func newHeadsScanner()

in v1storage/heads.go [53:90]

• 36 lines of code
• 10 McCabe index (conditional complexity)

func newHeadsScanner(filename string) *headsScanner {
	hs := &headsScanner{}
	defer func() {
		if hs.f != nil && hs.err != nil {
			hs.f.Close()
		}
	}()

	if hs.f, hs.err = os.Open(filename); hs.err != nil {
		return hs
	}
	hs.r = bufio.NewReaderSize(hs.f, fileBufSize)

	buf := make([]byte, len(headsMagicString))
	if _, hs.err = io.ReadFull(hs.r, buf); hs.err != nil {
		return hs
	}
	magic := string(buf)
	if magic != headsMagicString {
		hs.err = fmt.Errorf(
			"unexpected magic string, want %q, got %q",
			headsMagicString, magic,
		)
		return hs
	}
	hs.version, hs.err = binary.ReadVarint(hs.r)
	if (hs.version != headsFormatVersion && hs.version != headsFormatLegacyVersion) || hs.err != nil {
		hs.err = fmt.Errorf(
			"unknown or unreadable heads format version, want %d, got %d, error: %s",
			headsFormatVersion, hs.version, hs.err,
		)
		return hs
	}
	if hs.seriesTotal, hs.err = codable.DecodeUint64(hs.r); hs.err != nil {
		return hs
	}
	return hs
}