[FFmpeg-devel] [PATCH] http: block while waiting for reconnecting

[Timo Rothenpieler]

Am 30.12.2017 um 18:07 schrieb wm4:
> It makes no sense to return an error after the first reconnect, and then
> somehow resume the next time it's called.
> 
> Also make the wait reasonably interruptible. Since there is no mechanism
> for this in the API, polling is the best we can do. (Some effort could
> be put into making the wait more accurate, since the av_usleep() will
> not wait exactly 1000 microseconds, and the error will add up.)
> 
> (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.)
> ---
>   libavformat/http.c | 22 +++++++++++++---------
>   1 file changed, 13 insertions(+), 9 deletions(-)
> 
> diff --git a/libavformat/http.c b/libavformat/http.c
> index a376f1a488..2957648d61 100644
> --- a/libavformat/http.c
> +++ b/libavformat/http.c
> @@ -1443,25 +1443,29 @@ 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)
> +    while (   (read_ret  < 0 && s->reconnect        && (!h->is_streamed || s->reconnect_streamed) && s->filesize > 0 && s->off < s->filesize)
nit: could just get rid of the extra whitespace here and it will be 
perfectly aligned with the next line.

>           || (read_ret == 0 && s->reconnect_at_eof && (!h->is_streamed || s->reconnect_streamed))) {
> +        unsigned int wait = 0;
>           uint64_t target = h->is_streamed ? 0 : s->off;
>   
>           if (s->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);
> +        for (wait = 0; wait < 1000U*s->reconnect_delay; wait++) {
> +            if (ff_check_interrupt(&h->interrupt_callback))
> +                return AVERROR(EIO);
> +            av_usleep(1000);
> +        }
>           s->reconnect_delay = 1 + 2*s->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 AVERROR(EIO);
> +        } else
> +            read_ret = http_buf_read(h, buf, size);
> +    }
> +    s->reconnect_delay = 0;
>   
>       return read_ret;
>   }
> 

looks reasonable to me, but it's not my code and I don't have any 
experience with it.

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