text: /**
   * @file
   * lwIP Operating System abstraction
   *
   */
  
  /*
   * 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. 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 lwIP TCP/IP stack.
   *
   * Author: Adam Dunkels <adam@sics.se>
   *
   */
  
  #include "lwip/opt.h"
  
  #if (NO_SYS == 0) /* don't build if not configured for use in lwipopts.h */
  
  #include "lwip/sys.h"
  #include "lwip/def.h"
  #include "lwip/memp.h"
  #include "lwip/tcpip.h"
  
  /**
   * Struct used for sys_sem_wait_timeout() to tell wether the time
   * has run out or the semaphore has really become available.
   */
  struct sswt_cb
  {
    s16_t timeflag;
    sys_sem_t *psem;
  };
  
  /**
   * Wait (forever) for a message to arrive in an mbox.
   * While waiting, timeouts (for this thread) are processed.
   *
   * @param mbox the mbox to fetch the message from
   * @param msg the place to store the message
   */
  void
  sys_mbox_fetch(sys_mbox_t mbox, void **msg)
  {
    u32_t time_needed;
    struct sys_timeouts *timeouts;
    struct sys_timeo *tmptimeout;
    sys_timeout_handler h;
    void *arg;
  
   again:
    timeouts = sys_arch_timeouts();
  
    if (!timeouts || !timeouts->next) {
      UNLOCK_TCPIP_CORE();
      time_needed = sys_arch_mbox_fetch(mbox, msg, 0);
      LOCK_TCPIP_CORE();
    } else {
      if (timeouts->next->time > 0) {
        UNLOCK_TCPIP_CORE();
        time_needed = sys_arch_mbox_fetch(mbox, msg, timeouts->next->time);
        LOCK_TCPIP_CORE();
      } else {
        time_needed = SYS_ARCH_TIMEOUT;
      }
  
      if (time_needed == SYS_ARCH_TIMEOUT) {
        /* If time == SYS_ARCH_TIMEOUT, a timeout occured before a message
           could be fetched. We should now call the timeout handler and
           deallocate the memory allocated for the timeout. */
        tmptimeout = timeouts->next;
        timeouts->next = tmptimeout->next;
        h   = tmptimeout->h;
        arg = tmptimeout->arg;
        memp_free(MEMP_SYS_TIMEOUT, tmptimeout);
        if (h != NULL) {
          LWIP_DEBUGF(SYS_DEBUG, ("smf calling h=%p(%p)\n", (void*)&h, arg));
          h(arg);
        }
  
        /* We try again to fetch a message from the mbox. */
        goto again;
      } else {
        /* If time != SYS_ARCH_TIMEOUT, a message was received before the timeout
           occured. The time variable is set to the number of
           milliseconds we waited for the message. */
        if (time_needed < timeouts->next->time) {
          timeouts->next->time -= time_needed;
        } else {
          timeouts->next->time = 0;
        }
      }
    }
  }
  
  /**
   * Wait (forever) for a semaphore to become available.
   * While waiting, timeouts (for this thread) are processed.
   *
   * @param sem semaphore to wait for
   */
  void
  sys_sem_wait(sys_sem_t sem)
  {
    u32_t time_needed;
    struct sys_timeouts *timeouts;
    struct sys_timeo *tmptimeout;
    sys_timeout_handler h;
    void *arg;
  
   again:
  
    timeouts = sys_arch_timeouts();
  
    if (!timeouts || !timeouts->next) {
      sys_arch_sem_wait(sem, 0);
    } else {
      if (timeouts->next->time > 0) {
        time_needed = sys_arch_sem_wait(sem, timeouts->next->time);
      } else {
        time_needed = SYS_ARCH_TIMEOUT;
      }
  
      if (time_needed == SYS_ARCH_TIMEOUT) {
        /* If time == SYS_ARCH_TIMEOUT, a timeout occured before a message
          could be fetched. We should now call the timeout handler and
          deallocate the memory allocated for the timeout. */
        tmptimeout = timeouts->next;
        timeouts->next = tmptimeout->next;
        h = tmptimeout->h;
        arg = tmptimeout->arg;
        memp_free(MEMP_SYS_TIMEOUT, tmptimeout);
        if (h != NULL) {
          LWIP_DEBUGF(SYS_DEBUG, ("ssw h=%p(%p)\n", (void*)&h, (void *)arg));
          h(arg);
        }
  
        /* We try again to fetch a message from the mbox. */
        goto again;
      } else {
        /* If time != SYS_ARCH_TIMEOUT, a message was received before the timeout
           occured. The time variable is set to the number of
           milliseconds we waited for the message. */
        if (time_needed < timeouts->next->time) {
          timeouts->next->time -= time_needed;
        } else {
          timeouts->next->time = 0;
        }
      }
    }
  }
  
  /**
   * Create a one-shot timer (aka timeout). Timeouts are processed in the
   * following cases:
   * - while waiting for a message using sys_mbox_fetch()
   * - while waiting for a semaphore using sys_sem_wait() or sys_sem_wait_timeout()
   * - while sleeping using the inbuilt sys_msleep()
   *
   * @param msecs time in milliseconds after that the timer should expire
   * @param h callback function to call when msecs have elapsed
   * @param arg argument to pass to the callback function
   */
  void
  sys_timeout(u32_t msecs, sys_timeout_handler h, void *arg)
  {
    struct sys_timeouts *timeouts;
    struct sys_timeo *timeout, *t;
  
    timeout = memp_malloc(MEMP_SYS_TIMEOUT);
    if (timeout == NULL) {
      LWIP_ASSERT("sys_timeout: timeout != NULL", timeout != NULL);
      return;
    }
    timeout->next = NULL;
    timeout->h = h;
    timeout->arg = arg;
    timeout->time = msecs;
  
    timeouts = sys_arch_timeouts();
  
    LWIP_DEBUGF(SYS_DEBUG, ("sys_timeout: %p msecs=%"U32_F" h=%p arg=%p\n",
      (void *)timeout, msecs, (void*)&h, (void *)arg));
  
    if (timeouts == NULL) {
      LWIP_ASSERT("sys_timeout: timeouts != NULL", timeouts != NULL);
      return;
    }
  
    if (timeouts->next == NULL) {
      timeouts->next = timeout;
      return;
    }
  
    if (timeouts->next->time > msecs) {
      timeouts->next->time -= msecs;
      timeout->next = timeouts->next;
      timeouts->next = timeout;
    } else {
      for(t = timeouts->next; t != NULL; t = t->next) {
        timeout->time -= t->time;
        if (t->next == NULL || t->next->time > timeout->time) {
          if (t->next != NULL) {
            t->next->time -= timeout->time;
          }
          timeout->next = t->next;
          t->next = timeout;
          break;
        }
      }
    }
  }
  
  /**
   * Go through timeout list (for this task only) and remove the first matching
   * entry, even though the timeout has not triggered yet.
   *
   * @note This function only works as expected if there is only one timeout
   * calling 'h' in the list of timeouts.
   *
   * @param h callback function that would be called by the timeout
   * @param arg callback argument that would be passed to h
  */
  void
  sys_untimeout(sys_timeout_handler h, void *arg)
  {
    struct sys_timeouts *timeouts;
    struct sys_timeo *prev_t, *t;
  
    timeouts = sys_arch_timeouts();
  
    if (timeouts == NULL) {
      LWIP_ASSERT("sys_untimeout: timeouts != NULL", timeouts != NULL);
      return;
    }
    if (timeouts->next == NULL) {
      return;
    }
  
    for (t = timeouts->next, prev_t = NULL; t != NULL; prev_t = t, t = t->next) {
      if ((t->h == h) && (t->arg == arg)) {
        /* We have a match */
        /* Unlink from previous in list */
        if (prev_t == NULL)
          timeouts->next = t->next;
        else
          prev_t->next = t->next;
        /* If not the last one, add time of this one back to next */
        if (t->next != NULL)
          t->next->time += t->time;
        memp_free(MEMP_SYS_TIMEOUT, t);
        return;
      }
    }
    return;
  }
  
  /**
   * Timeout handler function for sys_sem_wait_timeout()
   *
   * @param arg struct sswt_cb* used to signal a semaphore and end waiting.
   */
  static void
  sswt_handler(void *arg)
  {
    struct sswt_cb *sswt_cb = (struct sswt_cb *) arg;
  
    /* Timeout. Set flag to TRUE and signal semaphore */
    sswt_cb->timeflag = 1;
    sys_sem_signal(*(sswt_cb->psem));
  }
  
  /**
   * Wait for a semaphore with timeout (specified in ms)
   *
   * @param sem semaphore to wait
   * @param timeout timeout in ms (0: wait forever)
   * @return 0 on timeout, 1 otherwise
   */
  int
  sys_sem_wait_timeout(sys_sem_t sem, u32_t timeout)
  {
    struct sswt_cb sswt_cb;
  
    sswt_cb.psem = &sem;
    sswt_cb.timeflag = 0;
  
    /* If timeout is zero, then just wait forever */
    if (timeout > 0) {
      /* Create a timer and pass it the address of our flag */
      sys_timeout(timeout, sswt_handler, &sswt_cb);
    }
    sys_sem_wait(sem);
    /* Was it a timeout? */
    if (sswt_cb.timeflag) {
      /* timeout */
      return 0;
    } else {
      /* Not a timeout. Remove timeout entry */
      sys_untimeout(sswt_handler, &sswt_cb);
      return 1;
    }
  }
  
  /**
   * Sleep for some ms. Timeouts are processed while sleeping.
   *
   * @param ms number of milliseconds to sleep
   */
  void
  sys_msleep(u32_t ms)
  {
    sys_sem_t delaysem = sys_sem_new(0);
  
    sys_sem_wait_timeout(delaysem, ms);
  
    sys_sem_free(delaysem);
  }
  
  
  #endif /* NO_SYS */
  