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/**

 * \addtogroup uip

 * @{

 */

/**

 * \defgroup slip Serial Line IP (SLIP) protocol

 * @{

 *

 * The SLIP protocol is a very simple way to transmit IP packets over

 * a serial line. It does not provide any framing or error control,

 * and is therefore not very widely used today.

 *

 * This SLIP implementation requires two functions for accessing the

 * serial device: slipdev_char_poll() and slipdev_char_put(). These

 * must be implemented specifically for the system on which the SLIP

 * protocol is to be run.

 */

/**

 * \file

 * SLIP protocol implementation

 * \author Adam Dunkels <adam@dunkels.com>

 */

/*

 * Copyright (c) 2001, Adam Dunkels.

 * All rights reserved.

 *

 * Redistribution and use in source and binary forms, with or without

 * modification, are permitted provided that the following conditions

 * are met:

 * 1. Redistributions of source code must retain the above copyright

 *    notice, this list of conditions and the following disclaimer.

 * 2. Redistributions in binary form must reproduce the above copyright

 *    notice, this list of conditions and the following disclaimer in the

 *    documentation and/or other materials provided with the distribution.

 * 3. The name of the author may not be used to endorse or promote

 *    products derived from this software without specific prior

 *    written permission.

 *

 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS

 * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED

 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE

 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY

 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL

 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE

 * GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS

 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,

 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING

 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS

 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

 *

 * This file is part of the uIP TCP/IP stack.

 *

 * $Id: slipdev.c 2 2011-07-17 20:13:17Z filepang@gmail.com $

 *

 */

/*

 * This is a generic implementation of the SLIP protocol over an RS232

 * (serial) device.

 *

 * Huge thanks to Ullrich von Bassewitz <uz@cc65.org> of cc65 fame for

 * and endless supply of bugfixes, insightsful comments and

 * suggestions, and improvements to this code!

 */

#include "uip.h"

#define SLIP_END     0300

#define SLIP_ESC     0333

#define SLIP_ESC_END 0334

#define SLIP_ESC_ESC 0335

static u8_t slip_buf[UIP_BUFSIZE];

static u16_t len, tmplen;

static u8_t lastc;

/*-----------------------------------------------------------------------------------*/

/**

 * Send the packet in the uip_buf and uip_appdata buffers using the

 * SLIP protocol.

 *

 * The first 40 bytes of the packet (the IP and TCP headers) are read

 * from the uip_buf buffer, and the following bytes (the application

 * data) are read from the uip_appdata buffer.

 *

 */

/*-----------------------------------------------------------------------------------*/

void

slipdev_send(void)

{

  u16_t i;

  u8_t *ptr;

  u8_t c;

  slipdev_char_put(SLIP_END);

  ptr = uip_buf;

  for(i = 0; i < uip_len; ++i) {

    if(i == 40) {

      ptr = (u8_t *)uip_appdata;

    }

    c = *ptr++;

    switch(c) {

    case SLIP_END:

      slipdev_char_put(SLIP_ESC);

      slipdev_char_put(SLIP_ESC_END);

      break;

    case SLIP_ESC:

      slipdev_char_put(SLIP_ESC);

      slipdev_char_put(SLIP_ESC_ESC);

      break;

    default:

      slipdev_char_put(c);

      break;

    }

  }

  slipdev_char_put(SLIP_END);

}

/*-----------------------------------------------------------------------------------*/

/**

 * Poll the SLIP device for an available packet.

 *

 * This function will poll the SLIP device to see if a packet is

 * available. It uses a buffer in which all avaliable bytes from the

 * RS232 interface are read into. When a full packet has been read

 * into the buffer, the packet is copied into the uip_buf buffer and

 * the length of the packet is returned.

 *

 * \return The length of the packet placed in the uip_buf buffer, or

 * zero if no packet is available.

 */

/*-----------------------------------------------------------------------------------*/

u16_t

slipdev_poll(void)

{

  u8_t c;

  while(slipdev_char_poll(c)) {

    switch(c) {

    case SLIP_ESC:

      lastc = c;

      break;

    case SLIP_END:

      lastc = c;

      /* End marker found, we copy our input buffer to the uip_buf

         buffer and return the size of the packet we copied. */

      memcpy(uip_buf, slip_buf, len);

      tmplen = len;

      len = 0;

      return tmplen;

    default:

      if(lastc == SLIP_ESC) {

        lastc = c;

        /* Previous read byte was an escape byte, so this byte will be

           interpreted differently from others. */

        switch(c) {

        case SLIP_ESC_END:

          c = SLIP_END;

          break;

        case SLIP_ESC_ESC:

          c = SLIP_ESC;

          break;

        }

      } else {

        lastc = c;

      }

      slip_buf[len] = c;

      ++len;

      if(len > UIP_BUFSIZE) {

        len = 0;

      }

      break;

    }

  }

  return 0;

}

/*-----------------------------------------------------------------------------------*/

/**

 * Initialize the SLIP module.

 *

 * This function does not initialize the underlying RS232 device, but

 * only the SLIP part.

 */

/*-----------------------------------------------------------------------------------*/

void

slipdev_init(void)

{

  lastc = len = 0;

}

/*-----------------------------------------------------------------------------------*/

/** @} */

/** @} */