[FFmpeg-devel] [PATCH] lavu/common: make GET_UTF8 less broken

[Stefano Sabatini]

On date Wednesday 2013-10-02 20:17:30 +0200, Stefano Sabatini encoded:
> Avoid to process data and push the pointer forward in case as soon as an
> error is encountered.
> 
> For example if the error is an assignment, this will allow to exit the
> while block as soon as possible.
> ---
>  libavutil/common.h | 16 +++++++++++-----
>  1 file changed, 11 insertions(+), 5 deletions(-)
> 
> diff --git a/libavutil/common.h b/libavutil/common.h
> index 9f0f998..58f7e42 100644
> --- a/libavutil/common.h
> +++ b/libavutil/common.h
> @@ -300,14 +300,20 @@ static av_always_inline av_const int av_popcount64_c(uint64_t x)
>      val= GET_BYTE;\
>      {\
>          uint32_t top = (val & 128) >> 1;\
> -        if ((val & 0xc0) == 0x80 || val >= 0xFE)\
> +        int err = 0;\
> +        if ((val & 0xc0) == 0x80 || val >= 0xFE) {\
> +            err = 1;\
>              ERROR\
> -        while (val & top) {\
> +        }\
> +        while (!err && (val & top)) {\
>              int tmp= GET_BYTE - 128;\
> -            if(tmp>>6)\
> +            if (tmp>>6) {\
> +                err = 1;\
>                  ERROR\
> -            val= (val<<6) + tmp;\
> -            top <<= 5;\
> +            } else {\
> +                val x = (val<<6) + tmp;\
> +                top <<= 5;\
> +            }\
>          }\
>          val &= (top << 1) - 1;\
>      }

Other problems: in the while loop, the characters should probably not
consumed, and the pointer restored to the second character.

In case ERROR is a struck control operation (e.g. "continue;" or
"break;") it will affect the while loop context, and not the external
user loop as intended.

In conclusion we should probably replace this with an inline function
or something faintly robust.
-- 
FFmpeg = Fancy and Fancy Mastodontic Porno Erotic Gargoyle