Function rt_audio_pipe_read

components/drivers/audio/dev_audio_pipe.c:50–106

* @brief Read audio pipe * * @param[in] dev pointer to audio device will be read * * @param[in] pos useless param * * @param[in] buffer pointer to ringbuffer of audio pipe to be read * * @param[in] size number of bytes will be read * * @return number of read bytes * * @note This function will execute time-consuming or affecting the * system operations like memcpy and disable int

 *       system operations like memcpy and disable interrupt.
 */
static rt_ssize_t rt_audio_pipe_read(rt_device_t dev,
                              rt_off_t    pos,
                              void       *buffer,
                              rt_size_t   size)
{
    rt_base_t level;
    rt_thread_t thread;
    struct rt_audio_pipe *pipe;
    rt_size_t read_nbytes;

    pipe = (struct rt_audio_pipe *)dev;
    RT_ASSERT(pipe != RT_NULL);

    if (!(pipe->flag & RT_PIPE_FLAG_BLOCK_RD))
    {
        level = rt_hw_interrupt_disable();
        read_nbytes = rt_ringbuffer_get(&(pipe->ringbuffer), (rt_uint8_t *)buffer, size);

        /* if the ringbuffer is empty, there won't be any writer waiting */
        if (read_nbytes)
            _rt_audio_pipe_resume_writer(pipe);

        rt_hw_interrupt_enable(level);

        return read_nbytes;
    }

    thread = rt_thread_self();

    /* current context checking */
    RT_DEBUG_NOT_IN_INTERRUPT;

    do
    {
        level = rt_hw_interrupt_disable();
        read_nbytes = rt_ringbuffer_get(&(pipe->ringbuffer), (rt_uint8_t *)buffer, size);
        if (read_nbytes == 0)
        {
            rt_thread_suspend(thread);
            /* waiting on suspended read list */
            rt_list_insert_before(&(pipe->suspended_read_list),
                                  &RT_THREAD_LIST_NODE(thread));
            rt_hw_interrupt_enable(level);

            rt_schedule();
        }
        else
        {
            _rt_audio_pipe_resume_writer(pipe);
            rt_hw_interrupt_enable(level);
            break;
        }
    }
    while (read_nbytes == 0);

    return read_nbytes;
}