Add some basic protocol definitions, this will be improved in the future

diff --git a/protocol/protocol.go b/protocol/protocol.go
new file mode 100644 (file)
index 0000000..c4f2cb1
--- /dev/null
+++ b/protocol/protocol.go
@@ -0,0 +1,116 @@
+package protocol
+
+import (
+       "bytes"
+       "encoding/binary"
+       "errors"
+       // "errors"
+       "fmt"
+       "io"
+       "io/ioutil"
+       // "os"
+)
+
+type (
+       MessageType byte
+       Integer     uint32
+       PieceIndex  Integer
+       PieceOffset Integer
+)
+
+const (
+       Choke MessageType = iota
+       Unchoke
+       Interested
+       NotInterested
+       Have
+       Bitfield
+       Request
+       Piece
+       Cancel
+)
+
+type Message struct {
+       KeepAlive bool
+       Type      MessageType
+       Bitfield  []bool
+       Index     PieceIndex
+       Begin     PieceOffset
+       Length    Integer
+       Piece     []byte
+}
+
+func (msg *Message) UnmarshalReader(r io.Reader) (err error) {
+       err = binary.Read(r, binary.BigEndian, &msg.Type)
+       switch err {
+       case nil:
+               msg.KeepAlive = false
+       case io.EOF:
+               msg.KeepAlive = true
+               err = nil
+               return
+       default:
+               return
+       }
+       switch msg.Type {
+       case Choke, Unchoke, Interested, NotInterested:
+       case Have:
+               err = binary.Read(r, binary.BigEndian, &msg.Index)
+       case Request, Cancel:
+               err = binary.Read(r, binary.BigEndian, &msg.Index)
+               if err != nil {
+                       return
+               }
+               err = binary.Read(r, binary.BigEndian, &msg.Begin)
+               if err != nil {
+                       return
+               }
+               err = binary.Read(r, binary.BigEndian, &msg.Length)
+       case Bitfield:
+               // var bf []byte
+               _, err = ioutil.ReadAll(r)
+               if err != nil {
+                       return
+               }
+       case Piece:
+       default:
+               return fmt.Errorf("unknown type: %v", msg.Type)
+       }
+       return
+}
+
+func (msg *Message) MarshalBinary() (b []byte, err error) {
+       w := &bytes.Buffer{}
+       if msg.KeepAlive {
+               b = w.Bytes()
+               return
+       }
+       err = w.WriteByte(byte(msg.Type))
+       if err != nil {
+               return
+       }
+       switch msg.Type {
+       case Choke, Unchoke, Interested, NotInterested:
+       case Have:
+               err = binary.Write(w, binary.BigEndian, msg.Index)
+       case Request, Cancel:
+               err = binary.Write(w, binary.BigEndian, msg.Index)
+               if err != nil {
+                       return
+               }
+               err = binary.Write(w, binary.BigEndian, msg.Begin)
+               if err != nil {
+                       return
+               }
+               err = binary.Write(w, binary.BigEndian, msg.Length)
+       case Bitfield, Piece:
+               panic("unimplemented")
+       default:
+               err = errors.New("unknown type")
+               return
+       }
+       if err == nil {
+               b = w.Bytes()
+       }
+       return
+}

diff --git a/protocol/protocol_test.go b/protocol/protocol_test.go
new file mode 100644 (file)
index 0000000..32db2a6
--- /dev/null
+++ b/protocol/protocol_test.go
@@ -0,0 +1,12 @@
+package protocol
+
+import (
+       "testing"
+)
+
+func TestConstants(t *testing.T) {
+       // check that iota works as expected in the const block
+       if NotInterested != 3 {
+               t.FailNow()
+       }
+}