialPointerMove);\n document.addEventListener('touchend', onInitialPointerMove);\n }\n\n function removeInitialPointerMoveListeners() {\n document.removeEventListener('mousemove', onInitialPointerMove);\n document.removeEventListener('mousedown', onInitialPointerMove);\n document.removeEventListener('mouseup', onInitialPointerMove);\n document.removeEventListener('pointermove', onInitialPointerMove);\n document.removeEventListener('pointerdown', onInitialPointerMove);\n document.removeEventListener('pointerup', onInitialPointerMove);\n document.removeEventListener('touchmove', onInitialPointerMove);\n document.removeEventListener('touchstart', onInitialPointerMove);\n document.removeEventListener('touchend', onInitialPointerMove);\n }\n\n /**\n * When the polfyill first loads, assume the user is in keyboard modality.\n * If any event is received from a pointing device (e.g. mouse, pointer,\n * touch), turn off keyboard modality.\n * This accounts for situations where focus enters the page from the URL bar.\n * @param {Event} e\n */\n function onInitialPointerMove(e) {\n // Work around a Safari quirk that fires a mousemove on whenever the\n // window blurs, even if you're tabbing out of the page. \u00AF\\_(\u30C4)_/\u00AF\n if (e.target.nodeName && e.target.nodeName.toLowerCase() === 'html') {\n return;\n }\n\n hadKeyboardEvent = false;\n removeInitialPointerMoveListeners();\n }\n\n // For some kinds of state, we are interested in changes at the global scope\n // only. For example, global pointer input, global key presses and global\n // visibility change should affect the state at every scope:\n document.addEventListener('keydown', onKeyDown, true);\n document.addEventListener('mousedown', onPointerDown, true);\n document.addEventListener('pointerdown', onPointerDown, true);\n document.addEventListener('touchstart', onPointerDown, true);\n document.addEventListener('visibilitychange', onVisibilityChange, true);\n\n addInitialPointerMoveListeners();\n\n // For focus and blur, we specifically care about state changes in the local\n // scope. This is because focus / blur events that originate from within a\n // shadow root are not re-dispatched from the host element if it was already\n // the active element in its own scope:\n scope.addEventListener('focus', onFocus, true);\n scope.addEventListener('blur', onBlur, true);\n\n // We detect that a node is a ShadowRoot by ensuring that it is a\n // DocumentFragment and also has a host property. This check covers native\n // implementation and polyfill implementation transparently. If we only cared\n // about the native implementation, we could just check if the scope was\n // an instance of a ShadowRoot.\n if (scope.nodeType === Node.DOCUMENT_FRAGMENT_NODE && scope.host) {\n // Since a ShadowRoot is a special kind of DocumentFragment, it does not\n // have a root element to add a class to. So, we add this attribute to the\n // host element instead:\n scope.host.setAttribute('data-js-focus-visible', '');\n } else if (scope.nodeType === Node.DOCUMENT_NODE) {\n document.documentElement.classList.add('js-focus-visible');\n document.documentElement.setAttribute('data-js-focus-visible', '');\n }\n }\n\n // It is important to wrap all references to global window and document in\n // these checks to support server-side rendering use cases\n // @see https://github.com/WICG/focus-visible/issues/199\n if (typeof window !== 'undefined' && typeof document !== 'undefined') {\n // Make the polyfill helper globally available. This can be used as a signal\n // to interested libraries that wish to coordinate with the polyfill for e.g.,\n // applying the polyfill to a shadow root:\n window.applyFocusVisiblePolyfill = applyFocusVisiblePolyfill;\n\n // Notify interested libraries of the polyfill's presence, in case the\n // polyfill was loaded lazily:\n var event;\n\n try {\n event = new CustomEvent('focus-visible-polyfill-ready');\n } catch (error) {\n // IE11 does not support using CustomEvent as a constructor directly:\n event = document.createEvent('CustomEvent');\n event.initCustomEvent('focus-visible-polyfill-ready', false, false, {});\n }\n\n window.dispatchEvent(event);\n }\n\n if (typeof document !== 'undefined') {\n // Apply the polyfill to the global document, so that no JavaScript\n // coordination is required to use the polyfill in the top-level document:\n applyFocusVisiblePolyfill(document);\n }\n\n})));\n", "/*!\n * clipboard.js v2.0.11\n * https://clipboardjs.com/\n *\n * Licensed MIT \u00A9 Zeno Rocha\n */\n(function webpackUniversalModuleDefinition(root, factory) {\n\tif(typeof exports === 'object' && typeof module === 'object')\n\t\tmodule.exports = factory();\n\telse if(typeof define === 'function' && define.amd)\n\t\tdefine([], factory);\n\telse if(typeof exports === 'object')\n\t\texports[\"ClipboardJS\"] = factory();\n\telse\n\t\troot[\"ClipboardJS\"] = factory();\n})(this, function() {\nreturn /******/ (function() { // webpackBootstrap\n/******/ \tvar __webpack_modules__ = ({\n\n/***/ 686:\n/***/ (function(__unused_webpack_module, __webpack_exports__, __webpack_require__) {\n\n\"use strict\";\n\n// EXPORTS\n__webpack_require__.d(__webpack_exports__, {\n \"default\": function() { return /* binding */ clipboard; }\n});\n\n// EXTERNAL MODULE: ./node_modules/tiny-emitter/index.js\nvar tiny_emitter = __webpack_require__(279);\nvar tiny_emitter_default = /*#__PURE__*/__webpack_require__.n(tiny_emitter);\n// EXTERNAL MODULE: ./node_modules/good-listener/src/listen.js\nvar listen = __webpack_require__(370);\nvar listen_default = /*#__PURE__*/__webpack_require__.n(listen);\n// EXTERNAL MODULE: ./node_modules/select/src/select.js\nvar src_select = __webpack_require__(817);\nvar select_default = /*#__PURE__*/__webpack_require__.n(src_select);\n;// CONCATENATED MODULE: ./src/common/command.js\n/**\n * Executes a given operation type.\n * @param {String} type\n * @return {Boolean}\n */\nfunction command(type) {\n try {\n return document.execCommand(type);\n } catch (err) {\n return false;\n }\n}\n;// CONCATENATED MODULE: ./src/actions/cut.js\n\n\n/**\n * Cut action wrapper.\n * @param {String|HTMLElement} target\n * @return {String}\n */\n\nvar ClipboardActionCut = function ClipboardActionCut(target) {\n var selectedText = select_default()(target);\n command('cut');\n return selectedText;\n};\n\n/* harmony default export */ var actions_cut = (ClipboardActionCut);\n;// CONCATENATED MODULE: ./src/common/create-fake-element.js\n/**\n * Creates a fake textarea element with a value.\n * @param {String} value\n * @return {HTMLElement}\n */\nfunction createFakeElement(value) {\n var isRTL = document.documentElement.getAttribute('dir') === 'rtl';\n var fakeElement = document.createElement('textarea'); // Prevent zooming on iOS\n\n fakeElement.style.fontSize = '12pt'; // Reset box model\n\n fakeElement.style.border = '0';\n fakeElement.style.padding = '0';\n fakeElement.style.margin = '0'; // Move element out of screen horizontally\n\n fakeElement.style.position = 'absolute';\n fakeElement.style[isRTL ? 'right' : 'left'] = '-9999px'; // Move element to the same position vertically\n\n var yPosition = window.pageYOffset || document.documentElement.scrollTop;\n fakeElement.style.top = \"\".concat(yPosition, \"px\");\n fakeElement.setAttribute('readonly', '');\n fakeElement.value = value;\n return fakeElement;\n}\n;// CONCATENATED MODULE: ./src/actions/copy.js\n\n\n\n/**\n * Create fake copy action wrapper using a fake element.\n * @param {String} target\n * @param {Object} options\n * @return {String}\n */\n\nvar fakeCopyAction = function fakeCopyAction(value, options) {\n var fakeElement = createFakeElement(value);\n options.container.appendChild(fakeElement);\n var selectedText = select_default()(fakeElement);\n command('copy');\n fakeElement.remove();\n return selectedText;\n};\n/**\n * Copy action wrapper.\n * @param {String|HTMLElement} target\n * @param {Object} options\n * @return {String}\n */\n\n\nvar ClipboardActionCopy = function ClipboardActionCopy(target) {\n var options = arguments.length > 1 && arguments[1] !== undefined ? arguments[1] : {\n container: document.body\n };\n var selectedText = '';\n\n if (typeof target === 'string') {\n selectedText = fakeCopyAction(target, options);\n } else if (target instanceof HTMLInputElement && !['text', 'search', 'url', 'tel', 'password'].includes(target === null || target === void 0 ? void 0 : target.type)) {\n // If input type doesn't support `setSelectionRange`. Simulate it. https://developer.mozilla.org/en-US/docs/Web/API/HTMLInputElement/setSelectionRange\n selectedText = fakeCopyAction(target.value, options);\n } else {\n selectedText = select_default()(target);\n command('copy');\n }\n\n return selectedText;\n};\n\n/* harmony default export */ var actions_copy = (ClipboardActionCopy);\n;// CONCATENATED MODULE: ./src/actions/default.js\nfunction _typeof(obj) { \"@babel/helpers - typeof\"; if (typeof Symbol === \"function\" && typeof Symbol.iterator === \"symbol\") { _typeof = function _typeof(obj) { return typeof obj; }; } else { _typeof = function _typeof(obj) { return obj && typeof Symbol === \"function\" && obj.constructor === Symbol && obj !== Symbol.prototype ? \"symbol\" : typeof obj; }; } return _typeof(obj); }\n\n\n\n/**\n * Inner function which performs selection from either `text` or `target`\n * properties and then executes copy or cut operations.\n * @param {Object} options\n */\n\nvar ClipboardActionDefault = function ClipboardActionDefault() {\n var options = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : {};\n // Defines base properties passed from constructor.\n var _options$action = options.action,\n action = _options$action === void 0 ? 'copy' : _options$action,\n container = options.container,\n target = options.target,\n text = options.text; // Sets the `action` to be performed which can be either 'copy' or 'cut'.\n\n if (action !== 'copy' && action !== 'cut') {\n throw new Error('Invalid \"action\" value, use either \"copy\" or \"cut\"');\n } // Sets the `target` property using an element that will be have its content copied.\n\n\n if (target !== undefined) {\n if (target && _typeof(target) === 'object' && target.nodeType === 1) {\n if (action === 'copy' && target.hasAttribute('disabled')) {\n throw new Error('Invalid \"target\" attribute. Please use \"readonly\" instead of \"disabled\" attribute');\n }\n\n if (action === 'cut' && (target.hasAttribute('readonly') || target.hasAttribute('disabled'))) {\n throw new Error('Invalid \"target\" attribute. You can\\'t cut text from elements with \"readonly\" or \"disabled\" attributes');\n }\n } else {\n throw new Error('Invalid \"target\" value, use a valid Element');\n }\n } // Define selection strategy based on `text` property.\n\n\n if (text) {\n return actions_copy(text, {\n container: container\n });\n } // Defines which selection strategy based on `target` property.\n\n\n if (target) {\n return action === 'cut' ? actions_cut(target) : actions_copy(target, {\n container: container\n });\n }\n};\n\n/* harmony default export */ var actions_default = (ClipboardActionDefault);\n;// CONCATENATED MODULE: ./src/clipboard.js\nfunction clipboard_typeof(obj) { \"@babel/helpers - typeof\"; if (typeof Symbol === \"function\" && typeof Symbol.iterator === \"symbol\") { clipboard_typeof = function _typeof(obj) { return typeof obj; }; } else { clipboard_typeof = function _typeof(obj) { return obj && typeof Symbol === \"function\" && obj.constructor === Symbol && obj !== Symbol.prototype ? \"symbol\" : typeof obj; }; } return clipboard_typeof(obj); }\n\nfunction _classCallCheck(instance, Constructor) { if (!(instance instanceof Constructor)) { throw new TypeError(\"Cannot call a class as a function\"); } }\n\nfunction _defineProperties(target, props) { for (var i = 0; i < props.length; i++) { var descriptor = props[i]; descriptor.enumerable = descriptor.enumerable || false; descriptor.configurable = true; if (\"value\" in descriptor) descriptor.writable = true; Object.defineProperty(target, descriptor.key, descriptor); } }\n\nfunction _createClass(Constructor, protoProps, staticProps) { if (protoProps) _defineProperties(Constructor.prototype, protoProps); if (staticProps) _defineProperties(Constructor, staticProps); return Constructor; }\n\nfunction _inherits(subClass, superClass) { if (typeof superClass !== \"function\" && superClass !== null) { throw new TypeError(\"Super expression must either be null or a function\"); } subClass.prototype = Object.create(superClass && superClass.prototype, { constructor: { value: subClass, writable: true, configurable: true } }); if (superClass) _setPrototypeOf(subClass, superClass); }\n\nfunction _setPrototypeOf(o, p) { _setPrototypeOf = Object.setPrototypeOf || function _setPrototypeOf(o, p) { o.__proto__ = p; return o; }; return _setPrototypeOf(o, p); }\n\nfunction _createSuper(Derived) { var hasNativeReflectConstruct = _isNativeReflectConstruct(); return function _createSuperInternal() { var Super = _getPrototypeOf(Derived), result; if (hasNativeReflectConstruct) { var NewTarget = _getPrototypeOf(this).constructor; result = Reflect.construct(Super, arguments, NewTarget); } else { result = Super.apply(this, arguments); } return _possibleConstructorReturn(this, result); }; }\n\nfunction _possibleConstructorReturn(self, call) { if (call && (clipboard_typeof(call) === \"object\" || typeof call === \"function\")) { return call; } return _assertThisInitialized(self); }\n\nfunction _assertThisInitialized(self) { if (self === void 0) { throw new ReferenceError(\"this hasn't been initialised - super() hasn't been called\"); } return self; }\n\nfunction _isNativeReflectConstruct() { if (typeof Reflect === \"undefined\" || !Reflect.construct) return false; if (Reflect.construct.sham) return false; if (typeof Proxy === \"function\") return true; try { Date.prototype.toString.call(Reflect.construct(Date, [], function () {})); return true; } catch (e) { return false; } }\n\nfunction _getPrototypeOf(o) { _getPrototypeOf = Object.setPrototypeOf ? Object.getPrototypeOf : function _getPrototypeOf(o) { return o.__proto__ || Object.getPrototypeOf(o); }; return _getPrototypeOf(o); }\n\n\n\n\n\n\n/**\n * Helper function to retrieve attribute value.\n * @param {String} suffix\n * @param {Element} element\n */\n\nfunction getAttributeValue(suffix, element) {\n var attribute = \"data-clipboard-\".concat(suffix);\n\n if (!element.hasAttribute(attribute)) {\n return;\n }\n\n return element.getAttribute(attribute);\n}\n/**\n * Base class which takes one or more elements, adds event listeners to them,\n * and instantiates a new `ClipboardAction` on each click.\n */\n\n\nvar Clipboard = /*#__PURE__*/function (_Emitter) {\n _inherits(Clipboard, _Emitter);\n\n var _super = _createSuper(Clipboard);\n\n /**\n * @param {String|HTMLElement|HTMLCollection|NodeList} trigger\n * @param {Object} options\n */\n function Clipboard(trigger, options) {\n var _this;\n\n _classCallCheck(this, Clipboard);\n\n _this = _super.call(this);\n\n _this.resolveOptions(options);\n\n _this.listenClick(trigger);\n\n return _this;\n }\n /**\n * Defines if attributes would be resolved using internal setter functions\n * or custom functions that were passed in the constructor.\n * @param {Object} options\n */\n\n\n _createClass(Clipboard, [{\n key: \"resolveOptions\",\n value: function resolveOptions() {\n var options = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : {};\n this.action = typeof options.action === 'function' ? options.action : this.defaultAction;\n this.target = typeof options.target === 'function' ? options.target : this.defaultTarget;\n this.text = typeof options.text === 'function' ? options.text : this.defaultText;\n this.container = clipboard_typeof(options.container) === 'object' ? options.container : document.body;\n }\n /**\n * Adds a click event listener to the passed trigger.\n * @param {String|HTMLElement|HTMLCollection|NodeList} trigger\n */\n\n }, {\n key: \"listenClick\",\n value: function listenClick(trigger) {\n var _this2 = this;\n\n this.listener = listen_default()(trigger, 'click', function (e) {\n return _this2.onClick(e);\n });\n }\n /**\n * Defines a new `ClipboardAction` on each click event.\n * @param {Event} e\n */\n\n }, {\n key: \"onClick\",\n value: function onClick(e) {\n var trigger = e.delegateTarget || e.currentTarget;\n var action = this.action(trigger) || 'copy';\n var text = actions_default({\n action: action,\n container: this.container,\n target: this.target(trigger),\n text: this.text(trigger)\n }); // Fires an event based on the copy operation result.\n\n this.emit(text ? 'success' : 'error', {\n action: action,\n text: text,\n trigger: trigger,\n clearSelection: function clearSelection() {\n if (trigger) {\n trigger.focus();\n }\n\n window.getSelection().removeAllRanges();\n }\n });\n }\n /**\n * Default `action` lookup function.\n * @param {Element} trigger\n */\n\n }, {\n key: \"defaultAction\",\n value: function defaultAction(trigger) {\n return getAttributeValue('action', trigger);\n }\n /**\n * Default `target` lookup function.\n * @param {Element} trigger\n */\n\n }, {\n key: \"defaultTarget\",\n value: function defaultTarget(trigger) {\n var selector = getAttributeValue('target', trigger);\n\n if (selector) {\n return document.querySelector(selector);\n }\n }\n /**\n * Allow fire programmatically a copy action\n * @param {String|HTMLElement} target\n * @param {Object} options\n * @returns Text copied.\n */\n\n }, {\n key: \"defaultText\",\n\n /**\n * Default `text` lookup function.\n * @param {Element} trigger\n */\n value: function defaultText(trigger) {\n return getAttributeValue('text', trigger);\n }\n /**\n * Destroy lifecycle.\n */\n\n }, {\n key: \"destroy\",\n value: function destroy() {\n this.listener.destroy();\n }\n }], [{\n key: \"copy\",\n value: function copy(target) {\n var options = arguments.length > 1 && arguments[1] !== undefined ? arguments[1] : {\n container: document.body\n };\n return actions_copy(target, options);\n }\n /**\n * Allow fire programmatically a cut action\n * @param {String|HTMLElement} target\n * @returns Text cutted.\n */\n\n }, {\n key: \"cut\",\n value: function cut(target) {\n return actions_cut(target);\n }\n /**\n * Returns the support of the given action, or all actions if no action is\n * given.\n * @param {String} [action]\n */\n\n }, {\n key: \"isSupported\",\n value: function isSupported() {\n var action = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : ['copy', 'cut'];\n var actions = typeof action === 'string' ? [action] : action;\n var support = !!document.queryCommandSupported;\n actions.forEach(function (action) {\n support = support && !!document.queryCommandSupported(action);\n });\n return support;\n }\n }]);\n\n return Clipboard;\n}((tiny_emitter_default()));\n\n/* harmony default export */ var clipboard = (Clipboard);\n\n/***/ }),\n\n/***/ 828:\n/***/ (function(module) {\n\nvar DOCUMENT_NODE_TYPE = 9;\n\n/**\n * A polyfill for Element.matches()\n */\nif (typeof Element !== 'undefined' && !Element.prototype.matches) {\n var proto = Element.prototype;\n\n proto.matches = proto.matchesSelector ||\n proto.mozMatchesSelector ||\n proto.msMatchesSelector ||\n proto.oMatchesSelector ||\n proto.webkitMatchesSelector;\n}\n\n/**\n * Finds the closest parent that matches a selector.\n *\n * @param {Element} element\n * @param {String} selector\n * @return {Function}\n */\nfunction closest (element, selector) {\n while (element && element.nodeType !== DOCUMENT_NODE_TYPE) {\n if (typeof element.matches === 'function' &&\n element.matches(selector)) {\n return element;\n }\n element = element.parentNode;\n }\n}\n\nmodule.exports = closest;\n\n\n/***/ }),\n\n/***/ 438:\n/***/ (function(module, __unused_webpack_exports, __webpack_require__) {\n\nvar closest = __webpack_require__(828);\n\n/**\n * Delegates event to a selector.\n *\n * @param {Element} element\n * @param {String} selector\n * @param {String} type\n * @param {Function} callback\n * @param {Boolean} useCapture\n * @return {Object}\n */\nfunction _delegate(element, selector, type, callback, useCapture) {\n var listenerFn = listener.apply(this, arguments);\n\n element.addEventListener(type, listenerFn, useCapture);\n\n return {\n destroy: function() {\n element.removeEventListener(type, listenerFn, useCapture);\n }\n }\n}\n\n/**\n * Delegates event to a selector.\n *\n * @param {Element|String|Array} [elements]\n * @param {String} selector\n * @param {String} type\n * @param {Function} callback\n * @param {Boolean} useCapture\n * @return {Object}\n */\nfunction delegate(elements, selector, type, callback, useCapture) {\n // Handle the regular Element usage\n if (typeof elements.addEventListener === 'function') {\n return _delegate.apply(null, arguments);\n }\n\n // Handle Element-less usage, it defaults to global delegation\n if (typeof type === 'function') {\n // Use `document` as the first parameter, then apply arguments\n // This is a short way to .unshift `arguments` without running into deoptimizations\n return _delegate.bind(null, document).apply(null, arguments);\n }\n\n // Handle Selector-based usage\n if (typeof elements === 'string') {\n elements = document.querySelectorAll(elements);\n }\n\n // Handle Array-like based usage\n return Array.prototype.map.call(elements, function (element) {\n return _delegate(element, selector, type, callback, useCapture);\n });\n}\n\n/**\n * Finds closest match and invokes callback.\n *\n * @param {Element} element\n * @param {String} selector\n * @param {String} type\n * @param {Function} callback\n * @return {Function}\n */\nfunction listener(element, selector, type, callback) {\n return function(e) {\n e.delegateTarget = closest(e.target, selector);\n\n if (e.delegateTarget) {\n callback.call(element, e);\n }\n }\n}\n\nmodule.exports = delegate;\n\n\n/***/ }),\n\n/***/ 879:\n/***/ (function(__unused_webpack_module, exports) {\n\n/**\n * Check if argument is a HTML element.\n *\n * @param {Object} value\n * @return {Boolean}\n */\nexports.node = function(value) {\n return value !== undefined\n && value instanceof HTMLElement\n && value.nodeType === 1;\n};\n\n/**\n * Check if argument is a list of HTML elements.\n *\n * @param {Object} value\n * @return {Boolean}\n */\nexports.nodeList = function(value) {\n var type = Object.prototype.toString.call(value);\n\n return value !== undefined\n && (type === '[object NodeList]' || type === '[object HTMLCollection]')\n && ('length' in value)\n && (value.length === 0 || exports.node(value[0]));\n};\n\n/**\n * Check if argument is a string.\n *\n * @param {Object} value\n * @return {Boolean}\n */\nexports.string = function(value) {\n return typeof value === 'string'\n || value instanceof String;\n};\n\n/**\n * Check if argument is a function.\n *\n * @param {Object} value\n * @return {Boolean}\n */\nexports.fn = function(value) {\n var type = Object.prototype.toString.call(value);\n\n return type === '[object Function]';\n};\n\n\n/***/ }),\n\n/***/ 370:\n/***/ (function(module, __unused_webpack_exports, __webpack_require__) {\n\nvar is = __webpack_require__(879);\nvar delegate = __webpack_require__(438);\n\n/**\n * Validates all params and calls the right\n * listener function based on its target type.\n *\n * @param {String|HTMLElement|HTMLCollection|NodeList} target\n * @param {String} type\n * @param {Function} callback\n * @return {Object}\n */\nfunction listen(target, type, callback) {\n if (!target && !type && !callback) {\n throw new Error('Missing required arguments');\n }\n\n if (!is.string(type)) {\n throw new TypeError('Second argument must be a String');\n }\n\n if (!is.fn(callback)) {\n throw new TypeError('Third argument must be a Function');\n }\n\n if (is.node(target)) {\n return listenNode(target, type, callback);\n }\n else if (is.nodeList(target)) {\n return listenNodeList(target, type, callback);\n }\n else if (is.string(target)) {\n return listenSelector(target, type, callback);\n }\n else {\n throw new TypeError('First argument must be a String, HTMLElement, HTMLCollection, or NodeList');\n }\n}\n\n/**\n * Adds an event listener to a HTML element\n * and returns a remove listener function.\n *\n * @param {HTMLElement} node\n * @param {String} type\n * @param {Function} callback\n * @return {Object}\n */\nfunction listenNode(node, type, callback) {\n node.addEventListener(type, callback);\n\n return {\n destroy: function() {\n node.removeEventListener(type, callback);\n }\n }\n}\n\n/**\n * Add an event listener to a list of HTML elements\n * and returns a remove listener function.\n *\n * @param {NodeList|HTMLCollection} nodeList\n * @param {String} type\n * @param {Function} callback\n * @return {Object}\n */\nfunction listenNodeList(nodeList, type, callback) {\n Array.prototype.forEach.call(nodeList, function(node) {\n node.addEventListener(type, callback);\n });\n\n return {\n destroy: function() {\n Array.prototype.forEach.call(nodeList, function(node) {\n node.removeEventListener(type, callback);\n });\n }\n }\n}\n\n/**\n * Add an event listener to a selector\n * and returns a remove listener function.\n *\n * @param {String} selector\n * @param {String} type\n * @param {Function} callback\n * @return {Object}\n */\nfunction listenSelector(selector, type, callback) {\n return delegate(document.body, selector, type, callback);\n}\n\nmodule.exports = listen;\n\n\n/***/ }),\n\n/***/ 817:\n/***/ (function(module) {\n\nfunction select(element) {\n var selectedText;\n\n if (element.nodeName === 'SELECT') {\n element.focus();\n\n selectedText = element.value;\n }\n else if (element.nodeName === 'INPUT' || element.nodeName === 'TEXTAREA') {\n var isReadOnly = element.hasAttribute('readonly');\n\n if (!isReadOnly) {\n element.setAttribute('readonly', '');\n }\n\n element.select();\n element.setSelectionRange(0, element.value.length);\n\n if (!isReadOnly) {\n element.removeAttribute('readonly');\n }\n\n selectedText = element.value;\n }\n else {\n if (element.hasAttribute('contenteditable')) {\n element.focus();\n }\n\n var selection = window.getSelection();\n var range = document.createRange();\n\n range.selectNodeContents(element);\n selection.removeAllRanges();\n selection.addRange(range);\n\n selectedText = selection.toString();\n }\n\n return selectedText;\n}\n\nmodule.exports = select;\n\n\n/***/ }),\n\n/***/ 279:\n/***/ (function(module) {\n\nfunction E () {\n // Keep this empty so it's easier to inherit from\n // (via https://github.com/lipsmack from https://github.com/scottcorgan/tiny-emitter/issues/3)\n}\n\nE.prototype = {\n on: function (name, callback, ctx) {\n var e = this.e || (this.e = {});\n\n (e[name] || (e[name] = [])).push({\n fn: callback,\n ctx: ctx\n });\n\n return this;\n },\n\n once: function (name, callback, ctx) {\n var self = this;\n function listener () {\n self.off(name, listener);\n callback.apply(ctx, arguments);\n };\n\n listener._ = callback\n return this.on(name, listener, ctx);\n },\n\n emit: function (name) {\n var data = [].slice.call(arguments, 1);\n var evtArr = ((this.e || (this.e = {}))[name] || []).slice();\n var i = 0;\n var len = evtArr.length;\n\n for (i; i < len; i++) {\n evtArr[i].fn.apply(evtArr[i].ctx, data);\n }\n\n return this;\n },\n\n off: function (name, callback) {\n var e = this.e || (this.e = {});\n var evts = e[name];\n var liveEvents = [];\n\n if (evts && callback) {\n for (var i = 0, len = evts.length; i < len; i++) {\n if (evts[i].fn !== callback && evts[i].fn._ !== callback)\n liveEvents.push(evts[i]);\n }\n }\n\n // Remove event from queue to prevent memory leak\n // Suggested by https://github.com/lazd\n // Ref: https://github.com/scottcorgan/tiny-emitter/commit/c6ebfaa9bc973b33d110a84a307742b7cf94c953#commitcomment-5024910\n\n (liveEvents.length)\n ? e[name] = liveEvents\n : delete e[name];\n\n return this;\n }\n};\n\nmodule.exports = E;\nmodule.exports.TinyEmitter = E;\n\n\n/***/ })\n\n/******/ \t});\n/************************************************************************/\n/******/ \t// The module cache\n/******/ \tvar __webpack_module_cache__ = {};\n/******/ \t\n/******/ \t// The require function\n/******/ \tfunction __webpack_require__(moduleId) {\n/******/ \t\t// Check if module is in cache\n/******/ \t\tif(__webpack_module_cache__[moduleId]) {\n/******/ \t\t\treturn __webpack_module_cache__[moduleId].exports;\n/******/ \t\t}\n/******/ \t\t// Create a new module (and put it into the cache)\n/******/ \t\tvar module = __webpack_module_cache__[moduleId] = {\n/******/ \t\t\t// no module.id needed\n/******/ \t\t\t// no module.loaded needed\n/******/ \t\t\texports: {}\n/******/ \t\t};\n/******/ \t\n/******/ \t\t// Execute the module function\n/******/ \t\t__webpack_modules__[moduleId](module, module.exports, __webpack_require__);\n/******/ \t\n/******/ \t\t// Return the exports of the module\n/******/ \t\treturn module.exports;\n/******/ \t}\n/******/ \t\n/************************************************************************/\n/******/ \t/* webpack/runtime/compat get default export */\n/******/ \t!function() {\n/******/ \t\t// getDefaultExport function for compatibility with non-harmony modules\n/******/ \t\t__webpack_require__.n = function(module) {\n/******/ \t\t\tvar getter = module && module.__esModule ?\n/******/ \t\t\t\tfunction() { return module['default']; } :\n/******/ \t\t\t\tfunction() { return module; };\n/******/ \t\t\t__webpack_require__.d(getter, { a: getter });\n/******/ \t\t\treturn getter;\n/******/ \t\t};\n/******/ \t}();\n/******/ \t\n/******/ \t/* webpack/runtime/define property getters */\n/******/ \t!function() {\n/******/ \t\t// define getter functions for harmony exports\n/******/ \t\t__webpack_require__.d = function(exports, definition) {\n/******/ \t\t\tfor(var key in definition) {\n/******/ \t\t\t\tif(__webpack_require__.o(definition, key) && !__webpack_require__.o(exports, key)) {\n/******/ \t\t\t\t\tObject.defineProperty(exports, key, { enumerable: true, get: definition[key] });\n/******/ \t\t\t\t}\n/******/ \t\t\t}\n/******/ \t\t};\n/******/ \t}();\n/******/ \t\n/******/ \t/* webpack/runtime/hasOwnProperty shorthand */\n/******/ \t!function() {\n/******/ \t\t__webpack_require__.o = function(obj, prop) { return Object.prototype.hasOwnProperty.call(obj, prop); }\n/******/ \t}();\n/******/ \t\n/************************************************************************/\n/******/ \t// module exports must be returned from runtime so entry inlining is disabled\n/******/ \t// startup\n/******/ \t// Load entry module and return exports\n/******/ \treturn __webpack_require__(686);\n/******/ })()\n.default;\n});", "/*!\n * escape-html\n * Copyright(c) 2012-2013 TJ Holowaychuk\n * Copyright(c) 2015 Andreas Lubbe\n * Copyright(c) 2015 Tiancheng \"Timothy\" Gu\n * MIT Licensed\n */\n\n'use strict';\n\n/**\n * Module variables.\n * @private\n */\n\nvar matchHtmlRegExp = /[\"'&<>]/;\n\n/**\n * Module exports.\n * @public\n */\n\nmodule.exports = escapeHtml;\n\n/**\n * Escape special characters in the given string of html.\n *\n * @param {string} string The string to escape for inserting into HTML\n * @return {string}\n * @public\n */\n\nfunction escapeHtml(string) {\n var str = '' + string;\n var match = matchHtmlRegExp.exec(str);\n\n if (!match) {\n return str;\n }\n\n var escape;\n var html = '';\n var index = 0;\n var lastIndex = 0;\n\n for (index = match.index; index < str.length; index++) {\n switch (str.charCodeAt(index)) {\n case 34: // \"\n escape = '"';\n break;\n case 38: // &\n escape = '&';\n break;\n case 39: // '\n escape = ''';\n break;\n case 60: // <\n escape = '<';\n break;\n case 62: // >\n escape = '>';\n break;\n default:\n continue;\n }\n\n if (lastIndex !== index) {\n html += str.substring(lastIndex, index);\n }\n\n lastIndex = index + 1;\n html += escape;\n }\n\n return lastIndex !== index\n ? html + str.substring(lastIndex, index)\n : html;\n}\n", "/*\n * Copyright (c) 2016-2024 Martin Donath \n *\n * Permission is hereby granted, free of charge, to any person obtaining a copy\n * of this software and associated documentation files (the \"Software\"), to\n * deal in the Software without restriction, including without limitation the\n * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or\n * sell copies of the Software, and to permit persons to whom the Software is\n * furnished to do so, subject to the following conditions:\n *\n * The above copyright notice and this permission notice shall be included in\n * all copies or substantial portions of the Software.\n *\n * THE SOFTWARE IS PROVIDED \"AS IS\", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR\n * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,\n * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL THE\n * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER\n * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING\n * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS\n * IN THE SOFTWARE.\n */\n\nimport \"focus-visible\"\n\nimport {\n EMPTY,\n NEVER,\n Observable,\n Subject,\n defer,\n delay,\n filter,\n map,\n merge,\n mergeWith,\n shareReplay,\n switchMap\n} from \"rxjs\"\n\nimport { configuration, feature } from \"./_\"\nimport {\n at,\n getActiveElement,\n getOptionalElement,\n requestJSON,\n setLocation,\n setToggle,\n watchDocument,\n watchKeyboard,\n watchLocation,\n watchLocationTarget,\n watchMedia,\n watchPrint,\n watchScript,\n watchViewport\n} from \"./browser\"\nimport {\n getComponentElement,\n getComponentElements,\n mountAnnounce,\n mountBackToTop,\n mountConsent,\n mountContent,\n mountDialog,\n mountHeader,\n mountHeaderTitle,\n mountPalette,\n mountProgress,\n mountSearch,\n mountSearchHiglight,\n mountSidebar,\n mountSource,\n mountTableOfContents,\n mountTabs,\n watchHeader,\n watchMain\n} from \"./components\"\nimport {\n SearchIndex,\n setupClipboardJS,\n setupInstantNavigation,\n setupVersionSelector\n} from \"./integrations\"\nimport {\n patchEllipsis,\n patchIndeterminate,\n patchScrollfix,\n patchScrolllock\n} from \"./patches\"\nimport \"./polyfills\"\n\n/* ----------------------------------------------------------------------------\n * Functions - @todo refactor\n * ------------------------------------------------------------------------- */\n\n/**\n * Fetch search index\n *\n * @returns Search index observable\n */\nfunction fetchSearchIndex(): Observable {\n if (location.protocol === \"file:\") {\n return watchScript(\n `${new URL(\"search/search_index.js\", config.base)}`\n )\n .pipe(\n // @ts-ignore - @todo fix typings\n map(() => __index),\n shareReplay(1)\n )\n } else {\n return requestJSON(\n new URL(\"search/search_index.json\", config.base)\n )\n }\n}\n\n/* ----------------------------------------------------------------------------\n * Application\n * ------------------------------------------------------------------------- */\n\n/* Yay, JavaScript is available */\ndocument.documentElement.classList.remove(\"no-js\")\ndocument.documentElement.classList.add(\"js\")\n\n/* Set up navigation observables and subjects */\nconst document$ = watchDocument()\nconst location$ = watchLocation()\nconst target$ = watchLocationTarget(location$)\nconst keyboard$ = watchKeyboard()\n\n/* Set up media observables */\nconst viewport$ = watchViewport()\nconst tablet$ = watchMedia(\"(min-width: 960px)\")\nconst screen$ = watchMedia(\"(min-width: 1220px)\")\nconst print$ = watchPrint()\n\n/* Retrieve search index, if search is enabled */\nconst config = configuration()\nconst index$ = document.forms.namedItem(\"search\")\n ? fetchSearchIndex()\n : NEVER\n\n/* Set up Clipboard.js integration */\nconst alert$ = new Subject()\nsetupClipboardJS({ alert$ })\n\n/* Set up progress indicator */\nconst progress$ = new Subject()\n\n/* Set up instant navigation, if enabled */\nif (feature(\"navigation.instant\"))\n setupInstantNavigation({ location$, viewport$, progress$ })\n .subscribe(document$)\n\n/* Set up version selector */\nif (config.version?.provider === \"mike\")\n setupVersionSelector({ document$ })\n\n/* Always close drawer and search on navigation */\nmerge(location$, target$)\n .pipe(\n delay(125)\n )\n .subscribe(() => {\n setToggle(\"drawer\", false)\n setToggle(\"search\", false)\n })\n\n/* Set up global keyboard handlers */\nkeyboard$\n .pipe(\n filter(({ mode }) => mode === \"global\")\n )\n .subscribe(key => {\n switch (key.type) {\n\n /* Go to previous page */\n case \"p\":\n case \",\":\n const prev = getOptionalElement(\"link[rel=prev]\")\n if (typeof prev !== \"undefined\")\n setLocation(prev)\n break\n\n /* Go to next page */\n case \"n\":\n case \".\":\n const next = getOptionalElement(\"link[rel=next]\")\n if (typeof next !== \"undefined\")\n setLocation(next)\n break\n\n /* Expand navigation, see https://bit.ly/3ZjG5io */\n case \"Enter\":\n const active = getActiveElement()\n if (active instanceof HTMLLabelElement)\n active.click()\n }\n })\n\n/* Set up patches */\npatchEllipsis({ document$ })\npatchIndeterminate({ document$, tablet$ })\npatchScrollfix({ document$ })\npatchScrolllock({ viewport$, tablet$ })\n\n/* Set up header and main area observable */\nconst header$ = watchHeader(getComponentElement(\"header\"), { viewport$ })\nconst main$ = document$\n .pipe(\n map(() => getComponentElement(\"main\")),\n switchMap(el => watchMain(el, { viewport$, header$ })),\n shareReplay(1)\n )\n\n/* Set up control component observables */\nconst control$ = merge(\n\n /* Consent */\n ...getComponentElements(\"consent\")\n .map(el => mountConsent(el, { target$ })),\n\n /* Dialog */\n ...getComponentElements(\"dialog\")\n .map(el => mountDialog(el, { alert$ })),\n\n /* Header */\n ...getComponentElements(\"header\")\n .map(el => mountHeader(el, { viewport$, header$, main$ })),\n\n /* Color palette */\n ...getComponentElements(\"palette\")\n .map(el => mountPalette(el)),\n\n /* Progress bar */\n ...getComponentElements(\"progress\")\n .map(el => mountProgress(el, { progress$ })),\n\n /* Search */\n ...getComponentElements(\"search\")\n .map(el => mountSearch(el, { index$, keyboard$ })),\n\n /* Repository information */\n ...getComponentElements(\"source\")\n .map(el => mountSource(el))\n)\n\n/* Set up content component observables */\nconst content$ = defer(() => merge(\n\n /* Announcement bar */\n ...getComponentElements(\"announce\")\n .map(el => mountAnnounce(el)),\n\n /* Content */\n ...getComponentElements(\"content\")\n .map(el => mountContent(el, { viewport$, target$, print$ })),\n\n /* Search highlighting */\n ...getComponentElements(\"content\")\n .map(el => feature(\"search.highlight\")\n ? mountSearchHiglight(el, { index$, location$ })\n : EMPTY\n ),\n\n /* Header title */\n ...getComponentElements(\"header-title\")\n .map(el => mountHeaderTitle(el, { viewport$, header$ })),\n\n /* Sidebar */\n ...getComponentElements(\"sidebar\")\n .map(el => el.getAttribute(\"data-md-type\") === \"navigation\"\n ? at(screen$, () => mountSidebar(el, { viewport$, header$, main$ }))\n : at(tablet$, () => mountSidebar(el, { viewport$, header$, main$ }))\n ),\n\n /* Navigation tabs */\n ...getComponentElements(\"tabs\")\n .map(el => mountTabs(el, { viewport$, header$ })),\n\n /* Table of contents */\n ...getComponentElements(\"toc\")\n .map(el => mountTableOfContents(el, {\n viewport$, header$, main$, target$\n })),\n\n /* Back-to-top button */\n ...getComponentElements(\"top\")\n .map(el => mountBackToTop(el, { viewport$, header$, main$, target$ }))\n))\n\n/* Set up component observables */\nconst component$ = document$\n .pipe(\n switchMap(() => content$),\n mergeWith(control$),\n shareReplay(1)\n )\n\n/* Subscribe to all components */\ncomponent$.subscribe()\n\n/* ----------------------------------------------------------------------------\n * Exports\n * ------------------------------------------------------------------------- */\n\nwindow.document$ = document$ /* Document observable */\nwindow.location$ = location$ /* Location subject */\nwindow.target$ = target$ /* Location target observable */\nwindow.keyboard$ = keyboard$ /* Keyboard observable */\nwindow.viewport$ = viewport$ /* Viewport observable */\nwindow.tablet$ = tablet$ /* Media tablet observable */\nwindow.screen$ = screen$ /* Media screen observable */\nwindow.print$ = print$ /* Media print observable */\nwindow.alert$ = alert$ /* Alert subject */\nwindow.progress$ = progress$ /* Progress indicator subject */\nwindow.component$ = component$ /* Component observable */\n", "/*! *****************************************************************************\r\nCopyright (c) Microsoft Corporation.\r\n\r\nPermission to use, copy, modify, and/or distribute this software for any\r\npurpose with or without fee is hereby granted.\r\n\r\nTHE SOFTWARE IS PROVIDED \"AS IS\" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH\r\nREGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY\r\nAND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,\r\nINDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM\r\nLOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR\r\nOTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR\r\nPERFORMANCE OF THIS SOFTWARE.\r\n***************************************************************************** */\r\n/* global Reflect, Promise */\r\n\r\nvar extendStatics = function(d, b) {\r\n extendStatics = Object.setPrototypeOf ||\r\n ({ __proto__: [] } instanceof Array && function (d, b) { d.__proto__ = b; }) ||\r\n function (d, b) { for (var p in b) if (Object.prototype.hasOwnProperty.call(b, p)) d[p] = b[p]; };\r\n return extendStatics(d, b);\r\n};\r\n\r\nexport function __extends(d, b) {\r\n if (typeof b !== \"function\" && b !== null)\r\n throw new TypeError(\"Class extends value \" + String(b) + \" is not a constructor or null\");\r\n extendStatics(d, b);\r\n function __() { this.constructor = d; }\r\n d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());\r\n}\r\n\r\nexport var __assign = function() {\r\n __assign = Object.assign || function __assign(t) {\r\n for (var s, i = 1, n = arguments.length; i < n; i++) {\r\n s = arguments[i];\r\n for (var p in s) if (Object.prototype.hasOwnProperty.call(s, p)) t[p] = s[p];\r\n }\r\n return t;\r\n }\r\n return __assign.apply(this, arguments);\r\n}\r\n\r\nexport function __rest(s, e) {\r\n var t = {};\r\n for (var p in s) if (Object.prototype.hasOwnProperty.call(s, p) && e.indexOf(p) < 0)\r\n t[p] = s[p];\r\n if (s != null && typeof Object.getOwnPropertySymbols === \"function\")\r\n for (var i = 0, p = Object.getOwnPropertySymbols(s); i < p.length; i++) {\r\n if (e.indexOf(p[i]) < 0 && Object.prototype.propertyIsEnumerable.call(s, p[i]))\r\n t[p[i]] = s[p[i]];\r\n }\r\n return t;\r\n}\r\n\r\nexport function __decorate(decorators, target, key, desc) {\r\n var c = arguments.length, r = c < 3 ? target : desc === null ? desc = Object.getOwnPropertyDescriptor(target, key) : desc, d;\r\n if (typeof Reflect === \"object\" && typeof Reflect.decorate === \"function\") r = Reflect.decorate(decorators, target, key, desc);\r\n else for (var i = decorators.length - 1; i >= 0; i--) if (d = decorators[i]) r = (c < 3 ? d(r) : c > 3 ? d(target, key, r) : d(target, key)) || r;\r\n return c > 3 && r && Object.defineProperty(target, key, r), r;\r\n}\r\n\r\nexport function __param(paramIndex, decorator) {\r\n return function (target, key) { decorator(target, key, paramIndex); }\r\n}\r\n\r\nexport function __metadata(metadataKey, metadataValue) {\r\n if (typeof Reflect === \"object\" && typeof Reflect.metadata === \"function\") return Reflect.metadata(metadataKey, metadataValue);\r\n}\r\n\r\nexport function __awaiter(thisArg, _arguments, P, generator) {\r\n function adopt(value) { return value instanceof P ? value : new P(function (resolve) { resolve(value); }); }\r\n return new (P || (P = Promise))(function (resolve, reject) {\r\n function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }\r\n function rejected(value) { try { step(generator[\"throw\"](value)); } catch (e) { reject(e); } }\r\n function step(result) { result.done ? resolve(result.value) : adopt(result.value).then(fulfilled, rejected); }\r\n step((generator = generator.apply(thisArg, _arguments || [])).next());\r\n });\r\n}\r\n\r\nexport function __generator(thisArg, body) {\r\n var _ = { label: 0, sent: function() { if (t[0] & 1) throw t[1]; return t[1]; }, trys: [], ops: [] }, f, y, t, g;\r\n return g = { next: verb(0), \"throw\": verb(1), \"return\": verb(2) }, typeof Symbol === \"function\" && (g[Symbol.iterator] = function() { return this; }), g;\r\n function verb(n) { return function (v) { return step([n, v]); }; }\r\n function step(op) {\r\n if (f) throw new TypeError(\"Generator is already executing.\");\r\n while (_) try {\r\n if (f = 1, y && (t = op[0] & 2 ? y[\"return\"] : op[0] ? y[\"throw\"] || ((t = y[\"return\"]) && t.call(y), 0) : y.next) && !(t = t.call(y, op[1])).done) return t;\r\n if (y = 0, t) op = [op[0] & 2, t.value];\r\n switch (op[0]) {\r\n case 0: case 1: t = op; break;\r\n case 4: _.label++; return { value: op[1], done: false };\r\n case 5: _.label++; y = op[1]; op = [0]; continue;\r\n case 7: op = _.ops.pop(); _.trys.pop(); continue;\r\n default:\r\n if (!(t = _.trys, t = t.length > 0 && t[t.length - 1]) && (op[0] === 6 || op[0] === 2)) { _ = 0; continue; }\r\n if (op[0] === 3 && (!t || (op[1] > t[0] && op[1] < t[3]))) { _.label = op[1]; break; }\r\n if (op[0] === 6 && _.label < t[1]) { _.label = t[1]; t = op; break; }\r\n if (t && _.label < t[2]) { _.label = t[2]; _.ops.push(op); break; }\r\n if (t[2]) _.ops.pop();\r\n _.trys.pop(); continue;\r\n }\r\n op = body.call(thisArg, _);\r\n } catch (e) { op = [6, e]; y = 0; } finally { f = t = 0; }\r\n if (op[0] & 5) throw op[1]; return { value: op[0] ? op[1] : void 0, done: true };\r\n }\r\n}\r\n\r\nexport var __createBinding = Object.create ? (function(o, m, k, k2) {\r\n if (k2 === undefined) k2 = k;\r\n Object.defineProperty(o, k2, { enumerable: true, get: function() { return m[k]; } });\r\n}) : (function(o, m, k, k2) {\r\n if (k2 === undefined) k2 = k;\r\n o[k2] = m[k];\r\n});\r\n\r\nexport function __exportStar(m, o) {\r\n for (var p in m) if (p !== \"default\" && !Object.prototype.hasOwnProperty.call(o, p)) __createBinding(o, m, p);\r\n}\r\n\r\nexport function __values(o) {\r\n var s = typeof Symbol === \"function\" && Symbol.iterator, m = s && o[s], i = 0;\r\n if (m) return m.call(o);\r\n if (o && typeof o.length === \"number\") return {\r\n next: function () {\r\n if (o && i >= o.length) o = void 0;\r\n return { value: o && o[i++], done: !o };\r\n }\r\n };\r\n throw new TypeError(s ? \"Object is not iterable.\" : \"Symbol.iterator is not defined.\");\r\n}\r\n\r\nexport function __read(o, n) {\r\n var m = typeof Symbol === \"function\" && o[Symbol.iterator];\r\n if (!m) return o;\r\n var i = m.call(o), r, ar = [], e;\r\n try {\r\n while ((n === void 0 || n-- > 0) && !(r = i.next()).done) ar.push(r.value);\r\n }\r\n catch (error) { e = { error: error }; }\r\n finally {\r\n try {\r\n if (r && !r.done && (m = i[\"return\"])) m.call(i);\r\n }\r\n finally { if (e) throw e.error; }\r\n }\r\n return ar;\r\n}\r\n\r\n/** @deprecated */\r\nexport function __spread() {\r\n for (var ar = [], i = 0; i < arguments.length; i++)\r\n ar = ar.concat(__read(arguments[i]));\r\n return ar;\r\n}\r\n\r\n/** @deprecated */\r\nexport function __spreadArrays() {\r\n for (var s = 0, i = 0, il = arguments.length; i < il; i++) s += arguments[i].length;\r\n for (var r = Array(s), k = 0, i = 0; i < il; i++)\r\n for (var a = arguments[i], j = 0, jl = a.length; j < jl; j++, k++)\r\n r[k] = a[j];\r\n return r;\r\n}\r\n\r\nexport function __spreadArray(to, from, pack) {\r\n if (pack || arguments.length === 2) for (var i = 0, l = from.length, ar; i < l; i++) {\r\n if (ar || !(i in from)) {\r\n if (!ar) ar = Array.prototype.slice.call(from, 0, i);\r\n ar[i] = from[i];\r\n }\r\n }\r\n return to.concat(ar || Array.prototype.slice.call(from));\r\n}\r\n\r\nexport function __await(v) {\r\n return this instanceof __await ? (this.v = v, this) : new __await(v);\r\n}\r\n\r\nexport function __asyncGenerator(thisArg, _arguments, generator) {\r\n if (!Symbol.asyncIterator) throw new TypeError(\"Symbol.asyncIterator is not defined.\");\r\n var g = generator.apply(thisArg, _arguments || []), i, q = [];\r\n return i = {}, verb(\"next\"), verb(\"throw\"), verb(\"return\"), i[Symbol.asyncIterator] = function () { return this; }, i;\r\n function verb(n) { if (g[n]) i[n] = function (v) { return new Promise(function (a, b) { q.push([n, v, a, b]) > 1 || resume(n, v); }); }; }\r\n function resume(n, v) { try { step(g[n](v)); } catch (e) { settle(q[0][3], e); } }\r\n function step(r) { r.value instanceof __await ? Promise.resolve(r.value.v).then(fulfill, reject) : settle(q[0][2], r); }\r\n function fulfill(value) { resume(\"next\", value); }\r\n function reject(value) { resume(\"throw\", value); }\r\n function settle(f, v) { if (f(v), q.shift(), q.length) resume(q[0][0], q[0][1]); }\r\n}\r\n\r\nexport function __asyncDelegator(o) {\r\n var i, p;\r\n return i = {}, verb(\"next\"), verb(\"throw\", function (e) { throw e; }), verb(\"return\"), i[Symbol.iterator] = function () { return this; }, i;\r\n function verb(n, f) { i[n] = o[n] ? function (v) { return (p = !p) ? { value: __await(o[n](v)), done: n === \"return\" } : f ? f(v) : v; } : f; }\r\n}\r\n\r\nexport function __asyncValues(o) {\r\n if (!Symbol.asyncIterator) throw new TypeError(\"Symbol.asyncIterator is not defined.\");\r\n var m = o[Symbol.asyncIterator], i;\r\n return m ? m.call(o) : (o = typeof __values === \"function\" ? __values(o) : o[Symbol.iterator](), i = {}, verb(\"next\"), verb(\"throw\"), verb(\"return\"), i[Symbol.asyncIterator] = function () { return this; }, i);\r\n function verb(n) { i[n] = o[n] && function (v) { return new Promise(function (resolve, reject) { v = o[n](v), settle(resolve, reject, v.done, v.value); }); }; }\r\n function settle(resolve, reject, d, v) { Promise.resolve(v).then(function(v) { resolve({ value: v, done: d }); }, reject); }\r\n}\r\n\r\nexport function __makeTemplateObject(cooked, raw) {\r\n if (Object.defineProperty) { Object.defineProperty(cooked, \"raw\", { value: raw }); } else { cooked.raw = raw; }\r\n return cooked;\r\n};\r\n\r\nvar __setModuleDefault = Object.create ? (function(o, v) {\r\n Object.defineProperty(o, \"default\", { enumerable: true, value: v });\r\n}) : function(o, v) {\r\n o[\"default\"] = v;\r\n};\r\n\r\nexport function __importStar(mod) {\r\n if (mod && mod.__esModule) return mod;\r\n var result = {};\r\n if (mod != null) for (var k in mod) if (k !== \"default\" && Object.prototype.hasOwnProperty.call(mod, k)) __createBinding(result, mod, k);\r\n __setModuleDefault(result, mod);\r\n return result;\r\n}\r\n\r\nexport function __importDefault(mod) {\r\n return (mod && mod.__esModule) ? mod : { default: mod };\r\n}\r\n\r\nexport function __classPrivateFieldGet(receiver, state, kind, f) {\r\n if (kind === \"a\" && !f) throw new TypeError(\"Private accessor was defined without a getter\");\r\n if (typeof state === \"function\" ? receiver !== state || !f : !state.has(receiver)) throw new TypeError(\"Cannot read private member from an object whose class did not declare it\");\r\n return kind === \"m\" ? f : kind === \"a\" ? f.call(receiver) : f ? f.value : state.get(receiver);\r\n}\r\n\r\nexport function __classPrivateFieldSet(receiver, state, value, kind, f) {\r\n if (kind === \"m\") throw new TypeError(\"Private method is not writable\");\r\n if (kind === \"a\" && !f) throw new TypeError(\"Private accessor was defined without a setter\");\r\n if (typeof state === \"function\" ? receiver !== state || !f : !state.has(receiver)) throw new TypeError(\"Cannot write private member to an object whose class did not declare it\");\r\n return (kind === \"a\" ? f.call(receiver, value) : f ? f.value = value : state.set(receiver, value)), value;\r\n}\r\n", "/**\n * Returns true if the object is a function.\n * @param value The value to check\n */\nexport function isFunction(value: any): value is (...args: any[]) => any {\n return typeof value === 'function';\n}\n", "/**\n * Used to create Error subclasses until the community moves away from ES5.\n *\n * This is because compiling from TypeScript down to ES5 has issues with subclassing Errors\n * as well as other built-in types: https://github.com/Microsoft/TypeScript/issues/12123\n *\n * @param createImpl A factory function to create the actual constructor implementation. The returned\n * function should be a named function that calls `_super` internally.\n */\nexport function createErrorClass(createImpl: (_super: any) => any): T {\n const _super = (instance: any) => {\n Error.call(instance);\n instance.stack = new Error().stack;\n };\n\n const ctorFunc = createImpl(_super);\n ctorFunc.prototype = Object.create(Error.prototype);\n ctorFunc.prototype.constructor = ctorFunc;\n return ctorFunc;\n}\n", "import { createErrorClass } from './createErrorClass';\n\nexport interface UnsubscriptionError extends Error {\n readonly errors: any[];\n}\n\nexport interface UnsubscriptionErrorCtor {\n /**\n * @deprecated Internal implementation detail. Do not construct error instances.\n * Cannot be tagged as internal: https://github.com/ReactiveX/rxjs/issues/6269\n */\n new (errors: any[]): UnsubscriptionError;\n}\n\n/**\n * An error thrown when one or more errors have occurred during the\n * `unsubscribe` of a {@link Subscription}.\n */\nexport const UnsubscriptionError: UnsubscriptionErrorCtor = createErrorClass(\n (_super) =>\n function UnsubscriptionErrorImpl(this: any, errors: (Error | string)[]) {\n _super(this);\n this.message = errors\n ? `${errors.length} errors occurred during unsubscription:\n${errors.map((err, i) => `${i + 1}) ${err.toString()}`).join('\\n ')}`\n : '';\n this.name = 'UnsubscriptionError';\n this.errors = errors;\n }\n);\n", "/**\n * Removes an item from an array, mutating it.\n * @param arr The array to remove the item from\n * @param item The item to remove\n */\nexport function arrRemove(arr: T[] | undefined | null, item: T) {\n if (arr) {\n const index = arr.indexOf(item);\n 0 <= index && arr.splice(index, 1);\n }\n}\n", "import { isFunction } from './util/isFunction';\nimport { UnsubscriptionError } from './util/UnsubscriptionError';\nimport { SubscriptionLike, TeardownLogic, Unsubscribable } from './types';\nimport { arrRemove } from './util/arrRemove';\n\n/**\n * Represents a disposable resource, such as the execution of an Observable. A\n * Subscription has one important method, `unsubscribe`, that takes no argument\n * and just disposes the resource held by the subscription.\n *\n * Additionally, subscriptions may be grouped together through the `add()`\n * method, which will attach a child Subscription to the current Subscription.\n * When a Subscription is unsubscribed, all its children (and its grandchildren)\n * will be unsubscribed as well.\n *\n * @class Subscription\n */\nexport class Subscription implements SubscriptionLike {\n /** @nocollapse */\n public static EMPTY = (() => {\n const empty = new Subscription();\n empty.closed = true;\n return empty;\n })();\n\n /**\n * A flag to indicate whether this Subscription has already been unsubscribed.\n */\n public closed = false;\n\n private _parentage: Subscription[] | Subscription | null = null;\n\n /**\n * The list of registered finalizers to execute upon unsubscription. Adding and removing from this\n * list occurs in the {@link #add} and {@link #remove} methods.\n */\n private _finalizers: Exclude[] | null = null;\n\n /**\n * @param initialTeardown A function executed first as part of the finalization\n * process that is kicked off when {@link #unsubscribe} is called.\n */\n constructor(private initialTeardown?: () => void) {}\n\n /**\n * Disposes the resources held by the subscription. May, for instance, cancel\n * an ongoing Observable execution or cancel any other type of work that\n * started when the Subscription was created.\n * @return {void}\n */\n unsubscribe(): void {\n let errors: any[] | undefined;\n\n if (!this.closed) {\n this.closed = true;\n\n // Remove this from it's parents.\n const { _parentage } = this;\n if (_parentage) {\n this._parentage = null;\n if (Array.isArray(_parentage)) {\n for (const parent of _parentage) {\n parent.remove(this);\n }\n } else {\n _parentage.remove(this);\n }\n }\n\n const { initialTeardown: initialFinalizer } = this;\n if (isFunction(initialFinalizer)) {\n try {\n initialFinalizer();\n } catch (e) {\n errors = e instanceof UnsubscriptionError ? e.errors : [e];\n }\n }\n\n const { _finalizers } = this;\n if (_finalizers) {\n this._finalizers = null;\n for (const finalizer of _finalizers) {\n try {\n execFinalizer(finalizer);\n } catch (err) {\n errors = errors ?? [];\n if (err instanceof UnsubscriptionError) {\n errors = [...errors, ...err.errors];\n } else {\n errors.push(err);\n }\n }\n }\n }\n\n if (errors) {\n throw new UnsubscriptionError(errors);\n }\n }\n }\n\n /**\n * Adds a finalizer to this subscription, so that finalization will be unsubscribed/called\n * when this subscription is unsubscribed. If this subscription is already {@link #closed},\n * because it has already been unsubscribed, then whatever finalizer is passed to it\n * will automatically be executed (unless the finalizer itself is also a closed subscription).\n *\n * Closed Subscriptions cannot be added as finalizers to any subscription. Adding a closed\n * subscription to a any subscription will result in no operation. (A noop).\n *\n * Adding a subscription to itself, or adding `null` or `undefined` will not perform any\n * operation at all. (A noop).\n *\n * `Subscription` instances that are added to this instance will automatically remove themselves\n * if they are unsubscribed. Functions and {@link Unsubscribable} objects that you wish to remove\n * will need to be removed manually with {@link #remove}\n *\n * @param teardown The finalization logic to add to this subscription.\n */\n add(teardown: TeardownLogic): void {\n // Only add the finalizer if it's not undefined\n // and don't add a subscription to itself.\n if (teardown && teardown !== this) {\n if (this.closed) {\n // If this subscription is already closed,\n // execute whatever finalizer is handed to it automatically.\n execFinalizer(teardown);\n } else {\n if (teardown instanceof Subscription) {\n // We don't add closed subscriptions, and we don't add the same subscription\n // twice. Subscription unsubscribe is idempotent.\n if (teardown.closed || teardown._hasParent(this)) {\n return;\n }\n teardown._addParent(this);\n }\n (this._finalizers = this._finalizers ?? []).push(teardown);\n }\n }\n }\n\n /**\n * Checks to see if a this subscription already has a particular parent.\n * This will signal that this subscription has already been added to the parent in question.\n * @param parent the parent to check for\n */\n private _hasParent(parent: Subscription) {\n const { _parentage } = this;\n return _parentage === parent || (Array.isArray(_parentage) && _parentage.includes(parent));\n }\n\n /**\n * Adds a parent to this subscription so it can be removed from the parent if it\n * unsubscribes on it's own.\n *\n * NOTE: THIS ASSUMES THAT {@link _hasParent} HAS ALREADY BEEN CHECKED.\n * @param parent The parent subscription to add\n */\n private _addParent(parent: Subscription) {\n const { _parentage } = this;\n this._parentage = Array.isArray(_parentage) ? (_parentage.push(parent), _parentage) : _parentage ? [_parentage, parent] : parent;\n }\n\n /**\n * Called on a child when it is removed via {@link #remove}.\n * @param parent The parent to remove\n */\n private _removeParent(parent: Subscription) {\n const { _parentage } = this;\n if (_parentage === parent) {\n this._parentage = null;\n } else if (Array.isArray(_parentage)) {\n arrRemove(_parentage, parent);\n }\n }\n\n /**\n * Removes a finalizer from this subscription that was previously added with the {@link #add} method.\n *\n * Note that `Subscription` instances, when unsubscribed, will automatically remove themselves\n * from every other `Subscription` they have been added to. This means that using the `remove` method\n * is not a common thing and should be used thoughtfully.\n *\n * If you add the same finalizer instance of a function or an unsubscribable object to a `Subscription` instance\n * more than once, you will need to call `remove` the same number of times to remove all instances.\n *\n * All finalizer instances are removed to free up memory upon unsubscription.\n *\n * @param teardown The finalizer to remove from this subscription\n */\n remove(teardown: Exclude): void {\n const { _finalizers } = this;\n _finalizers && arrRemove(_finalizers, teardown);\n\n if (teardown instanceof Subscription) {\n teardown._removeParent(this);\n }\n }\n}\n\nexport const EMPTY_SUBSCRIPTION = Subscription.EMPTY;\n\nexport function isSubscription(value: any): value is Subscription {\n return (\n value instanceof Subscription ||\n (value && 'closed' in value && isFunction(value.remove) && isFunction(value.add) && isFunction(value.unsubscribe))\n );\n}\n\nfunction execFinalizer(finalizer: Unsubscribable | (() => void)) {\n if (isFunction(finalizer)) {\n finalizer();\n } else {\n finalizer.unsubscribe();\n }\n}\n", "import { Subscriber } from './Subscriber';\nimport { ObservableNotification } from './types';\n\n/**\n * The {@link GlobalConfig} object for RxJS. It is used to configure things\n * like how to react on unhandled errors.\n */\nexport const config: GlobalConfig = {\n onUnhandledError: null,\n onStoppedNotification: null,\n Promise: undefined,\n useDeprecatedSynchronousErrorHandling: false,\n useDeprecatedNextContext: false,\n};\n\n/**\n * The global configuration object for RxJS, used to configure things\n * like how to react on unhandled errors. Accessible via {@link config}\n * object.\n */\nexport interface GlobalConfig {\n /**\n * A registration point for unhandled errors from RxJS. These are errors that\n * cannot were not handled by consuming code in the usual subscription path. For\n * example, if you have this configured, and you subscribe to an observable without\n * providing an error handler, errors from that subscription will end up here. This\n * will _always_ be called asynchronously on another job in the runtime. This is because\n * we do not want errors thrown in this user-configured handler to interfere with the\n * behavior of the library.\n */\n onUnhandledError: ((err: any) => void) | null;\n\n /**\n * A registration point for notifications that cannot be sent to subscribers because they\n * have completed, errored or have been explicitly unsubscribed. By default, next, complete\n * and error notifications sent to stopped subscribers are noops. However, sometimes callers\n * might want a different behavior. For example, with sources that attempt to report errors\n * to stopped subscribers, a caller can configure RxJS to throw an unhandled error instead.\n * This will _always_ be called asynchronously on another job in the runtime. This is because\n * we do not want errors thrown in this user-configured handler to interfere with the\n * behavior of the library.\n */\n onStoppedNotification: ((notification: ObservableNotification, subscriber: Subscriber) => void) | null;\n\n /**\n * The promise constructor used by default for {@link Observable#toPromise toPromise} and {@link Observable#forEach forEach}\n * methods.\n *\n * @deprecated As of version 8, RxJS will no longer support this sort of injection of a\n * Promise constructor. If you need a Promise implementation other than native promises,\n * please polyfill/patch Promise as you see appropriate. Will be removed in v8.\n */\n Promise?: PromiseConstructorLike;\n\n /**\n * If true, turns on synchronous error rethrowing, which is a deprecated behavior\n * in v6 and higher. This behavior enables bad patterns like wrapping a subscribe\n * call in a try/catch block. It also enables producer interference, a nasty bug\n * where a multicast can be broken for all observers by a downstream consumer with\n * an unhandled error. DO NOT USE THIS FLAG UNLESS IT'S NEEDED TO BUY TIME\n * FOR MIGRATION REASONS.\n *\n * @deprecated As of version 8, RxJS will no longer support synchronous throwing\n * of unhandled errors. All errors will be thrown on a separate call stack to prevent bad\n * behaviors described above. Will be removed in v8.\n */\n useDeprecatedSynchronousErrorHandling: boolean;\n\n /**\n * If true, enables an as-of-yet undocumented feature from v5: The ability to access\n * `unsubscribe()` via `this` context in `next` functions created in observers passed\n * to `subscribe`.\n *\n * This is being removed because the performance was severely problematic, and it could also cause\n * issues when types other than POJOs are passed to subscribe as subscribers, as they will likely have\n * their `this` context overwritten.\n *\n * @deprecated As of version 8, RxJS will no longer support altering the\n * context of next functions provided as part of an observer to Subscribe. Instead,\n * you will have access to a subscription or a signal or token that will allow you to do things like\n * unsubscribe and test closed status. Will be removed in v8.\n */\n useDeprecatedNextContext: boolean;\n}\n", "import type { TimerHandle } from './timerHandle';\ntype SetTimeoutFunction = (handler: () => void, timeout?: number, ...args: any[]) => TimerHandle;\ntype ClearTimeoutFunction = (handle: TimerHandle) => void;\n\ninterface TimeoutProvider {\n setTimeout: SetTimeoutFunction;\n clearTimeout: ClearTimeoutFunction;\n delegate:\n | {\n setTimeout: SetTimeoutFunction;\n clearTimeout: ClearTimeoutFunction;\n }\n | undefined;\n}\n\nexport const timeoutProvider: TimeoutProvider = {\n // When accessing the delegate, use the variable rather than `this` so that\n // the functions can be called without being bound to the provider.\n setTimeout(handler: () => void, timeout?: number, ...args) {\n const { delegate } = timeoutProvider;\n if (delegate?.setTimeout) {\n return delegate.setTimeout(handler, timeout, ...args);\n }\n return setTimeout(handler, timeout, ...args);\n },\n clearTimeout(handle) {\n const { delegate } = timeoutProvider;\n return (delegate?.clearTimeout || clearTimeout)(handle as any);\n },\n delegate: undefined,\n};\n", "import { config } from '../config';\nimport { timeoutProvider } from '../scheduler/timeoutProvider';\n\n/**\n * Handles an error on another job either with the user-configured {@link onUnhandledError},\n * or by throwing it on that new job so it can be picked up by `window.onerror`, `process.on('error')`, etc.\n *\n * This should be called whenever there is an error that is out-of-band with the subscription\n * or when an error hits a terminal boundary of the subscription and no error handler was provided.\n *\n * @param err the error to report\n */\nexport function reportUnhandledError(err: any) {\n timeoutProvider.setTimeout(() => {\n const { onUnhandledError } = config;\n if (onUnhandledError) {\n // Execute the user-configured error handler.\n onUnhandledError(err);\n } else {\n // Throw so it is picked up by the runtime's uncaught error mechanism.\n throw err;\n }\n });\n}\n", "/* tslint:disable:no-empty */\nexport function noop() { }\n", "import { CompleteNotification, NextNotification, ErrorNotification } from './types';\n\n/**\n * A completion object optimized for memory use and created to be the\n * same \"shape\" as other notifications in v8.\n * @internal\n */\nexport const COMPLETE_NOTIFICATION = (() => createNotification('C', undefined, undefined) as CompleteNotification)();\n\n/**\n * Internal use only. Creates an optimized error notification that is the same \"shape\"\n * as other notifications.\n * @internal\n */\nexport function errorNotification(error: any): ErrorNotification {\n return createNotification('E', undefined, error) as any;\n}\n\n/**\n * Internal use only. Creates an optimized next notification that is the same \"shape\"\n * as other notifications.\n * @internal\n */\nexport function nextNotification(value: T) {\n return createNotification('N', value, undefined) as NextNotification;\n}\n\n/**\n * Ensures that all notifications created internally have the same \"shape\" in v8.\n *\n * TODO: This is only exported to support a crazy legacy test in `groupBy`.\n * @internal\n */\nexport function createNotification(kind: 'N' | 'E' | 'C', value: any, error: any) {\n return {\n kind,\n value,\n error,\n };\n}\n", "import { config } from '../config';\n\nlet context: { errorThrown: boolean; error: any } | null = null;\n\n/**\n * Handles dealing with errors for super-gross mode. Creates a context, in which\n * any synchronously thrown errors will be passed to {@link captureError}. Which\n * will record the error such that it will be rethrown after the call back is complete.\n * TODO: Remove in v8\n * @param cb An immediately executed function.\n */\nexport function errorContext(cb: () => void) {\n if (config.useDeprecatedSynchronousErrorHandling) {\n const isRoot = !context;\n if (isRoot) {\n context = { errorThrown: false, error: null };\n }\n cb();\n if (isRoot) {\n const { errorThrown, error } = context!;\n context = null;\n if (errorThrown) {\n throw error;\n }\n }\n } else {\n // This is the general non-deprecated path for everyone that\n // isn't crazy enough to use super-gross mode (useDeprecatedSynchronousErrorHandling)\n cb();\n }\n}\n\n/**\n * Captures errors only in super-gross mode.\n * @param err the error to capture\n */\nexport function captureError(err: any) {\n if (config.useDeprecatedSynchronousErrorHandling && context) {\n context.errorThrown = true;\n context.error = err;\n }\n}\n", "import { isFunction } from './util/isFunction';\nimport { Observer, ObservableNotification } from './types';\nimport { isSubscription, Subscription } from './Subscription';\nimport { config } from './config';\nimport { reportUnhandledError } from './util/reportUnhandledError';\nimport { noop } from './util/noop';\nimport { nextNotification, errorNotification, COMPLETE_NOTIFICATION } from './NotificationFactories';\nimport { timeoutProvider } from './scheduler/timeoutProvider';\nimport { captureError } from './util/errorContext';\n\n/**\n * Implements the {@link Observer} interface and extends the\n * {@link Subscription} class. While the {@link Observer} is the public API for\n * consuming the values of an {@link Observable}, all Observers get converted to\n * a Subscriber, in order to provide Subscription-like capabilities such as\n * `unsubscribe`. Subscriber is a common type in RxJS, and crucial for\n * implementing operators, but it is rarely used as a public API.\n *\n * @class Subscriber\n */\nexport class Subscriber extends Subscription implements Observer {\n /**\n * A static factory for a Subscriber, given a (potentially partial) definition\n * of an Observer.\n * @param next The `next` callback of an Observer.\n * @param error The `error` callback of an\n * Observer.\n * @param complete The `complete` callback of an\n * Observer.\n * @return A Subscriber wrapping the (partially defined)\n * Observer represented by the given arguments.\n * @nocollapse\n * @deprecated Do not use. Will be removed in v8. There is no replacement for this\n * method, and there is no reason to be creating instances of `Subscriber` directly.\n * If you have a specific use case, please file an issue.\n */\n static create(next?: (x?: T) => void, error?: (e?: any) => void, complete?: () => void): Subscriber {\n return new SafeSubscriber(next, error, complete);\n }\n\n /** @deprecated Internal implementation detail, do not use directly. Will be made internal in v8. */\n protected isStopped: boolean = false;\n /** @deprecated Internal implementation detail, do not use directly. Will be made internal in v8. */\n protected destination: Subscriber | Observer; // this `any` is the escape hatch to erase extra type param (e.g. R)\n\n /**\n * @deprecated Internal implementation detail, do not use directly. Will be made internal in v8.\n * There is no reason to directly create an instance of Subscriber. This type is exported for typings reasons.\n */\n constructor(destination?: Subscriber | Observer) {\n super();\n if (destination) {\n this.destination = destination;\n // Automatically chain subscriptions together here.\n // if destination is a Subscription, then it is a Subscriber.\n if (isSubscription(destination)) {\n destination.add(this);\n }\n } else {\n this.destination = EMPTY_OBSERVER;\n }\n }\n\n /**\n * The {@link Observer} callback to receive notifications of type `next` from\n * the Observable, with a value. The Observable may call this method 0 or more\n * times.\n * @param {T} [value] The `next` value.\n * @return {void}\n */\n next(value?: T): void {\n if (this.isStopped) {\n handleStoppedNotification(nextNotification(value), this);\n } else {\n this._next(value!);\n }\n }\n\n /**\n * The {@link Observer} callback to receive notifications of type `error` from\n * the Observable, with an attached `Error`. Notifies the Observer that\n * the Observable has experienced an error condition.\n * @param {any} [err] The `error` exception.\n * @return {void}\n */\n error(err?: any): void {\n if (this.isStopped) {\n handleStoppedNotification(errorNotification(err), this);\n } else {\n this.isStopped = true;\n this._error(err);\n }\n }\n\n /**\n * The {@link Observer} callback to receive a valueless notification of type\n * `complete` from the Observable. Notifies the Observer that the Observable\n * has finished sending push-based notifications.\n * @return {void}\n */\n complete(): void {\n if (this.isStopped) {\n handleStoppedNotification(COMPLETE_NOTIFICATION, this);\n } else {\n this.isStopped = true;\n this._complete();\n }\n }\n\n unsubscribe(): void {\n if (!this.closed) {\n this.isStopped = true;\n super.unsubscribe();\n this.destination = null!;\n }\n }\n\n protected _next(value: T): void {\n this.destination.next(value);\n }\n\n protected _error(err: any): void {\n try {\n this.destination.error(err);\n } finally {\n this.unsubscribe();\n }\n }\n\n protected _complete(): void {\n try {\n this.destination.complete();\n } finally {\n this.unsubscribe();\n }\n }\n}\n\n/**\n * This bind is captured here because we want to be able to have\n * compatibility with monoid libraries that tend to use a method named\n * `bind`. In particular, a library called Monio requires this.\n */\nconst _bind = Function.prototype.bind;\n\nfunction bind any>(fn: Fn, thisArg: any): Fn {\n return _bind.call(fn, thisArg);\n}\n\n/**\n * Internal optimization only, DO NOT EXPOSE.\n * @internal\n */\nclass ConsumerObserver implements Observer {\n constructor(private partialObserver: Partial>) {}\n\n next(value: T): void {\n const { partialObserver } = this;\n if (partialObserver.next) {\n try {\n partialObserver.next(value);\n } catch (error) {\n handleUnhandledError(error);\n }\n }\n }\n\n error(err: any): void {\n const { partialObserver } = this;\n if (partialObserver.error) {\n try {\n partialObserver.error(err);\n } catch (error) {\n handleUnhandledError(error);\n }\n } else {\n handleUnhandledError(err);\n }\n }\n\n complete(): void {\n const { partialObserver } = this;\n if (partialObserver.complete) {\n try {\n partialObserver.complete();\n } catch (error) {\n handleUnhandledError(error);\n }\n }\n }\n}\n\nexport class SafeSubscriber extends Subscriber {\n constructor(\n observerOrNext?: Partial> | ((value: T) => void) | null,\n error?: ((e?: any) => void) | null,\n complete?: (() => void) | null\n ) {\n super();\n\n let partialObserver: Partial>;\n if (isFunction(observerOrNext) || !observerOrNext) {\n // The first argument is a function, not an observer. The next\n // two arguments *could* be observers, or they could be empty.\n partialObserver = {\n next: (observerOrNext ?? undefined) as (((value: T) => void) | undefined),\n error: error ?? undefined,\n complete: complete ?? undefined,\n };\n } else {\n // The first argument is a partial observer.\n let context: any;\n if (this && config.useDeprecatedNextContext) {\n // This is a deprecated path that made `this.unsubscribe()` available in\n // next handler functions passed to subscribe. This only exists behind a flag\n // now, as it is *very* slow.\n context = Object.create(observerOrNext);\n context.unsubscribe = () => this.unsubscribe();\n partialObserver = {\n next: observerOrNext.next && bind(observerOrNext.next, context),\n error: observerOrNext.error && bind(observerOrNext.error, context),\n complete: observerOrNext.complete && bind(observerOrNext.complete, context),\n };\n } else {\n // The \"normal\" path. Just use the partial observer directly.\n partialObserver = observerOrNext;\n }\n }\n\n // Wrap the partial observer to ensure it's a full observer, and\n // make sure proper error handling is accounted for.\n this.destination = new ConsumerObserver(partialObserver);\n }\n}\n\nfunction handleUnhandledError(error: any) {\n if (config.useDeprecatedSynchronousErrorHandling) {\n captureError(error);\n } else {\n // Ideal path, we report this as an unhandled error,\n // which is thrown on a new call stack.\n reportUnhandledError(error);\n }\n}\n\n/**\n * An error handler used when no error handler was supplied\n * to the SafeSubscriber -- meaning no error handler was supplied\n * do the `subscribe` call on our observable.\n * @param err The error to handle\n */\nfunction defaultErrorHandler(err: any) {\n throw err;\n}\n\n/**\n * A handler for notifications that cannot be sent to a stopped subscriber.\n * @param notification The notification being sent\n * @param subscriber The stopped subscriber\n */\nfunction handleStoppedNotification(notification: ObservableNotification, subscriber: Subscriber) {\n const { onStoppedNotification } = config;\n onStoppedNotification && timeoutProvider.setTimeout(() => onStoppedNotification(notification, subscriber));\n}\n\n/**\n * The observer used as a stub for subscriptions where the user did not\n * pass any arguments to `subscribe`. Comes with the default error handling\n * behavior.\n */\nexport const EMPTY_OBSERVER: Readonly> & { closed: true } = {\n closed: true,\n next: noop,\n error: defaultErrorHandler,\n complete: noop,\n};\n", "/**\n * Symbol.observable or a string \"@@observable\". Used for interop\n *\n * @deprecated We will no longer be exporting this symbol in upcoming versions of RxJS.\n * Instead polyfill and use Symbol.observable directly *or* use https://www.npmjs.com/package/symbol-observable\n */\nexport const observable: string | symbol = (() => (typeof Symbol === 'function' && Symbol.observable) || '@@observable')();\n", "/**\n * This function takes one parameter and just returns it. Simply put,\n * this is like `(x: T): T => x`.\n *\n * ## Examples\n *\n * This is useful in some cases when using things like `mergeMap`\n *\n * ```ts\n * import { interval, take, map, range, mergeMap, identity } from 'rxjs';\n *\n * const source$ = interval(1000).pipe(take(5));\n *\n * const result$ = source$.pipe(\n * map(i => range(i)),\n * mergeMap(identity) // same as mergeMap(x => x)\n * );\n *\n * result$.subscribe({\n * next: console.log\n * });\n * ```\n *\n * Or when you want to selectively apply an operator\n *\n * ```ts\n * import { interval, take, identity } from 'rxjs';\n *\n * const shouldLimit = () => Math.random() < 0.5;\n *\n * const source$ = interval(1000);\n *\n * const result$ = source$.pipe(shouldLimit() ? take(5) : identity);\n *\n * result$.subscribe({\n * next: console.log\n * });\n * ```\n *\n * @param x Any value that is returned by this function\n * @returns The value passed as the first parameter to this function\n */\nexport function identity(x: T): T {\n return x;\n}\n", "import { identity } from './identity';\nimport { UnaryFunction } from '../types';\n\nexport function pipe(): typeof identity;\nexport function pipe(fn1: UnaryFunction): UnaryFunction;\nexport function pipe(fn1: UnaryFunction, fn2: UnaryFunction): UnaryFunction;\nexport function pipe(fn1: UnaryFunction, fn2: UnaryFunction, fn3: UnaryFunction): UnaryFunction;\nexport function pipe(\n fn1: UnaryFunction,\n fn2: UnaryFunction,\n fn3: UnaryFunction,\n fn4: UnaryFunction\n): UnaryFunction;\nexport function pipe(\n fn1: UnaryFunction,\n fn2: UnaryFunction,\n fn3: UnaryFunction,\n fn4: UnaryFunction,\n fn5: UnaryFunction\n): UnaryFunction;\nexport function pipe(\n fn1: UnaryFunction,\n fn2: UnaryFunction,\n fn3: UnaryFunction,\n fn4: UnaryFunction,\n fn5: UnaryFunction,\n fn6: UnaryFunction\n): UnaryFunction;\nexport function pipe(\n fn1: UnaryFunction,\n fn2: UnaryFunction,\n fn3: UnaryFunction,\n fn4: UnaryFunction,\n fn5: UnaryFunction,\n fn6: UnaryFunction,\n fn7: UnaryFunction\n): UnaryFunction;\nexport function pipe(\n fn1: UnaryFunction,\n fn2: UnaryFunction,\n fn3: UnaryFunction,\n fn4: UnaryFunction,\n fn5: UnaryFunction,\n fn6: UnaryFunction,\n fn7: UnaryFunction,\n fn8: UnaryFunction\n): UnaryFunction;\nexport function pipe(\n fn1: UnaryFunction,\n fn2: UnaryFunction,\n fn3: UnaryFunction,\n fn4: UnaryFunction,\n fn5: UnaryFunction,\n fn6: UnaryFunction,\n fn7: UnaryFunction,\n fn8: UnaryFunction,\n fn9: UnaryFunction\n): UnaryFunction;\nexport function pipe(\n fn1: UnaryFunction,\n fn2: UnaryFunction,\n fn3: UnaryFunction,\n fn4: UnaryFunction,\n fn5: UnaryFunction,\n fn6: UnaryFunction,\n fn7: UnaryFunction,\n fn8: UnaryFunction,\n fn9: UnaryFunction,\n ...fns: UnaryFunction[]\n): UnaryFunction;\n\n/**\n * pipe() can be called on one or more functions, each of which can take one argument (\"UnaryFunction\")\n * and uses it to return a value.\n * It returns a function that takes one argument, passes it to the first UnaryFunction, and then\n * passes the result to the next one, passes that result to the next one, and so on. \n */\nexport function pipe(...fns: Array>): UnaryFunction {\n return pipeFromArray(fns);\n}\n\n/** @internal */\nexport function pipeFromArray(fns: Array>): UnaryFunction {\n if (fns.length === 0) {\n return identity as UnaryFunction;\n }\n\n if (fns.length === 1) {\n return fns[0];\n }\n\n return function piped(input: T): R {\n return fns.reduce((prev: any, fn: UnaryFunction) => fn(prev), input as any);\n };\n}\n", "import { Operator } from './Operator';\nimport { SafeSubscriber, Subscriber } from './Subscriber';\nimport { isSubscription, Subscription } from './Subscription';\nimport { TeardownLogic, OperatorFunction, Subscribable, Observer } from './types';\nimport { observable as Symbol_observable } from './symbol/observable';\nimport { pipeFromArray } from './util/pipe';\nimport { config } from './config';\nimport { isFunction } from './util/isFunction';\nimport { errorContext } from './util/errorContext';\n\n/**\n * A representation of any set of values over any amount of time. This is the most basic building block\n * of RxJS.\n *\n * @class Observable\n */\nexport class Observable implements Subscribable {\n /**\n * @deprecated Internal implementation detail, do not use directly. Will be made internal in v8.\n */\n source: Observable | undefined;\n\n /**\n * @deprecated Internal implementation detail, do not use directly. Will be made internal in v8.\n */\n operator: Operator | undefined;\n\n /**\n * @constructor\n * @param {Function} subscribe the function that is called when the Observable is\n * initially subscribed to. This function is given a Subscriber, to which new values\n * can be `next`ed, or an `error` method can be called to raise an error, or\n * `complete` can be called to notify of a successful completion.\n */\n constructor(subscribe?: (this: Observable, subscriber: Subscriber) => TeardownLogic) {\n if (subscribe) {\n this._subscribe = subscribe;\n }\n }\n\n // HACK: Since TypeScript inherits static properties too, we have to\n // fight against TypeScript here so Subject can have a different static create signature\n /**\n * Creates a new Observable by calling the Observable constructor\n * @owner Observable\n * @method create\n * @param {Function} subscribe? the subscriber function to be passed to the Observable constructor\n * @return {Observable} a new observable\n * @nocollapse\n * @deprecated Use `new Observable()` instead. Will be removed in v8.\n */\n static create: (...args: any[]) => any = (subscribe?: (subscriber: Subscriber) => TeardownLogic) => {\n return new Observable(subscribe);\n };\n\n /**\n * Creates a new Observable, with this Observable instance as the source, and the passed\n * operator defined as the new observable's operator.\n * @method lift\n * @param operator the operator defining the operation to take on the observable\n * @return a new observable with the Operator applied\n * @deprecated Internal implementation detail, do not use directly. Will be made internal in v8.\n * If you have implemented an operator using `lift`, it is recommended that you create an\n * operator by simply returning `new Observable()` directly. See \"Creating new operators from\n * scratch\" section here: https://rxjs.dev/guide/operators\n */\n lift(operator?: Operator): Observable {\n const observable = new Observable();\n observable.source = this;\n observable.operator = operator;\n return observable;\n }\n\n subscribe(observerOrNext?: Partial> | ((value: T) => void)): Subscription;\n /** @deprecated Instead of passing separate callback arguments, use an observer argument. Signatures taking separate callback arguments will be removed in v8. Details: https://rxjs.dev/deprecations/subscribe-arguments */\n subscribe(next?: ((value: T) => void) | null, error?: ((error: any) => void) | null, complete?: (() => void) | null): Subscription;\n /**\n * Invokes an execution of an Observable and registers Observer handlers for notifications it will emit.\n *\n * Use it when you have all these Observables, but still nothing is happening.\n *\n * `subscribe` is not a regular operator, but a method that calls Observable's internal `subscribe` function. It\n * might be for example a function that you passed to Observable's constructor, but most of the time it is\n * a library implementation, which defines what will be emitted by an Observable, and when it be will emitted. This means\n * that calling `subscribe` is actually the moment when Observable starts its work, not when it is created, as it is often\n * the thought.\n *\n * Apart from starting the execution of an Observable, this method allows you to listen for values\n * that an Observable emits, as well as for when it completes or errors. You can achieve this in two\n * of the following ways.\n *\n * The first way is creating an object that implements {@link Observer} interface. It should have methods\n * defined by that interface, but note that it should be just a regular JavaScript object, which you can create\n * yourself in any way you want (ES6 class, classic function constructor, object literal etc.). In particular, do\n * not attempt to use any RxJS implementation details to create Observers - you don't need them. Remember also\n * that your object does not have to implement all methods. If you find yourself creating a method that doesn't\n * do anything, you can simply omit it. Note however, if the `error` method is not provided and an error happens,\n * it will be thrown asynchronously. Errors thrown asynchronously cannot be caught using `try`/`catch`. Instead,\n * use the {@link onUnhandledError} configuration option or use a runtime handler (like `window.onerror` or\n * `process.on('error)`) to be notified of unhandled errors. Because of this, it's recommended that you provide\n * an `error` method to avoid missing thrown errors.\n *\n * The second way is to give up on Observer object altogether and simply provide callback functions in place of its methods.\n * This means you can provide three functions as arguments to `subscribe`, where the first function is equivalent\n * of a `next` method, the second of an `error` method and the third of a `complete` method. Just as in case of an Observer,\n * if you do not need to listen for something, you can omit a function by passing `undefined` or `null`,\n * since `subscribe` recognizes these functions by where they were placed in function call. When it comes\n * to the `error` function, as with an Observer, if not provided, errors emitted by an Observable will be thrown asynchronously.\n *\n * You can, however, subscribe with no parameters at all. This may be the case where you're not interested in terminal events\n * and you also handled emissions internally by using operators (e.g. using `tap`).\n *\n * Whichever style of calling `subscribe` you use, in both cases it returns a Subscription object.\n * This object allows you to call `unsubscribe` on it, which in turn will stop the work that an Observable does and will clean\n * up all resources that an Observable used. Note that cancelling a subscription will not call `complete` callback\n * provided to `subscribe` function, which is reserved for a regular completion signal that comes from an Observable.\n *\n * Remember that callbacks provided to `subscribe` are not guaranteed to be called asynchronously.\n * It is an Observable itself that decides when these functions will be called. For example {@link of}\n * by default emits all its values synchronously. Always check documentation for how given Observable\n * will behave when subscribed and if its default behavior can be modified with a `scheduler`.\n *\n * #### Examples\n *\n * Subscribe with an {@link guide/observer Observer}\n *\n * ```ts\n * import { of } from 'rxjs';\n *\n * const sumObserver = {\n * sum: 0,\n * next(value) {\n * console.log('Adding: ' + value);\n * this.sum = this.sum + value;\n * },\n * error() {\n * // We actually could just remove this method,\n * // since we do not really care about errors right now.\n * },\n * complete() {\n * console.log('Sum equals: ' + this.sum);\n * }\n * };\n *\n * of(1, 2, 3) // Synchronously emits 1, 2, 3 and then completes.\n * .subscribe(sumObserver);\n *\n * // Logs:\n * // 'Adding: 1'\n * // 'Adding: 2'\n * // 'Adding: 3'\n * // 'Sum equals: 6'\n * ```\n *\n * Subscribe with functions ({@link deprecations/subscribe-arguments deprecated})\n *\n * ```ts\n * import { of } from 'rxjs'\n *\n * let sum = 0;\n *\n * of(1, 2, 3).subscribe(\n * value => {\n * console.log('Adding: ' + value);\n * sum = sum + value;\n * },\n * undefined,\n * () => console.log('Sum equals: ' + sum)\n * );\n *\n * // Logs:\n * // 'Adding: 1'\n * // 'Adding: 2'\n * // 'Adding: 3'\n * // 'Sum equals: 6'\n * ```\n *\n * Cancel a subscription\n *\n * ```ts\n * import { interval } from 'rxjs';\n *\n * const subscription = interval(1000).subscribe({\n * next(num) {\n * console.log(num)\n * },\n * complete() {\n * // Will not be called, even when cancelling subscription.\n * console.log('completed!');\n * }\n * });\n *\n * setTimeout(() => {\n * subscription.unsubscribe();\n * console.log('unsubscribed!');\n * }, 2500);\n *\n * // Logs:\n * // 0 after 1s\n * // 1 after 2s\n * // 'unsubscribed!' after 2.5s\n * ```\n *\n * @param {Observer|Function} observerOrNext (optional) Either an observer with methods to be called,\n * or the first of three possible handlers, which is the handler for each value emitted from the subscribed\n * Observable.\n * @param {Function} error (optional) A handler for a terminal event resulting from an error. If no error handler is provided,\n * the error will be thrown asynchronously as unhandled.\n * @param {Function} complete (optional) A handler for a terminal event resulting from successful completion.\n * @return {Subscription} a subscription reference to the registered handlers\n * @method subscribe\n */\n subscribe(\n observerOrNext?: Partial> | ((value: T) => void) | null,\n error?: ((error: any) => void) | null,\n complete?: (() => void) | null\n ): Subscription {\n const subscriber = isSubscriber(observerOrNext) ? observerOrNext : new SafeSubscriber(observerOrNext, error, complete);\n\n errorContext(() => {\n const { operator, source } = this;\n subscriber.add(\n operator\n ? // We're dealing with a subscription in the\n // operator chain to one of our lifted operators.\n operator.call(subscriber, source)\n : source\n ? // If `source` has a value, but `operator` does not, something that\n // had intimate knowledge of our API, like our `Subject`, must have\n // set it. We're going to just call `_subscribe` directly.\n this._subscribe(subscriber)\n : // In all other cases, we're likely wrapping a user-provided initializer\n // function, so we need to catch errors and handle them appropriately.\n this._trySubscribe(subscriber)\n );\n });\n\n return subscriber;\n }\n\n /** @internal */\n protected _trySubscribe(sink: Subscriber): TeardownLogic {\n try {\n return this._subscribe(sink);\n } catch (err) {\n // We don't need to return anything in this case,\n // because it's just going to try to `add()` to a subscription\n // above.\n sink.error(err);\n }\n }\n\n /**\n * Used as a NON-CANCELLABLE means of subscribing to an observable, for use with\n * APIs that expect promises, like `async/await`. You cannot unsubscribe from this.\n *\n * **WARNING**: Only use this with observables you *know* will complete. If the source\n * observable does not complete, you will end up with a promise that is hung up, and\n * potentially all of the state of an async function hanging out in memory. To avoid\n * this situation, look into adding something like {@link timeout}, {@link take},\n * {@link takeWhile}, or {@link takeUntil} amongst others.\n *\n * #### Example\n *\n * ```ts\n * import { interval, take } from 'rxjs';\n *\n * const source$ = interval(1000).pipe(take(4));\n *\n * async function getTotal() {\n * let total = 0;\n *\n * await source$.forEach(value => {\n * total += value;\n * console.log('observable -> ' + value);\n * });\n *\n * return total;\n * }\n *\n * getTotal().then(\n * total => console.log('Total: ' + total)\n * );\n *\n * // Expected:\n * // 'observable -> 0'\n * // 'observable -> 1'\n * // 'observable -> 2'\n * // 'observable -> 3'\n * // 'Total: 6'\n * ```\n *\n * @param next a handler for each value emitted by the observable\n * @return a promise that either resolves on observable completion or\n * rejects with the handled error\n */\n forEach(next: (value: T) => void): Promise;\n\n /**\n * @param next a handler for each value emitted by the observable\n * @param promiseCtor a constructor function used to instantiate the Promise\n * @return a promise that either resolves on observable completion or\n * rejects with the handled error\n * @deprecated Passing a Promise constructor will no longer be available\n * in upcoming versions of RxJS. This is because it adds weight to the library, for very\n * little benefit. If you need this functionality, it is recommended that you either\n * polyfill Promise, or you create an adapter to convert the returned native promise\n * to whatever promise implementation you wanted. Will be removed in v8.\n */\n forEach(next: (value: T) => void, promiseCtor: PromiseConstructorLike): Promise;\n\n forEach(next: (value: T) => void, promiseCtor?: PromiseConstructorLike): Promise {\n promiseCtor = getPromiseCtor(promiseCtor);\n\n return new promiseCtor((resolve, reject) => {\n const subscriber = new SafeSubscriber({\n next: (value) => {\n try {\n next(value);\n } catch (err) {\n reject(err);\n subscriber.unsubscribe();\n }\n },\n error: reject,\n complete: resolve,\n });\n this.subscribe(subscriber);\n }) as Promise;\n }\n\n /** @internal */\n protected _subscribe(subscriber: Subscriber): TeardownLogic {\n return this.source?.subscribe(subscriber);\n }\n\n /**\n * An interop point defined by the es7-observable spec https://github.com/zenparsing/es-observable\n * @method Symbol.observable\n * @return {Observable} this instance of the observable\n */\n [Symbol_observable]() {\n return this;\n }\n\n /* tslint:disable:max-line-length */\n pipe(): Observable;\n pipe(op1: OperatorFunction): Observable;\n pipe(op1: OperatorFunction, op2: OperatorFunction): Observable;\n pipe(op1: OperatorFunction, op2: OperatorFunction, op3: OperatorFunction): Observable;\n pipe(\n op1: OperatorFunction,\n op2: OperatorFunction,\n op3: OperatorFunction,\n op4: OperatorFunction\n ): Observable;\n pipe(\n op1: OperatorFunction,\n op2: OperatorFunction,\n op3: OperatorFunction,\n op4: OperatorFunction,\n op5: OperatorFunction\n ): Observable;\n pipe(\n op1: OperatorFunction,\n op2: OperatorFunction,\n op3: OperatorFunction,\n op4: OperatorFunction,\n op5: OperatorFunction,\n op6: OperatorFunction\n ): Observable;\n pipe(\n op1: OperatorFunction,\n op2: OperatorFunction,\n op3: OperatorFunction,\n op4: OperatorFunction,\n op5: OperatorFunction,\n op6: OperatorFunction,\n op7: OperatorFunction\n ): Observable;\n pipe(\n op1: OperatorFunction,\n op2: OperatorFunction,\n op3: OperatorFunction,\n op4: OperatorFunction,\n op5: OperatorFunction,\n op6: OperatorFunction,\n op7: OperatorFunction,\n op8: OperatorFunction\n ): Observable;\n pipe(\n op1: OperatorFunction,\n op2: OperatorFunction,\n op3: OperatorFunction,\n op4: OperatorFunction,\n op5: OperatorFunction,\n op6: OperatorFunction,\n op7: OperatorFunction,\n op8: OperatorFunction,\n op9: OperatorFunction\n ): Observable;\n pipe(\n op1: OperatorFunction,\n op2: OperatorFunction,\n op3: OperatorFunction,\n op4: OperatorFunction,\n op5: OperatorFunction,\n op6: OperatorFunction,\n op7: OperatorFunction,\n op8: OperatorFunction,\n op9: OperatorFunction,\n ...operations: OperatorFunction[]\n ): Observable;\n /* tslint:enable:max-line-length */\n\n /**\n * Used to stitch together functional operators into a chain.\n * @method pipe\n * @return {Observable} the Observable result of all of the operators having\n * been called in the order they were passed in.\n *\n * ## Example\n *\n * ```ts\n * import { interval, filter, map, scan } from 'rxjs';\n *\n * interval(1000)\n * .pipe(\n * filter(x => x % 2 === 0),\n * map(x => x + x),\n * scan((acc, x) => acc + x)\n * )\n * .subscribe(x => console.log(x));\n * ```\n */\n pipe(...operations: OperatorFunction[]): Observable {\n return pipeFromArray(operations)(this);\n }\n\n /* tslint:disable:max-line-length */\n /** @deprecated Replaced with {@link firstValueFrom} and {@link lastValueFrom}. Will be removed in v8. Details: https://rxjs.dev/deprecations/to-promise */\n toPromise(): Promise;\n /** @deprecated Replaced with {@link firstValueFrom} and {@link lastValueFrom}. Will be removed in v8. Details: https://rxjs.dev/deprecations/to-promise */\n toPromise(PromiseCtor: typeof Promise): Promise;\n /** @deprecated Replaced with {@link firstValueFrom} and {@link lastValueFrom}. Will be removed in v8. Details: https://rxjs.dev/deprecations/to-promise */\n toPromise(PromiseCtor: PromiseConstructorLike): Promise;\n /* tslint:enable:max-line-length */\n\n /**\n * Subscribe to this Observable and get a Promise resolving on\n * `complete` with the last emission (if any).\n *\n * **WARNING**: Only use this with observables you *know* will complete. If the source\n * observable does not complete, you will end up with a promise that is hung up, and\n * potentially all of the state of an async function hanging out in memory. To avoid\n * this situation, look into adding something like {@link timeout}, {@link take},\n * {@link takeWhile}, or {@link takeUntil} amongst others.\n *\n * @method toPromise\n * @param [promiseCtor] a constructor function used to instantiate\n * the Promise\n * @return A Promise that resolves with the last value emit, or\n * rejects on an error. If there were no emissions, Promise\n * resolves with undefined.\n * @deprecated Replaced with {@link firstValueFrom} and {@link lastValueFrom}. Will be removed in v8. Details: https://rxjs.dev/deprecations/to-promise\n */\n toPromise(promiseCtor?: PromiseConstructorLike): Promise {\n promiseCtor = getPromiseCtor(promiseCtor);\n\n return new promiseCtor((resolve, reject) => {\n let value: T | undefined;\n this.subscribe(\n (x: T) => (value = x),\n (err: any) => reject(err),\n () => resolve(value)\n );\n }) as Promise;\n }\n}\n\n/**\n * Decides between a passed promise constructor from consuming code,\n * A default configured promise constructor, and the native promise\n * constructor and returns it. If nothing can be found, it will throw\n * an error.\n * @param promiseCtor The optional promise constructor to passed by consuming code\n */\nfunction getPromiseCtor(promiseCtor: PromiseConstructorLike | undefined) {\n return promiseCtor ?? config.Promise ?? Promise;\n}\n\nfunction isObserver(value: any): value is Observer {\n return value && isFunction(value.next) && isFunction(value.error) && isFunction(value.complete);\n}\n\nfunction isSubscriber(value: any): value is Subscriber {\n return (value && value instanceof Subscriber) || (isObserver(value) && isSubscription(value));\n}\n", "import { Observable } from '../Observable';\nimport { Subscriber } from '../Subscriber';\nimport { OperatorFunction } from '../types';\nimport { isFunction } from './isFunction';\n\n/**\n * Used to determine if an object is an Observable with a lift function.\n */\nexport function hasLift(source: any): source is { lift: InstanceType['lift'] } {\n return isFunction(source?.lift);\n}\n\n/**\n * Creates an `OperatorFunction`. Used to define operators throughout the library in a concise way.\n * @param init The logic to connect the liftedSource to the subscriber at the moment of subscription.\n */\nexport function operate(\n init: (liftedSource: Observable, subscriber: Subscriber) => (() => void) | void\n): OperatorFunction {\n return (source: Observable) => {\n if (hasLift(source)) {\n return source.lift(function (this: Subscriber, liftedSource: Observable) {\n try {\n return init(liftedSource, this);\n } catch (err) {\n this.error(err);\n }\n });\n }\n throw new TypeError('Unable to lift unknown Observable type');\n };\n}\n", "import { Subscriber } from '../Subscriber';\n\n/**\n * Creates an instance of an `OperatorSubscriber`.\n * @param destination The downstream subscriber.\n * @param onNext Handles next values, only called if this subscriber is not stopped or closed. Any\n * error that occurs in this function is caught and sent to the `error` method of this subscriber.\n * @param onError Handles errors from the subscription, any errors that occur in this handler are caught\n * and send to the `destination` error handler.\n * @param onComplete Handles completion notification from the subscription. Any errors that occur in\n * this handler are sent to the `destination` error handler.\n * @param onFinalize Additional teardown logic here. This will only be called on teardown if the\n * subscriber itself is not already closed. This is called after all other teardown logic is executed.\n */\nexport function createOperatorSubscriber