From c1fca72552386868d28ce7541691e53e55673549 Mon Sep 17 00:00:00 2001
From: Felix Lange <fjl@twurst.com>
Date: Mon, 24 Nov 2014 19:02:48 +0100
Subject: [PATCH] p2p: use package rlp

---
 p2p/message.go      | 101 ++++++++++++++------------------------------
 p2p/message_test.go |   3 ++
 p2p/peer_test.go    |   2 +-
 3 files changed, 35 insertions(+), 71 deletions(-)

diff --git a/p2p/message.go b/p2p/message.go
index 89ad189d76..ade39d25a3 100644
--- a/p2p/message.go
+++ b/p2p/message.go
@@ -3,12 +3,12 @@ package p2p
 import (
 	"bytes"
 	"encoding/binary"
-	"fmt"
 	"io"
 	"io/ioutil"
 	"math/big"
 
 	"github.com/ethereum/go-ethereum/ethutil"
+	"github.com/ethereum/go-ethereum/rlp"
 )
 
 // Msg defines the structure of a p2p message.
@@ -43,16 +43,10 @@ func encodePayload(params ...interface{}) []byte {
 
 // Data returns the decoded RLP payload items in a message.
 func (msg Msg) Data() (*ethutil.Value, error) {
-	// TODO: avoid copying when we have a better RLP decoder
-	buf := new(bytes.Buffer)
-	var s []interface{}
-	if _, err := buf.ReadFrom(msg.Payload); err != nil {
-		return nil, err
-	}
-	for buf.Len() > 0 {
-		s = append(s, ethutil.DecodeWithReader(buf))
-	}
-	return ethutil.NewValue(s), nil
+	s := rlp.NewListStream(msg.Payload, uint64(msg.Size))
+	var v []interface{}
+	err := s.Decode(&v)
+	return ethutil.NewValue(v), err
 }
 
 // Discard reads any remaining payload data into a black hole.
@@ -137,13 +131,9 @@ func makeListHeader(length uint32) []byte {
 	return append([]byte{lenb}, enc...)
 }
 
-type byteReader interface {
-	io.Reader
-	io.ByteReader
-}
-
 // readMsg reads a message header from r.
-func readMsg(r byteReader) (msg Msg, err error) {
+// 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 {
@@ -155,64 +145,35 @@ func readMsg(r byteReader) (msg Msg, err error) {
 	size := binary.BigEndian.Uint32(start[4:])
 
 	// decode start of RLP message to get the message code
-	_, hdrlen, err := readListHeader(r)
+	posr := &postrack{r, 0}
+	s := rlp.NewStream(posr)
+	if _, err := s.List(); err != nil {
+		return msg, err
+	}
+	code, err := s.Uint()
 	if err != nil {
 		return msg, err
 	}
-	code, codelen, err := readMsgCode(r)
-	if err != nil {
-		return msg, err
-	}
-
-	rlpsize := size - hdrlen - codelen
-	return Msg{
-		Code:    code,
-		Size:    rlpsize,
-		Payload: io.LimitReader(r, int64(rlpsize)),
-	}, nil
+	payloadsize := size - posr.p
+	return Msg{code, payloadsize, io.LimitReader(r, int64(payloadsize))}, nil
 }
 
-// readListHeader reads an RLP list header from r.
-func readListHeader(r byteReader) (len uint64, hdrlen uint32, err error) {
-	b, err := r.ReadByte()
-	if err != nil {
-		return 0, 0, err
-	}
-	if b < 0xC0 {
-		return 0, 0, fmt.Errorf("expected list start byte >= 0xC0, got %x", b)
-	} else if b < 0xF7 {
-		len = uint64(b - 0xc0)
-		hdrlen = 1
-	} else {
-		lenlen := b - 0xF7
-		lenbuf := make([]byte, 8)
-		if _, err := io.ReadFull(r, lenbuf[8-lenlen:]); err != nil {
-			return 0, 0, err
-		}
-		len = binary.BigEndian.Uint64(lenbuf)
-		hdrlen = 1 + uint32(lenlen)
-	}
-	return len, hdrlen, nil
+// postrack wraps an rlp.ByteReader with a position counter.
+type postrack struct {
+	r rlp.ByteReader
+	p uint32
 }
 
-// readUint reads an RLP-encoded unsigned integer from r.
-func readMsgCode(r byteReader) (code uint64, codelen uint32, err error) {
-	b, err := r.ReadByte()
-	if err != nil {
-		return 0, 0, err
-	}
-	if b < 0x80 {
-		return uint64(b), 1, nil
-	} else if b < 0x89 { // max length for uint64 is 8 bytes
-		codelen = uint32(b - 0x80)
-		if codelen == 0 {
-			return 0, 1, nil
-		}
-		buf := make([]byte, 8)
-		if _, err := io.ReadFull(r, buf[8-codelen:]); err != nil {
-			return 0, 0, err
-		}
-		return binary.BigEndian.Uint64(buf), codelen, nil
-	}
-	return 0, 0, fmt.Errorf("bad RLP type for message code: %x", b)
+func (r *postrack) Read(buf []byte) (int, error) {
+	n, err := r.r.Read(buf)
+	r.p += uint32(n)
+	return n, err
+}
+
+func (r *postrack) ReadByte() (byte, error) {
+	b, err := r.r.ReadByte()
+	if err == nil {
+		r.p++
+	}
+	return b, err
 }
diff --git a/p2p/message_test.go b/p2p/message_test.go
index 1edabc4e7b..02d70a28ba 100644
--- a/p2p/message_test.go
+++ b/p2p/message_test.go
@@ -46,6 +46,9 @@ func TestEncodeDecodeMsg(t *testing.T) {
 	if err != nil {
 		t.Fatalf("first payload item decode error: %v", err)
 	}
+	if v := data.Len(); v != 2 {
+		t.Errorf("incorrect data.Len(): got %v, expected %d", v, 1)
+	}
 	if v := data.Get(0).Uint(); v != 1 {
 		t.Errorf("incorrect data[0]: got %v, expected %d", v, 1)
 	}
diff --git a/p2p/peer_test.go b/p2p/peer_test.go
index 1afa0ab170..56cd4d8902 100644
--- a/p2p/peer_test.go
+++ b/p2p/peer_test.go
@@ -57,7 +57,7 @@ func TestPeerProtoReadMsg(t *testing.T) {
 			if err != nil {
 				t.Errorf("data decoding error: %v", err)
 			}
-			expdata := []interface{}{1, []byte{0x30, 0x30, 0x30}}
+			expdata := []interface{}{[]byte{0x01}, []byte{0x30, 0x30, 0x30}}
 			if !reflect.DeepEqual(data.Slice(), expdata) {
 				t.Errorf("incorrect msg data %#v", data.Slice())
 			}