Function rt_pipe_read

components/drivers/ipc/pipe.c:495–527

* @brief This function will read the specified length of data from the pipe. * * @param device is a pointer to the pipe device descriptor. * * @param pos is a parameter compatible with POSIX standard interface (currently meaningless, just pass in 0). * * @param buffer is a pointer to the buffer to store the read data. * * @param count is the length of data to be read. * *

 *           When the return value is 0, it means the pipe device handle is empty or the count is 0.
 */
rt_ssize_t rt_pipe_read(rt_device_t device, rt_off_t pos, void *buffer, rt_size_t count)
{
    uint8_t *pbuf;
    rt_size_t read_bytes = 0;
    rt_pipe_t *pipe = (rt_pipe_t *)device;

    if (device == RT_NULL)
    {
        rt_set_errno(-EINVAL);
        return 0;
    }
    if (count == 0)
    {
        return 0;
    }

    pbuf = (uint8_t*)buffer;
    rt_mutex_take(&pipe->lock, RT_WAITING_FOREVER);

    while (read_bytes < count)
    {
        int len = rt_ringbuffer_get(pipe->fifo, &pbuf[read_bytes], count - read_bytes);
        if (len <= 0)
        {
            break;
        }

        read_bytes += len;
    }
    rt_mutex_release(&pipe->lock);

    return read_bytes;
}

/**
 * @brief    This function will write the specified length of data to the pipe.