kolibrios-fun/programs/develop/libraries/libmpg123/getbits.h
Sergey Semyonov (Serge) a316fa7c9d libmpg123 1.9.0
git-svn-id: svn://kolibrios.org@1905 a494cfbc-eb01-0410-851d-a64ba20cac60
2011-03-11 10:57:03 +00:00

101 lines
2.6 KiB
C

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