Function udp_read

libavformat/udp.c:977–1042

}

static int udp_read(URLContext *h, uint8_t *buf, int size)
{
    UDPContext *s = h->priv_data;
    int ret;
#if HAVE_PTHREAD_CANCEL
    int avail, nonblock = h->flags & AVIO_FLAG_NONBLOCK;

    if (s->rx_fifo) {
        pthread_mutex_lock(&s->mutex);
        do {
            avail = av_fifo_can_read(s->rx_fifo);
            if (avail) { // >=size) {
                UDPQueuedPacketHeader header;

                av_fifo_read(s->rx_fifo, &header, sizeof(header));

                s->last_recv_addr = header.addr;
                s->last_recv_addr_len = header.addr_len;

                avail = header.pkt_size;
                if(avail > size){
                    av_log(h, AV_LOG_WARNING, "Part of datagram lost due to insufficient buffer size\n");
                    avail = size;
                }

                av_fifo_read(s->rx_fifo, buf, avail);
                av_fifo_drain2(s->rx_fifo, header.pkt_size - avail);
                pthread_mutex_unlock(&s->mutex);
                return avail;
            } else if(s->circular_buffer_error){
                int err = s->circular_buffer_error;
                pthread_mutex_unlock(&s->mutex);
                return err;
            } else if(nonblock) {
                pthread_mutex_unlock(&s->mutex);
                return AVERROR(EAGAIN);
            } else {
                /* FIXME: using the monotonic clock would be better,
                   but it does not exist on all supported platforms. */
                int64_t t = av_gettime() + 100000;
                struct timespec tv = { .tv_sec  =  t / 1000000,
                                       .tv_nsec = (t % 1000000) * 1000 };
                int err = pthread_cond_timedwait(&s->cond, &s->mutex, &tv);
                if (err) {
                    pthread_mutex_unlock(&s->mutex);
                    return AVERROR(err == ETIMEDOUT ? EAGAIN : err);
                }
                nonblock = 1;
            }
        } while(1);
    }
#endif

    if (!(h->flags & AVIO_FLAG_NONBLOCK)) {
        ret = ff_network_wait_fd(s->udp_fd, 0);
        if (ret < 0)
            return ret;
    }