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put_bits.h
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1 /*
2  * copyright (c) 2004 Michael Niedermayer <michaelni@gmx.at>
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 writer API
24  */
25 
26 #ifndef AVCODEC_PUT_BITS_H
27 #define AVCODEC_PUT_BITS_H
28 
29 #include <stdint.h>
30 #include <stddef.h>
31 
32 #include "libavutil/intreadwrite.h"
33 #include "libavutil/avassert.h"
34 
35 typedef struct PutBitContext {
36  uint32_t bit_buf;
37  int bit_left;
41 
42 /**
43  * Initialize the PutBitContext s.
44  *
45  * @param buffer the buffer where to put bits
46  * @param buffer_size the size in bytes of buffer
47  */
48 static inline void init_put_bits(PutBitContext *s, uint8_t *buffer,
49  int buffer_size)
50 {
51  if (buffer_size < 0) {
52  buffer_size = 0;
53  buffer = NULL;
54  }
55 
56  s->size_in_bits = 8 * buffer_size;
57  s->buf = buffer;
58  s->buf_end = s->buf + buffer_size;
59  s->buf_ptr = s->buf;
60  s->bit_left = 32;
61  s->bit_buf = 0;
62 }
63 
64 /**
65  * Rebase the bit writer onto a reallocated buffer.
66  *
67  * @param buffer the buffer where to put bits
68  * @param buffer_size the size in bytes of buffer,
69  * must be larger than the previous size
70  */
72  int buffer_size)
73 {
74  av_assert0(8*buffer_size > s->size_in_bits);
75 
76  s->buf_end = buffer + buffer_size;
77  s->buf_ptr = buffer + (s->buf_ptr - s->buf);
78  s->buf = buffer;
79  s->size_in_bits = 8 * buffer_size;
80 }
81 
82 /**
83  * @return the total number of bits written to the bitstream.
84  */
85 static inline int put_bits_count(PutBitContext *s)
86 {
87  return (s->buf_ptr - s->buf) * 8 + 32 - s->bit_left;
88 }
89 
90 /**
91  * @return the number of bits available in the bitstream.
92  */
93 static inline int put_bits_left(PutBitContext* s)
94 {
95  return (s->buf_end - s->buf_ptr) * 8 - 32 + s->bit_left;
96 }
97 
98 /**
99  * Pad the end of the output stream with zeros.
100  */
101 static inline void flush_put_bits(PutBitContext *s)
102 {
103 #ifndef BITSTREAM_WRITER_LE
104  if (s->bit_left < 32)
105  s->bit_buf <<= s->bit_left;
106 #endif
107  while (s->bit_left < 32) {
108  av_assert0(s->buf_ptr < s->buf_end);
109 #ifdef BITSTREAM_WRITER_LE
110  *s->buf_ptr++ = s->bit_buf;
111  s->bit_buf >>= 8;
112 #else
113  *s->buf_ptr++ = s->bit_buf >> 24;
114  s->bit_buf <<= 8;
115 #endif
116  s->bit_left += 8;
117  }
118  s->bit_left = 32;
119  s->bit_buf = 0;
120 }
121 
122 #ifdef BITSTREAM_WRITER_LE
123 #define avpriv_align_put_bits align_put_bits_unsupported_here
124 #define avpriv_put_string ff_put_string_unsupported_here
125 #define avpriv_copy_bits avpriv_copy_bits_unsupported_here
126 #else
127 /**
128  * Pad the bitstream with zeros up to the next byte boundary.
129  */
131 
132 /**
133  * Put the string string in the bitstream.
134  *
135  * @param terminate_string 0-terminates the written string if value is 1
136  */
137 void avpriv_put_string(PutBitContext *pb, const char *string,
138  int terminate_string);
139 
140 /**
141  * Copy the content of src to the bitstream.
142  *
143  * @param length the number of bits of src to copy
144  */
145 void avpriv_copy_bits(PutBitContext *pb, const uint8_t *src, int length);
146 #endif
147 
148 /**
149  * Write up to 31 bits into a bitstream.
150  * Use put_bits32 to write 32 bits.
151  */
152 static inline void put_bits(PutBitContext *s, int n, unsigned int value)
153 {
154  unsigned int bit_buf;
155  int bit_left;
156 
157  av_assert2(n <= 31 && value < (1U << n));
158 
159  bit_buf = s->bit_buf;
160  bit_left = s->bit_left;
161 
162  /* XXX: optimize */
163 #ifdef BITSTREAM_WRITER_LE
164  bit_buf |= value << (32 - bit_left);
165  if (n >= bit_left) {
166  if (3 < s->buf_end - s->buf_ptr) {
167  AV_WL32(s->buf_ptr, bit_buf);
168  s->buf_ptr += 4;
169  } else {
170  av_log(NULL, AV_LOG_ERROR, "Internal error, put_bits buffer too small\n");
171  av_assert2(0);
172  }
173  bit_buf = value >> bit_left;
174  bit_left += 32;
175  }
176  bit_left -= n;
177 #else
178  if (n < bit_left) {
179  bit_buf = (bit_buf << n) | value;
180  bit_left -= n;
181  } else {
182  bit_buf <<= bit_left;
183  bit_buf |= value >> (n - bit_left);
184  if (3 < s->buf_end - s->buf_ptr) {
185  AV_WB32(s->buf_ptr, bit_buf);
186  s->buf_ptr += 4;
187  } else {
188  av_log(NULL, AV_LOG_ERROR, "Internal error, put_bits buffer too small\n");
189  av_assert2(0);
190  }
191  bit_left += 32 - n;
192  bit_buf = value;
193  }
194 #endif
195 
196  s->bit_buf = bit_buf;
197  s->bit_left = bit_left;
198 }
199 
200 static inline void put_sbits(PutBitContext *pb, int n, int32_t value)
201 {
202  av_assert2(n >= 0 && n <= 31);
203 
204  put_bits(pb, n, av_mod_uintp2(value, n));
205 }
206 
207 /**
208  * Write exactly 32 bits into a bitstream.
209  */
210 static void av_unused put_bits32(PutBitContext *s, uint32_t value)
211 {
212  int lo = value & 0xffff;
213  int hi = value >> 16;
214 #ifdef BITSTREAM_WRITER_LE
215  put_bits(s, 16, lo);
216  put_bits(s, 16, hi);
217 #else
218  put_bits(s, 16, hi);
219  put_bits(s, 16, lo);
220 #endif
221 }
222 
223 /**
224  * Return the pointer to the byte where the bitstream writer will put
225  * the next bit.
226  */
228 {
229  return s->buf_ptr;
230 }
231 
232 /**
233  * Skip the given number of bytes.
234  * PutBitContext must be flushed & aligned to a byte boundary before calling this.
235  */
236 static inline void skip_put_bytes(PutBitContext *s, int n)
237 {
238  av_assert2((put_bits_count(s) & 7) == 0);
239  av_assert2(s->bit_left == 32);
240  av_assert0(n <= s->buf_end - s->buf_ptr);
241  s->buf_ptr += n;
242 }
243 
244 /**
245  * Skip the given number of bits.
246  * Must only be used if the actual values in the bitstream do not matter.
247  * If n is 0 the behavior is undefined.
248  */
249 static inline void skip_put_bits(PutBitContext *s, int n)
250 {
251  s->bit_left -= n;
252  s->buf_ptr -= 4 * (s->bit_left >> 5);
253  s->bit_left &= 31;
254 }
255 
256 /**
257  * Change the end of the buffer.
258  *
259  * @param size the new size in bytes of the buffer where to put bits
260  */
261 static inline void set_put_bits_buffer_size(PutBitContext *s, int size)
262 {
263  av_assert0(size <= INT_MAX/8 - 32);
264  s->buf_end = s->buf + size;
265  s->size_in_bits = 8*size;
266 }
267 
268 #endif /* AVCODEC_PUT_BITS_H */
static void av_unused put_bits32(PutBitContext *s, uint32_t value)
Write exactly 32 bits into a bitstream.
Definition: put_bits.h:210
#define NULL
Definition: coverity.c:32
void avpriv_put_string(PutBitContext *pb, const char *string, int terminate_string)
Put the string string in the bitstream.
Definition: bitstream.c:54
const char * s
Definition: avisynth_c.h:768
static void put_sbits(PutBitContext *pb, int n, int32_t value)
Definition: put_bits.h:200
static void skip_put_bits(PutBitContext *s, int n)
Skip the given number of bits.
Definition: put_bits.h:249
#define av_assert0(cond)
assert() equivalent, that is always enabled.
Definition: avassert.h:37
uint8_t
#define av_assert2(cond)
assert() equivalent, that does lie in speed critical code.
Definition: avassert.h:63
static void rebase_put_bits(PutBitContext *s, uint8_t *buffer, int buffer_size)
Rebase the bit writer onto a reallocated buffer.
Definition: put_bits.h:71
ptrdiff_t size
Definition: opengl_enc.c:101
#define av_log(a,...)
#define U(x)
Definition: vp56_arith.h:37
int size_in_bits
Definition: put_bits.h:39
#define AV_LOG_ERROR
Something went wrong and cannot losslessly be recovered.
Definition: log.h:176
static uint8_t * put_bits_ptr(PutBitContext *s)
Return the pointer to the byte where the bitstream writer will put the next bit.
Definition: put_bits.h:227
static int put_bits_left(PutBitContext *s)
Definition: put_bits.h:93
uint8_t * buf
Definition: put_bits.h:38
simple assert() macros that are a bit more flexible than ISO C assert().
GLsizei GLsizei * length
Definition: opengl_enc.c:115
static void put_bits(PutBitContext *s, int n, unsigned int value)
Write up to 31 bits into a bitstream.
Definition: put_bits.h:152
static int put_bits_count(PutBitContext *s)
Definition: put_bits.h:85
static void skip_put_bytes(PutBitContext *s, int n)
Skip the given number of bytes.
Definition: put_bits.h:236
GLsizei GLboolean const GLfloat * value
Definition: opengl_enc.c:109
int32_t
int n
Definition: avisynth_c.h:684
#define src
Definition: vp9dsp.c:530
static void set_put_bits_buffer_size(PutBitContext *s, int size)
Change the end of the buffer.
Definition: put_bits.h:261
int bit_left
Definition: put_bits.h:37
uint8_t * buf_end
Definition: put_bits.h:38
uint8_t * buf_ptr
Definition: put_bits.h:38
void avpriv_copy_bits(PutBitContext *pb, const uint8_t *src, int length)
Copy the content of src to the bitstream.
Definition: bitstream.c:65
#define AV_WB32(p, v)
Definition: intreadwrite.h:419
void avpriv_align_put_bits(PutBitContext *s)
Pad the bitstream with zeros up to the next byte boundary.
Definition: bitstream.c:49
uint32_t bit_buf
Definition: put_bits.h:36
static void flush_put_bits(PutBitContext *s)
Pad the end of the output stream with zeros.
Definition: put_bits.h:101
static void init_put_bits(PutBitContext *s, uint8_t *buffer, int buffer_size)
Initialize the PutBitContext s.
Definition: put_bits.h:48
GLuint buffer
Definition: opengl_enc.c:102
#define av_unused
Definition: attributes.h:126
#define AV_WL32(p, v)
Definition: intreadwrite.h:426