Function readRawGoBuildID

builder/buildid.go:111–127

The Go toolchain stores a build ID in the binary that we can use, as a fallback if binary file specific build IDs can't be obtained. This function reads that build ID from the binary.

(f *os.File, prefixSize int)

// fallback if binary file specific build IDs can't be obtained.
// This function reads that build ID from the binary.
func readRawGoBuildID(f *os.File, prefixSize int) ([]byte, error) {
	fileStart := make([]byte, prefixSize)
	_, err := io.ReadFull(f, fileStart)
	if err != nil {
		return nil, fmt.Errorf("could not read build id from %s: %v", f.Name(), err)
	}
	index := bytes.Index(fileStart, []byte("\xff Go build ID: \""))
	if index < 0 || index > len(fileStart)-103 {
		return nil, fmt.Errorf("could not find build id in %s", f.Name())
	}
	buf := fileStart[index : index+103]
	if bytes.HasPrefix(buf, []byte("\xff Go build ID: \"")) && bytes.HasSuffix(buf, []byte("\"\n \xff")) {
		return buf[len("\xff Go build ID: \"") : len(buf)-1], nil
	}

	return nil, nil
}