1 files changed, 133 insertions, 53 deletions
diff --git a/p2p/message.go b/p2p/message.go
index 446e74dff..d3b8b74d4 100644
--- a/p2p/message.go
+++ b/p2p/message.go
@@ -1,75 +1,155 @@
 package p2p
 
 import (
-	// "fmt"
+	"bytes"
+	"encoding/binary"
+	"io"
+	"io/ioutil"
+	"math/big"
+
 	"github.com/ethereum/go-ethereum/ethutil"
+	"github.com/ethereum/go-ethereum/rlp"
 )
 
-type MsgCode uint8
-
+// Msg defines the structure of a p2p message.
+//
+// Note that a Msg can only be sent once since the Payload reader is
+// consumed during sending. It is not possible to create a Msg and
+// send it any number of times. If you want to reuse an encoded
+// structure, encode the payload into a byte array and create a
+// separate Msg with a bytes.Reader as Payload for each send.
 type Msg struct {
-	code    MsgCode // this is the raw code as per adaptive msg code scheme
-	data    *ethutil.Value
-	encoded []byte
+	Code    uint64
+	Size    uint32 // size of the paylod
+	Payload io.Reader
+}
+
+// NewMsg creates an RLP-encoded message with the given code.
+func NewMsg(code uint64, params ...interface{}) Msg {
+	buf := new(bytes.Buffer)
+	for _, p := range params {
+		buf.Write(ethutil.Encode(p))
+	}
+	return Msg{Code: code, Size: uint32(buf.Len()), Payload: buf}
+}
+
+func encodePayload(params ...interface{}) []byte {
+	buf := new(bytes.Buffer)
+	for _, p := range params {
+		buf.Write(ethutil.Encode(p))
+	}
+	return buf.Bytes()
+}
+
+// Decode parse the RLP content of a message into
+// the given value, which must be a pointer.
+//
+// For the decoding rules, please see package rlp.
+func (msg Msg) Decode(val interface{}) error {
+	s := rlp.NewListStream(msg.Payload, uint64(msg.Size))
+	return s.Decode(val)
+}
+
+// Discard reads any remaining payload data into a black hole.
+func (msg Msg) Discard() error {
+	_, err := io.Copy(ioutil.Discard, msg.Payload)
+	return err
+}
+
+type MsgReader interface {
+	ReadMsg() (Msg, error)
 }
 
-func (self *Msg) Code() MsgCode {
-	return self.code
+type MsgWriter interface {
+	// WriteMsg sends an existing message.
+	// The Payload reader of the message is consumed.
+	// Note that messages can be sent only once.
+	WriteMsg(Msg) error
+
+	// EncodeMsg writes an RLP-encoded message with the given
+	// code and data elements.
+	EncodeMsg(code uint64, data ...interface{}) error
+}
+
+// MsgReadWriter provides reading and writing of encoded messages.
+type MsgReadWriter interface {
+	MsgReader
+	MsgWriter
 }
 
-func (self *Msg) Data() *ethutil.Value {
-	return self.data
+var magicToken = []byte{34, 64, 8, 145}
+
+func writeMsg(w io.Writer, msg Msg) error {
+	// TODO: handle case when Size + len(code) + len(listhdr) overflows uint32
+	code := ethutil.Encode(uint32(msg.Code))
+	listhdr := makeListHeader(msg.Size + uint32(len(code)))
+	payloadLen := uint32(len(listhdr)) + uint32(len(code)) + msg.Size
+
+	start := make([]byte, 8)
+	copy(start, magicToken)
+	binary.BigEndian.PutUint32(start[4:], payloadLen)
+
+	for _, b := range [][]byte{start, listhdr, code} {
+		if _, err := w.Write(b); err != nil {
+			return err
+		}
+	}
+	_, err := io.CopyN(w, msg.Payload, int64(msg.Size))
+	return err
 }
 
-func NewMsg(code MsgCode, params ...interface{}) (msg *Msg, err error) {
-
-	// // data := [][]interface{}{}
-	// data := []interface{}{}
-	// for _, value := range params {
-	// 	if encodable, ok := value.(ethutil.RlpEncodeDecode); ok {
-	// 		data = append(data, encodable.RlpValue())
-	// 	} else if raw, ok := value.([]interface{}); ok {
-	// 		data = append(data, raw)
-	// 	} else {
-	// 		// data = append(data, interface{}(raw))
-	// 		err = fmt.Errorf("Unable to encode object of type %T", value)
-	// 		return
-	// 	}
-	// }
-	return &Msg{
-		code: code,
-		data: ethutil.NewValue(interface{}(params)),
-	}, nil
+func makeListHeader(length uint32) []byte {
+	if length < 56 {
+		return []byte{byte(length + 0xc0)}
+	}
+	enc := big.NewInt(int64(length)).Bytes()
+	lenb := byte(len(enc)) + 0xf7
+	return append([]byte{lenb}, enc...)
 }
 
-func NewMsgFromBytes(encoded []byte) (msg *Msg, err error) {
-	value := ethutil.NewValueFromBytes(encoded)
-	// Type of message
-	code := value.Get(0).Uint()
-	// Actual data
-	data := value.SliceFrom(1)
-
-	msg = &Msg{
-		code: MsgCode(code),
-		data: data,
-		// data:    ethutil.NewValue(data),
-		encoded: encoded,
+// readMsg reads a message header from r.
+// It takes an rlp.ByteReader to ensure that the decoding doesn't buffer.
+func readMsg(r rlp.ByteReader) (msg Msg, err error) {
+	// read magic and payload size
+	start := make([]byte, 8)
+	if _, err = io.ReadFull(r, start); err != nil {
+		return msg, newPeerError(errRead, "%v", err)
+	}
+	if !bytes.HasPrefix(start, magicToken) {
+		return msg, newPeerError(errMagicTokenMismatch, "got %x, want %x", start[:4], magicToken)
+	}
+	size := binary.BigEndian.Uint32(start[4:])
+
+	// decode start of RLP message to get the message code
+	posr := &postrack{r, 0}
+	s := rlp.NewStream(posr)
+	if _, err := s.List(); err != nil {
+		return msg, err
 	}
-	return
+	code, err := s.Uint()
+	if err != nil {
+		return msg, err
+	}
+	payloadsize := size - posr.p
+	return Msg{code, payloadsize, io.LimitReader(r, int64(payloadsize))}, nil
+}
+
+// postrack wraps an rlp.ByteReader with a position counter.
+type postrack struct {
+	r rlp.ByteReader
+	p uint32
 }
 
-func (self *Msg) Decode(offset MsgCode) {
-	self.code = self.code - offset
+func (r *postrack) Read(buf []byte) (int, error) {
+	n, err := r.r.Read(buf)
+	r.p += uint32(n)
+	return n, err
 }
 
-// encode takes an offset argument to implement adaptive message coding
-// the encoded message is memoized to make msgs relayed to several peers more efficient
-func (self *Msg) Encode(offset MsgCode) (res []byte) {
-	if len(self.encoded) == 0 {
-		res = ethutil.NewValue(append([]interface{}{byte(self.code + offset)}, self.data.Slice()...)).Encode()
-		self.encoded = res
-	} else {
-		res = self.encoded
+func (r *postrack) ReadByte() (byte, error) {
+	b, err := r.r.ReadByte()
+	if err == nil {
+		r.p++
 	}
-	return
+	return b, err
 }