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authorMáximo Cuadros <mcuadros@gmail.com>2016-11-08 23:46:38 +0100
committerGitHub <noreply@github.com>2016-11-08 23:46:38 +0100
commitac095bb12c4d29722b60ba9f20590fa7cfa6bc7d (patch)
tree223f36f336ba3414b1e45cac8af6c4744a5d7ef6 /plumbing/format/idxfile/decoder.go
parente523701393598f4fa241dd407af9ff8925507a1a (diff)
downloadgo-git-ac095bb12c4d29722b60ba9f20590fa7cfa6bc7d.tar.gz
new plumbing package (#118)
* plumbing: now core was renamed to core, and formats and clients moved inside
Diffstat (limited to 'plumbing/format/idxfile/decoder.go')
-rw-r--r--plumbing/format/idxfile/decoder.go148
1 files changed, 148 insertions, 0 deletions
diff --git a/plumbing/format/idxfile/decoder.go b/plumbing/format/idxfile/decoder.go
new file mode 100644
index 0000000..e3ffc4b
--- /dev/null
+++ b/plumbing/format/idxfile/decoder.go
@@ -0,0 +1,148 @@
+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
+}