read elements

[ani]

Hi,

I'm using the nrf_queue library and I need to peek more than one element at a time.

How to do?

[Andy]

I requested a feature for this like a year ago. It's very easy to implement, you just have to add a "peek" argument to some functions and adjust the definitions here and there. The gist of the thing is this (I just added the just_peek boolean and some if conditions):

/**@brief Read elements from the queue. This function assumes that there are enough elements
 *        in the queue to read and that this process will not be interrupted.
 *
 * @param[in]   p_queue             Pointer to the nrf_queue_t instance.
 * @param[out]  p_data              Pointer to the buffer where elements will be copied.
 * @param[in]   element_count       Number of elements to read.
 * @param[in]   just_peek           Should not advance the front of the queue.
 */
static void queue_read(nrf_queue_t const * p_queue, void * p_data, uint32_t element_count, bool just_peek)
{
    size_t front        = p_queue->p_cb->front;
    size_t back         = p_queue->p_cb->back;
    size_t continuous   = (front <= back) ? (back - front) : (p_queue->size + 1 - front);
    void const * p_read_ptr = (void const *)((size_t)p_queue->p_buffer
                                           + front * p_queue->element_size);

    if (element_count <= continuous)
    {
        memcpy(p_data,
               p_read_ptr,
               element_count * p_queue->element_size);

        if (!just_peek)
        {
			p_queue->p_cb->front = ((front + element_count) <= p_queue->size)
								 ? (front + element_count)
								 : 0;
        }
    }
    else
    {
        size_t first_read_length = continuous * p_queue->element_size;
        memcpy(p_data,
               p_read_ptr,
               first_read_length);

        size_t elements_left = element_count - continuous;
        memcpy((void *)((size_t)p_data + first_read_length),
               p_queue->p_buffer,
               elements_left * p_queue->element_size);

        if (!just_peek)
        {
        	p_queue->p_cb->front = elements_left;
        }
    }
}