Function MessageQueueGet

source/rtos2/RTX/Source/rtx_msgqueue.c:90–139

Get a Message from Queue with Highest Priority. \param[in] mq message queue object. \return message object or NULL.

/// \param[in]  mq              message queue object.
/// \return message object or NULL.
static os_message_t *MessageQueueGet (os_message_queue_t *mq) {
#if (EXCLUSIVE_ACCESS == 0)
  uint32_t      primask = __get_PRIMASK();
#endif
  os_message_t *msg;
  uint32_t      count;
  uint8_t       flags;

#if (EXCLUSIVE_ACCESS == 0)
  __disable_irq();

  count = mq->msg_count;
  if (count != 0U) {
    mq->msg_count--;
  }

  if (primask == 0U) {
    __enable_irq();
  }
#else
  count = atomic_dec32_nz(&mq->msg_count);
#endif

  if (count != 0U) {
    msg = mq->msg_first;

    while (msg != NULL) {
#if (EXCLUSIVE_ACCESS == 0)
      __disable_irq();

      flags = msg->flags;
      msg->flags = 1U;

      if (primask == 0U) {
        __enable_irq();
      }
#else
      flags = atomic_wr8(&msg->flags, 1U);
#endif
      if (flags == 0U) {
        break;
      }
      msg = msg->next;
    }
  } else {
    msg = NULL;
  }

  return msg;
}

/// Remove a Message from Queue
/// \param[in]  mq              message queue object.