基本实现FastPath协议

protocol/fastpath/fastpath.go

@@ -0,0 +1,68 @@
+package fastpath
+
+import (
+	"encoding/binary"
+	"errors"
+	"rdp_channel/protocol/core/transport"
+)
+
+// 协议常量
+const (
+	FASTPATH_PDU_HEADER_LENGTH  = 0x4 // updateHeader(1 bytes) + compressionFlags(1 bytes) + size(2 bytes)
+	FASTPATH__MAX_PACKET_LENGTH = 0xffff
+
+	FASTPATH_UPDATETYPE_ORDERS uint32 = 0x0
+	FASTPATH_UPDATETYPE_BITMAP uint32 = 0x1
+)
+
+const (
+	// update header: https://learn.microsoft.com/en-us/openspecs/windows_protocols/ms-rdpbcgr/a1c4caa8-00ed-45bb-a06e-5177473766d3
+	FASTPATH_UPDATE_HEADER     uint8 = 0x8
+	FASTPATH_COMPRESSION_FLAGS uint8 = 0x0
+)
+
+var (
+	FASTPATH_INVALID_PACKET_LENGTH = errors.New("[FASTPATH] invalid packet length")
+)
+
+type FastPath struct {
+	transport transport.Transport
+}
+
+func New(transport transport.Transport) *FastPath {
+	return &FastPath{
+		transport: transport,
+	}
+}
+
+func (fp *FastPath) Write(data []byte) (int, error) {
+	/*
+		构造PDU
+		格式参考：https://learn.microsoft.com/en-us/openspecs/windows_protocols/ms-rdpbcgr/0ae3c114-1439-4465-8d3f-6585227eff7d
+	*/
+	dataLen := len(data)
+	if dataLen > FASTPATH__MAX_PACKET_LENGTH {
+		return dataLen, FASTPATH_INVALID_PACKET_LENGTH
+	}
+
+	size := uint16(FASTPATH_PDU_HEADER_LENGTH + dataLen)
+	pdu := make([]byte, size)
+
+	pdu[0] = FASTPATH_UPDATE_HEADER
+	pdu[1] = FASTPATH_COMPRESSION_FLAGS
+	binary.LittleEndian.PutUint16(pdu[2:4], size)
+
+	copy(pdu[4:], data)
+
+	return fp.transport.Write(pdu)
+}
+
+func (fp *FastPath) Read() (int, []byte, error) {
+	_, packet, err := fp.transport.Read()
+	if err != nil {
+		return 0, nil, err
+	}
+
+	data := packet[FASTPATH_PDU_HEADER_LENGTH:]
+	return len(data), data, nil
+}