求助大神，rt_ringbuffer_peak疑问求解

rt_size_t rt_ringbuffer_peak(struct rt_ringbuffer *rb, rt_uint8_t **ptr)
{
    RT_ASSERT(rb != RT_NULL);
    *ptr = RT_NULL;
    /* whether has enough data  */
    rt_size_t size = rt_ringbuffer_data_len(rb);
    /* no data */
    if (size == 0)
        return 0;
    *ptr = &rb->buffer_ptr[rb->read_index];
    if((rt_size_t)(rb->buffer_size - rb->read_index) > size)
    {
        rb->read_index += size;
        return size;
    }
    size = rb->buffer_size - rb->read_index;
    /* we are going into the other side of the mirror */
    rb->read_mirror = ~rb->read_mirror;
    rb->read_index = 0;
    return size;
}
请教一下ringbuffer.c,里面的一段代码，谢谢！rt_ringbuffer_peak里的最后的rb->read_index = 0;有点不理解，不应该是rb->read_index += size;才对吗？