[FFmpeg-devel] [PATCH 2/5] fate: avoid framemd5, use framecrc its faster

[Reimar Döffinger]

On Fri, May 17, 2013 at 07:58:54PM +0200, Giorgio Vazzana wrote:
> diff --git a/libavutil/md5.c b/libavutil/md5.c
> index f8f08f1..a212150 100644
> --- a/libavutil/md5.c
> +++ b/libavutil/md5.c
> @@ -146,8 +146,12 @@ void av_md5_update(AVMD5 *ctx, const uint8_t
> *src, const int len)
>      j = ctx->len & 63;
>      ctx->len += len;
> 
> -    for (i = 0; i < len; i++) {
> -        ctx->block[j++] = src[i];
> +    i = 0;
> +    while (i < len) {
> +        int l = (len-i <= 64-j) ? len-i : 64-j;

FFMIN(len - i, 64 - j);

> +        memcpy(ctx->block + j, src + i, l);
> +        i += l;
> +        j += l;

Personally I think it would make much more sense
to change the code to copy at most 63 bytes (i.e.
if there were bytes left over from last time)
and use the rest directly from src.
In "body()" you'd then have to use AV_RL32.
That might cost performance on architectures
that do not support unaligned reads, but they are
so rare, and I doubt even there the cost will be
much higher than for the memcpy.