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
}
