ulreq: adds encoder and decoder for upload-request messages (#106)

* ulreq: adds encoder and decoder for upload-request messages

* ulreq: stop using _test suffix for testing package names (@mcuadros comment)

1 files changed, 287 insertions, 0 deletions

diff --git a/formats/packp/ulreq/decoder.go b/formats/packp/ulreq/decoder.go
new file mode 100644
index 0000000..63ccd4d
--- /dev/null
+++ b/formats/packp/ulreq/decoder.go
@@ -0,0 +1,287 @@
+package ulreq
+
+import (
+	"bytes"
+	"encoding/hex"
+	"fmt"
+	"io"
+	"strconv"
+	"time"
+
+	"gopkg.in/src-d/go-git.v4/core"
+	"gopkg.in/src-d/go-git.v4/formats/packp/pktline"
+)
+
+const (
+	hashSize = 40
+)
+
+var (
+	eol             = []byte("\n")
+	sp              = []byte(" ")
+	want            = []byte("want ")
+	shallow         = []byte("shallow ")
+	deepen          = []byte("deepen")
+	deepenCommits   = []byte("deepen ")
+	deepenSince     = []byte("deepen-since ")
+	deepenReference = []byte("deepen-not ")
+)
+
+// 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
+	err   error            // sticky error, use the parser.error() method to fill this out
+	data  *UlReq           // parsed data is stored here
+}
+
+// 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 upload-request form its input and
+// stores it in the value pointed to by v.
+func (d *Decoder) Decode(v *UlReq) error {
+	d.data = v
+
+	for state := decodeFirstWant; 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
+		}
+
+		d.error("EOF")
+		return false
+	}
+
+	d.line = d.s.Bytes()
+	d.line = bytes.TrimSuffix(d.line, eol)
+
+	return true
+}
+
+// Expected format: want <hash>[ capabilities]
+func decodeFirstWant(d *Decoder) decoderStateFn {
+	if ok := d.nextLine(); !ok {
+		return nil
+	}
+
+	if !bytes.HasPrefix(d.line, want) {
+		d.error("missing 'want ' prefix")
+		return nil
+	}
+	d.line = bytes.TrimPrefix(d.line, want)
+
+	hash, ok := d.readHash()
+	if !ok {
+		return nil
+	}
+	d.data.Wants = append(d.data.Wants, hash)
+
+	return decodeCaps
+}
+
+func (d *Decoder) readHash() (core.Hash, bool) {
+	if len(d.line) < hashSize {
+		d.err = fmt.Errorf("malformed hash: %v", d.line)
+		return core.ZeroHash, false
+	}
+
+	var hash core.Hash
+	if _, err := hex.Decode(hash[:], d.line[:hashSize]); err != nil {
+		d.error("invalid hash text: %s", err)
+		return core.ZeroHash, false
+	}
+	d.line = d.line[hashSize:]
+
+	return hash, true
+}
+
+// Expected format: sp cap1 sp cap2 sp cap3...
+func decodeCaps(d *Decoder) decoderStateFn {
+	if len(d.line) == 0 {
+		return decodeOtherWants
+	}
+
+	d.line = bytes.TrimPrefix(d.line, sp)
+
+	for _, c := range bytes.Split(d.line, sp) {
+		name, values := readCapability(c)
+		d.data.Capabilities.Add(name, values...)
+	}
+
+	return decodeOtherWants
+}
+
+// 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
+}
+
+// Expected format: want <hash>
+func decodeOtherWants(d *Decoder) decoderStateFn {
+	if ok := d.nextLine(); !ok {
+		return nil
+	}
+
+	if bytes.HasPrefix(d.line, shallow) {
+		return decodeShallow
+	}
+
+	if bytes.HasPrefix(d.line, deepen) {
+		return decodeDeepen
+	}
+
+	if len(d.line) == 0 {
+		return nil
+	}
+
+	if !bytes.HasPrefix(d.line, want) {
+		d.error("unexpected payload while expecting a want: %q", d.line)
+		return nil
+	}
+	d.line = bytes.TrimPrefix(d.line, want)
+
+	hash, ok := d.readHash()
+	if !ok {
+		return nil
+	}
+	d.data.Wants = append(d.data.Wants, hash)
+
+	return decodeOtherWants
+}
+
+// Expected format: shallow <hash>
+func decodeShallow(d *Decoder) decoderStateFn {
+	if bytes.HasPrefix(d.line, deepen) {
+		return decodeDeepen
+	}
+
+	if len(d.line) == 0 {
+		return nil
+	}
+
+	if !bytes.HasPrefix(d.line, shallow) {
+		d.error("unexpected payload while expecting a shallow: %q", d.line)
+		return nil
+	}
+	d.line = bytes.TrimPrefix(d.line, shallow)
+
+	hash, ok := d.readHash()
+	if !ok {
+		return nil
+	}
+	d.data.Shallows = append(d.data.Shallows, hash)
+
+	if ok := d.nextLine(); !ok {
+		return nil
+	}
+
+	return decodeShallow
+}
+
+// Expected format: deepen <n> / deepen-since <ul> / deepen-not <ref>
+func decodeDeepen(d *Decoder) decoderStateFn {
+	if bytes.HasPrefix(d.line, deepenCommits) {
+		return decodeDeepenCommits
+	}
+
+	if bytes.HasPrefix(d.line, deepenSince) {
+		return decodeDeepenSince
+	}
+
+	if bytes.HasPrefix(d.line, deepenReference) {
+		return decodeDeepenReference
+	}
+
+	if len(d.line) == 0 {
+		return nil
+	}
+
+	d.error("unexpected deepen specification: %q", d.line)
+	return nil
+}
+
+func decodeDeepenCommits(d *Decoder) decoderStateFn {
+	d.line = bytes.TrimPrefix(d.line, deepenCommits)
+
+	var n int
+	if n, d.err = strconv.Atoi(string(d.line)); d.err != nil {
+		return nil
+	}
+	if n < 0 {
+		d.err = fmt.Errorf("negative depth")
+		return nil
+	}
+	d.data.Depth = DepthCommits(n)
+
+	return decodeFlush
+}
+
+func decodeDeepenSince(d *Decoder) decoderStateFn {
+	d.line = bytes.TrimPrefix(d.line, deepenSince)
+
+	var secs int64
+	secs, d.err = strconv.ParseInt(string(d.line), 10, 64)
+	if d.err != nil {
+		return nil
+	}
+	t := time.Unix(secs, 0).UTC()
+	d.data.Depth = DepthSince(t)
+
+	return decodeFlush
+}
+
+func decodeDeepenReference(d *Decoder) decoderStateFn {
+	d.line = bytes.TrimPrefix(d.line, deepenReference)
+
+	d.data.Depth = DepthReference(string(d.line))
+
+	return decodeFlush
+}
+
+func decodeFlush(d *Decoder) decoderStateFn {
+	if ok := d.nextLine(); !ok {
+		return nil
+	}
+
+	if len(d.line) != 0 {
+		d.err = fmt.Errorf("unexpected payload while expecting a flush-pkt: %q", d.line)
+	}
+
+	return nil
+}