text: /**
   * @file
   * SLIP Interface
   *
   */
  
  /*
   * Copyright (c) 2001-2004 Swedish Institute of Computer Science.
   * 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. Neither the name of the Institute nor the names of its contributors 
   *    may be used to endorse or promote products derived from this software 
   *    without specific prior written permission. 
   *
   * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``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 INSTITUTE OR CONTRIBUTORS 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 built upon the file: src/arch\rtxc/netif\sioslip.c
   *
   * Author: Magnus Ivarsson <magnus.ivarsson(at)volvo.com> 
   */
  
  /* 
   * This is an arch independent SLIP netif. The specific serial hooks must be
   * provided by another file. They are sio_open, sio_read/sio_tryread and sio_send
   */
  
  #include "netif\slipif.h"
  #include "lwip\opt.h"
  
  #if LWIP_HAVE_SLIPIF
  
  #include "lwip\def.h"
  #include "lwip\pbuf.h"
  #include "lwip\sys.h"
  #include "lwip\stats.h"
  #include "lwip\snmp.h"
  #include "lwip\sio.h"
  
  #define SLIP_BLOCK     1
  #define SLIP_DONTBLOCK 0
  
  #define SLIP_END     0300 /* 0xC0 */
  #define SLIP_ESC     0333 /* 0xDB */
  #define SLIP_ESC_END 0334 /* 0xDC */
  #define SLIP_ESC_ESC 0335 /* 0xDD */
  
  #define SLIP_MAX_SIZE 1500
  
  enum slipif_recv_state {
      SLIP_RECV_NORMAL,
      SLIP_RECV_ESCAPE,
  };
  
  struct slipif_priv {
    sio_fd_t sd;
    /* q is the whole pbuf chain for a packet, p is the current pbuf in the chain */
    struct pbuf *p, *q;
    enum slipif_recv_state state;
    u16_t i, recved;
  };
  
  /**
   * Send a pbuf doing the necessary SLIP encapsulation
   *
   * Uses the serial layer's sio_send()
   *
   * @param netif the lwip network interface structure for this slipif
   * @param p the pbuf chaing packet to send
   * @param ipaddr the ip address to send the packet to (not used for slipif)
   * @return always returns ERR_OK since the serial layer does not provide return values
   */
  err_t
  slipif_output(struct netif *netif, struct pbuf *p, struct ip_addr *ipaddr)
  {
    struct slipif_priv *priv;
    struct pbuf *q;
    u16_t i;
    u8_t c;
  
    LWIP_ASSERT("netif != NULL", (netif != NULL));
    LWIP_ASSERT("netif->state != NULL", (netif->state != NULL));
    LWIP_ASSERT("p != NULL", (p != NULL));
  
    LWIP_UNUSED_ARG(ipaddr);
  
    priv = netif->state;
  
    /* Send pbuf out on the serial I/O device. */
    sio_send(SLIP_END, priv->sd);
  
    for (q = p; q != NULL; q = q->next) {
      for (i = 0; i < q->len; i++) {
        c = ((u8_t *)q->payload)[i];
        switch (c) {
        case SLIP_END:
          sio_send(SLIP_ESC, priv->sd);
          sio_send(SLIP_ESC_END, priv->sd);
          break;
        case SLIP_ESC:
          sio_send(SLIP_ESC, priv->sd);
          sio_send(SLIP_ESC_ESC, priv->sd);
          break;
        default:
          sio_send(c, priv->sd);
          break;
        }
      }
    }
    sio_send(SLIP_END, priv->sd);
    return ERR_OK;
  }
  
  /**
   * Static function for easy use of blockig or non-blocking
   * sio_read
   *
   * @param fd serial device handle
   * @param data pointer to data buffer for receiving
   * @param len maximum length (in bytes) of data to receive
   * @param block if 1, call sio_read; if 0, call sio_tryread
   * @return return value of sio_read of sio_tryread
   */
  static u32_t
  slip_sio_read(sio_fd_t fd, u8_t* data, u32_t len, u8_t block)
  {
    if (block) {
      return sio_read(fd, data, len);
    } else {
      return sio_tryread(fd, data, len);
    }
  }
  
  /**
   * Handle the incoming SLIP stream character by character
   *
   * Poll the serial layer by calling sio_read() or sio_tryread().
   *
   * @param netif the lwip network interface structure for this slipif
   * @param block if 1, block until data is received; if 0, return when all data
   *        from the buffer is received (multiple calls to this function will
   *        return a complete packet, NULL is returned before - used for polling)
   * @return The IP packet when SLIP_END is received
   */
  static struct pbuf *
  slipif_input(struct netif *netif, u8_t block)
  {
    struct slipif_priv *priv;
    u8_t c;
    struct pbuf *t;
  
    LWIP_ASSERT("netif != NULL", (netif != NULL));
    LWIP_ASSERT("netif->state != NULL", (netif->state != NULL));
  
    priv = netif->state;
  
    while (slip_sio_read(priv->sd, &c, 1, block) > 0) {
      switch (priv->state) {
      case SLIP_RECV_NORMAL:
        switch (c) {
        case SLIP_END:
          if (priv->recved > 0) {
            /* Received whole packet. */
            /* Trim the pbuf to the size of the received packet. */
            pbuf_realloc(priv->q, priv->recved);
  
            LINK_STATS_INC(link.recv);
  
            LWIP_DEBUGF(SLIP_DEBUG, ("slipif: Got packet\n"));
            t = priv->q;
            priv->p = priv->q = NULL;
            priv->i = priv->recved = 0;
            return t;
          }
          continue;
        case SLIP_ESC:
          priv->state = SLIP_RECV_ESCAPE;
          continue;
        }
        break;
      case SLIP_RECV_ESCAPE:
        switch (c) {
        case SLIP_ESC_END:
          c = SLIP_END;
          break;
        case SLIP_ESC_ESC:
          c = SLIP_ESC;
          break;
        }
        priv->state = SLIP_RECV_NORMAL;
        /* FALLTHROUGH */
      }
  
      /* byte received, packet not yet completely received */
      if (priv->p == NULL) {
        /* allocate a new pbuf */
        LWIP_DEBUGF(SLIP_DEBUG, ("slipif_input: alloc\n"));
        priv->p = pbuf_alloc(PBUF_LINK, (PBUF_POOL_BUFSIZE - PBUF_LINK_HLEN), PBUF_POOL);
  
        if (priv->p == NULL) {
          LINK_STATS_INC(link.drop);
          LWIP_DEBUGF(SLIP_DEBUG, ("slipif_input: no new pbuf! (DROP)\n"));
          /* don't process any further since we got no pbuf to receive to */
          break;
        }
  
        if (priv->q != NULL) {
          /* 'chain' the pbuf to the existing chain */
          pbuf_cat(priv->q, priv->p);
        } else {
          /* p is the first pbuf in the chain */
          priv->q = priv->p;
        }
      }
  
      /* this automatically drops bytes if > SLIP_MAX_SIZE */
      if ((priv->p != NULL) && (priv->recved <= SLIP_MAX_SIZE)) {
        ((u8_t *)priv->p->payload)[priv->i] = c;
        priv->recved++;
        priv->i++;
        if (priv->i >= priv->p->len) {
          /* on to the next pbuf */
          priv->i = 0;
          if (priv->p->next != NULL && priv->p->next->len > 0) {
            /* p is a chain, on to the next in the chain */
              priv->p = priv->p->next;
          } else {
            /* p is a single pbuf, set it to NULL so next time a new
             * pbuf is allocated */
              priv->p = NULL;
          }
        }
      }
    }
  
    return NULL;
  }
  
  #if !NO_SYS
  /**
   * The SLIP input thread.
   *
   * Feed the IP layer with incoming packets
   *
   * @param nf the lwip network interface structure for this slipif
   */
  static void
  slipif_loop_thread(void *nf)
  {
    struct pbuf *p;
    struct netif *netif = (struct netif *)nf;
  
    while (1) {
      p = slipif_input(netif, SLIP_BLOCK);
      if (p != NULL) {
        if (netif->input(p, netif) != ERR_OK) {
          pbuf_free(p);
          p = NULL;
        }
      }
    }
  }
  #endif /* !NO_SYS */
  
  /**
   * SLIP netif initialization
   *
   * Call the arch specific sio_open and remember
   * the opened device in the state field of the netif.
   *
   * @param netif the lwip network interface structure for this slipif
   * @return ERR_OK if serial line could be opened,
   *         ERR_MEM if no memory could be allocated,
   *         ERR_IF is serial line couldn't be opened
   *
   * @note netif->num must contain the number of the serial port to open
   *       (0 by default)
   */
  err_t
  slipif_init(struct netif *netif)
  {
    struct slipif_priv *priv;
  
    LWIP_DEBUGF(SLIP_DEBUG, ("slipif_init: netif->num=%"U16_F"\n", (u16_t)netif->num));
  
    /* Allocate private data */
    priv = mem_malloc(sizeof(struct slipif_priv));
    if (!priv) {
      return ERR_MEM;
    }
  
    netif->name[0] = 's';
    netif->name[1] = 'l';
    netif->output = slipif_output;
    netif->mtu = SLIP_MAX_SIZE;
    netif->flags |= NETIF_FLAG_POINTTOPOINT;
  
    /* Try to open the serial port (netif->num contains the port number). */
    priv->sd = sio_open(netif->num);
    if (!priv->sd) {
      /* Opening the serial port failed. */
      mem_free(priv);
      return ERR_IF;
    }
  
    /* Initialize private data */
    priv->p = NULL;
    priv->q = NULL;
    priv->state = SLIP_RECV_NORMAL;
    priv->i = 0;
    priv->recved = 0;
  
    netif->state = priv;
  
    /* initialize the snmp variables and counters inside the struct netif
     * ifSpeed: no assumption can be made without knowing more about the
     * serial line!
     */
    NETIF_INIT_SNMP(netif, snmp_ifType_slip, 0);
  
    /* Create a thread to poll the serial line. */
    sys_thread_new(SLIPIF_THREAD_NAME, slipif_loop_thread, netif,
      SLIPIF_THREAD_STACKSIZE, SLIPIF_THREAD_PRIO);
    return ERR_OK;
  }
  
  /**
   * Polls the serial device and feeds the IP layer with incoming packets.
   *
   * @param netif The lwip network interface structure for this slipif
   */
  void
  slipif_poll(struct netif *netif)
  {
    struct pbuf *p;
    struct slipif_priv *priv;
  
    LWIP_ASSERT("netif != NULL", (netif != NULL));
    LWIP_ASSERT("netif->state != NULL", (netif->state != NULL));
  
    priv = netif->state;
  
    while ((p = slipif_input(netif, SLIP_DONTBLOCK)) != NULL) {
      if (netif->input(p, netif) != ERR_OK) {
        pbuf_free(p);
      }
    }
  }
  
  #endif /* LWIP_HAVE_SLIPIF */
  