FFmpeg
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 "config.h"
33 #include "libavutil/intreadwrite.h"
34 #include "libavutil/avassert.h"
35 #include "libavutil/common.h"
36 
37 #if ARCH_X86_64
38 // TODO: Benchmark and optionally enable on other 64-bit architectures.
39 typedef uint64_t BitBuf;
40 #define AV_WBBUF AV_WB64
41 #define AV_WLBUF AV_WL64
42 #else
43 typedef uint32_t BitBuf;
44 #define AV_WBBUF AV_WB32
45 #define AV_WLBUF AV_WL32
46 #endif
47 
48 static const int BUF_BITS = 8 * sizeof(BitBuf);
49 
50 typedef struct PutBitContext {
52  int bit_left;
53  uint8_t *buf, *buf_ptr, *buf_end;
55 
56 /**
57  * Initialize the PutBitContext s.
58  *
59  * @param buffer the buffer where to put bits
60  * @param buffer_size the size in bytes of buffer
61  */
62 static inline void init_put_bits(PutBitContext *s, uint8_t *buffer,
63  int buffer_size)
64 {
65  if (buffer_size < 0) {
66  buffer_size = 0;
67  buffer = NULL;
68  }
69 
70  s->buf = buffer;
71  s->buf_end = s->buf + buffer_size;
72  s->buf_ptr = s->buf;
73  s->bit_left = BUF_BITS;
74  s->bit_buf = 0;
75 }
76 
77 /**
78  * @return the total number of bits written to the bitstream.
79  */
80 static inline int put_bits_count(PutBitContext *s)
81 {
82  return (s->buf_ptr - s->buf) * 8 + BUF_BITS - s->bit_left;
83 }
84 
85 /**
86  * @return the number of bytes output so far; may only be called
87  * when the PutBitContext is freshly initialized or flushed.
88  */
89 static inline int put_bytes_output(const PutBitContext *s)
90 {
91  av_assert2(s->bit_left == BUF_BITS);
92  return s->buf_ptr - s->buf;
93 }
94 
95 /**
96  * @param round_up When set, the number of bits written so far will be
97  * rounded up to the next byte.
98  * @return the number of bytes output so far.
99  */
100 static inline int put_bytes_count(const PutBitContext *s, int round_up)
101 {
102  return s->buf_ptr - s->buf + ((BUF_BITS - s->bit_left + (round_up ? 7 : 0)) >> 3);
103 }
104 
105 /**
106  * Rebase the bit writer onto a reallocated buffer.
107  *
108  * @param buffer the buffer where to put bits
109  * @param buffer_size the size in bytes of buffer,
110  * must be large enough to hold everything written so far
111  */
112 static inline void rebase_put_bits(PutBitContext *s, uint8_t *buffer,
113  int buffer_size)
114 {
115  av_assert0(8*buffer_size >= put_bits_count(s));
116 
117  s->buf_end = buffer + buffer_size;
118  s->buf_ptr = buffer + (s->buf_ptr - s->buf);
119  s->buf = buffer;
120 }
121 
122 /**
123  * @return the number of bits available in the bitstream.
124  */
125 static inline int put_bits_left(PutBitContext* s)
126 {
127  return (s->buf_end - s->buf_ptr) * 8 - BUF_BITS + s->bit_left;
128 }
129 
130 /**
131  * @param round_up When set, the number of bits written will be
132  * rounded up to the next byte.
133  * @return the number of bytes left.
134  */
135 static inline int put_bytes_left(const PutBitContext *s, int round_up)
136 {
137  return s->buf_end - s->buf_ptr - ((BUF_BITS - s->bit_left + (round_up ? 7 : 0)) >> 3);
138 }
139 
140 /**
141  * Pad the end of the output stream with zeros.
142  */
143 static inline void flush_put_bits(PutBitContext *s)
144 {
145 #ifndef BITSTREAM_WRITER_LE
146  if (s->bit_left < BUF_BITS)
147  s->bit_buf <<= s->bit_left;
148 #endif
149  while (s->bit_left < BUF_BITS) {
150  av_assert0(s->buf_ptr < s->buf_end);
151 #ifdef BITSTREAM_WRITER_LE
152  *s->buf_ptr++ = s->bit_buf;
153  s->bit_buf >>= 8;
154 #else
155  *s->buf_ptr++ = s->bit_buf >> (BUF_BITS - 8);
156  s->bit_buf <<= 8;
157 #endif
158  s->bit_left += 8;
159  }
160  s->bit_left = BUF_BITS;
161  s->bit_buf = 0;
162 }
163 
164 static inline void flush_put_bits_le(PutBitContext *s)
165 {
166  while (s->bit_left < BUF_BITS) {
167  av_assert0(s->buf_ptr < s->buf_end);
168  *s->buf_ptr++ = s->bit_buf;
169  s->bit_buf >>= 8;
170  s->bit_left += 8;
171  }
172  s->bit_left = BUF_BITS;
173  s->bit_buf = 0;
174 }
175 
176 #ifdef BITSTREAM_WRITER_LE
177 #define ff_put_string ff_put_string_unsupported_here
178 #define ff_copy_bits ff_copy_bits_unsupported_here
179 #else
180 
181 /**
182  * Put the string string in the bitstream.
183  *
184  * @param terminate_string 0-terminates the written string if value is 1
185  */
186 void ff_put_string(PutBitContext *pb, const char *string,
187  int terminate_string);
188 
189 /**
190  * Copy the content of src to the bitstream.
191  *
192  * @param length the number of bits of src to copy
193  */
194 void ff_copy_bits(PutBitContext *pb, const uint8_t *src, int length);
195 #endif
196 
197 static inline void put_bits_no_assert(PutBitContext *s, int n, BitBuf value)
198 {
199  BitBuf bit_buf;
200  int bit_left;
201 
202  bit_buf = s->bit_buf;
203  bit_left = s->bit_left;
204 
205  /* XXX: optimize */
206 #ifdef BITSTREAM_WRITER_LE
207  bit_buf |= value << (BUF_BITS - bit_left);
208  if (n >= bit_left) {
209  if (s->buf_end - s->buf_ptr >= sizeof(BitBuf)) {
210  AV_WLBUF(s->buf_ptr, bit_buf);
211  s->buf_ptr += sizeof(BitBuf);
212  } else {
213  av_log(NULL, AV_LOG_ERROR, "Internal error, put_bits buffer too small\n");
214  av_assert2(0);
215  }
216  bit_buf = value >> bit_left;
217  bit_left += BUF_BITS;
218  }
219  bit_left -= n;
220 #else
221  if (n < bit_left) {
222  bit_buf = (bit_buf << n) | value;
223  bit_left -= n;
224  } else {
225  bit_buf <<= bit_left;
226  bit_buf |= value >> (n - bit_left);
227  if (s->buf_end - s->buf_ptr >= sizeof(BitBuf)) {
228  AV_WBBUF(s->buf_ptr, bit_buf);
229  s->buf_ptr += sizeof(BitBuf);
230  } else {
231  av_log(NULL, AV_LOG_ERROR, "Internal error, put_bits buffer too small\n");
232  av_assert2(0);
233  }
234  bit_left += BUF_BITS - n;
235  bit_buf = value;
236  }
237 #endif
238 
239  s->bit_buf = bit_buf;
240  s->bit_left = bit_left;
241 }
242 
243 /**
244  * Write up to 31 bits into a bitstream.
245  * Use put_bits32 to write 32 bits.
246  */
247 static inline void put_bits(PutBitContext *s, int n, BitBuf value)
248 {
249  av_assert2(n <= 31 && value < (1UL << n));
251 }
252 
253 static inline void put_bits_le(PutBitContext *s, int n, BitBuf value)
254 {
255  BitBuf bit_buf;
256  int bit_left;
257 
258  av_assert2(n <= 31 && value < (1UL << n));
259 
260  bit_buf = s->bit_buf;
261  bit_left = s->bit_left;
262 
263  bit_buf |= value << (BUF_BITS - bit_left);
264  if (n >= bit_left) {
265  if (s->buf_end - s->buf_ptr >= sizeof(BitBuf)) {
266  AV_WLBUF(s->buf_ptr, bit_buf);
267  s->buf_ptr += sizeof(BitBuf);
268  } else {
269  av_log(NULL, AV_LOG_ERROR, "Internal error, put_bits buffer too small\n");
270  av_assert2(0);
271  }
272  bit_buf = value >> bit_left;
273  bit_left += BUF_BITS;
274  }
275  bit_left -= n;
276 
277  s->bit_buf = bit_buf;
278  s->bit_left = bit_left;
279 }
280 
281 static inline void put_sbits(PutBitContext *pb, int n, int32_t value)
282 {
283  av_assert2(n >= 0 && n <= 31);
284 
285  put_bits(pb, n, av_mod_uintp2(value, n));
286 }
287 
288 /**
289  * Write exactly 32 bits into a bitstream.
290  */
291 static void av_unused put_bits32(PutBitContext *s, uint32_t value)
292 {
293  BitBuf bit_buf;
294  int bit_left;
295 
296  if (BUF_BITS > 32) {
297  put_bits_no_assert(s, 32, value);
298  return;
299  }
300 
301  bit_buf = s->bit_buf;
302  bit_left = s->bit_left;
303 
304 #ifdef BITSTREAM_WRITER_LE
305  bit_buf |= (BitBuf)value << (BUF_BITS - bit_left);
306  if (s->buf_end - s->buf_ptr >= sizeof(BitBuf)) {
307  AV_WLBUF(s->buf_ptr, bit_buf);
308  s->buf_ptr += sizeof(BitBuf);
309  } else {
310  av_log(NULL, AV_LOG_ERROR, "Internal error, put_bits buffer too small\n");
311  av_assert2(0);
312  }
313  bit_buf = (uint64_t)value >> bit_left;
314 #else
315  bit_buf = (uint64_t)bit_buf << bit_left;
316  bit_buf |= (BitBuf)value >> (BUF_BITS - bit_left);
317  if (s->buf_end - s->buf_ptr >= sizeof(BitBuf)) {
318  AV_WBBUF(s->buf_ptr, bit_buf);
319  s->buf_ptr += sizeof(BitBuf);
320  } else {
321  av_log(NULL, AV_LOG_ERROR, "Internal error, put_bits buffer too small\n");
322  av_assert2(0);
323  }
324  bit_buf = value;
325 #endif
326 
327  s->bit_buf = bit_buf;
328  s->bit_left = bit_left;
329 }
330 
331 /**
332  * Write up to 64 bits into a bitstream.
333  */
334 static inline void put_bits64(PutBitContext *s, int n, uint64_t value)
335 {
336  av_assert2((n == 64) || (n < 64 && value < (UINT64_C(1) << n)));
337 
338  if (n < 32)
339  put_bits(s, n, value);
340  else if (n == 32)
341  put_bits32(s, value);
342  else if (n < 64) {
343  uint32_t lo = value & 0xffffffff;
344  uint32_t hi = value >> 32;
345 #ifdef BITSTREAM_WRITER_LE
346  put_bits32(s, lo);
347  put_bits(s, n - 32, hi);
348 #else
349  put_bits(s, n - 32, hi);
350  put_bits32(s, lo);
351 #endif
352  } else {
353  uint32_t lo = value & 0xffffffff;
354  uint32_t hi = value >> 32;
355 #ifdef BITSTREAM_WRITER_LE
356  put_bits32(s, lo);
357  put_bits32(s, hi);
358 #else
359  put_bits32(s, hi);
360  put_bits32(s, lo);
361 #endif
362 
363  }
364 }
365 
366 /**
367  * Return the pointer to the byte where the bitstream writer will put
368  * the next bit.
369  */
370 static inline uint8_t *put_bits_ptr(PutBitContext *s)
371 {
372  return s->buf_ptr;
373 }
374 
375 /**
376  * Skip the given number of bytes.
377  * PutBitContext must be flushed & aligned to a byte boundary before calling this.
378  */
379 static inline void skip_put_bytes(PutBitContext *s, int n)
380 {
381  av_assert2((put_bits_count(s) & 7) == 0);
382  av_assert2(s->bit_left == BUF_BITS);
383  av_assert0(n <= s->buf_end - s->buf_ptr);
384  s->buf_ptr += n;
385 }
386 
387 /**
388  * Skip the given number of bits.
389  * Must only be used if the actual values in the bitstream do not matter.
390  * If n is < 0 the behavior is undefined.
391  */
392 static inline void skip_put_bits(PutBitContext *s, int n)
393 {
394  unsigned bits = BUF_BITS - s->bit_left + n;
395  s->buf_ptr += sizeof(BitBuf) * (bits / BUF_BITS);
396  s->bit_left = BUF_BITS - (bits & (BUF_BITS - 1));
397 }
398 
399 /**
400  * Change the end of the buffer.
401  *
402  * @param size the new size in bytes of the buffer where to put bits
403  */
404 static inline void set_put_bits_buffer_size(PutBitContext *s, int size)
405 {
406  av_assert0(size <= INT_MAX/8 - BUF_BITS);
407  s->buf_end = s->buf + size;
408 }
409 
410 /**
411  * Pad the bitstream with zeros up to the next byte boundary.
412  */
413 static inline void align_put_bits(PutBitContext *s)
414 {
415  put_bits(s, s->bit_left & 7, 0);
416 }
417 
418 #undef AV_WBBUF
419 #undef AV_WLBUF
420 
421 #endif /* AVCODEC_PUT_BITS_H */
put_bits32
static void av_unused put_bits32(PutBitContext *s, uint32_t value)
Write exactly 32 bits into a bitstream.
Definition: put_bits.h:291
align_put_bits
static void align_put_bits(PutBitContext *s)
Pad the bitstream with zeros up to the next byte boundary.
Definition: put_bits.h:413
put_bytes_output
static int put_bytes_output(const PutBitContext *s)
Definition: put_bits.h:89
put_sbits
static void put_sbits(PutBitContext *pb, int n, int32_t value)
Definition: put_bits.h:281
ff_put_string
void ff_put_string(PutBitContext *pb, const char *string, int terminate_string)
Put the string string in the bitstream.
Definition: bitstream.c:39
init_put_bits
static void init_put_bits(PutBitContext *s, uint8_t *buffer, int buffer_size)
Initialize the PutBitContext s.
Definition: put_bits.h:62
BitBuf
uint32_t BitBuf
Definition: put_bits.h:43
av_unused
#define av_unused
Definition: attributes.h:131
av_mod_uintp2
#define av_mod_uintp2
Definition: common.h:122
BUF_BITS
static const int BUF_BITS
Definition: put_bits.h:48
put_bits64
static void put_bits64(PutBitContext *s, int n, uint64_t value)
Write up to 64 bits into a bitstream.
Definition: put_bits.h:334
put_bytes_count
static int put_bytes_count(const PutBitContext *s, int round_up)
Definition: put_bits.h:100
AV_WBBUF
#define AV_WBBUF
Definition: put_bits.h:44
ff_copy_bits
void ff_copy_bits(PutBitContext *pb, const uint8_t *src, int length)
Copy the content of src to the bitstream.
Definition: bitstream.c:49
put_bits_left
static int put_bits_left(PutBitContext *s)
Definition: put_bits.h:125
put_bytes_left
static int put_bytes_left(const PutBitContext *s, int round_up)
Definition: put_bits.h:135
avassert.h
AV_LOG_ERROR
#define AV_LOG_ERROR
Something went wrong and cannot losslessly be recovered.
Definition: log.h:180
intreadwrite.h
s
#define s(width, name)
Definition: cbs_vp9.c:256
rebase_put_bits
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:112
skip_put_bits
static void skip_put_bits(PutBitContext *s, int n)
Skip the given number of bits.
Definition: put_bits.h:392
bits
uint8_t bits
Definition: vp3data.h:128
av_assert0
#define av_assert0(cond)
assert() equivalent, that is always enabled.
Definition: avassert.h:37
PutBitContext
Definition: put_bits.h:50
AV_WLBUF
#define AV_WLBUF
Definition: put_bits.h:45
PutBitContext::buf
uint8_t * buf
Definition: put_bits.h:53
NULL
#define NULL
Definition: coverity.c:32
BitBuf
Definition: kmvc.c:54
flush_put_bits_le
static void flush_put_bits_le(PutBitContext *s)
Definition: put_bits.h:164
put_bits
static void put_bits(PutBitContext *s, int n, BitBuf value)
Write up to 31 bits into a bitstream.
Definition: put_bits.h:247
set_put_bits_buffer_size
static void set_put_bits_buffer_size(PutBitContext *s, int size)
Change the end of the buffer.
Definition: put_bits.h:404
put_bits_no_assert
static void put_bits_no_assert(PutBitContext *s, int n, BitBuf value)
Definition: put_bits.h:197
size
int size
Definition: twinvq_data.h:10344
PutBitContext::bit_left
int bit_left
Definition: put_bits.h:52
PutBitContext::bit_buf
BitBuf bit_buf
Definition: put_bits.h:51
PutBitContext::buf_end
uint8_t * buf_end
Definition: put_bits.h:53
av_assert2
#define av_assert2(cond)
assert() equivalent, that does lie in speed critical code.
Definition: avassert.h:64
put_bits_count
static int put_bits_count(PutBitContext *s)
Definition: put_bits.h:80
common.h
value
it s the only field you need to keep assuming you have a context There is some magic you don t need to care about around this just let it vf default value
Definition: writing_filters.txt:86
put_bits_ptr
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:370
PutBitContext::buf_ptr
uint8_t * buf_ptr
Definition: put_bits.h:53
buffer
the frame and frame reference mechanism is intended to as much as expensive copies of that data while still allowing the filters to produce correct results The data is stored in buffers represented by AVFrame structures Several references can point to the same frame buffer
Definition: filter_design.txt:49
skip_put_bytes
static void skip_put_bytes(PutBitContext *s, int n)
Skip the given number of bytes.
Definition: put_bits.h:379
flush_put_bits
static void flush_put_bits(PutBitContext *s)
Pad the end of the output stream with zeros.
Definition: put_bits.h:143
src
INIT_CLIP pixel * src
Definition: h264pred_template.c:418
int32_t
int32_t
Definition: audioconvert.c:56
put_bits_le
static void put_bits_le(PutBitContext *s, int n, BitBuf value)
Definition: put_bits.h:253
av_log
#define av_log(a,...)
Definition: tableprint_vlc.h:27