sdk/include/reactos/libs/libmpg123/getbits.h

   1 /*
   2         getbits
   3
   4         copyright ?-2009 by the mpg123 project - free software under the terms of the LGPL 2.1
   5         see COPYING and AUTHORS files in distribution or http://mpg123.org
   6         initially written by Michael Hipp
   7
   8         All code is in the header to suggest/force inlining of these small often-used functions.
   9         This indeed has some impact on performance.
  10 */
  11
  12 #ifndef _MPG123_GETBITS_H_
  13 #define _MPG123_GETBITS_H_
  14
  15 #include "mpg123lib_intern.h"
  16
  17 #define backbits(fr,nob) ((void)( \
  18   fr->bitindex    -= nob, \
  19   fr->wordpointer += (fr->bitindex>>3), \
  20   fr->bitindex    &= 0x7 ))
  21
  22 #define getbitoffset(fr) ((-fr->bitindex)&0x7)
  23 #define getbyte(fr)      (*fr->wordpointer++)
  24
  25 /* There is something wrong with that macro... the function below works also for the layer1 test case. */
  26 #define macro_getbits(fr, nob) ( \
  27   fr->ultmp = fr->wordpointer[0],\
  28   fr->ultmp <<= 8, \
  29   fr->ultmp |= fr->wordpointer[1], \
  30   fr->ultmp <<= 8, \
  31   fr->ultmp |= fr->wordpointer[2], \
  32   fr->ultmp <<= fr->bitindex, \
  33   fr->ultmp &= 0xffffff, \
  34   fr->bitindex += nob, \
  35   fr->ultmp >>= (24-nob), \
  36   fr->wordpointer += (fr->bitindex>>3), \
  37   fr->bitindex &= 7, \
  38   fr->ultmp)
  39
  40 static unsigned int getbits(mpg123_handle *fr, int number_of_bits)
  41 {
  42   unsigned long rval;
  43
  44 #ifdef DEBUG_GETBITS
  45 fprintf(stderr,"g%d",number_of_bits);
  46 #endif
  47   /* Safety catch until we got the nasty code fully figured out. */
  48   /* No, that catch stays here, even if we think we got it figured out! */
  49   if( (long)(fr->wordpointer-fr->bsbuf)*8
  50       + fr->bitindex+number_of_bits > (long)fr->framesize*8 )
  51     return 0;
  52 /*  This is actually slow: if(!number_of_bits)
  53     return 0; */
  54
  55 #if 0
  56    check_buffer_range(number_of_bits+fr->bitindex);
  57 #endif
  58
  59   {
  60     rval = fr->wordpointer[0];
  61     rval <<= 8;
  62     rval |= fr->wordpointer[1];
  63     rval <<= 8;
  64     rval |= fr->wordpointer[2];
  65
  66     rval <<= fr->bitindex;
  67     rval &= 0xffffff;
  68
  69     fr->bitindex += number_of_bits;
  70
  71     rval >>= (24-number_of_bits);
  72
  73     fr->wordpointer += (fr->bitindex>>3);
  74     fr->bitindex &= 7;
  75   }
  76
  77 #ifdef DEBUG_GETBITS
  78 fprintf(stderr,":%lx\n",rval);
  79 #endif
  80
  81   return rval;
  82 }
  83
  84
  85 #define skipbits(fr, nob) fr->ultmp = ( \
  86   fr->ultmp = fr->wordpointer[0], fr->ultmp <<= 8, fr->ultmp |= fr->wordpointer[1], \
  87   fr->ultmp <<= 8, fr->ultmp |= fr->wordpointer[2], fr->ultmp <<= fr->bitindex, \
  88   fr->ultmp &= 0xffffff, fr->bitindex += nob, \
  89   fr->ultmp >>= (24-nob), fr->wordpointer += (fr->bitindex>>3), \
  90   fr->bitindex &= 7 )
  91
  92 #define getbits_fast(fr, nob) ( \
  93   fr->ultmp = (unsigned char) (fr->wordpointer[0] << fr->bitindex), \
  94   fr->ultmp |= ((unsigned long) fr->wordpointer[1]<<fr->bitindex)>>8, \
  95   fr->ultmp <<= nob, fr->ultmp >>= 8, \
  96   fr->bitindex += nob, fr->wordpointer += (fr->bitindex>>3), \
  97   fr->bitindex &= 7, fr->ultmp )
  98
  99 #define get1bit(fr) ( \
 100   fr->uctmp = *fr->wordpointer << fr->bitindex, fr->bitindex++, \
 101   fr->wordpointer += (fr->bitindex>>3), fr->bitindex &= 7, fr->uctmp>>7 )
 102
 103
 104 #endif