Add gRPC Transport support (#356)

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

transport/internet/grpc/encoding/hunkconn.go

@@ -0,0 +1,123 @@
+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 HunkConn interface {
+	Send(*Hunk) error
+	Recv() (*Hunk, error)
+	SendMsg(m interface{}) error
+	RecvMsg(m interface{}) error
+}
+
+type StreamCloser interface {
+	CloseSend() error
+}
+
+type HunkReaderWriter struct {
+	hc     HunkConn
+	cancel context.CancelFunc
+	done   *done.Instance
+
+	buf   []byte
+	index int
+}
+
+func NewHunkReadWriter(hc HunkConn, cancel context.CancelFunc) *HunkReaderWriter {
+	return &HunkReaderWriter{hc, cancel, done.New(), nil, 0}
+}
+
+func NewHunkConn(hc HunkConn, cancel context.CancelFunc) net.Conn {
+	wrc := NewHunkReadWriter(hc, cancel)
+	return cnc.NewConnection(
+		cnc.ConnectionInput(wrc),
+		cnc.ConnectionOutput(wrc),
+		cnc.ConnectionOnClose(wrc),
+	)
+}
+
+func (h *HunkReaderWriter) 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
+	h.index = 0
+
+	return nil
+}
+
+func (h *HunkReaderWriter) Read(buf []byte) (int, error) {
+	if h.done.Done() {
+		return 0, io.EOF
+	}
+
+	if h.index >= len(h.buf) {
+		if err := h.forceFetch(); err != nil {
+			return 0, err
+		}
+	}
+	n := copy(buf, h.buf[h.index:])
+	h.index += n
+
+	return n, nil
+}
+
+func (h *HunkReaderWriter) ReadMultiBuffer() (buf.MultiBuffer, error) {
+	if h.done.Done() {
+		return nil, io.EOF
+	}
+	if h.index >= len(h.buf) {
+		if err := h.forceFetch(); err != nil {
+			return nil, err
+		}
+	}
+
+	if cap(h.buf) == buf.Size {
+		b := h.buf
+		h.index = len(h.buf)
+		return buf.MultiBuffer{buf.NewExisted(b)}, nil
+	}
+
+	b := buf.New()
+	_, err := b.ReadFrom(h)
+	if err != nil {
+		return nil, err
+	}
+	return buf.MultiBuffer{b}, nil
+}
+
+func (h *HunkReaderWriter) Write(buf []byte) (int, error) {
+	if h.done.Done() {
+		return 0, io.ErrClosedPipe
+	}
+
+	err := h.hc.Send(&Hunk{Data: buf[:]})
+	if err != nil {
+		return 0, newError("failed to send data over gRPC tunnel").Base(err)
+	}
+	return len(buf), nil
+}
+
+func (h *HunkReaderWriter) Close() error {
+	if h.cancel != nil {
+		h.cancel()
+	}
+	if sc, match := h.hc.(StreamCloser); match {
+		return sc.CloseSend()
+	}
+
+	return h.done.Close()
+}