[FFmpeg-devel] [PATCH 1/2] lavu: add AV_DYNARRAY_ADD() macro.

[Lukasz Marek]

On 08.03.2014 21:26, Nicolas George wrote:
> TODO minor bump and APIchanges entry
>
> Signed-off-by: Nicolas George <george at nsup.org>
> ---
>   libavutil/dynarray.h | 72 ++++++++++++++++++++++++++++++++++++++++++++++++++++
>   1 file changed, 72 insertions(+)
>   create mode 100644 libavutil/dynarray.h
>
>
> I had to add the av_elt_size parameter: without it, the element size is
> guessed using sizeof, but that means it must be a build-time constant since
> VLAs are forbidden, and that would have prevented from using it to implement
> av_dynarray2_add().
>
> I did not implement av_dynarray_add_nofree() because I do not have a test
> case.
>
>
> diff --git a/libavutil/dynarray.h b/libavutil/dynarray.h
> new file mode 100644
> index 0000000..740a34b
> --- /dev/null
> +++ b/libavutil/dynarray.h
> @@ -0,0 +1,72 @@
> +/*
> + * This file is part of FFmpeg.
> + *
> + * FFmpeg is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU Lesser General Public License
> + * as published by the Free Software Foundation; either
> + * version 2.1 of the License, or (at your option) any later version.
> + *
> + * FFmpeg is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU Lesser General Public License for more details.
> + *
> + * You should have received a copy of the GNU Lesser General Public License
> + * along with FFmpeg; if not, write to the Free Software Foundation, Inc.,
> + * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
> + */
> +
> +#ifndef AVUTIL_DYNARRAY_H
> +#define AVUTIL_DYNARRAY_H
> +
> +#include "log.h"
> +#include "mem.h"
> +
> +/**
> + * Add an element of to a dynamic array.
> + *
> + * The array is reallocated when its number of elements reaches powers of 2.
> + * Therefore, the amortized cost of adding an element is constant.
> + *
> + * In case of success, the pointer to the array is updated in order to
> + * point to the new grown array, and the size is incremented.
> + *
> + * @param av_size_max  maximum size of the array, usually the MAX macro of
> + *                     the type of the size
> + * @param av_elt_size  size of the elements in the array, in bytes
> + * @param av_array     pointer to the array, must be a lvalue
> + * @param av_size      size of the array, must be an interger lvalue
> + * @param av_success   statement to execute on success; at this point, the
> + *                     size variable is not yet incremented
> + * @param av_failure   statement to execute on failure; if this happens, the
> + *                     array and size are not changed; the statement can end
> + *                     with a return or a goto
> + */
> +#define AV_DYNARRAY_ADD(av_size_max, av_elt_size, av_array, av_size, \
> +                        av_success, av_failure) \
> +    do { \
> +        size_t av_size_new = (av_size); \
> +        if (!((av_size) & ((av_size) - 1))) { \
> +            av_size_new = (av_size) ? (av_size) << 1 : 1; \
> +            if (av_size_new > (av_size_max) / (av_elt_size)) { \
> +                av_size_new = 0; \
> +            } else { \
> +                void *av_array_new = \
> +                    av_realloc((av_array), av_size_new * (av_elt_size)); \
> +                av_log(NULL, AV_LOG_DEBUG, "Resizing array to %zd\n", \
> +                       av_size_new); \
> +                if (!av_array_new) \
> +                    av_size_new = 0; \
> +                else \
> +                    (av_array) = av_array_new; \
> +            } \
> +        } \
> +        if (av_size_new) { \
> +            { av_success } \
> +            (av_size)++; \
> +        } else { \
> +            { av_failure } \

braces around av_failure seems redundant

> +        } \
> +    } while (0)
> +
> +#endif /* AVUTIL_DYNARRAY_H */
>

Seems OK

-- 
Best Regards,
Lukasz Marek

When you look long into an abyss, the abyss looks into you. - Friedrich 
Nietzsche