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
39 HandshakeExtendedID = 0
41 RequestMetadataExtensionMsgType = 0
42 DataMetadataExtensionMsgType = 1
43 RejectMetadataExtensionMsgType = 2
49 Index, Begin, Length Integer
53 ExtendedPayload []byte
57 func (msg Message) MarshalBinary() (data []byte, err error) {
58 buf := &bytes.Buffer{}
60 err = buf.WriteByte(byte(msg.Type))
65 case Choke, Unchoke, Interested, NotInterested:
67 err = binary.Write(buf, binary.BigEndian, msg.Index)
69 for _, i := range []Integer{msg.Index, msg.Begin, msg.Length} {
70 err = binary.Write(buf, binary.BigEndian, i)
76 _, err = buf.Write(marshalBitfield(msg.Bitfield))
78 for _, i := range []Integer{msg.Index, msg.Begin} {
79 err = binary.Write(buf, binary.BigEndian, i)
84 n, err := buf.Write(msg.Piece)
88 if n != len(msg.Piece) {
92 err = buf.WriteByte(msg.ExtendedID)
96 _, err = buf.Write(msg.ExtendedPayload)
98 err = binary.Write(buf, binary.BigEndian, msg.Port)
100 err = fmt.Errorf("unknown message type: %v", msg.Type)
103 data = make([]byte, 4+buf.Len())
104 binary.BigEndian.PutUint32(data, uint32(buf.Len()))
105 if buf.Len() != copy(data[4:], buf.Bytes()) {
111 type Decoder struct {
113 MaxLength Integer // TODO: Should this include the length header or not?
116 // io.EOF is returned if the source terminates cleanly on a message boundary.
117 func (d *Decoder) Decode(msg *Message) (err error) {
119 err = binary.Read(d.R, binary.BigEndian, &length)
122 err = fmt.Errorf("error reading message length: %s", err)
126 if length > d.MaxLength {
127 return errors.New("message too long")
133 msg.Keepalive = false
134 b := make([]byte, length)
135 _, err = io.ReadFull(d.R, b)
138 err = io.ErrUnexpectedEOF
140 if err != io.ErrUnexpectedEOF {
141 err = fmt.Errorf("error reading message: %s", err)
145 r := bytes.NewReader(b)
146 // Check that all of r was utilized.
152 err = fmt.Errorf("%d bytes unused in message type %d", r.Len(), msg.Type)
155 msg.Keepalive = false
156 c, err := r.ReadByte()
160 msg.Type = MessageType(c)
162 case Choke, Unchoke, Interested, NotInterested:
165 err = msg.Index.Read(r)
166 case Request, Cancel:
167 for _, data := range []*Integer{&msg.Index, &msg.Begin, &msg.Length} {
174 b := make([]byte, length-1)
175 _, err = io.ReadFull(r, b)
176 msg.Bitfield = unmarshalBitfield(b)
178 for _, pi := range []*Integer{&msg.Index, &msg.Begin} {
187 msg.Piece, err = ioutil.ReadAll(r)
189 msg.ExtendedID, err = r.ReadByte()
193 msg.ExtendedPayload, err = ioutil.ReadAll(r)
195 err = binary.Read(r, binary.BigEndian, &msg.Port)
197 err = fmt.Errorf("unknown message type %#v", c)
204 func (b Bytes) MarshalBinary() ([]byte, error) {
208 func unmarshalBitfield(b []byte) (bf []bool) {
209 for _, c := range b {
210 for i := 7; i >= 0; i-- {
211 bf = append(bf, (c>>uint(i))&1 == 1)
217 func marshalBitfield(bf []bool) (b []byte) {
218 b = make([]byte, (len(bf)+7)/8)
219 for i, have := range bf {
224 c |= 1 << uint(7-i%8)