[FFmpeg-devel] [PATCH] Per-frame metadata

[Stefano Sabatini]

On date Monday 2011-04-11 16:59:36 +0200, Nicolas George encoded:
> Hi.
> 
> The attached series of patches introduce per-frame metadata, and in
> particular PNG zTXt and tEXt chunks decoding.
> 
> I did not try to make it work for CC subtitles, as I do not know what
> exactly would be required, but I believe this is a first step in that
> direction too.
> 
> Regards,
> 
> -- 
>   Nicolas George

> From c0557275f39dc7bc8049fa04cb0347e065147152 Mon Sep 17 00:00:00 2001
> From: Nicolas George <nicolas.george at normalesup.org>
> Date: Sun, 20 Mar 2011 19:39:20 +0100
> Subject: [PATCH 1/5] Introduce av_size_mult and av_realloc_f.
> 
> av_size_mult helps checking for overflow when computing the size of a memory
> area.
> 
> av_realloc_f helps avoiding memory-leaks in typical uses of realloc.
> 
> Signed-off-by: Nicolas George <nicolas.george at normalesup.org>
> ---
>  libavutil/mem.c |   15 +++++++++++++++
>  libavutil/mem.h |   25 +++++++++++++++++++++++++
>  2 files changed, 40 insertions(+), 0 deletions(-)
> 
> diff --git a/libavutil/mem.c b/libavutil/mem.c
> index 7ffd6cb..26fb8c6 100644
> --- a/libavutil/mem.c
> +++ b/libavutil/mem.c
> @@ -136,6 +136,21 @@ void *av_realloc(void *ptr, FF_INTERNAL_MEM_TYPE size)
>  #endif
>  }
>  
> +void *av_realloc_f(void *ptr, size_t nelem, size_t elsize)
> +{
> +    size_t size;
> +    void *r;
> +
> +    if (av_size_mult(elsize, nelem, &size)) {
> +        av_free(ptr);
> +        return NULL;
> +    }
> +    r = av_realloc(ptr, size);
> +    if (!r && size)
> +        av_free(ptr);
> +    return r;
> +}
> +
>  void av_free(void *ptr)
>  {
>  #if CONFIG_MEMALIGN_HACK
> diff --git a/libavutil/mem.h b/libavutil/mem.h
> index 2bfbd0e..f661438 100644
> --- a/libavutil/mem.h
> +++ b/libavutil/mem.h
> @@ -95,6 +95,16 @@ void *av_malloc(FF_INTERNAL_MEM_TYPE size) av_malloc_attrib av_alloc_size(1);
>  void *av_realloc(void *ptr, FF_INTERNAL_MEM_TYPE size) av_alloc_size(2);
>  
>  /**
> + * Allocate or reallocate a block of memory.
> + * This function does the same thing as av_realloc, except:
> + * - It takes two arguments and checks the result of the multiplication for
> + *   integer overflow.
> + * - It frees the input block in case of failure, thus avoiding the memory
> + *   leak with the classic "buf = realloc(buf); if (!buf) return -1;".
> + */
> +void *av_realloc_f(void *ptr, size_t nelem, size_t elsize);
> +
> +/**
>   * Free a memory block which has been allocated with av_malloc(z)() or
>   * av_realloc().
>   * @param ptr Pointer to the memory block which should be freed.
> @@ -131,4 +141,19 @@ char *av_strdup(const char *s) av_malloc_attrib;
>   */
>  void av_freep(void *ptr);
>  
> +/**

> + * Multiplies two size_t values checking for overflow.

Nit: multiply

> + * @return  0 if success, -1 if overflow.

-1 -> AVERROR(EINVAL)

> + */
> +static inline int av_size_mult(size_t a, size_t b, size_t *r)
> +{
> +    size_t t = a * b;
> +    /* Hack inspired from glibc: only try the division if nelem and elsize
> +     * are both greater than sqrt(SIZE_MAX). */
> +    if ((a | b) >= ((size_t)1 << (sizeof(size_t) * 4)) && a && t / a != b)

> +        return -1;

ditto

> +    *r = t;
> +    return 0;
> +}
> +
>  #endif /* AVUTIL_MEM_H */
> -- 
> 1.7.4.1
> 

[...]

> From 74809f4f0e77b136bc5b0ea8f894b160928ed3df Mon Sep 17 00:00:00 2001
> From: Nicolas George <nicolas.george at normalesup.org>
> Date: Wed, 23 Mar 2011 19:56:25 +0100
> Subject: [PATCH 3/5] Move metadata API to libavcodec.
> 
> The deprecated functions stay in libavformat until they are removed.
> To avoid problems with a double definition of AVMetadataConv, a preprocessor
> macro is defined; this will be removed after the major version bump.
> 
> Signed-off-by: Nicolas George <nicolas.george at normalesup.org>

Would it make sense to move metadata to libavutil rather than to
libavcodec?

For example you may need to display metadata from a lavfi filter.

[...]
-- 
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