func (pk *PackReader) extractAt(off int64) (typ int, data []byte, err error) {
var buf [16]byte // 109-bit sizes should be enough for everybody.
_, err = pk.pack.ReadAt(buf[:], off)
if err == io.EOF || err == io.ErrUnexpectedEOF {
err = nil
}
if err != nil {
return
}
varint, n := binary.Uvarint(buf[:])
objsize := int64((varint>>7)<<4 | (varint & 0xf))
objtype := int(varint>>4) & 0x7 // 3 bits.
switch objtype {
case pkCommit, pkTree, pkBlob, pkTag:
// objsize is the *uncompressed* size.
data = make([]byte, objsize)
n, err := readCompressed(pk.pack, off+int64(n), data)
return objtype, data[:n], err
case pkRefDelta:
// Ref delta: parent hash (20 bytes) + deflated delta (objsize bytes)
var parent Hash
_, err := pk.pack.ReadAt(parent[:], off+int64(n))
if err != nil {
return typ, data, err
}
patch := make([]byte, objsize)
_, err = readCompressed(pk.pack, off+int64(n)+20, patch)
// FIXME: check that parent object is always in the same pack.
typ, data, err = pk.extract(parent)
if err != nil {
return typ, patch, err
}
data, err = gitdelta.Patch(data, patch)
if err != nil {
return typ, patch, err
}
return typ, data, err
case pkOfsDelta:
// Offset delta: distance to parent (varint bytes) + deflated delta (objsize bytes)
parentOff, n2, err := readVaroffset(pk.pack, off+int64(n))
if err != nil {
return objtype, data, err
}
patch := make([]byte, objsize)
_, err = readCompressed(pk.pack, off+int64(n+n2), patch)
typ, data, err = pk.extractAt(off - parentOff)
if err != nil {
return typ, patch, err
}
data, err = gitdelta.Patch(data, patch)
if err != nil {
return typ, patch, err
}
return typ, data, err
}
return typ, data, errInvalidPackEntryType
}
// Patch applies a diff on a revision and returns a new revision patched to the
// latest version.
//
// TODO NOTE TODO NOTE This function will not be compleeted until the Revision
// struct is moved inside shared application code so that the client
// application can use it.
func (r *Revision) Patch(diff []byte) *Revision {
oldbytes := r.bytes()
patched, err := gitdelta.Patch(oldbytes, diff)
if err != nil {
panic(err)
}
content := make([]string, 0)
reader := bytes.NewReader(patched)
scanner := bufio.NewScanner(reader)
for scanner.Scan() {
item := scanner.Text()
if item != "" {
content = append(content, item)
}
}
if err := scanner.Err(); err != nil {
panic(err)
}
return NewRevision(content)
}