package index import ( "bytes" "crypto/sha1" "errors" "hash" "io" "time" "gopkg.in/src-d/go-git.v4/utils/binary" ) var ( // EncodeVersionSupported is the range of supported index versions EncodeVersionSupported uint32 = 2 // ErrInvalidTimestamp is returned by Encode if a Index with a Entry with // negative timestamp values ErrInvalidTimestamp = errors.New("negative timestamps are not allowed") ) // An Encoder writes an Index to an output stream. type Encoder struct { w io.Writer hash hash.Hash } // NewEncoder returns a new encoder that writes to w. func NewEncoder(w io.Writer) *Encoder { h := sha1.New() mw := io.MultiWriter(w, h) return &Encoder{mw, h} } // Encode writes the Index to the stream of the encoder. func (e *Encoder) Encode(idx *Index) error { // TODO: support versions v3 and v4 // TODO: support extensions if idx.Version != EncodeVersionSupported { return ErrUnsupportedVersion } if err := e.encodeHeader(idx); err != nil { return err } if err := e.encodeEntries(idx); err != nil { return err } return e.encodeFooter() } func (e *Encoder) encodeHeader(idx *Index) error { return binary.Write(e.w, indexSignature, idx.Version, uint32(len(idx.Entries)), ) } func (e *Encoder) encodeEntries(idx *Index) error { for _, entry := range idx.Entries { if err := e.encodeEntry(&entry); err != nil { return err } wrote := entryHeaderLength + len(entry.Name) if err := e.padEntry(wrote); err != nil { return err } } return nil } func (e *Encoder) encodeEntry(entry *Entry) error { if entry.IntentToAdd || entry.SkipWorktree { return ErrUnsupportedVersion } sec, nsec, err := e.timeToUint32(&entry.CreatedAt) if err != nil { return err } msec, mnsec, err := e.timeToUint32(&entry.ModifiedAt) if err != nil { return err } flags := uint16(entry.Stage&0x3) << 12 if l := len(entry.Name); l < nameMask { flags |= uint16(l) } else { flags |= nameMask } flow := []interface{}{ sec, nsec, msec, mnsec, entry.Dev, entry.Inode, entry.Mode, entry.UID, entry.GID, entry.Size, entry.Hash[:], flags, } if err := binary.Write(e.w, flow...); err != nil { return err } return binary.Write(e.w, []byte(entry.Name)) } func (e *Encoder) timeToUint32(t *time.Time) (uint32, uint32, error) { if t.IsZero() { return 0, 0, nil } if t.Unix() < 0 || t.UnixNano() < 0 { return 0, 0, ErrInvalidTimestamp } return uint32(t.Unix()), uint32(t.Nanosecond()), nil } func (e *Encoder) padEntry(wrote int) error { padLen := 8 - wrote%8 _, err := e.w.Write(bytes.Repeat([]byte{'\x00'}, padLen)) return err } func (e *Encoder) encodeFooter() error { return binary.Write(e.w, e.hash.Sum(nil)) }