text: /*
   * Copyright (c) 2014-2016 IBM Corporation.
   * All rights reserved.
   *
   *  Redistribution and use in source and binary forms, with or without
   *  modification, are permitted provided that the following conditions are met:
   *  * Redistributions of source code must retain the above copyright
   *    notice, this list of conditions and the following disclaimer.
   *  * 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.
   *  * Neither the name of the <organization> 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 COPYRIGHT HOLDERS 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 <COPYRIGHT HOLDER> 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.
   */
  
  #include "lmic.h"
  
  // RUNTIME STATE
  static struct {
      osjob_t* scheduledjobs;
      osjob_t* runnablejobs;
  } OS;
  
  void os_init () {
      memset(&OS, 0x00, sizeof(OS));
      hal_init();
      radio_init();
      LMIC_init();
  }
  
  ostime_t os_getTime () {
      return hal_ticks();
  }
  
  // unlink job from queue, return if removed
  static int unlinkjob (osjob_t** pnext, osjob_t* job) {
      for( ; *pnext; pnext = &((*pnext)->next)) {
          if(*pnext == job) { // unlink
              *pnext = job->next;
              return 1;
          }
      }
      return 0;
  }
  
  // clear scheduled job
  void os_clearCallback (osjob_t* job) {
      hal_disableIRQs();
      unlinkjob(&OS.scheduledjobs, job) || unlinkjob(&OS.runnablejobs, job);
      hal_enableIRQs();
  }
  
  // schedule immediately runnable job
  void os_setCallback (osjob_t* job, osjobcb_t cb) {
      osjob_t** pnext;
      hal_disableIRQs();
      // remove if job was already queued
      unlinkjob(&OS.runnablejobs, job);
      // fill-in job
      job->func = cb;
      job->next = NULL;
      // add to end of run queue
      for(pnext=&OS.runnablejobs; *pnext; pnext=&((*pnext)->next));
      *pnext = job;
      hal_enableIRQs();
  }
  
  // schedule timed job
  void os_setTimedCallback (osjob_t* job, ostime_t time, osjobcb_t cb) {
      osjob_t** pnext;
      hal_disableIRQs();
      // remove if job was already queued
      unlinkjob(&OS.scheduledjobs, job);
      // fill-in job
      job->deadline = time;
      job->func = cb;
      job->next = NULL;
      // insert into schedule
      for(pnext=&OS.scheduledjobs; *pnext; pnext=&((*pnext)->next)) {
          if((*pnext)->deadline - time > 0) { // (cmp diff, not abs!)
              // enqueue before next element and stop
              job->next = *pnext;
              break;
          }
      }
      *pnext = job;
      hal_enableIRQs();
  }
  
  // execute jobs from timer and from run queue
  void os_run () {
    osjob_t* j = NULL;
    hal_disableIRQs();
    // check for runnable jobs
    if(OS.runnablejobs) {
        j = OS.runnablejobs;
        OS.runnablejobs = j->next;
    } else if(OS.scheduledjobs && hal_checkTimer(OS.scheduledjobs->deadline)) { // check for expired timed jobs
        j = OS.scheduledjobs;
        OS.scheduledjobs = j->next;
    } else { // nothing pending
        hal_sleep(); // wake by irq (timer already restarted)
    }
    hal_enableIRQs();
    if(j) { // run job callback
        j->func(j);
    }
  }
  