Function pipe_fops_read

components/drivers/ipc/pipe.c:225–266

static ssize_t pipe_fops_read(struct dfs_file *fd, void *buf, size_t count, off_t *pos)
#else
static ssize_t pipe_fops_read(struct dfs_file *fd, void *buf, size_t count)
#endif
{
    int len = 0;
    rt_pipe_t *pipe;

    pipe = (rt_pipe_t *)fd->vnode->data;

    /* no process has the pipe open for writing, return end-of-file */
    rt_mutex_take(&pipe->lock, RT_WAITING_FOREVER);

    while (1)
    {
        len = rt_ringbuffer_get(pipe->fifo, buf, count);

        if (len > 0 || pipe->writer == 0)
        {
            break;
        }
        else
        {
            if (fd->flags & O_NONBLOCK)
            {
                len = -EAGAIN;
                goto out;
            }

            rt_mutex_release(&pipe->lock);
            rt_wqueue_wakeup(&pipe->writer_queue, (void*)POLLOUT);
            if (rt_wqueue_wait_interruptible(&pipe->reader_queue, 0, -1) == -RT_EINTR)
                return -EINTR;
            rt_mutex_take(&pipe->lock, RT_WAITING_FOREVER);
        }
    }

    /* wakeup writer */
    rt_wqueue_wakeup(&pipe->writer_queue, (void*)POLLOUT);

out:
    rt_mutex_release(&pipe->lock);
    return len;
}

/**
 * @brief    This function will write data to pipe.