initial commit

handler/relay/conn.go

@@ -0,0 +1,81 @@
+package relay
+
+import (
+	"bytes"
+	"encoding/binary"
+	"errors"
+	"io"
+	"math"
+	"net"
+)
+
+type tcpConn struct {
+	net.Conn
+	wbuf bytes.Buffer
+}
+
+func (c *tcpConn) Read(b []byte) (n int, err error) {
+	if err != nil {
+		return
+	}
+	return c.Conn.Read(b)
+}
+
+func (c *tcpConn) Write(b []byte) (n int, err error) {
+	n = len(b) // force byte length consistent
+	if c.wbuf.Len() > 0 {
+		c.wbuf.Write(b) // append the data to the cached header
+		_, err = c.wbuf.WriteTo(c.Conn)
+		return
+	}
+	_, err = c.Conn.Write(b)
+	return
+}
+
+type udpConn struct {
+	net.Conn
+	wbuf bytes.Buffer
+}
+
+func (c *udpConn) Read(b []byte) (n int, err error) {
+	var bb [2]byte
+	_, err = io.ReadFull(c.Conn, bb[:])
+	if err != nil {
+		return
+	}
+
+	dlen := int(binary.BigEndian.Uint16(bb[:]))
+	if len(b) >= dlen {
+		return io.ReadFull(c.Conn, b[:dlen])
+	}
+	buf := make([]byte, dlen)
+	_, err = io.ReadFull(c.Conn, buf)
+	n = copy(b, buf)
+
+	return
+}
+
+func (c *udpConn) Write(b []byte) (n int, err error) {
+	if len(b) > math.MaxUint16 {
+		err = errors.New("write: data maximum exceeded")
+		return
+	}
+
+	n = len(b)
+	if c.wbuf.Len() > 0 {
+		var bb [2]byte
+		binary.BigEndian.PutUint16(bb[:], uint16(len(b)))
+		c.wbuf.Write(bb[:])
+		c.wbuf.Write(b) // append the data to the cached header
+		_, err = c.wbuf.WriteTo(c.Conn)
+		return
+	}
+
+	var bb [2]byte
+	binary.BigEndian.PutUint16(bb[:], uint16(len(b)))
+	_, err = c.Conn.Write(bb[:])
+	if err != nil {
+		return
+	}
+	return c.Conn.Write(b)
+}