text: /**
   * FreeRDP: A Remote Desktop Protocol Client
   * Transport Packets (TPKTs)
   *
   * Copyright 2011 Marc-Andre Moreau <marcandre.moreau@gmail.com>
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  #include "tpdu.h"
  
  #include "tpkt.h"
  
  /**
   * TPKTs are defined in:
   *
   * http://tools.ietf.org/html/rfc1006/
   * RFC 1006 - ISO Transport Service on top of the TCP
   *
   * http://www.itu.int/rec/T-REC-T.123/
   * ITU-T T.123 (01/2007) - Network-specific data protocol stacks for multimedia conferencing
   *
   *       TPKT Header
   *  ____________________   byte
   * |                    |
   * |     3 (version)    |   1
   * |____________________|
   * |                    |
   * |      Reserved      |   2
   * |____________________|
   * |                    |
   * |    Length (MSB)    |   3
   * |____________________|
   * |                    |
   * |    Length (LSB)    |   4
   * |____________________|
   * |                    |
   * |     X.224 TPDU     |   5 - ?
   *          ....
   *
   * A TPKT header is of fixed length 4, and the following X.224 TPDU is at least three bytes long.
   * Therefore, the minimum TPKT length is 7, and the maximum TPKT length is 65535. Because the TPKT
   * length includes the TPKT header (4 bytes), the maximum X.224 TPDU length is 65531.
   */
  
  /**
   * Verify if a packet has valid TPKT header.\n
   * @param s
   * @return boolean
   */
  
  boolean tpkt_verify_header(STREAM* s)
  {
  	uint8 version;
  
  	stream_peek_uint8(s, version);
  	if (version == 3)
  		return true;
  	else
  		return false;
  }
  
  /**
   * Read a TPKT header.\n
   * @param s
   * @return length
   */
  
  uint16 tpkt_read_header(STREAM* s)
  {
  	uint8 version;
  	uint16 length;
  
  	stream_peek_uint8(s, version);
  
  	if (version == 3)
  	{
  		stream_seek(s, 2);
  		stream_read_uint16_be(s, length);
  	}
  	else
  	{
  		/* not a TPKT header */
  		length = 0;
  	}
  
  	return length;
  }
  
  /**
   * Write a TPKT header.\n
   * @param s
   * @param length
   */
  
  void tpkt_write_header(STREAM* s, uint16 length)
  {
  	stream_write_uint8(s, 3); /* version */
  	stream_write_uint8(s, 0); /* reserved */
  	stream_write_uint16_be(s, length); /* length */
  }
  