126 lines
2.6 KiB
Go
126 lines
2.6 KiB
Go
package peer_protocol
|
|
|
|
import (
|
|
"bufio"
|
|
"encoding/binary"
|
|
"fmt"
|
|
"io"
|
|
"io/ioutil"
|
|
"sync"
|
|
|
|
"github.com/pkg/errors"
|
|
)
|
|
|
|
type Decoder struct {
|
|
R *bufio.Reader
|
|
Pool *sync.Pool
|
|
MaxLength Integer // TODO: Should this include the length header or not?
|
|
}
|
|
|
|
// io.EOF is returned if the source terminates cleanly on a message boundary.
|
|
// TODO: Is that before or after the message?
|
|
func (d *Decoder) Decode(msg *Message) (err error) {
|
|
var length Integer
|
|
err = binary.Read(d.R, binary.BigEndian, &length)
|
|
if err != nil {
|
|
if err != io.EOF {
|
|
err = fmt.Errorf("error reading message length: %s", err)
|
|
}
|
|
return
|
|
}
|
|
if length > d.MaxLength {
|
|
return errors.New("message too long")
|
|
}
|
|
if length == 0 {
|
|
msg.Keepalive = true
|
|
return
|
|
}
|
|
msg.Keepalive = false
|
|
r := &io.LimitedReader{R: d.R, N: int64(length)}
|
|
// Check that all of r was utilized.
|
|
defer func() {
|
|
if err != nil {
|
|
return
|
|
}
|
|
if r.N != 0 {
|
|
err = fmt.Errorf("%d bytes unused in message type %d", r.N, msg.Type)
|
|
}
|
|
}()
|
|
msg.Keepalive = false
|
|
c, err := readByte(r)
|
|
if err != nil {
|
|
return
|
|
}
|
|
msg.Type = MessageType(c)
|
|
switch msg.Type {
|
|
case Choke, Unchoke, Interested, NotInterested, HaveAll, HaveNone:
|
|
return
|
|
case Have, AllowedFast, Suggest:
|
|
err = msg.Index.Read(r)
|
|
case Request, Cancel, Reject:
|
|
for _, data := range []*Integer{&msg.Index, &msg.Begin, &msg.Length} {
|
|
err = data.Read(r)
|
|
if err != nil {
|
|
break
|
|
}
|
|
}
|
|
case Bitfield:
|
|
b := make([]byte, length-1)
|
|
_, err = io.ReadFull(r, b)
|
|
msg.Bitfield = unmarshalBitfield(b)
|
|
case Piece:
|
|
for _, pi := range []*Integer{&msg.Index, &msg.Begin} {
|
|
err := pi.Read(r)
|
|
if err != nil {
|
|
return err
|
|
}
|
|
}
|
|
dataLen := r.N
|
|
msg.Piece = (*d.Pool.Get().(*[]byte))
|
|
if int64(cap(msg.Piece)) < dataLen {
|
|
return errors.New("piece data longer than expected")
|
|
}
|
|
msg.Piece = msg.Piece[:dataLen]
|
|
_, err := io.ReadFull(r, msg.Piece)
|
|
if err != nil {
|
|
return errors.Wrap(err, "reading piece data")
|
|
}
|
|
case Extended:
|
|
var b byte
|
|
b, err = readByte(r)
|
|
if err != nil {
|
|
break
|
|
}
|
|
msg.ExtendedID = ExtensionNumber(b)
|
|
msg.ExtendedPayload, err = ioutil.ReadAll(r)
|
|
case Port:
|
|
err = binary.Read(r, binary.BigEndian, &msg.Port)
|
|
default:
|
|
err = fmt.Errorf("unknown message type %#v", c)
|
|
}
|
|
return
|
|
}
|
|
|
|
func readByte(r io.Reader) (b byte, err error) {
|
|
var arr [1]byte
|
|
n, err := r.Read(arr[:])
|
|
b = arr[0]
|
|
if n == 1 {
|
|
err = nil
|
|
return
|
|
}
|
|
if err == nil {
|
|
panic(err)
|
|
}
|
|
return
|
|
}
|
|
|
|
func unmarshalBitfield(b []byte) (bf []bool) {
|
|
for _, c := range b {
|
|
for i := 7; i >= 0; i-- {
|
|
bf = append(bf, (c>>uint(i))&1 == 1)
|
|
}
|
|
}
|
|
return
|
|
}
|