1 files changed, 255 insertions, 0 deletions
diff --git a/p2p/message.go b/p2p/message.go
new file mode 100644
index 000000000..b42acbe3c
--- /dev/null
+++ b/p2p/message.go
@@ -0,0 +1,255 @@
+package p2p
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"net"
+	"sync"
+	"sync/atomic"
+	"time"
+
+	"github.com/ethereum/go-ethereum/rlp"
+)
+
+// 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    uint64
+	Size    uint32 // size of the paylod
+	Payload io.Reader
+}
+
+// Decode parses 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 {
+	if err := rlp.Decode(msg.Payload, val); err != nil {
+		return newPeerError(errInvalidMsg, "(code %x) (size %d) %v", msg.Code, msg.Size, err)
+	}
+	return nil
+}
+
+func (msg Msg) String() string {
+	return fmt.Sprintf("msg #%v (%v bytes)", msg.Code, msg.Size)
+}
+
+// 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)
+}
+
+type MsgWriter interface {
+	// WriteMsg sends a message. It will block until the message's
+	// Payload has been consumed by the other end.
+	//
+	// Note that messages can be sent only once because their
+	// payload reader is drained.
+	WriteMsg(Msg) error
+}
+
+// MsgReadWriter provides reading and writing of encoded messages.
+// Implementations should ensure that ReadMsg and WriteMsg can be
+// called simultaneously from multiple goroutines.
+type MsgReadWriter interface {
+	MsgReader
+	MsgWriter
+}
+
+// Send writes an RLP-encoded message with the given code.
+// data should encode as an RLP list.
+func Send(w MsgWriter, msgcode uint64, data interface{}) error {
+	size, r, err := rlp.EncodeToReader(data)
+	if err != nil {
+		return err
+	}
+	return w.WriteMsg(Msg{Code: msgcode, Size: uint32(size), Payload: r})
+}
+
+// SendItems writes an RLP with the given code and data elements.
+// For a call such as:
+//
+//    SendItems(w, code, e1, e2, e3)
+//
+// the message payload will be an RLP list containing the items:
+//
+//    [e1, e2, e3]
+//
+func SendItems(w MsgWriter, msgcode uint64, elems ...interface{}) error {
+	return Send(w, msgcode, elems)
+}
+
+// netWrapper wraps a MsgReadWriter with locks around
+// ReadMsg/WriteMsg and applies read/write deadlines.
+type netWrapper struct {
+	rmu, wmu sync.Mutex
+
+	rtimeout, wtimeout time.Duration
+	conn               net.Conn
+	wrapped            MsgReadWriter
+}
+
+func (rw *netWrapper) ReadMsg() (Msg, error) {
+	rw.rmu.Lock()
+	defer rw.rmu.Unlock()
+	rw.conn.SetReadDeadline(time.Now().Add(rw.rtimeout))
+	return rw.wrapped.ReadMsg()
+}
+
+func (rw *netWrapper) WriteMsg(msg Msg) error {
+	rw.wmu.Lock()
+	defer rw.wmu.Unlock()
+	rw.conn.SetWriteDeadline(time.Now().Add(rw.wtimeout))
+	return rw.wrapped.WriteMsg(msg)
+}
+
+// eofSignal wraps a reader with eof signaling. the eof channel is
+// closed when the wrapped reader returns an error or when count bytes
+// have been read.
+type eofSignal struct {
+	wrapped io.Reader
+	count   uint32 // number of bytes left
+	eof     chan<- struct{}
+}
+
+// note: when using eofSignal to detect whether a message payload
+// has been read, Read might not be called for zero sized messages.
+func (r *eofSignal) Read(buf []byte) (int, error) {
+	if r.count == 0 {
+		if r.eof != nil {
+			r.eof <- struct{}{}
+			r.eof = nil
+		}
+		return 0, io.EOF
+	}
+
+	max := len(buf)
+	if int(r.count) < len(buf) {
+		max = int(r.count)
+	}
+	n, err := r.wrapped.Read(buf[:max])
+	r.count -= uint32(n)
+	if (err != nil || r.count == 0) && r.eof != nil {
+		r.eof <- struct{}{} // tell Peer that msg has been consumed
+		r.eof = nil
+	}
+	return n, err
+}
+
+// MsgPipe creates a message pipe. Reads on one end are matched
+// with writes on the other. The pipe is full-duplex, both ends
+// implement MsgReadWriter.
+func MsgPipe() (*MsgPipeRW, *MsgPipeRW) {
+	var (
+		c1, c2  = make(chan Msg), make(chan Msg)
+		closing = make(chan struct{})
+		closed  = new(int32)
+		rw1     = &MsgPipeRW{c1, c2, closing, closed}
+		rw2     = &MsgPipeRW{c2, c1, closing, closed}
+	)
+	return rw1, rw2
+}
+
+// ErrPipeClosed is returned from pipe operations after the
+// pipe has been closed.
+var ErrPipeClosed = errors.New("p2p: read or write on closed message pipe")
+
+// MsgPipeRW is an endpoint of a MsgReadWriter pipe.
+type MsgPipeRW struct {
+	w       chan<- Msg
+	r       <-chan Msg
+	closing chan struct{}
+	closed  *int32
+}
+
+// WriteMsg sends a messsage on the pipe.
+// It blocks until the receiver has consumed the message payload.
+func (p *MsgPipeRW) WriteMsg(msg Msg) error {
+	if atomic.LoadInt32(p.closed) == 0 {
+		consumed := make(chan struct{}, 1)
+		msg.Payload = &eofSignal{msg.Payload, msg.Size, consumed}
+		select {
+		case p.w <- msg:
+			if msg.Size > 0 {
+				// wait for payload read or discard
+				select {
+				case <-consumed:
+				case <-p.closing:
+				}
+			}
+			return nil
+		case <-p.closing:
+		}
+	}
+	return ErrPipeClosed
+}
+
+// ReadMsg returns a message sent on the other end of the pipe.
+func (p *MsgPipeRW) ReadMsg() (Msg, error) {
+	if atomic.LoadInt32(p.closed) == 0 {
+		select {
+		case msg := <-p.r:
+			return msg, nil
+		case <-p.closing:
+		}
+	}
+	return Msg{}, ErrPipeClosed
+}
+
+// Close unblocks any pending ReadMsg and WriteMsg calls on both ends
+// of the pipe. They will return ErrPipeClosed. Close also
+// interrupts any reads from a message payload.
+func (p *MsgPipeRW) Close() error {
+	if atomic.AddInt32(p.closed, 1) != 1 {
+		// someone else is already closing
+		atomic.StoreInt32(p.closed, 1) // avoid overflow
+		return nil
+	}
+	close(p.closing)
+	return nil
+}
+
+// ExpectMsg reads a message from r and verifies that its
+// code and encoded RLP content match the provided values.
+// If content is nil, the payload is discarded and not verified.
+func ExpectMsg(r MsgReader, code uint64, content interface{}) error {
+	msg, err := r.ReadMsg()
+	if err != nil {
+		return err
+	}
+	if msg.Code != code {
+		return fmt.Errorf("message code mismatch: got %d, expected %d", msg.Code, code)
+	}
+	if content == nil {
+		return msg.Discard()
+	} else {
+		contentEnc, err := rlp.EncodeToBytes(content)
+		if err != nil {
+			panic("content encode error: " + err.Error())
+		}
+		if int(msg.Size) != len(contentEnc) {
+			return fmt.Errorf("message size mismatch: got %d, want %d", msg.Size, len(contentEnc))
+		}
+		actualContent, err := ioutil.ReadAll(msg.Payload)
+		if err != nil {
+			return err
+		}
+		if !bytes.Equal(actualContent, contentEnc) {
+			return fmt.Errorf("message payload mismatch:\ngot:  %x\nwant: %x", actualContent, contentEnc)
+		}
+	}
+	return nil
+}