Add append conn

common/bufio/append.go

@@ -0,0 +1,81 @@
+package bufio
+
+import (
+	"github.com/sagernet/sing/common"
+	"github.com/sagernet/sing/common/buf"
+	N "github.com/sagernet/sing/common/network"
+)
+
+type appendConn struct {
+	N.ExtendedConn
+	reader N.ExtendedReader
+	writer N.ExtendedWriter
+}
+
+func NewAppendConn(conn N.ExtendedConn, reader N.ExtendedReader, writer N.ExtendedWriter) N.ExtendedConn {
+	return &appendConn{
+		ExtendedConn: conn,
+		reader:       reader,
+		writer:       writer,
+	}
+}
+
+func (c *appendConn) Read(p []byte) (n int, err error) {
+	if c.reader == nil {
+		return c.ExtendedConn.Read(p)
+	} else {
+		return c.reader.Read(p)
+	}
+}
+
+func (c *appendConn) ReadBuffer(buffer *buf.Buffer) error {
+	if c.reader == nil {
+		return c.ExtendedConn.ReadBuffer(buffer)
+	} else {
+		return c.reader.ReadBuffer(buffer)
+	}
+}
+
+func (c *appendConn) Write(p []byte) (n int, err error) {
+	if c.writer == nil {
+		return c.ExtendedConn.Write(p)
+	} else {
+		return c.writer.Write(p)
+	}
+}
+
+func (c *appendConn) WriteBuffer(buffer *buf.Buffer) error {
+	if c.writer == nil {
+		return c.ExtendedConn.WriteBuffer(buffer)
+	} else {
+		return c.writer.WriteBuffer(buffer)
+	}
+}
+
+func (c *appendConn) Close() error {
+	return common.Close(
+		c.ExtendedConn,
+		c.reader,
+		c.writer,
+	)
+}
+
+func (c *appendConn) UpstreamReader() any {
+	return c.reader
+}
+
+func (c *appendConn) ReaderReplaceable() bool {
+	return true
+}
+
+func (c *appendConn) UpstreamWriter() any {
+	return c.writer
+}
+
+func (c *appendConn) WriterReplaceable() bool {
+	return true
+}
+
+func (c *appendConn) Upstream() any {
+	return c.ExtendedConn
+}