[FFmpeg-devel] [PATCH] fifo: add av_fifo_grow()

[Alexander Strasser]

Hi Michael,

Michael Niedermayer wrote:
[...]
> diff --git a/libavutil/fifo.c b/libavutil/fifo.c
[...]
> +int av_fifo_grow(AVFifoBuffer *f, unsigned int size)
> +{
> +    unsigned int old_size = f->end - f->buffer;
> +    if(size + (unsigned)av_fifo_size(f) < size)
> +        return AVERROR(EINVAL);
> +
> +    size += av_fifo_size(f);
> +
> +    if (old_size < size)
> +        return av_fifo_realloc2(f, FFMAX(size, 2*size));
> +    return 0;
> +}

  I am no means an expert concerning the AVFifoBuffer implementation,
but it looks like some of this is already done in av_fifo_realloc2
and does not need to be duplicated in here.

  Where am I missing the point? :(

>  // src must NOT be const as it can be a context for func that may need updating (like a pointer or byte counter)
>  int av_fifo_generic_write(AVFifoBuffer *f, void *src, int size, int (*func)(void*, void*, int))
>  {
> diff --git a/libavutil/fifo.h b/libavutil/fifo.h
> index 22a9aa5..eabeec3 100644
> --- a/libavutil/fifo.h
> +++ b/libavutil/fifo.h
> @@ -103,6 +103,18 @@ int av_fifo_generic_write(AVFifoBuffer *f, void *src, int size, int (*func)(void
>  int av_fifo_realloc2(AVFifoBuffer *f, unsigned int size);
>  
>  /**
> + * Enlarge an AVFifoBuffer.
> + * In case of reallocation failure, the old FIFO is kept unchanged.
> + * The new fifo size may be larger than the requested size.
> + *
> + * @param f AVFifoBuffer to resize
> + * @param additional_space the additional space in addition to av_fifo_size()
> + *        which the user wants.

  This could profit from a less awkward wording more in line with the
other AVFifoBuffer docs. What do think of
"the amount of space in bytes to allocate in addition to av_fifo_size()"
?

> + * @return <1 for failure, >=0 otherwise
> + */
> +int av_fifo_grow(AVFifoBuffer *f, unsigned int additional_space);
> +
> +/**
>   * Read and discard the specified amount of data from an AVFifoBuffer.
>   * @param f AVFifoBuffer to read from
>   * @param size amount of data to read in bytes
> -- 
> 1.7.9.5

  Alexander