Add gRPC Transport support (#356)

Co-authored-by: JimhHan <50871214+JimhHan@users.noreply.github.com>

transport/internet/grpc/encoding/multiconn.go

@@ -0,0 +1,108 @@
+package encoding
+
+import (
+	"context"
+	"io"
+	"net"
+
+	"github.com/xtls/xray-core/common/buf"
+	"github.com/xtls/xray-core/common/net/cnc"
+	"github.com/xtls/xray-core/common/signal/done"
+)
+
+type MultiHunkConn interface {
+	Send(*MultiHunk) error
+	Recv() (*MultiHunk, error)
+	SendMsg(m interface{}) error
+	RecvMsg(m interface{}) error
+}
+
+type MultiHunkReaderWriter struct {
+	hc     MultiHunkConn
+	cancel context.CancelFunc
+	done   *done.Instance
+
+	buf [][]byte
+}
+
+func NewMultiHunkReadWriter(hc MultiHunkConn, cancel context.CancelFunc) *MultiHunkReaderWriter {
+	return &MultiHunkReaderWriter{hc, cancel, done.New(), nil}
+}
+
+func NewMultiHunkConn(hc MultiHunkConn, cancel context.CancelFunc) net.Conn {
+	wrc := NewMultiHunkReadWriter(hc, cancel)
+	return cnc.NewConnection(
+		cnc.ConnectionInputMulti(wrc),
+		cnc.ConnectionOutputMulti(wrc),
+		cnc.ConnectionOnClose(wrc),
+	)
+}
+
+func (h *MultiHunkReaderWriter) forceFetch() error {
+	hunk, err := h.hc.Recv()
+	if err != nil {
+		if err == io.EOF {
+			return err
+		}
+
+		return newError("failed to fetch hunk from gRPC tunnel").Base(err)
+	}
+
+	h.buf = hunk.Data
+
+	return nil
+}
+
+func (h *MultiHunkReaderWriter) ReadMultiBuffer() (buf.MultiBuffer, error) {
+	if h.done.Done() {
+		return nil, io.EOF
+	}
+
+	if err := h.forceFetch(); err != nil {
+		return nil, err
+	}
+
+	var mb = make(buf.MultiBuffer, 0, len(h.buf))
+	for _, b := range h.buf {
+		if cap(b) >= buf.Size {
+			mb = append(mb, buf.NewExisted(b))
+			continue
+		}
+
+		nb := buf.New()
+		nb.Extend(int32(len(b)))
+		copy(nb.Bytes(), b)
+
+		mb = append(mb, nb)
+	}
+	return mb, nil
+}
+
+func (h *MultiHunkReaderWriter) WriteMultiBuffer(mb buf.MultiBuffer) error {
+	defer buf.ReleaseMulti(mb)
+	if h.done.Done() {
+		return io.ErrClosedPipe
+	}
+
+	hunk := &MultiHunk{Data: make([][]byte, len(mb))}
+	for _, b := range mb {
+		hunk.Data = append(hunk.Data, b.Bytes())
+	}
+
+	err := h.hc.Send(hunk)
+	if err != nil {
+		return err
+	}
+	return nil
+}
+
+func (h *MultiHunkReaderWriter) Close() error {
+	if h.cancel != nil {
+		h.cancel()
+	}
+	if sc, match := h.hc.(StreamCloser); match {
+		return sc.CloseSend()
+	}
+
+	return h.done.Close()
+}