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|
package packfile
import (
"compress/zlib"
"crypto/sha1"
"fmt"
"io"
"gopkg.in/src-d/go-git.v4/plumbing"
"gopkg.in/src-d/go-git.v4/plumbing/storer"
"gopkg.in/src-d/go-git.v4/utils/binary"
)
// Encoder gets the data from the storage and write it into the writer in PACK
// format
type Encoder struct {
storage storer.ObjectStorer
w *offsetWriter
zw *zlib.Writer
hasher plumbing.Hasher
offsets map[plumbing.Hash]int64
}
// NewEncoder creates a new packfile encoder using a specific Writer and
// ObjectStorer
func NewEncoder(w io.Writer, s storer.ObjectStorer) *Encoder {
h := plumbing.Hasher{
Hash: sha1.New(),
}
mw := io.MultiWriter(w, h)
ow := newOffsetWriter(mw)
zw := zlib.NewWriter(mw)
return &Encoder{
storage: s,
w: ow,
zw: zw,
hasher: h,
offsets: make(map[plumbing.Hash]int64),
}
}
// Encode creates a packfile containing all the objects referenced in hashes
// and writes it to the writer in the Encoder.
func (e *Encoder) Encode(hashes []plumbing.Hash) (plumbing.Hash, error) {
var objects []*ObjectToPack
for _, h := range hashes {
o, err := e.storage.Object(plumbing.AnyObject, h)
if err != nil {
return plumbing.ZeroHash, err
}
// TODO delta selection logic
objects = append(objects, newObjectToPack(o))
}
return e.encode(objects)
}
func (e *Encoder) encode(objects []*ObjectToPack) (plumbing.Hash, error) {
if err := e.head(len(objects)); err != nil {
return plumbing.ZeroHash, err
}
for _, o := range objects {
if err := e.entry(o); err != nil {
return plumbing.ZeroHash, err
}
}
return e.footer()
}
func (e *Encoder) head(numEntries int) error {
return binary.Write(
e.w,
signature,
int32(VersionSupported),
int32(numEntries),
)
}
func (e *Encoder) entry(o *ObjectToPack) error {
offset := e.w.Offset()
if err := e.entryHead(o.Object.Type(), o.Object.Size()); err != nil {
return err
}
// Save the position using the original hash, maybe a delta will need it
e.offsets[o.Original.Hash()] = offset
if err := e.writeDeltaHeaderIfAny(o, offset); err != nil {
return err
}
e.zw.Reset(e.w)
or, err := o.Object.Reader()
if err != nil {
return err
}
_, err = io.Copy(e.zw, or)
if err != nil {
return err
}
return e.zw.Close()
}
func (e *Encoder) writeDeltaHeaderIfAny(o *ObjectToPack, offset int64) error {
if o.IsDelta() {
switch o.Object.Type() {
case plumbing.OFSDeltaObject:
if err := e.writeOfsDeltaHeader(offset, o.Base.Original.Hash()); err != nil {
return err
}
case plumbing.REFDeltaObject:
if err := e.writeRefDeltaHeader(o.Base.Original.Hash()); err != nil {
return err
}
}
}
return nil
}
func (e *Encoder) writeRefDeltaHeader(source plumbing.Hash) error {
return binary.Write(e.w, source)
}
func (e *Encoder) writeOfsDeltaHeader(deltaOffset int64, source plumbing.Hash) error {
// because it is an offset delta, we need the source
// object position
offset, ok := e.offsets[source]
if !ok {
return fmt.Errorf("delta source not found. Hash: %v", source)
}
return binary.WriteVariableWidthInt(e.w, deltaOffset-offset)
}
func (e *Encoder) entryHead(typeNum plumbing.ObjectType, size int64) error {
t := int64(typeNum)
header := []byte{}
c := (t << firstLengthBits) | (size & maskFirstLength)
size >>= firstLengthBits
for {
if size == 0 {
break
}
header = append(header, byte(c|maskContinue))
c = size & int64(maskLength)
size >>= lengthBits
}
header = append(header, byte(c))
_, err := e.w.Write(header)
return err
}
func (e *Encoder) footer() (plumbing.Hash, error) {
h := e.hasher.Sum()
return h, binary.Write(e.w, h)
}
type offsetWriter struct {
w io.Writer
offset int64
}
func newOffsetWriter(w io.Writer) *offsetWriter {
return &offsetWriter{w: w}
}
func (ow *offsetWriter) Write(p []byte) (n int, err error) {
n, err = ow.w.Write(p)
ow.offset += int64(n)
return n, err
}
func (ow *offsetWriter) Offset() int64 {
return ow.offset
}
|
