func (idx *PackIndexV2) Decode(reader io.Reader) error {
hash := sha1.New()
r := io.TeeReader(reader, hash)
header := &(idx.packIndexV2Header)
if err := binary.Read(r, binary.BigEndian, header); err != nil {
return err
}
if header.Magic != packIndexV2HeaderMagic {
return errors.New("invalid pack index header")
}
if header.Version != 2 {
return Errorf("unexpected pack index header version %d", header.Version)
}
entryCount := int(header.Fanout[255])
idx.objectNames = make([]core.Sha1, entryCount)
if err := binary.Read(r, binary.BigEndian, idx.objectNames); err != nil {
return err
}
idx.crc32Checksums = make([]core.Crc32, entryCount)
if err := binary.Read(r, binary.BigEndian, idx.crc32Checksums); err != nil {
return err
}
idx.offsets = make([]uint32, entryCount)
if err := binary.Read(r, binary.BigEndian, idx.offsets); err != nil {
return err
}
higherOffsetCount := 0
for _, offset := range idx.offsets {
if (offset >> 31) == 1 {
higherOffsetCount += 1
}
}
idx.higherOffsets = make([]uint64, higherOffsetCount)
if err := binary.Read(r, binary.BigEndian, idx.higherOffsets); err != nil {
return err
}
if err := binary.Read(r, binary.BigEndian, &idx.packfileSha1); err != nil {
return err
}
if err := binary.Read(reader, binary.BigEndian, &idx.packIndexSha1); err != nil {
return err
}
actualSha1 := core.Sha1FromByteSlice(hash.Sum(nil))
if idx.packIndexSha1 != actualSha1 {
return Errorf("pack index SHA-1 is %s, expected %s", actualSha1, idx.packIndexSha1)
}
return nil
}
// Decode takes a reader and treats the stream it yields as an index file and
// parses it. An error is returned if the stream forms an invalid index file.
// Otherwise nil is returned.
//
// If ReaderLen is left as a zero value, then the integrity of the index file
// being decoded will not be verified against the SHA-1 hash located in the
// index file itself. Conversely, if ReaderLen is given a non-zero value, an
// index file may be decoded successfully and still return an error from Decode
// due to failing the integrity verification.
//
// See
// https://www.kernel.org/pub/software/scm/git/docs/technical/index-format.txt
// for more information on the file format.
func (idx *Index) Decode(reader io.Reader) error {
var shaWriter hash.Hash
if idx.ReaderLen != 0 {
shaWriter = sha1.New()
limitWriter := util.SilentLimitWriter(shaWriter, idx.ReaderLen-sha1.Size)
reader = io.TeeReader(reader, limitWriter)
}
r := bufio.NewReader(reader)
header, err := decodeIndexHeader(idx, r)
if err != nil {
return err
}
if err = decodeIndexEntries(idx, r, header.EntriesCount); err != nil {
return err
}
if err = decodeIndexExtensionsAndSha1(idx, r); err != nil {
return err
}
if idx.ReaderLen != 0 && shaWriter != nil {
actualSha1 := core.Sha1FromByteSlice(shaWriter.Sum(nil))
if actualSha1 != idx.sha1 {
return Errorf("index SHA-1 was %s, expected %s", actualSha1, idx.sha1)
}
}
return nil
}
func (idx *PackIndexV1) Decode(reader io.Reader) error {
hash := sha1.New()
r := io.TeeReader(reader, hash)
header := &(idx.packIndexV1Header)
if err := binary.Read(r, binary.BigEndian, header); err != nil {
return err
}
entryCount := int(header.Fanout[255])
idx.entries = make([]packIndexV1Entry, entryCount)
if err := binary.Read(r, binary.BigEndian, idx.entries); err != nil {
return err
}
if err := binary.Read(r, binary.BigEndian, &idx.packfileSha1); err != nil {
return err
}
if err := binary.Read(reader, binary.BigEndian, &idx.packIndexSha1); err != nil {
return err
}
actualSha1 := core.Sha1FromByteSlice(hash.Sum(nil))
if idx.packIndexSha1 != actualSha1 {
return Errorf("pack index SHA-1 is %s, expected %s", actualSha1, idx.packIndexSha1)
}
return nil
}
func tryReadSha1(r *bufio.Reader) (sha1 core.Sha1, err error) {
sha1Size := 20
if tentativeSha1, _ := r.Peek(sha1Size + 1); len(tentativeSha1) == sha1Size {
return core.Sha1FromByteSlice(tentativeSha1), nil
} else {
return core.Sha1{}, errSha1NotYetReached
}
}