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package idxfile
import (
"crypto/sha1"
"hash"
"io"
"gopkg.in/src-d/go-git.v4/utils/binary"
)
// Encoder writes MemoryIndex structs to an output stream.
type Encoder struct {
io.Writer
hash hash.Hash
}
// NewEncoder returns a new stream encoder that writes to w.
func NewEncoder(w io.Writer) *Encoder {
h := sha1.New()
mw := io.MultiWriter(w, h)
return &Encoder{mw, h}
}
// Encode encodes an MemoryIndex to the encoder writer.
func (e *Encoder) Encode(idx *MemoryIndex) (int, error) {
flow := []func(*MemoryIndex) (int, error){
e.encodeHeader,
e.encodeFanout,
e.encodeHashes,
e.encodeCRC32,
e.encodeOffsets,
e.encodeChecksums,
}
sz := 0
for _, f := range flow {
i, err := f(idx)
sz += i
if err != nil {
return sz, err
}
}
return sz, nil
}
func (e *Encoder) encodeHeader(idx *MemoryIndex) (int, error) {
c, err := e.Write(idxHeader)
if err != nil {
return c, err
}
return c + 4, binary.WriteUint32(e, idx.Version)
}
func (e *Encoder) encodeFanout(idx *MemoryIndex) (int, error) {
for _, c := range idx.Fanout {
if err := binary.WriteUint32(e, c); err != nil {
return 0, err
}
}
return fanout * 4, nil
}
func (e *Encoder) encodeHashes(idx *MemoryIndex) (int, error) {
var size int
for k := 0; k < fanout; k++ {
pos := idx.FanoutMapping[k]
if pos == noMapping {
continue
}
n, err := e.Write(idx.Names[pos])
if err != nil {
return size, err
}
size += n
}
return size, nil
}
func (e *Encoder) encodeCRC32(idx *MemoryIndex) (int, error) {
var size int
for k := 0; k < fanout; k++ {
pos := idx.FanoutMapping[k]
if pos == noMapping {
continue
}
n, err := e.Write(idx.CRC32[pos])
if err != nil {
return size, err
}
size += n
}
return size, nil
}
func (e *Encoder) encodeOffsets(idx *MemoryIndex) (int, error) {
var size int
for k := 0; k < fanout; k++ {
pos := idx.FanoutMapping[k]
if pos == noMapping {
continue
}
n, err := e.Write(idx.Offset32[pos])
if err != nil {
return size, err
}
size += n
}
if len(idx.Offset64) > 0 {
n, err := e.Write(idx.Offset64)
if err != nil {
return size, err
}
size += n
}
return size, nil
}
func (e *Encoder) encodeChecksums(idx *MemoryIndex) (int, error) {
if _, err := e.Write(idx.PackfileChecksum[:]); err != nil {
return 0, err
}
copy(idx.IdxChecksum[:], e.hash.Sum(nil)[:20])
if _, err := e.Write(idx.IdxChecksum[:]); err != nil {
return 0, err
}
return 40, nil
}
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