package idxfile
import (
"bytes"
"errors"
"io"
"gopkg.in/src-d/go-git.v4/plumbing"
"gopkg.in/src-d/go-git.v4/utils/binary"
)
var (
// ErrUnsupportedVersion is returned by Decode when the idx file version
// is not supported.
ErrUnsupportedVersion = errors.New("Unsuported version")
// ErrMalformedIdxFile is returned by Decode when the idx file is corrupted.
ErrMalformedIdxFile = errors.New("Malformed IDX file")
)
// A Decoder reads and decodes idx files from an input stream.
type Decoder struct {
io.Reader
}
// NewDecoder returns a new decoder that reads from r.
func NewDecoder(r io.Reader) *Decoder {
return &Decoder{r}
}
// Decode reads the whole idx object from its input and stores it in the
// value pointed to by idx.
func (d *Decoder) Decode(idx *Idxfile) error {
if err := validateHeader(d); err != nil {
return err
}
flow := []func(*Idxfile, io.Reader) error{
readVersion,
readFanout,
readObjectNames,
readCRC32,
readOffsets,
readChecksums,
}
for _, f := range flow {
if err := f(idx, d); err != nil {
return err
}
}
if !idx.isValid() {
return ErrMalformedIdxFile
}
return nil
}
func validateHeader(r io.Reader) error {
var h = make([]byte, 4)
if _, err := r.Read(h); err != nil {
return err
}
if !bytes.Equal(h, idxHeader) {
return ErrMalformedIdxFile
}
return nil
}
func readVersion(idx *Idxfile, r io.Reader) error {
v, err := binary.ReadUint32(r)
if err != nil {
return err
}
if v > VersionSupported {
return ErrUnsupportedVersion
}
idx.Version = v
return nil
}
func readFanout(idx *Idxfile, r io.Reader) error {
var err error
for i := 0; i < 255; i++ {
idx.Fanout[i], err = binary.ReadUint32(r)
if err != nil {
return err
}
}
idx.ObjectCount, err = binary.ReadUint32(r)
return err
}
func readObjectNames(idx *Idxfile, r io.Reader) error {
c := int(idx.ObjectCount)
for i := 0; i < c; i++ {
var ref plumbing.Hash
if _, err := r.Read(ref[:]); err != nil {
return err
}
idx.Entries = append(idx.Entries, Entry{Hash: ref})
}
return nil
}
func readCRC32(idx *Idxfile, r io.Reader) error {
c := int(idx.ObjectCount)
for i := 0; i < c; i++ {
if err := binary.Read(r, &idx.Entries[i].CRC32); err != nil {
return err
}
}
return nil
}
func readOffsets(idx *Idxfile, r io.Reader) error {
c := int(idx.ObjectCount)
for i := 0; i < c; i++ {
o, err := binary.ReadUint32(r)
if err != nil {
return err
}
idx.Entries[i].Offset = uint64(o)
}
return nil
}
func readChecksums(idx *Idxfile, r io.Reader) error {
if _, err := r.Read(idx.PackfileChecksum[:]); err != nil {
return err
}
if _, err := r.Read(idx.IdxChecksum[:]); err != nil {
return err
}
return nil
}
