[FFmpeg-devel] [PATCH v2 1/2] http: block while waiting for reconnecting

[wm4]

On Tue,  2 Jan 2018 17:19:14 +0100
wm4 <nfxjfg at googlemail.com> wrote:

> It makes no sense to return an error after the first reconnect, and then
> somehow resume the next time it's called. Usually this will lead to
> demuxer errors. Make reconnecting block instead, until it has either
> successfully reconnected, or given up.
> 
> Also make the wait reasonably interruptible. Since there is no mechanism
> for this in the API, polling is the best we can do. This behaves roughly
> the same as other interruptible network functions in libavformat.
> 
> (The original code would work if it returned AVERROR(EAGAIN) or so,
> which would make retry_transfer_wrapper() repeat the read call. But I
> think having an explicit loop for this is better anyway.)
> 
> I also snuck in a fix for reconnect_at_eof. It has to check for
> AVERROR_EOF, not 0.
> ---
>  libavformat/http.c    | 19 ++++++++++---------
>  libavformat/network.c | 18 ++++++++++++++++++
>  libavformat/network.h |  9 +++++++++
>  3 files changed, 37 insertions(+), 9 deletions(-)
> 
> diff --git a/libavformat/http.c b/libavformat/http.c
> index 8f7e56de54..5eff87f8bb 100644
> --- a/libavformat/http.c
> +++ b/libavformat/http.c
> @@ -117,7 +117,6 @@ typedef struct HTTPContext {
>      int reconnect;
>      int reconnect_at_eof;
>      int reconnect_streamed;
> -    int reconnect_delay;
>      int reconnect_delay_max;
>      int listen;
>      char *resource;
> @@ -1433,6 +1432,7 @@ static int http_read_stream(URLContext *h, uint8_t *buf, int size)
>      HTTPContext *s = h->priv_data;
>      int err, new_location, read_ret;
>      int64_t seek_ret;
> +    int reconnect_delay = 0;
>  
>      if (!s->hd)
>          return AVERROR_EOF;
> @@ -1448,25 +1448,26 @@ static int http_read_stream(URLContext *h, uint8_t *buf, int size)
>          return http_buf_read_compressed(h, buf, size);
>  #endif /* CONFIG_ZLIB */
>      read_ret = http_buf_read(h, buf, size);
> -    if (   (read_ret  < 0 && s->reconnect        && (!h->is_streamed || s->reconnect_streamed) && s->filesize > 0 && s->off < s->filesize)
> -        || (read_ret == 0 && s->reconnect_at_eof && (!h->is_streamed || s->reconnect_streamed))) {
> +    while ((read_ret  < 0           && s->reconnect        && (!h->is_streamed || s->reconnect_streamed) && s->filesize > 0 && s->off < s->filesize)
> +        || (read_ret == AVERROR_EOF && s->reconnect_at_eof && (!h->is_streamed || s->reconnect_streamed))) {
>          uint64_t target = h->is_streamed ? 0 : s->off;
>  
> -        if (s->reconnect_delay > s->reconnect_delay_max)
> +        if (reconnect_delay > s->reconnect_delay_max)
>              return AVERROR(EIO);
>  
>          av_log(h, AV_LOG_INFO, "Will reconnect at %"PRIu64" error=%s.\n", s->off, av_err2str(read_ret));
> -        av_usleep(1000U*1000*s->reconnect_delay);
> -        s->reconnect_delay = 1 + 2*s->reconnect_delay;
> +        err = ff_network_sleep_interruptible(1000U*1000*reconnect_delay, &h->interrupt_callback);
> +        if (err != AVERROR(ETIMEDOUT))
> +            return err;
> +        reconnect_delay = 1 + 2*reconnect_delay;
>          seek_ret = http_seek_internal(h, target, SEEK_SET, 1);
> -        if (seek_ret != target) {
> +        if (seek_ret >= 0 && seek_ret != target) {
>              av_log(h, AV_LOG_ERROR, "Failed to reconnect at %"PRIu64".\n", target);
>              return read_ret;
>          }
>  
>          read_ret = http_buf_read(h, buf, size);
> -    } else
> -        s->reconnect_delay = 0;
> +    }
>  
>      return read_ret;
>  }
> diff --git a/libavformat/network.c b/libavformat/network.c
> index 6c3d9def3b..e9eb4b443a 100644
> --- a/libavformat/network.c
> +++ b/libavformat/network.c
> @@ -103,6 +103,24 @@ int ff_network_wait_fd_timeout(int fd, int write, int64_t timeout, AVIOInterrupt
>      }
>  }
>  
> +int ff_network_sleep_interruptible(int64_t timeout, AVIOInterruptCB *int_cb)
> +{
> +    int64_t wait_start = av_gettime_relative();
> +
> +    while (1) {
> +        int64_t time_left;
> +
> +        if (ff_check_interrupt(int_cb))
> +            return AVERROR_EXIT;
> +
> +        time_left = timeout - (av_gettime_relative() - wait_start);
> +        if (time_left <= 0)
> +            return AVERROR(ETIMEDOUT);
> +
> +        av_usleep(FFMIN(time_left, POLLING_TIME * 1000));
> +    }
> +}
> +
>  void ff_network_close(void)
>  {
>  #if HAVE_WINSOCK2_H
> diff --git a/libavformat/network.h b/libavformat/network.h
> index b78e3ad6ed..a663115541 100644
> --- a/libavformat/network.h
> +++ b/libavformat/network.h
> @@ -96,6 +96,15 @@ int ff_network_wait_fd(int fd, int write);
>   */
>  int ff_network_wait_fd_timeout(int fd, int write, int64_t timeout, AVIOInterruptCB *int_cb);
>  
> +/**
> + * Waits for up to 'timeout' microseconds. If the usert's int_cb is set and
> + * triggered, return before that.
> + * @timeout Timeout in microseconds. Maybe have lower actual precision.
> + * @param int_cb Interrupt callback, is checked regularly.
> + * @return AVERROR(ETIMEDOUT) if timeout expirted, AVERROR_EXIT if interrupted by int_cb
> + */
> +int ff_network_sleep_interruptible(int64_t timeout, AVIOInterruptCB *int_cb);
> +
>  int ff_inet_aton (const char * str, struct in_addr * add);
>  
>  #if !HAVE_STRUCT_SOCKADDR_STORAGE

Ping.