[FFmpeg-devel] [PATCH 3/3] Deobfuscate LE SHOW_[SU]BITS; these are simple sign/zero extend

[Michael Niedermayer]

On Sun, Feb 21, 2010 at 12:35:59AM +0000, Mans Rullgard wrote:
> ---
>  libavcodec/get_bits.h |    4 ++--
>  1 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/libavcodec/get_bits.h b/libavcodec/get_bits.h
> index bb40ff4..7c4ee43 100644
> --- a/libavcodec/get_bits.h
> +++ b/libavcodec/get_bits.h
> @@ -166,10 +166,10 @@ for examples see get_bits, show_bits, skip_bits, get_vlc
>  
>  # ifdef ALT_BITSTREAM_READER_LE
>  #   define SHOW_UBITS(name, gb, num)\
> -        ((name##_cache) & (NEG_USR32(0xffffffff,num)))
> +        zero_extend(name##_cache, num)
>  
>  #   define SHOW_SBITS(name, gb, num)\
> -        NEG_SSR32((name##_cache)<<(32-(num)), num)
> +        sign_extend(name##_cache, num)
>  # else
>  #   define SHOW_UBITS(name, gb, num)\
>          NEG_USR32(name##_cache, num)

i prefer the code the way it was

[...]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Republics decline into democracies and democracies degenerate into
despotisms. -- Aristotle
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