101 lines
2.6 KiB
C
101 lines
2.6 KiB
C
/*
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getbits
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copyright ?-2009 by the mpg123 project - free software under the terms of the LGPL 2.1
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see COPYING and AUTHORS files in distribution or http://mpg123.org
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initially written by Michael Hipp
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All code is in the header to suggest/force inlining of these small often-used functions.
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This indeed has some impact on performance.
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*/
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#ifndef _MPG123_GETBITS_H_
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#define _MPG123_GETBITS_H_
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#include "mpg123lib_intern.h"
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#define backbits(fr,nob) ((void)( \
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fr->bitindex -= nob, \
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fr->wordpointer += (fr->bitindex>>3), \
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fr->bitindex &= 0x7 ))
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#define getbitoffset(fr) ((-fr->bitindex)&0x7)
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#define getbyte(fr) (*fr->wordpointer++)
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/* There is something wrong with that macro... the function below works also for the layer1 test case. */
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#define macro_getbits(fr, nob) ( \
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fr->ultmp = fr->wordpointer[0],\
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fr->ultmp <<= 8, \
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fr->ultmp |= fr->wordpointer[1], \
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fr->ultmp <<= 8, \
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fr->ultmp |= fr->wordpointer[2], \
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fr->ultmp <<= fr->bitindex, \
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fr->ultmp &= 0xffffff, \
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fr->bitindex += nob, \
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fr->ultmp >>= (24-nob), \
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fr->wordpointer += (fr->bitindex>>3), \
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fr->bitindex &= 7, \
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fr->ultmp)
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static unsigned int getbits(mpg123_handle *fr, int number_of_bits)
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{
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unsigned long rval;
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#ifdef DEBUG_GETBITS
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fprintf(stderr,"g%d",number_of_bits);
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#endif
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/* This is actually slow: if(!number_of_bits)
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return 0; */
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#if 0
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check_buffer_range(number_of_bits+fr->bitindex);
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#endif
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{
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rval = fr->wordpointer[0];
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rval <<= 8;
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rval |= fr->wordpointer[1];
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rval <<= 8;
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rval |= fr->wordpointer[2];
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rval <<= fr->bitindex;
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rval &= 0xffffff;
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fr->bitindex += number_of_bits;
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rval >>= (24-number_of_bits);
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fr->wordpointer += (fr->bitindex>>3);
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fr->bitindex &= 7;
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}
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#ifdef DEBUG_GETBITS
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fprintf(stderr,":%lx\n",rval);
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#endif
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return (unsigned int) rval;
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}
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#define skipbits(fr, nob) fr->ultmp = ( \
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fr->ultmp = fr->wordpointer[0], fr->ultmp <<= 8, fr->ultmp |= fr->wordpointer[1], \
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fr->ultmp <<= 8, fr->ultmp |= fr->wordpointer[2], fr->ultmp <<= fr->bitindex, \
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fr->ultmp &= 0xffffff, fr->bitindex += nob, \
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fr->ultmp >>= (24-nob), fr->wordpointer += (fr->bitindex>>3), \
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fr->bitindex &= 7 )
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#define getbits_fast(fr, nob) ( \
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fr->ultmp = (unsigned char) (fr->wordpointer[0] << fr->bitindex), \
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fr->ultmp |= ((unsigned long) fr->wordpointer[1]<<fr->bitindex)>>8, \
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fr->ultmp <<= nob, fr->ultmp >>= 8, \
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fr->bitindex += nob, fr->wordpointer += (fr->bitindex>>3), \
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fr->bitindex &= 7, fr->ultmp )
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#define get1bit(fr) ( \
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fr->uctmp = *fr->wordpointer << fr->bitindex, fr->bitindex++, \
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fr->wordpointer += (fr->bitindex>>3), fr->bitindex &= 7, fr->uctmp>>7 )
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#endif
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