[FFmpeg-devel] [HACK] Remove MAX_STREAMS usages

[Michael Niedermayer]

On Tue, Aug 10, 2010 at 01:14:56AM +0200, Aurelien Jacobs wrote:
> On Sun, Aug 08, 2010 at 10:40:40PM +0200, Reimar D?ffinger wrote:
> > Hello,
> > this is just a quick hack that removes all usages of
> > MAX_STREAMS.
> > 
> > [...]
> 
> And here are the last bits I extracted/reworked from this patch.
> 
> First patch in this email uses nb_streams instead of MAX_STREAMS to
> dynamically alloc arrays in libavformat/utils.c. This is compatible
> with both the old API and the new API.
> 
> Second and last patch actually add the new API, finally getting ride of
> MAX_STREAMS. It is obviously disabled until next major bump.
> 
> Aurel
>  utils.c |   37 +++++++++++++++++++++++++++----------
>  1 file changed, 27 insertions(+), 10 deletions(-)
> 553bd8bafb70b124e3ed2747f577f4ae057e8094  max_stream.diff
> commit f04d73bbdcb67af2e6d1145c652a6b2978c0c83f
> Author: Aurelien Jacobs <aurel at gnuage.org>
> Date:   Tue Aug 10 00:21:06 2010 +0200
> 
>     dynamically use nb_streams instead of static use of MAX_STREAMS
> 
> diff --git a/libavformat/utils.c b/libavformat/utils.c
> index 1aa965c..edd3d19 100644
> --- a/libavformat/utils.c
> +++ b/libavformat/utils.c
> @@ -1871,10 +1871,13 @@ static void av_estimate_timings_from_pts(AVFormatContext *ic, int64_t old_offset
>      AVPacket pkt1, *pkt = &pkt1;
>      AVStream *st;
>      int read_size, i, ret;
> -    int64_t end_time, start_time[MAX_STREAMS];
> +    int64_t end_time, *start_time;
>      int64_t filesize, offset, duration;
>      int retry=0;
>  
> +    if (!(start_time = av_malloc(ic->nb_streams * sizeof(*start_time))))
> +        return;
> +
>      ic->cur_st = NULL;
>  
>      /* flush packet queue */
> @@ -1935,6 +1938,7 @@ static void av_estimate_timings_from_pts(AVFormatContext *ic, int64_t old_offset
>      }while(   end_time==AV_NOPTS_VALUE
>             && filesize > (DURATION_MAX_READ_SIZE<<retry)
>             && ++retry <= DURATION_MAX_RETRY);
> +    av_free(start_time);
>  
>      fill_all_stream_timings(ic);
>  
> @@ -2160,15 +2164,23 @@ int av_find_stream_info(AVFormatContext *ic)
>      int i, count, ret, read_size, j;
>      AVStream *st;
>      AVPacket pkt1, *pkt;
> -    int64_t last_dts[MAX_STREAMS];
> -    int64_t duration_gcd[MAX_STREAMS]={0};
> -    int duration_count[MAX_STREAMS]={0};
> +    int64_t *last_dts;
> +    int64_t *duration_gcd;
> +    int *duration_count;
>      double (*duration_error)[MAX_STD_TIMEBASES];
>      int64_t old_offset = url_ftell(ic->pb);
> -    int64_t codec_info_duration[MAX_STREAMS]={0};
> +    int64_t *codec_info_duration;
>  
> -    duration_error = av_mallocz(MAX_STREAMS * sizeof(*duration_error));
> -    if (!duration_error) return AVERROR(ENOMEM);
> +    last_dts            = av_mallocz(ic->nb_streams * sizeof(*last_dts));
> +    duration_gcd        = av_mallocz(ic->nb_streams * sizeof(*duration_gcd));
> +    duration_count      = av_mallocz(ic->nb_streams * sizeof(*duration_count));
> +    duration_error      = av_mallocz(ic->nb_streams * sizeof(*duration_error));
> +    codec_info_duration = av_mallocz(ic->nb_streams * sizeof(*codec_info_duration));
> +    if (!last_dts || !duration_gcd || !duration_count || !duration_error ||
> +        !codec_info_duration) {
> +        ret = AVERROR(ENOMEM);
> +        goto err_out;
> +    }

possibly exploitable
the number of streams can increase any time if more are found


[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

I am the wisest man alive, for I know one thing, and that is that I know
nothing. -- Socrates
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