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Instead of registering a single method to implement a callback interface, foreign code now registers a VTable. VTable sounds fancy, but it's just a repr(C) struct where each field is a callback function. This gives us some more flexibility with the method signatures. Before, all arguments were passed using a RustBuffer, but not all FFI types can be written to a RustBuffer. In particular, I want to be able to pass callback function pointers. This also makes the callback interface FFI closer to the Rust one. I wanted to make it match exactly, but it didn't work out. Unfortunately, we can't directly return the return value on Python because of an old ctypes bug (https://bugs.python.org/issue5710). Instead, input an out param for the return type. The other main possibility would be to change `RustBuffer` to be a simple `*mut u8` (#1779), which would then be returnable by Python. However, it seems bad to restrict ourselves from ever returning a struct in the future. Eventually, we want to stop using `RustBuffer` for all complex data types and that probably means using a struct instead in some cases. Renamed `CALL_PANIC` to `CALL_UNEXPECTED_ERROR` in the foreign bindings templates. This matches the name in the Rust code and makes more sense for foreign trait implementations. Switched the keywords fixture tests to use traits rather than callback interfaces. The old tests were testing unsupported things like returning callback interfaces which just happened to pass. Removed the reexport-scaffolding-macro fixture. I don't think this one is giving us a lot of value anymore and I don't want to keep updating it when the FFI changes.
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143 changes: 53 additions & 90 deletions
143
uniffi_bindgen/src/bindings/kotlin/templates/CallbackInterfaceImpl.kt
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -1,107 +1,70 @@ | ||
| {% if self.include_once_check("CallbackInterfaceRuntime.kt") %}{% include "CallbackInterfaceRuntime.kt" %}{% endif %} | ||
|
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| // Implement the foreign callback handler for {{ interface_name }} | ||
| internal class {{ callback_handler_class }} : ForeignCallback { | ||
| @Suppress("TooGenericExceptionCaught") | ||
| override fun invoke(handle: Handle, method: Int, argsData: Pointer, argsLen: Int, outBuf: RustBufferByReference): Int { | ||
| val cb = {{ ffi_converter_name }}.handleMap.get(handle) | ||
| return when (method) { | ||
| IDX_CALLBACK_FREE -> { | ||
| {{ ffi_converter_name }}.handleMap.remove(handle) | ||
| {%- let trait_impl=format!("uniffiCallbackInterface{}", name) %} | ||
|
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||
| // Successful return | ||
| // See docs of ForeignCallback in `uniffi_core/src/ffi/foreigncallbacks.rs` | ||
| UNIFFI_CALLBACK_SUCCESS | ||
| } | ||
| {% for meth in methods.iter() -%} | ||
| {% let method_name = format!("invoke_{}", meth.name())|fn_name -%} | ||
| {{ loop.index }} -> { | ||
| // Call the method, write to outBuf and return a status code | ||
| // See docs of ForeignCallback in `uniffi_core/src/ffi/foreigncallbacks.rs` for info | ||
| try { | ||
| this.{{ method_name }}(cb, argsData, argsLen, outBuf) | ||
| } catch (e: Throwable) { | ||
| // Unexpected error | ||
| try { | ||
| // Try to serialize the error into a string | ||
| outBuf.setValue({{ Type::String.borrow()|ffi_converter_name }}.lower(e.toString())) | ||
| } catch (e: Throwable) { | ||
| // If that fails, then it's time to give up and just return | ||
| } | ||
| UNIFFI_CALLBACK_UNEXPECTED_ERROR | ||
| } | ||
| } | ||
| {% endfor %} | ||
| else -> { | ||
| // An unexpected error happened. | ||
| // See docs of ForeignCallback in `uniffi_core/src/ffi/foreigncallbacks.rs` | ||
| try { | ||
| // Try to serialize the error into a string | ||
| outBuf.setValue({{ Type::String.borrow()|ffi_converter_name }}.lower("Invalid Callback index")) | ||
| } catch (e: Throwable) { | ||
| // If that fails, then it's time to give up and just return | ||
| } | ||
| UNIFFI_CALLBACK_UNEXPECTED_ERROR | ||
| // Put the implementation in an object so we don't pollute the top-level namespace | ||
| internal object {{ trait_impl }} { | ||
| {%- for (ffi_callback, meth) in vtable_methods.iter() %} | ||
| internal object {{ meth.name()|var_name }}: {{ ffi_callback.name()|ffi_callback_name }} { | ||
| override fun callback( | ||
| {%- for arg in ffi_callback.arguments() -%} | ||
| {{ arg.name().borrow()|var_name }}: {{ arg.type_().borrow()|ffi_type_name_by_value }}, | ||
| {%- endfor -%} | ||
| {%- if ffi_callback.has_rust_call_status_arg() -%} | ||
| uniffiCallStatus: RustCallStatus, | ||
| {%- endif -%} | ||
| ) | ||
| {%- match ffi_callback.return_type() %} | ||
| {%- when Some(return_type) %}: {{ return_type|ffi_type_name_by_value }}, | ||
| {%- when None %} | ||
| {%- endmatch %} { | ||
| val uniffiObj = {{ ffi_converter_name }}.handleMap.get(uniffiHandle) | ||
| val makeCall = { -> | ||
| uniffiObj.{{ meth.name()|fn_name() }}( | ||
| {%- for arg in meth.arguments() %} | ||
| {{ arg|lift_fn }}({{ arg.name()|var_name }}), | ||
| {%- endfor %} | ||
| ) | ||
| } | ||
| } | ||
| } | ||
|
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| {% for meth in methods.iter() -%} | ||
| {% let method_name = format!("invoke_{}", meth.name())|fn_name %} | ||
| @Suppress("UNUSED_PARAMETER") | ||
| private fun {{ method_name }}(kotlinCallbackInterface: {{ interface_name }}, argsData: Pointer, argsLen: Int, outBuf: RustBufferByReference): Int { | ||
| {%- if meth.arguments().len() > 0 %} | ||
| val argsBuf = argsData.getByteBuffer(0, argsLen.toLong()).also { | ||
| it.order(ByteOrder.BIG_ENDIAN) | ||
| } | ||
| {%- endif %} | ||
| {%- match meth.return_type() %} | ||
| {%- when Some(return_type) %} | ||
| val writeReturn = { value: {{ return_type|type_name(ci) }} -> uniffiOutReturn.setValue({{ return_type|lower_fn }}(value)) } | ||
| {%- when None %} | ||
| val writeReturn = { _: Unit -> Unit } | ||
| {%- endmatch %} | ||
|
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||
| {%- match meth.return_type() %} | ||
| {%- when Some with (return_type) %} | ||
| fun makeCall() : Int { | ||
| val returnValue = kotlinCallbackInterface.{{ meth.name()|fn_name }}( | ||
| {%- for arg in meth.arguments() %} | ||
| {{ arg|read_fn }}(argsBuf) | ||
| {% if !loop.last %}, {% endif %} | ||
| {%- endfor %} | ||
| ) | ||
| outBuf.setValue({{ return_type|ffi_converter_name }}.lowerIntoRustBuffer(returnValue)) | ||
| return UNIFFI_CALLBACK_SUCCESS | ||
| } | ||
| {%- when None %} | ||
| fun makeCall() : Int { | ||
| kotlinCallbackInterface.{{ meth.name()|fn_name }}( | ||
| {%- for arg in meth.arguments() %} | ||
| {{ arg|read_fn }}(argsBuf) | ||
| {%- if !loop.last %}, {% endif %} | ||
| {%- endfor %} | ||
| {%- match meth.throws_type() %} | ||
| {%- when None %} | ||
| uniffiTraitInterfaceCall(uniffiCallStatus, makeCall, writeReturn) | ||
| {%- when Some(error_type) %} | ||
| uniffiTraitInterfaceCallWithError( | ||
| uniffiCallStatus, | ||
| makeCall, | ||
| writeReturn, | ||
| { e: {{error_type|type_name(ci) }} -> {{ error_type|lower_fn }}(e) } | ||
| ) | ||
| return UNIFFI_CALLBACK_SUCCESS | ||
| {%- endmatch %} | ||
| } | ||
| {%- endmatch %} | ||
| } | ||
| {%- endfor %} | ||
|
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||
| {%- match meth.throws_type() %} | ||
| {%- when None %} | ||
| fun makeCallAndHandleError() : Int = makeCall() | ||
| {%- when Some(error_type) %} | ||
| fun makeCallAndHandleError() : Int = try { | ||
| makeCall() | ||
| } catch (e: {{ error_type|type_name(ci) }}) { | ||
| // Expected error, serialize it into outBuf | ||
| outBuf.setValue({{ error_type|ffi_converter_name }}.lowerIntoRustBuffer(e)) | ||
| UNIFFI_CALLBACK_ERROR | ||
| internal object uniffiFree: {{ "CallbackInterfaceFree"|ffi_callback_name }} { | ||
| override fun callback(handle: Long) { | ||
| {{ ffi_converter_name }}.handleMap.remove(handle) | ||
| } | ||
| {%- endmatch %} | ||
|
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| return makeCallAndHandleError() | ||
| } | ||
| {% endfor %} | ||
|
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| internal var vtable = {{ vtable|ffi_type_name_by_value }}( | ||
| {%- for (ffi_callback, meth) in vtable_methods.iter() %} | ||
| {{ meth.name()|var_name() }}, | ||
| {%- endfor %} | ||
| uniffiFree | ||
| ) | ||
|
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||
| // Registers the foreign callback with the Rust side. | ||
| // This method is generated for each callback interface. | ||
| internal fun register(lib: _UniFFILib) { | ||
| lib.{{ ffi_init_callback.name() }}(this) | ||
| lib.{{ ffi_init_callback.name() }}(vtable) | ||
| } | ||
| } | ||
|
|
||
| internal val {{ callback_handler_obj }} = {{ callback_handler_class }}() |
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6 changes: 3 additions & 3 deletions
6
uniffi_bindgen/src/bindings/kotlin/templates/CallbackInterfaceTemplate.kt
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