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|
package idxfile
import (
"bufio"
"bytes"
"errors"
"io"
"github.com/go-git/go-git/v5/utils/binary"
)
var (
// ErrUnsupportedVersion is returned by Decode when the idx file version
// is not supported.
ErrUnsupportedVersion = errors.New("Unsupported version")
// ErrMalformedIdxFile is returned by Decode when the idx file is corrupted.
ErrMalformedIdxFile = errors.New("Malformed IDX file")
)
const (
fanout = 256
objectIDLength = 20
)
// Decoder reads and decodes idx files from an input stream.
type Decoder struct {
*bufio.Reader
}
// NewDecoder builds a new idx stream decoder, that reads from r.
func NewDecoder(r io.Reader) *Decoder {
return &Decoder{bufio.NewReader(r)}
}
// Decode reads from the stream and decode the content into the MemoryIndex struct.
func (d *Decoder) Decode(idx *MemoryIndex) error {
if err := validateHeader(d); err != nil {
return err
}
flow := []func(*MemoryIndex, io.Reader) error{
readVersion,
readFanout,
readObjectNames,
readCRC32,
readOffsets,
readChecksums,
}
for _, f := range flow {
if err := f(idx, d); err != nil {
return err
}
}
return nil
}
func validateHeader(r io.Reader) error {
var h = make([]byte, 4)
if _, err := io.ReadFull(r, h); err != nil {
return err
}
if !bytes.Equal(h, idxHeader) {
return ErrMalformedIdxFile
}
return nil
}
func readVersion(idx *MemoryIndex, 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 *MemoryIndex, r io.Reader) error {
for k := 0; k < fanout; k++ {
n, err := binary.ReadUint32(r)
if err != nil {
return err
}
idx.Fanout[k] = n
idx.FanoutMapping[k] = noMapping
}
return nil
}
func readObjectNames(idx *MemoryIndex, r io.Reader) error {
for k := 0; k < fanout; k++ {
var buckets uint32
if k == 0 {
buckets = idx.Fanout[k]
} else {
buckets = idx.Fanout[k] - idx.Fanout[k-1]
}
if buckets == 0 {
continue
}
idx.FanoutMapping[k] = len(idx.Names)
nameLen := int(buckets * objectIDLength)
bin := make([]byte, nameLen)
if _, err := io.ReadFull(r, bin); err != nil {
return err
}
idx.Names = append(idx.Names, bin)
idx.Offset32 = append(idx.Offset32, make([]byte, buckets*4))
idx.CRC32 = append(idx.CRC32, make([]byte, buckets*4))
}
return nil
}
func readCRC32(idx *MemoryIndex, r io.Reader) error {
for k := 0; k < fanout; k++ {
if pos := idx.FanoutMapping[k]; pos != noMapping {
if _, err := io.ReadFull(r, idx.CRC32[pos]); err != nil {
return err
}
}
}
return nil
}
func readOffsets(idx *MemoryIndex, r io.Reader) error {
var o64cnt int
for k := 0; k < fanout; k++ {
if pos := idx.FanoutMapping[k]; pos != noMapping {
if _, err := io.ReadFull(r, idx.Offset32[pos]); err != nil {
return err
}
for p := 0; p < len(idx.Offset32[pos]); p += 4 {
if idx.Offset32[pos][p]&(byte(1)<<7) > 0 {
o64cnt++
}
}
}
}
if o64cnt > 0 {
idx.Offset64 = make([]byte, o64cnt*8)
if _, err := io.ReadFull(r, idx.Offset64); err != nil {
return err
}
}
return nil
}
func readChecksums(idx *MemoryIndex, r io.Reader) error {
if _, err := io.ReadFull(r, idx.PackfileChecksum[:]); err != nil {
return err
}
if _, err := io.ReadFull(r, idx.IdxChecksum[:]); err != nil {
return err
}
return nil
}
|
