Method readExtension

plumbing/format/index/decoder.go:273–318

(idx *Index)

}

func (d *Decoder) readExtension(idx *Index) error {
	var header [4]byte

	if _, err := io.ReadFull(d.r, header[:]); err != nil {
		return err
	}

	r, err := d.getExtensionReader()
	if err != nil {
		return err
	}

	switch {
	case bytes.Equal(header[:], treeExtSignature):
		idx.Cache = &Tree{}
		d := &treeExtensionDecoder{r}
		if err := d.Decode(idx.Cache); err != nil {
			return err
		}
	case bytes.Equal(header[:], resolveUndoExtSignature):
		idx.ResolveUndo = &ResolveUndo{}
		d := &resolveUndoDecoder{r}
		if err := d.Decode(idx.ResolveUndo); err != nil {
			return err
		}
	case bytes.Equal(header[:], endOfIndexEntryExtSignature):
		idx.EndOfIndexEntry = &EndOfIndexEntry{}
		d := &endOfIndexEntryDecoder{r}
		if err := d.Decode(idx.EndOfIndexEntry); err != nil {
			return err
		}
	default:
		// See https://git-scm.com/docs/index-format, which says:
		// If the first byte is 'A'..'Z' the extension is optional and can be ignored.
		if header[0] < 'A' || header[0] > 'Z' {
			return ErrUnknownExtension
		}

		d := &unknownExtensionDecoder{r}
		if err := d.Decode(); err != nil {
			return err
		}
	}

	return nil
}

func (d *Decoder) getExtensionReader() (*bufio.Reader, error) {
	len, err := binary.ReadUint32(d.r)