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bit alignement and absolute positionning for bit-reader

db4
prunedtree 2009-06-05 03:26:50 -07:00
parent 5e31d6266e
commit 9612b43034
1 changed files with 13 additions and 6 deletions
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19
basis/bitstreams/bitstreams.factor
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@ -56,13 +56,20 @@ TUPLE: lsb0-bit-writer < bit-writer ;
GENERIC: peek ( n bitstream -- value ) GENERIC: peek ( n bitstream -- value )
GENERIC: poke ( value n bitstream -- ) GENERIC: poke ( value n bitstream -- )
: get-abp ( bitstream -- abp )
[ byte-pos>> 8 * ] [ bit-pos>> + ] bi ; inline
: set-abp ( abp bitstream -- )
[ 8 /mod ] dip [ (>>bit-pos) ] [ (>>byte-pos) ] bi ; inline
: seek ( n bitstream -- ) : seek ( n bitstream -- )
{ [ get-abp + ] [ set-abp ] bi ; inline
[ byte-pos>> 8 * ]
[ bit-pos>> + + 8 /mod ] : (align) ( n m -- n' )
[ (>>bit-pos) ] [ /mod 0 > [ 1+ ] when ] [ * ] bi ; inline
[ (>>byte-pos) ]
} cleave ; inline : align ( n bitstream -- )
[ get-abp swap (align) ] [ set-abp ] bi ; inline
: read ( n bitstream -- value ) : read ( n bitstream -- value )
[ peek ] [ seek ] 2bi ; inline [ peek ] [ seek ] 2bi ; inline