FFmpeg
bitstream.h
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1 /*
2  * Copyright (c) 2016 Alexandra Hájková
3  *
4  * This file is part of FFmpeg.
5  *
6  * FFmpeg is free software; you can redistribute it and/or
7  * modify it under the terms of the GNU Lesser General Public
8  * License as published by the Free Software Foundation; either
9  * version 2.1 of the License, or (at your option) any later version.
10  *
11  * FFmpeg is distributed in the hope that it will be useful,
12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14  * Lesser General Public License for more details.
15  *
16  * You should have received a copy of the GNU Lesser General Public
17  * License along with FFmpeg; if not, write to the Free Software
18  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
19  */
20 
21 /**
22  * @file
23  * bitstream reader API header.
24  */
25 
26 /*
27  * Bit order (endianness) is controlled by #defining BITSTREAM_BE and/or
28  * BITSTREAM_LE before #including this header. The corresponding bitreading
29  * functions are provided as bits_*_be()/bits_*_le() respectively.
30  *
31  * If neither or only BITSTREAM_BE is defined, then the default (unsuffixed)
32  * bits_*() will resolve to the big-endian implementation. If only BITSTREAM_LE
33  * is defined, little-endian will be the default.
34  *
35  * If both are defined, then the default can be controlled by defining at most
36  * one of BITSTREAM_DEFAULT_LE/BE. When BITSTREAM_DEFAULT_* is not defined, no
37  * default is provided and you must always explicitly use the _be() or _le()
38  * variants.
39  */
40 
41 #ifndef AVCODEC_BITSTREAM_H
42 #define AVCODEC_BITSTREAM_H
43 
44 #include <stdint.h>
45 
46 #include "config.h"
47 
48 #include "libavutil/avassert.h"
49 #include "libavutil/common.h"
50 #include "libavutil/intreadwrite.h"
51 #include "libavutil/log.h"
52 
53 #include "mathops.h"
54 #include "vlc.h"
55 
56 #ifndef UNCHECKED_BITSTREAM_READER
57 #define UNCHECKED_BITSTREAM_READER !CONFIG_SAFE_BITSTREAM_READER
58 #endif
59 
60 // select the default endianness, if any
61 #if defined(BITSTREAM_LE) && defined(BITSTREAM_BE)
62 
63 # if defined(BITSTREAM_DEFAULT_BE) && defined(BITSTREAM_DEFAULT_LE)
64 # error "At most one of BITSTREAM_DEFAULT_BE/LE must be defined"
65 # elif defined(BITSTREAM_DEFAULT_BE)
66 # define BITS_DEFAULT_BE
67 # elif defined(BITSTREAM_DEFAULT_LE)
68 # define BITS_DEFAULT_LE
69 # endif
70 
71 #elif defined(BITSTREAM_LE)
72 # define BITS_DEFAULT_LE
73 #else // select BE if nothing is requested explicitly
74 # define BITS_DEFAULT_BE
75 # define BITSTREAM_WANT_BE
76 #endif
77 
78 #if defined(BITS_DEFAULT_LE)
79 
80 # define BitstreamContext BitstreamContextLE
81 # define bits_init bits_init_le
82 # define bits_init8 bits_init8_le
83 # define bits_tell bits_tell_le
84 # define bits_size bits_size_le
85 # define bits_left bits_left_le
86 # define bits_read_bit bits_read_bit_le
87 # define bits_read_nz bits_read_nz_le
88 # define bits_read bits_read_le
89 # define bits_read_63 bits_read_63_le
90 # define bits_read_64 bits_read_64_le
91 # define bits_read_signed bits_read_signed_le
92 # define bits_read_signed_nz bits_read_signed_nz_le
93 # define bits_peek_nz bits_peek_nz_le
94 # define bits_peek bits_peek_le
95 # define bits_peek_signed bits_peek_signed_le
96 # define bits_peek_signed_nz bits_peek_signed_nz_le
97 # define bits_skip bits_skip_le
98 # define bits_seek bits_seek_le
99 # define bits_align bits_align_le
100 # define bits_read_xbits bits_read_xbits_le
101 # define bits_decode012 bits_decode012_le
102 # define bits_decode210 bits_decode210_le
103 # define bits_apply_sign bits_apply_sign_le
104 # define bits_read_vlc bits_read_vlc_le
105 
106 #elif defined(BITS_DEFAULT_BE)
107 
108 # define BitstreamContext BitstreamContextBE
109 # define bits_init bits_init_be
110 # define bits_init8 bits_init8_be
111 # define bits_tell bits_tell_be
112 # define bits_size bits_size_be
113 # define bits_left bits_left_be
114 # define bits_read_bit bits_read_bit_be
115 # define bits_read_nz bits_read_nz_be
116 # define bits_read bits_read_be
117 # define bits_read_63 bits_read_63_be
118 # define bits_read_64 bits_read_64_be
119 # define bits_read_signed bits_read_signed_be
120 # define bits_read_signed_nz bits_read_signed_nz_be
121 # define bits_peek_nz bits_peek_nz_be
122 # define bits_peek bits_peek_be
123 # define bits_peek_signed bits_peek_signed_be
124 # define bits_peek_signed_nz bits_peek_signed_nz_be
125 # define bits_skip bits_skip_be
126 # define bits_seek bits_seek_be
127 # define bits_align bits_align_be
128 # define bits_read_xbits bits_read_xbits_be
129 # define bits_decode012 bits_decode012_be
130 # define bits_decode210 bits_decode210_be
131 # define bits_apply_sign bits_apply_sign_be
132 # define bits_read_vlc bits_read_vlc_be
133 
134 #endif
135 
136 #undef BITS_DEFAULT_LE
137 #undef BITS_DEFAULT_BE
138 
139 #define BITS_RL_VLC(level, run, bc, table, bits, max_depth) \
140  do { \
141  int n, nb_bits; \
142  unsigned int index = bits_peek(bc, bits); \
143  level = table[index].level; \
144  n = table[index].len; \
145  \
146  if (max_depth > 1 && n < 0) { \
147  bits_skip(bc, bits); \
148  \
149  nb_bits = -n; \
150  \
151  index = bits_peek(bc, nb_bits) + level; \
152  level = table[index].level; \
153  n = table[index].len; \
154  if (max_depth > 2 && n < 0) { \
155  bits_skip(bc, nb_bits); \
156  nb_bits = -n; \
157  \
158  index = bits_peek(bc, nb_bits) + level; \
159  level = table[index].level; \
160  n = table[index].len; \
161  } \
162  } \
163  run = table[index].run; \
164  bits_skip(bc, n); \
165  } while (0)
166 
167 #endif /* AVCODEC_BITSTREAM_H */
168 
169 // the following is deliberately outside of the standard #include guards
170 
171 #if defined(BITSTREAM_LE) && !defined(BITSTREAM_WANT_LE)
172 # define BITSTREAM_WANT_LE
173 #endif
174 
175 #if defined(BITSTREAM_BE) && !defined(BITSTREAM_WANT_BE)
176 # define BITSTREAM_WANT_BE
177 #endif
178 
179 #if defined(BITSTREAM_WANT_LE) && !defined(AVCODEC_BITSTREAM_LE)
180 #define AVCODEC_BITSTREAM_LE
181 
182 #define BITSTREAM_TEMPLATE_LE
183 #include "bitstream_template.h"
184 #undef BITSTREAM_TEMPLATE_LE
185 
186 #endif
187 
188 #if defined(BITSTREAM_WANT_BE) && !defined(AVCODEC_BITSTREAM_BE)
189 #define AVCODEC_BITSTREAM_BE
190 
191 #include "bitstream_template.h"
192 
193 #endif
194 
195 #undef BITSTREAM_WANT_LE
196 #undef BITSTREAM_WANT_BE
bitstream_template.h
avassert.h
intreadwrite.h
mathops.h
log.h
common.h
vlc.h