feat(p2p): support tcp protocol

gold/p2p/tcp/pdu.go

@@ -0,0 +1,65 @@
+package tcp
+
+import (
+	"encoding/binary"
+	"io"
+	"net"
+
+	"github.com/fumiama/WireGold/helper"
+)
+
+type packetType uint8
+
+const (
+	packetTypeKeepAlive packetType = iota
+	packetTypeNormal
+)
+
+type packet struct {
+	typ packetType
+	len uint16
+	dat []byte
+	io.ReaderFrom
+	io.WriterTo
+}
+
+func (p *packet) pack() (net.Buffers, func()) {
+	d, cl := helper.OpenWriterF(func(w *helper.Writer) {
+		w.WriteByte(byte(p.typ))
+		w.WriteUInt16(p.len)
+	})
+	return net.Buffers{d, p.dat}, cl
+}
+
+func (p *packet) Read(_ []byte) (int, error) {
+	panic("stub")
+}
+
+func (p *packet) Write(_ []byte) (int, error) {
+	panic("stub")
+}
+
+func (p *packet) ReadFrom(r io.Reader) (n int64, err error) {
+	var buf [3]byte
+	cnt, err := io.ReadFull(r, buf[:])
+	n = int64(cnt)
+	if err != nil {
+		return
+	}
+	p.typ = packetType(buf[0])
+	p.len = binary.LittleEndian.Uint16(buf[1:3])
+	w := helper.SelectWriter()
+	copied, err := io.CopyN(w, r, int64(p.len))
+	n += copied
+	if err != nil {
+		return
+	}
+	p.dat = w.Bytes()
+	return
+}
+
+func (p *packet) WriteTo(w io.Writer) (n int64, err error) {
+	buf, cl := p.pack()
+	defer cl()
+	return io.Copy(w, &buf)
+}