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
43 AllowedFast = 0x11 // 17
47 HandshakeExtendedID = 0
49 RequestMetadataExtensionMsgType = 0
50 DataMetadataExtensionMsgType = 1
51 RejectMetadataExtensionMsgType = 2
57 Index, Begin, Length Integer
61 ExtendedPayload []byte
65 func (msg Message) MarshalBinary() (data []byte, err error) {
66 buf := &bytes.Buffer{}
68 err = buf.WriteByte(byte(msg.Type))
73 case Choke, Unchoke, Interested, NotInterested, HaveAll, HaveNone:
75 err = binary.Write(buf, binary.BigEndian, msg.Index)
76 case Request, Cancel, Reject:
77 for _, i := range []Integer{msg.Index, msg.Begin, msg.Length} {
78 err = binary.Write(buf, binary.BigEndian, i)
84 _, err = buf.Write(marshalBitfield(msg.Bitfield))
86 for _, i := range []Integer{msg.Index, msg.Begin} {
87 err = binary.Write(buf, binary.BigEndian, i)
92 n, err := buf.Write(msg.Piece)
96 if n != len(msg.Piece) {
100 err = buf.WriteByte(msg.ExtendedID)
104 _, err = buf.Write(msg.ExtendedPayload)
106 err = binary.Write(buf, binary.BigEndian, msg.Port)
108 err = fmt.Errorf("unknown message type: %v", msg.Type)
111 data = make([]byte, 4+buf.Len())
112 binary.BigEndian.PutUint32(data, uint32(buf.Len()))
113 if buf.Len() != copy(data[4:], buf.Bytes()) {
119 type Decoder struct {
121 MaxLength Integer // TODO: Should this include the length header or not?
124 // io.EOF is returned if the source terminates cleanly on a message boundary.
125 func (d *Decoder) Decode(msg *Message) (err error) {
127 err = binary.Read(d.R, binary.BigEndian, &length)
130 err = fmt.Errorf("error reading message length: %s", err)
134 if length > d.MaxLength {
135 return errors.New("message too long")
141 msg.Keepalive = false
142 b := make([]byte, length)
143 _, err = io.ReadFull(d.R, b)
146 err = io.ErrUnexpectedEOF
148 if err != io.ErrUnexpectedEOF {
149 err = fmt.Errorf("error reading message: %s", err)
153 r := bytes.NewReader(b)
154 // Check that all of r was utilized.
160 err = fmt.Errorf("%d bytes unused in message type %d", r.Len(), msg.Type)
163 msg.Keepalive = false
164 c, err := r.ReadByte()
168 msg.Type = MessageType(c)
170 case Choke, Unchoke, Interested, NotInterested, HaveAll, HaveNone:
173 err = msg.Index.Read(r)
174 case Request, Cancel, Reject:
175 for _, data := range []*Integer{&msg.Index, &msg.Begin, &msg.Length} {
182 b := make([]byte, length-1)
183 _, err = io.ReadFull(r, b)
184 msg.Bitfield = unmarshalBitfield(b)
186 for _, pi := range []*Integer{&msg.Index, &msg.Begin} {
195 msg.Piece, err = ioutil.ReadAll(r)
197 msg.ExtendedID, err = r.ReadByte()
201 msg.ExtendedPayload, err = ioutil.ReadAll(r)
203 err = binary.Read(r, binary.BigEndian, &msg.Port)
205 err = fmt.Errorf("unknown message type %#v", c)
212 func (b Bytes) MarshalBinary() ([]byte, error) {
216 func unmarshalBitfield(b []byte) (bf []bool) {
217 for _, c := range b {
218 for i := 7; i >= 0; i-- {
219 bf = append(bf, (c>>uint(i))&1 == 1)
225 func marshalBitfield(bf []bool) (b []byte) {
226 b = make([]byte, (len(bf)+7)/8)
227 for i, have := range bf {
232 c |= 1 << uint(7-i%8)