条件编译

只看该作者 · 2010-7-19 15:13

再学习陈明计先生写的Small RTOS51的过程中，在任务切换函数的条件编译看不明白
是一个什么层次，请教高手指点！

不明白处前面打了？

void  OSSched(void)
{
uint8 temp;
OS_ENTER_CRITICAL();
？#if EN_OS_INT_ENTER > 0
if (OSIntNesting == 0)             /* ÊÇ·ñÊÇÖÐ¶ÏÖÐµ÷ÓÃ */
{
？#endif
#if OS_MAX_TASKS < 9
            /* ²éÕÒ´¦ÓÚ¾ÍÐ÷×´Ì¬µÄÈÎÎñÖÐÓÅÏÈ¼¶×î¸ßµÄÈÎÎñ */
      temp = OSTaskRuning;
      for (OSNextTaskID = 0; OSNextTaskID < OS_MAX_TASKS; OSNextTaskID++)
      {
         if ((temp & 0x01) != 0)
         {
            break;
         }
         temp = temp >> 1;
      }
      OS_TASK_SW();                /* ½øÐÐÈÎÎñµ÷¶È */
#else
            /* ²éÕÒ´¦ÓÚ¾ÍÐ÷×´Ì¬µÄÈÎÎñÖÐÓÅÏÈ¼¶×î¸ßµÄÈÎÎñ */
      temp = OSTaskRuning % 256;
      for (OSNextTaskID = 0; OSNextTaskID < 8; OSNextTaskID++)
      {
         if ((temp & 0x01) != 0)
         {
            goto TaskSw;
         }
         temp = temp >> 1;
      }
      temp = OSTaskRuning / 256 ;
      for (; OSNextTaskID < OS_MAX_TASKS; OSNextTaskID++)
      {
         if ((temp & 0x01) != 0)
         {
            break;
         }
         temp = temp >> 1;
      }
TaskSw:
      OS_TASK_SW();                /* ½øÐÐÈÎÎñµ÷¶È */
#endif
？#if EN_OS_INT_ENTER > 0
}
？#endif
OS_EXIT_CRITICAL();
}