go-rosbag

Go Rosbag parser. Designed to provide ease of use, speed, and streamability.

Usage

View Messages as map[string]interface{}

package main

import (
	"fmt"
	"io"
	"os"

	"github.com/lherman-cs/go-rosbag"
)

func main() {
	f, _ := os.Open("example.bag")
	defer f.Close()

	decoder := rosbag.NewDecoder(f)
	for {
		record, err := decoder.Read()
		if err == io.EOF {
			break
		}

		switch record := record.(type) {
		case *rosbag.RecordMessageData:
			data := make(map[string]interface{})
			// After ViewAs gets called, the variable "data" will be used to map
			// the underlying buffer to Go data structures, and they'll SHARE the
			// same underlying buffer.
			_ = record.ViewAs(data)
			fmt.Println(data)
		}
    
    		// Mark the current record is no longer used, the underlying buffer can be reused.
		record.Close()
	}
}

View Messages as structs

package main

import (
	"fmt"
	"io"
	"os"

	"github.com/lherman-cs/go-rosbag"
)

type Pixel struct {
	R uint8	`rosbag:"r"`
	G uint8	`rosbag:"g"`
	B uint8	`rosbag:"b"`
}

func main() {
	f, _ := os.Open("example.bag")
	defer f.Close()

	decoder := rosbag.NewDecoder(f)
	for {
		record, err := decoder.Read()
		if err == io.EOF {
			break
		}

		switch record := record.(type) {
		case *rosbag.RecordMessageData:
			if record.ConnectionHeader().Topic == "/pixel" {
				var pixel Pixel
				_ = record.ViewAs(&pixel)
				fmt.Println(pixel)
			}
		}
    
    		// Mark the current record is no longer used, the underlying buffer can be reused.
		record.Close()
	}
}

Data Type Mapping

Primitive Types

ROS Type	Go Type
bool	bool
int8	int8
byte	int8
uint8	uint8
char	uint8
int16	int16
uint16	uint16
int32	uint32
int64	uint64
float32	float32
float64	float64
string	string
time	time.Time
duration	time.Duration

Array Handling

Both fixed-length and variable-length arrays are mapped to Go slices. For example, uint8[] with a length of 3 and uint8[3] will be mapped to []uint8 in Go.

Benchmark

Hardware specs:

• Model: MacBook Pro (15-inch, 2017)
• Processor: 2.8 GHz Quad-Core Intel Core i7
• Memory: 16 GB 2133 MHz LPDDR3
• Storage: 256GB PCIe-based onboard SSD

The following benchmark result (source) was taken by parsing a 696 MB rosbag file from webviz. The bag contains frames and metadata from a car.

Time taken: 147 ms
Throughput: 4.59 GB/s
Memory usage: 33.60 MB

For a reference, time cat <bag> > /dev/null takes 118 ms. This means, go-rosbag only adds 29 ms to the total runtime!

Examples

Please see the examples directory within this repository.

Code Coverage

Currently, the unit tests only cover the happy path, and it's not extensive as I want it to be. I'm still working on adding coverage during my free time.

Alternatives

There are two known alternatives to go-rosbag (at least that I know of):

• https://github.com/starship-technologies/gobag: This project seems to be lacking a good way to process large rosbags, and unmarshall messages to structs.
• https://github.com/brychanrobot/goros/blob/master/rosbag.go: This project seems to be incomplete and abandoned.

Contributing

Any contribution is welcomed! I will review pull requests as soon as possible.

License

go-rosbag is licensed under Apache license version 2.0. See LICENSE file.