package idxfile
import (
"crypto/sha1"
"hash"
"io"
"sort"
"gopkg.in/src-d/go-git.v4/utils/binary"
)
// Encoder writes Idxfile 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 Idxfile to the encoder writer.
func (e *Encoder) Encode(idx *Idxfile) (int, error) {
idx.Entries.Sort()
flow := []func(*Idxfile) (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 *Idxfile) (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 *Idxfile) (int, error) {
fanout := idx.calculateFanout()
for _, c := range fanout {
if err := binary.WriteUint32(e, c); err != nil {
return 0, err
}
}
return 1024, nil
}
func (e *Encoder) encodeHashes(idx *Idxfile) (int, error) {
sz := 0
for _, ent := range idx.Entries {
i, err := e.Write(ent.Hash[:])
sz += i
if err != nil {
return sz, err
}
}
return sz, nil
}
func (e *Encoder) encodeCRC32(idx *Idxfile) (int, error) {
sz := 0
for _, ent := range idx.Entries {
err := binary.Write(e, ent.CRC32)
sz += 4
if err != nil {
return sz, err
}
}
return sz, nil
}
func (e *Encoder) encodeOffsets(idx *Idxfile) (int, error) {
sz := 0
for _, ent := range idx.Entries {
if err := binary.WriteUint32(e, uint32(ent.Offset)); err != nil {
return sz, err
}
sz += 4
}
return sz, nil
}
func (e *Encoder) encodeChecksums(idx *Idxfile) (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
}
// EntryList implements sort.Interface allowing sorting in increasing order.
type EntryList []*Entry
func (p EntryList) Len() int { return len(p) }
func (p EntryList) Less(i, j int) bool { return p[i].Hash.String() < p[j].Hash.String() }
func (p EntryList) Swap(i, j int) { p[i], p[j] = p[j], p[i] }
func (p EntryList) Sort() { sort.Sort(p) }
