18 func (i *Integer) Read(r io.Reader) error {
19 return binary.Read(r, binary.BigEndian, i)
23 Protocol = "\x13BitTorrent protocol"
27 Choke MessageType = iota
41 Index, Begin, Length Integer
46 func (msg Message) MarshalBinary() (data []byte, err error) {
47 buf := &bytes.Buffer{}
49 err = buf.WriteByte(byte(msg.Type))
54 case Choke, Unchoke, Interested, NotInterested:
56 err = binary.Write(buf, binary.BigEndian, msg.Index)
58 for _, i := range []Integer{msg.Index, msg.Begin, msg.Length} {
59 err = binary.Write(buf, binary.BigEndian, i)
65 _, err = buf.Write(marshalBitfield(msg.Bitfield))
67 for _, i := range []Integer{msg.Index, msg.Begin} {
68 err = binary.Write(buf, binary.BigEndian, i)
73 n, err := buf.Write(msg.Piece)
77 if n != len(msg.Piece) {
81 err = fmt.Errorf("unknown message type: %s", msg.Type)
84 data = make([]byte, 4+buf.Len())
85 binary.BigEndian.PutUint32(data, uint32(buf.Len()))
86 if buf.Len() != copy(data[4:], buf.Bytes()) {
94 MaxLength Integer // TODO: Should this include the length header or not?
97 func (d *Decoder) Decode(msg *Message) (err error) {
99 err = binary.Read(d.R, binary.BigEndian, &length)
103 if length > d.MaxLength {
104 return errors.New("message too long")
110 msg.Keepalive = false
111 b := make([]byte, length)
112 _, err = io.ReadFull(d.R, b)
114 err = io.ErrUnexpectedEOF
120 r := bytes.NewReader(b)
122 written, _ := io.Copy(ioutil.Discard, r)
123 if written != 0 && err == nil {
124 err = fmt.Errorf("short read on message type %d, left %d bytes", msg.Type, written)
125 } else if err == io.EOF {
126 err = io.ErrUnexpectedEOF
129 msg.Keepalive = false
130 c, err := r.ReadByte()
134 msg.Type = MessageType(c)
136 case Choke, Unchoke, Interested, NotInterested:
139 err = msg.Index.Read(r)
140 case Request, Cancel:
141 for _, data := range []*Integer{&msg.Index, &msg.Begin, &msg.Length} {
148 b := make([]byte, length-1)
149 _, err = io.ReadFull(r, b)
150 msg.Bitfield = unmarshalBitfield(b)
152 for _, pi := range []*Integer{&msg.Index, &msg.Begin} {
161 msg.Piece, err = ioutil.ReadAll(r)
163 err = fmt.Errorf("unknown message type %#v", c)
170 func (b Bytes) MarshalBinary() ([]byte, error) {
174 func unmarshalBitfield(b []byte) (bf []bool) {
175 for _, c := range b {
176 for i := 7; i >= 0; i-- {
177 bf = append(bf, (c>>uint(i))&1 == 1)
183 func marshalBitfield(bf []bool) (b []byte) {
184 b = make([]byte, (len(bf)+7)/8)
185 for i, have := range bf {
190 c |= 1 << uint(7-i%8)