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-rw-r--r--plumbing/format/packp/advrefs/decoder.go288
1 files changed, 288 insertions, 0 deletions
diff --git a/plumbing/format/packp/advrefs/decoder.go b/plumbing/format/packp/advrefs/decoder.go
new file mode 100644
index 0000000..b654882
--- /dev/null
+++ b/plumbing/format/packp/advrefs/decoder.go
@@ -0,0 +1,288 @@
+package advrefs
+
+import (
+ "bytes"
+ "encoding/hex"
+ "errors"
+ "fmt"
+ "io"
+
+ "gopkg.in/src-d/go-git.v4/plumbing"
+ "gopkg.in/src-d/go-git.v4/plumbing/format/packp/pktline"
+)
+
+// A Decoder reads and decodes AdvRef values from an input stream.
+type Decoder struct {
+ s *pktline.Scanner // a pkt-line scanner from the input stream
+ line []byte // current pkt-line contents, use parser.nextLine() to make it advance
+ nLine int // current pkt-line number for debugging, begins at 1
+ hash plumbing.Hash // last hash read
+ err error // sticky error, use the parser.error() method to fill this out
+ data *AdvRefs // parsed data is stored here
+}
+
+// ErrEmpty is returned by Decode when there was no advertised-message at all
+var ErrEmpty = errors.New("empty advertised-ref message")
+
+// NewDecoder returns a new decoder that reads from r.
+//
+// Will not read more data from r than necessary.
+func NewDecoder(r io.Reader) *Decoder {
+ return &Decoder{
+ s: pktline.NewScanner(r),
+ }
+}
+
+// Decode reads the next advertised-refs message form its input and
+// stores it in the value pointed to by v.
+func (d *Decoder) Decode(v *AdvRefs) error {
+ d.data = v
+
+ for state := decodePrefix; state != nil; {
+ state = state(d)
+ }
+
+ return d.err
+}
+
+type decoderStateFn func(*Decoder) decoderStateFn
+
+// fills out the parser stiky error
+func (d *Decoder) error(format string, a ...interface{}) {
+ d.err = fmt.Errorf("pkt-line %d: %s", d.nLine,
+ fmt.Sprintf(format, a...))
+}
+
+// Reads a new pkt-line from the scanner, makes its payload available as
+// p.line and increments p.nLine. A successful invocation returns true,
+// otherwise, false is returned and the sticky error is filled out
+// accordingly. Trims eols at the end of the payloads.
+func (d *Decoder) nextLine() bool {
+ d.nLine++
+
+ if !d.s.Scan() {
+ if d.err = d.s.Err(); d.err != nil {
+ return false
+ }
+
+ if d.nLine == 1 {
+ d.err = ErrEmpty
+ return false
+ }
+
+ d.error("EOF")
+ return false
+ }
+
+ d.line = d.s.Bytes()
+ d.line = bytes.TrimSuffix(d.line, eol)
+
+ return true
+}
+
+// The HTTP smart prefix is often followed by a flush-pkt.
+func decodePrefix(d *Decoder) decoderStateFn {
+ if ok := d.nextLine(); !ok {
+ return nil
+ }
+
+ if isPrefix(d.line) {
+ tmp := make([]byte, len(d.line))
+ copy(tmp, d.line)
+ d.data.Prefix = append(d.data.Prefix, tmp)
+ if ok := d.nextLine(); !ok {
+ return nil
+ }
+ }
+
+ if isFlush(d.line) {
+ d.data.Prefix = append(d.data.Prefix, pktline.Flush)
+ if ok := d.nextLine(); !ok {
+ return nil
+ }
+ }
+
+ return decodeFirstHash
+}
+
+func isPrefix(payload []byte) bool {
+ return payload[0] == '#'
+}
+
+func isFlush(payload []byte) bool {
+ return len(payload) == 0
+}
+
+// If the first hash is zero, then a no-refs is comming. Otherwise, a
+// list-of-refs is comming, and the hash will be followed by the first
+// advertised ref.
+func decodeFirstHash(p *Decoder) decoderStateFn {
+ if len(p.line) < hashSize {
+ p.error("cannot read hash, pkt-line too short")
+ return nil
+ }
+
+ if _, err := hex.Decode(p.hash[:], p.line[:hashSize]); err != nil {
+ p.error("invalid hash text: %s", err)
+ return nil
+ }
+
+ p.line = p.line[hashSize:]
+
+ if p.hash.IsZero() {
+ return decodeSkipNoRefs
+ }
+
+ return decodeFirstRef
+}
+
+// Skips SP "capabilities^{}" NUL
+func decodeSkipNoRefs(p *Decoder) decoderStateFn {
+ if len(p.line) < len(noHeadMark) {
+ p.error("too short zero-id ref")
+ return nil
+ }
+
+ if !bytes.HasPrefix(p.line, noHeadMark) {
+ p.error("malformed zero-id ref")
+ return nil
+ }
+
+ p.line = p.line[len(noHeadMark):]
+
+ return decodeCaps
+}
+
+// decode the refname, expectes SP refname NULL
+func decodeFirstRef(l *Decoder) decoderStateFn {
+ if len(l.line) < 3 {
+ l.error("line too short after hash")
+ return nil
+ }
+
+ if !bytes.HasPrefix(l.line, sp) {
+ l.error("no space after hash")
+ return nil
+ }
+ l.line = l.line[1:]
+
+ chunks := bytes.SplitN(l.line, null, 2)
+ if len(chunks) < 2 {
+ l.error("NULL not found")
+ return nil
+ }
+ ref := chunks[0]
+ l.line = chunks[1]
+
+ if bytes.Equal(ref, []byte(head)) {
+ l.data.Head = &l.hash
+ } else {
+ l.data.References[string(ref)] = l.hash
+ }
+
+ return decodeCaps
+}
+
+func decodeCaps(p *Decoder) decoderStateFn {
+ if len(p.line) == 0 {
+ return decodeOtherRefs
+ }
+
+ for _, c := range bytes.Split(p.line, sp) {
+ name, values := readCapability(c)
+ p.data.Capabilities.Add(name, values...)
+ }
+
+ return decodeOtherRefs
+}
+
+// Capabilities are a single string or a name=value.
+// Even though we are only going to read at moust 1 value, we return
+// a slice of values, as Capability.Add receives that.
+func readCapability(data []byte) (name string, values []string) {
+ pair := bytes.SplitN(data, []byte{'='}, 2)
+ if len(pair) == 2 {
+ values = append(values, string(pair[1]))
+ }
+
+ return string(pair[0]), values
+}
+
+// The refs are either tips (obj-id SP refname) or a peeled (obj-id SP refname^{}).
+// If there are no refs, then there might be a shallow or flush-ptk.
+func decodeOtherRefs(p *Decoder) decoderStateFn {
+ if ok := p.nextLine(); !ok {
+ return nil
+ }
+
+ if bytes.HasPrefix(p.line, shallow) {
+ return decodeShallow
+ }
+
+ if len(p.line) == 0 {
+ return nil
+ }
+
+ saveTo := p.data.References
+ if bytes.HasSuffix(p.line, peeled) {
+ p.line = bytes.TrimSuffix(p.line, peeled)
+ saveTo = p.data.Peeled
+ }
+
+ ref, hash, err := readRef(p.line)
+ if err != nil {
+ p.error("%s", err)
+ return nil
+ }
+ saveTo[ref] = hash
+
+ return decodeOtherRefs
+}
+
+// Reads a ref-name
+func readRef(data []byte) (string, plumbing.Hash, error) {
+ chunks := bytes.Split(data, sp)
+ switch {
+ case len(chunks) == 1:
+ return "", plumbing.ZeroHash, fmt.Errorf("malformed ref data: no space was found")
+ case len(chunks) > 2:
+ return "", plumbing.ZeroHash, fmt.Errorf("malformed ref data: more than one space found")
+ default:
+ return string(chunks[1]), plumbing.NewHash(string(chunks[0])), nil
+ }
+}
+
+// Keeps reading shallows until a flush-pkt is found
+func decodeShallow(p *Decoder) decoderStateFn {
+ if !bytes.HasPrefix(p.line, shallow) {
+ p.error("malformed shallow prefix, found %q... instead", p.line[:len(shallow)])
+ return nil
+ }
+ p.line = bytes.TrimPrefix(p.line, shallow)
+
+ if len(p.line) != hashSize {
+ p.error(fmt.Sprintf(
+ "malformed shallow hash: wrong length, expected 40 bytes, read %d bytes",
+ len(p.line)))
+ return nil
+ }
+
+ text := p.line[:hashSize]
+ var h plumbing.Hash
+ if _, err := hex.Decode(h[:], text); err != nil {
+ p.error("invalid hash text: %s", err)
+ return nil
+ }
+
+ p.data.Shallows = append(p.data.Shallows, h)
+
+ if ok := p.nextLine(); !ok {
+ return nil
+ }
+
+ if len(p.line) == 0 {
+ return nil // succesfull parse of the advertised-refs message
+ }
+
+ return decodeShallow
+}