ReactOS  0.4.15-dev-1150-g593bcce
getbits.h
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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 #include "debug.h"
17 
18 #define backbits(fr,nob) ((void)( \
19  fr->bits_avail += nob, \
20  fr->bitindex -= nob, \
21  fr->wordpointer += (fr->bitindex>>3), \
22  fr->bitindex &= 0x7 ))
23 
24 #define getbitoffset(fr) ((-fr->bitindex)&0x7)
25 /* Precomputing the bytes to be read is error-prone, and some over-read
26  is even expected for Huffman. Just play safe and return zeros in case
27  of overflow. This assumes you made bitindex zero already! */
28 #define getbyte(fr) ( (fr)->bits_avail-=8, (fr)->bits_avail >= 0 \
29  ? *((fr)->wordpointer++) \
30  : 0 )
31 
32 static unsigned int getbits(mpg123_handle *fr, int number_of_bits)
33 {
34  unsigned long rval;
35 
36 #ifdef DEBUG_GETBITS
37 fprintf(stderr,"g%d",number_of_bits);
38 #endif
39  fr->bits_avail -= number_of_bits;
40  /* Safety catch until we got the nasty code fully figured out. */
41  /* No, that catch stays here, even if we think we got it figured out! */
42  if(fr->bits_avail < 0)
43  {
44  if(NOQUIET)
45  error2( "Tried to read %i bits with %li available."
46  , number_of_bits, fr->bits_avail );
47  return 0;
48  }
49 /* This is actually slow: if(!number_of_bits)
50  return 0; */
51 
52 #if 0
53  check_buffer_range(number_of_bits+fr->bitindex);
54 #endif
55 
56  {
57  rval = fr->wordpointer[0];
58  rval <<= 8;
59  rval |= fr->wordpointer[1];
60  rval <<= 8;
61  rval |= fr->wordpointer[2];
62 
63  rval <<= fr->bitindex;
64  rval &= 0xffffff;
65 
66  fr->bitindex += number_of_bits;
67 
68  rval >>= (24-number_of_bits);
69 
70  fr->wordpointer += (fr->bitindex>>3);
71  fr->bitindex &= 7;
72  }
73 
74 #ifdef DEBUG_GETBITS
75 fprintf(stderr,":%lx\n",rval);
76 #endif
77 
78  return rval;
79 }
80 
81 
82 #define skipbits(fr, nob) fr->ultmp = ( \
83  fr->ultmp = fr->wordpointer[0], fr->ultmp <<= 8, fr->ultmp |= fr->wordpointer[1], \
84  fr->ultmp <<= 8, fr->ultmp |= fr->wordpointer[2], fr->ultmp <<= fr->bitindex, \
85  fr->ultmp &= 0xffffff, fr->bitindex += nob, fr->bits_avail -= nob, \
86  fr->ultmp >>= (24-nob), fr->wordpointer += (fr->bitindex>>3), \
87  fr->bitindex &= 7 )
88 
89 #define getbits_fast(fr, nob) ( \
90  fr->ultmp = (unsigned char) (fr->wordpointer[0] << fr->bitindex), \
91  fr->ultmp |= ((unsigned long) fr->wordpointer[1]<<fr->bitindex)>>8, \
92  fr->ultmp <<= nob, fr->ultmp >>= 8, \
93  fr->bitindex += nob, fr->bits_avail -= nob, \
94  fr->wordpointer += (fr->bitindex>>3), \
95  fr->bitindex &= 7, fr->ultmp )
96 
97 #define get1bit(fr) ( \
98  fr->uctmp = *fr->wordpointer << fr->bitindex, \
99  ++fr->bitindex, --fr->bits_avail, \
100  fr->wordpointer += (fr->bitindex>>3), fr->bitindex &= 7, fr->uctmp>>7 )
101 
102 
103 #endif
unsigned char * wordpointer
Definition: frame.h:229
_Check_return_opt_ _CRTIMP int __cdecl fprintf(_Inout_ FILE *_File, _In_z_ _Printf_format_string_ const char *_Format,...)
#define error2(s, a, b)
Definition: debug.h:126
static unsigned int getbits(mpg123_handle *fr, int number_of_bits)
Definition: getbits.h:32
#define NOQUIET
float rval
Definition: cylfrac.c:48
FILE * stderr