FFmpeg  4.4.6
bitstream.c
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1 /*
2  * Common bit i/o utils
3  * Copyright (c) 2000, 2001 Fabrice Bellard
4  * Copyright (c) 2002-2004 Michael Niedermayer <michaelni@gmx.at>
5  * Copyright (c) 2010 Loren Merritt
6  *
7  * alternative bitstream reader & writer by Michael Niedermayer <michaelni@gmx.at>
8  *
9  * This file is part of FFmpeg.
10  *
11  * FFmpeg is free software; you can redistribute it and/or
12  * modify it under the terms of the GNU Lesser General Public
13  * License as published by the Free Software Foundation; either
14  * version 2.1 of the License, or (at your option) any later version.
15  *
16  * FFmpeg is distributed in the hope that it will be useful,
17  * but WITHOUT ANY WARRANTY; without even the implied warranty of
18  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
19  * Lesser General Public License for more details.
20  *
21  * You should have received a copy of the GNU Lesser General Public
22  * License along with FFmpeg; if not, write to the Free Software
23  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
24  */
25 
26 /**
27  * @file
28  * bitstream api.
29  */
30 
31 #include "libavutil/avassert.h"
32 #include "libavutil/qsort.h"
33 #include "avcodec.h"
34 #include "internal.h"
35 #include "mathops.h"
36 #include "put_bits.h"
37 #include "vlc.h"
38 
39 const uint8_t ff_log2_run[41]={
40  0, 0, 0, 0, 1, 1, 1, 1,
41  2, 2, 2, 2, 3, 3, 3, 3,
42  4, 4, 5, 5, 6, 6, 7, 7,
43  8, 9,10,11,12,13,14,15,
44 16,17,18,19,20,21,22,23,
45 24,
46 };
47 
48 #if FF_API_AVPRIV_PUT_BITS
50 {
52 }
53 void avpriv_copy_bits(PutBitContext *pb, const uint8_t *src, int length)
54 {
55  ff_copy_bits(pb, src, length);
56 }
57 #endif
58 
59 void ff_put_string(PutBitContext *pb, const char *string, int terminate_string)
60 {
61  while (*string) {
62  put_bits(pb, 8, *string);
63  string++;
64  }
65  if (terminate_string)
66  put_bits(pb, 8, 0);
67 }
68 
69 void ff_copy_bits(PutBitContext *pb, const uint8_t *src, int length)
70 {
71  int words = length >> 4;
72  int bits = length & 15;
73  int i;
74 
75  if (length == 0)
76  return;
77 
78  av_assert0(length <= put_bits_left(pb));
79 
80  if (CONFIG_SMALL || words < 16 || put_bits_count(pb) & 7) {
81  for (i = 0; i < words; i++)
82  put_bits(pb, 16, AV_RB16(src + 2 * i));
83  } else {
84  for (i = 0; put_bits_count(pb) & 31; i++)
85  put_bits(pb, 8, src[i]);
86  flush_put_bits(pb);
87  memcpy(put_bits_ptr(pb), src + i, 2 * words - i);
88  skip_put_bytes(pb, 2 * words - i);
89  }
90 
91  put_bits(pb, bits, AV_RB16(src + 2 * words) >> (16 - bits));
92 }
93 
94 /* VLC decoding */
95 
96 #define GET_DATA(v, table, i, wrap, size) \
97 { \
98  const uint8_t *ptr = (const uint8_t *)table + i * wrap; \
99  switch(size) { \
100  case 1: \
101  v = *(const uint8_t *)ptr; \
102  break; \
103  case 2: \
104  v = *(const uint16_t *)ptr; \
105  break; \
106  case 4: \
107  default: \
108  av_assert1(size == 4); \
109  v = *(const uint32_t *)ptr; \
110  break; \
111  } \
112 }
113 
114 
115 static int alloc_table(VLC *vlc, int size, int use_static)
116 {
117  int index = vlc->table_size;
118 
119  vlc->table_size += size;
120  if (vlc->table_size > vlc->table_allocated) {
121  if (use_static)
122  abort(); // cannot do anything, init_vlc() is used with too little memory
123  vlc->table_allocated += (1 << vlc->bits);
124  vlc->table = av_realloc_f(vlc->table, vlc->table_allocated, sizeof(VLC_TYPE) * 2);
125  if (!vlc->table) {
126  vlc->table_allocated = 0;
127  vlc->table_size = 0;
128  return AVERROR(ENOMEM);
129  }
130  memset(vlc->table + vlc->table_allocated - (1 << vlc->bits), 0, sizeof(VLC_TYPE) * 2 << vlc->bits);
131  }
132  return index;
133 }
134 
135 #define LOCALBUF_ELEMS 1500 // the maximum currently needed is 1296 by rv34
136 
137 typedef struct VLCcode {
140  /** codeword, with the first bit-to-be-read in the msb
141  * (even if intended for a little-endian bitstream reader) */
142  uint32_t code;
143 } VLCcode;
144 
145 static int vlc_common_init(VLC *vlc_arg, int nb_bits, int nb_codes,
146  VLC **vlc, VLC *localvlc, VLCcode **buf,
147  int flags)
148 {
149  *vlc = vlc_arg;
150  (*vlc)->bits = nb_bits;
152  av_assert0(nb_codes <= LOCALBUF_ELEMS);
153  *localvlc = *vlc_arg;
154  *vlc = localvlc;
155  (*vlc)->table_size = 0;
156  } else {
157  (*vlc)->table = NULL;
158  (*vlc)->table_allocated = 0;
159  (*vlc)->table_size = 0;
160  }
161  if (nb_codes > LOCALBUF_ELEMS) {
162  *buf = av_malloc_array(nb_codes, sizeof(VLCcode));
163  if (!*buf)
164  return AVERROR(ENOMEM);
165  }
166 
167  return 0;
168 }
169 
170 static int compare_vlcspec(const void *a, const void *b)
171 {
172  const VLCcode *sa = a, *sb = b;
173  return (sa->code >> 1) - (sb->code >> 1);
174 }
175 /**
176  * Build VLC decoding tables suitable for use with get_vlc().
177  *
178  * @param vlc the context to be initialized
179  *
180  * @param table_nb_bits max length of vlc codes to store directly in this table
181  * (Longer codes are delegated to subtables.)
182  *
183  * @param nb_codes number of elements in codes[]
184  *
185  * @param codes descriptions of the vlc codes
186  * These must be ordered such that codes going into the same subtable are contiguous.
187  * Sorting by VLCcode.code is sufficient, though not necessary.
188  */
189 static int build_table(VLC *vlc, int table_nb_bits, int nb_codes,
190  VLCcode *codes, int flags)
191 {
192  int table_size, table_index, index, code_prefix, symbol, subtable_bits;
193  int i, j, k, n, nb, inc;
194  uint32_t code;
195  volatile VLC_TYPE (* volatile table)[2]; // the double volatile is needed to prevent an internal compiler error in gcc 4.2
196 
197  if (table_nb_bits > 30)
198  return AVERROR(EINVAL);
199  table_size = 1 << table_nb_bits;
200  table_index = alloc_table(vlc, table_size, flags & INIT_VLC_USE_NEW_STATIC);
201  ff_dlog(NULL, "new table index=%d size=%d\n", table_index, table_size);
202  if (table_index < 0)
203  return table_index;
204  table = (volatile VLC_TYPE (*)[2])&vlc->table[table_index];
205 
206  /* first pass: map codes and compute auxiliary table sizes */
207  for (i = 0; i < nb_codes; i++) {
208  n = codes[i].bits;
209  code = codes[i].code;
210  symbol = codes[i].symbol;
211  ff_dlog(NULL, "i=%d n=%d code=0x%"PRIx32"\n", i, n, code);
212  if (n <= table_nb_bits) {
213  /* no need to add another table */
214  j = code >> (32 - table_nb_bits);
215  nb = 1 << (table_nb_bits - n);
216  inc = 1;
217  if (flags & INIT_VLC_OUTPUT_LE) {
218  j = bitswap_32(code);
219  inc = 1 << n;
220  }
221  for (k = 0; k < nb; k++) {
222  int bits = table[j][1];
223  int oldsym = table[j][0];
224  ff_dlog(NULL, "%4x: code=%d n=%d\n", j, i, n);
225  if ((bits || oldsym) && (bits != n || oldsym != symbol)) {
226  av_log(NULL, AV_LOG_ERROR, "incorrect codes\n");
227  return AVERROR_INVALIDDATA;
228  }
229  table[j][1] = n; //bits
230  table[j][0] = symbol;
231  j += inc;
232  }
233  } else {
234  /* fill auxiliary table recursively */
235  n -= table_nb_bits;
236  code_prefix = code >> (32 - table_nb_bits);
237  subtable_bits = n;
238  codes[i].bits = n;
239  codes[i].code = code << table_nb_bits;
240  for (k = i+1; k < nb_codes; k++) {
241  n = codes[k].bits - table_nb_bits;
242  if (n <= 0)
243  break;
244  code = codes[k].code;
245  if (code >> (32 - table_nb_bits) != code_prefix)
246  break;
247  codes[k].bits = n;
248  codes[k].code = code << table_nb_bits;
249  subtable_bits = FFMAX(subtable_bits, n);
250  }
251  subtable_bits = FFMIN(subtable_bits, table_nb_bits);
252  j = (flags & INIT_VLC_OUTPUT_LE) ? bitswap_32(code_prefix) >> (32 - table_nb_bits) : code_prefix;
253  table[j][1] = -subtable_bits;
254  ff_dlog(NULL, "%4x: n=%d (subtable)\n",
255  j, codes[i].bits + table_nb_bits);
256  index = build_table(vlc, subtable_bits, k-i, codes+i, flags);
257  if (index < 0)
258  return index;
259  /* note: realloc has been done, so reload tables */
260  table = (volatile VLC_TYPE (*)[2])&vlc->table[table_index];
261  table[j][0] = index; //code
262  if (table[j][0] != index) {
263  avpriv_request_sample(NULL, "strange codes");
264  return AVERROR_PATCHWELCOME;
265  }
266  i = k-1;
267  }
268  }
269 
270  for (i = 0; i < table_size; i++) {
271  if (table[i][1] == 0) //bits
272  table[i][0] = -1; //codes
273  }
274 
275  return table_index;
276 }
277 
278 static int vlc_common_end(VLC *vlc, int nb_bits, int nb_codes, VLCcode *codes,
279  int flags, VLC *vlc_arg, VLCcode localbuf[LOCALBUF_ELEMS])
280 {
281  int ret = build_table(vlc, nb_bits, nb_codes, codes, flags);
282 
284  if (vlc->table_size != vlc->table_allocated &&
286  av_log(NULL, AV_LOG_ERROR, "needed %d had %d\n", vlc->table_size, vlc->table_allocated);
287  av_assert0(ret >= 0);
288  *vlc_arg = *vlc;
289  } else {
290  if (codes != localbuf)
291  av_free(codes);
292  if (ret < 0) {
293  av_freep(&vlc->table);
294  return ret;
295  }
296  }
297  return 0;
298 }
299 
300 /* Build VLC decoding tables suitable for use with get_vlc().
301 
302  'nb_bits' sets the decoding table size (2^nb_bits) entries. The
303  bigger it is, the faster is the decoding. But it should not be too
304  big to save memory and L1 cache. '9' is a good compromise.
305 
306  'nb_codes' : number of vlcs codes
307 
308  'bits' : table which gives the size (in bits) of each vlc code.
309 
310  'codes' : table which gives the bit pattern of of each vlc code.
311 
312  'symbols' : table which gives the values to be returned from get_vlc().
313 
314  'xxx_wrap' : give the number of bytes between each entry of the
315  'bits' or 'codes' tables.
316 
317  'xxx_size' : gives the number of bytes of each entry of the 'bits'
318  or 'codes' tables. Currently 1,2 and 4 are supported.
319 
320  'wrap' and 'size' make it possible to use any memory configuration and types
321  (byte/word/long) to store the 'bits', 'codes', and 'symbols' tables.
322 */
323 int ff_init_vlc_sparse(VLC *vlc_arg, int nb_bits, int nb_codes,
324  const void *bits, int bits_wrap, int bits_size,
325  const void *codes, int codes_wrap, int codes_size,
326  const void *symbols, int symbols_wrap, int symbols_size,
327  int flags)
328 {
329  VLCcode localbuf[LOCALBUF_ELEMS], *buf = localbuf;
330  int i, j, ret;
331  VLC localvlc, *vlc;
332 
333  ret = vlc_common_init(vlc_arg, nb_bits, nb_codes, &vlc, &localvlc,
334  &buf, flags);
335  if (ret < 0)
336  return ret;
337 
338  av_assert0(symbols_size <= 2 || !symbols);
339  j = 0;
340 #define COPY(condition)\
341  for (i = 0; i < nb_codes; i++) { \
342  unsigned len; \
343  GET_DATA(len, bits, i, bits_wrap, bits_size); \
344  if (!(condition)) \
345  continue; \
346  if (len > 3*nb_bits || len > 32) { \
347  av_log(NULL, AV_LOG_ERROR, "Too long VLC (%u) in init_vlc\n", len);\
348  if (buf != localbuf) \
349  av_free(buf); \
350  return AVERROR(EINVAL); \
351  } \
352  buf[j].bits = len; \
353  GET_DATA(buf[j].code, codes, i, codes_wrap, codes_size); \
354  if (buf[j].code >= (1LL<<buf[j].bits)) { \
355  av_log(NULL, AV_LOG_ERROR, "Invalid code %"PRIx32" for %d in " \
356  "init_vlc\n", buf[j].code, i); \
357  if (buf != localbuf) \
358  av_free(buf); \
359  return AVERROR(EINVAL); \
360  } \
361  if (flags & INIT_VLC_INPUT_LE) \
362  buf[j].code = bitswap_32(buf[j].code); \
363  else \
364  buf[j].code <<= 32 - buf[j].bits; \
365  if (symbols) \
366  GET_DATA(buf[j].symbol, symbols, i, symbols_wrap, symbols_size) \
367  else \
368  buf[j].symbol = i; \
369  j++; \
370  }
371  COPY(len > nb_bits);
372  // qsort is the slowest part of init_vlc, and could probably be improved or avoided
373  AV_QSORT(buf, j, struct VLCcode, compare_vlcspec);
374  COPY(len && len <= nb_bits);
375  nb_codes = j;
376 
377  return vlc_common_end(vlc, nb_bits, nb_codes, buf,
378  flags, vlc_arg, localbuf);
379 }
380 
381 int ff_init_vlc_from_lengths(VLC *vlc_arg, int nb_bits, int nb_codes,
382  const int8_t *lens, int lens_wrap,
383  const void *symbols, int symbols_wrap, int symbols_size,
384  int offset, int flags, void *logctx)
385 {
386  VLCcode localbuf[LOCALBUF_ELEMS], *buf = localbuf;
387  VLC localvlc, *vlc;
388  uint64_t code;
389  int ret, j, len_max = FFMIN(32, 3 * nb_bits);
390 
391  ret = vlc_common_init(vlc_arg, nb_bits, nb_codes, &vlc, &localvlc,
392  &buf, flags);
393  if (ret < 0)
394  return ret;
395 
396  j = code = 0;
397  for (int i = 0; i < nb_codes; i++, lens += lens_wrap) {
398  int len = *lens;
399  if (len > 0) {
400  unsigned sym;
401 
402  buf[j].bits = len;
403  if (symbols)
404  GET_DATA(sym, symbols, i, symbols_wrap, symbols_size)
405  else
406  sym = i;
407  buf[j].symbol = sym + offset;
408  buf[j++].code = code;
409  } else if (len < 0) {
410  len = -len;
411  } else
412  continue;
413  if (len > len_max || code & ((1U << (32 - len)) - 1)) {
414  av_log(logctx, AV_LOG_ERROR, "Invalid VLC (length %u)\n", len);
415  goto fail;
416  }
417  code += 1U << (32 - len);
418  if (code > UINT32_MAX + 1ULL) {
419  av_log(logctx, AV_LOG_ERROR, "Overdetermined VLC tree\n");
420  goto fail;
421  }
422  }
423  return vlc_common_end(vlc, nb_bits, j, buf,
424  flags, vlc_arg, localbuf);
425 fail:
426  if (buf != localbuf)
427  av_free(buf);
428  return AVERROR_INVALIDDATA;
429 }
430 
431 void ff_free_vlc(VLC *vlc)
432 {
433  av_freep(&vlc->table);
434 }
uint8_t
simple assert() macros that are a bit more flexible than ISO C assert().
#define av_assert0(cond)
assert() equivalent, that is always enabled.
Definition: avassert.h:37
Libavcodec external API header.
#define AV_RB16
Definition: intreadwrite.h:53
int ff_init_vlc_sparse(VLC *vlc_arg, int nb_bits, int nb_codes, const void *bits, int bits_wrap, int bits_size, const void *codes, int codes_wrap, int codes_size, const void *symbols, int symbols_wrap, int symbols_size, int flags)
Definition: bitstream.c:323
#define GET_DATA(v, table, i, wrap, size)
Definition: bitstream.c:96
static int vlc_common_end(VLC *vlc, int nb_bits, int nb_codes, VLCcode *codes, int flags, VLC *vlc_arg, VLCcode localbuf[LOCALBUF_ELEMS])
Definition: bitstream.c:278
#define LOCALBUF_ELEMS
Definition: bitstream.c:135
void ff_free_vlc(VLC *vlc)
Definition: bitstream.c:431
int ff_init_vlc_from_lengths(VLC *vlc_arg, int nb_bits, int nb_codes, const int8_t *lens, int lens_wrap, const void *symbols, int symbols_wrap, int symbols_size, int offset, int flags, void *logctx)
Build VLC decoding tables suitable for use with get_vlc2()
Definition: bitstream.c:381
static int alloc_table(VLC *vlc, int size, int use_static)
Definition: bitstream.c:115
void ff_copy_bits(PutBitContext *pb, const uint8_t *src, int length)
Copy the content of src to the bitstream.
Definition: bitstream.c:69
void avpriv_align_put_bits(PutBitContext *s)
Definition: bitstream.c:49
#define COPY(condition)
static int compare_vlcspec(const void *a, const void *b)
Definition: bitstream.c:170
void avpriv_copy_bits(PutBitContext *pb, const uint8_t *src, int length)
Definition: bitstream.c:53
static int build_table(VLC *vlc, int table_nb_bits, int nb_codes, VLCcode *codes, int flags)
Build VLC decoding tables suitable for use with get_vlc().
Definition: bitstream.c:189
static int vlc_common_init(VLC *vlc_arg, int nb_bits, int nb_codes, VLC **vlc, VLC *localvlc, VLCcode **buf, int flags)
Definition: bitstream.c:145
void ff_put_string(PutBitContext *pb, const char *string, int terminate_string)
Put the string string in the bitstream.
Definition: bitstream.c:59
const uint8_t ff_log2_run[41]
Definition: bitstream.c:39
#define flags(name, subs,...)
Definition: cbs_av1.c:572
#define s(width, name)
Definition: cbs_vp9.c:257
#define fail()
Definition: checkasm.h:133
#define FFMIN(a, b)
Definition: common.h:105
#define FFMAX(a, b)
Definition: common.h:103
#define CONFIG_SMALL
Definition: config.h:566
#define NULL
Definition: coverity.c:32
#define AVERROR_PATCHWELCOME
Not yet implemented in FFmpeg, patches welcome.
Definition: error.h:62
#define AVERROR_INVALIDDATA
Invalid data found when processing input.
Definition: error.h:59
#define AVERROR(e)
Definition: error.h:43
#define AV_LOG_ERROR
Something went wrong and cannot losslessly be recovered.
Definition: log.h:194
int index
Definition: gxfenc.c:89
for(j=16;j >0;--j)
int i
Definition: input.c:407
static void put_bits(Jpeg2000EncoderContext *s, int val, int n)
put n times val bit
Definition: j2kenc.c:218
common internal API header
static av_always_inline uint32_t bitswap_32(uint32_t x)
Definition: mathops.h:243
static const uint16_t table[]
Definition: prosumer.c:206
bitstream writer API
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:342
static int put_bits_count(PutBitContext *s)
Definition: put_bits.h:76
static int put_bits_left(PutBitContext *s)
Definition: put_bits.h:102
static void flush_put_bits(PutBitContext *s)
Pad the end of the output stream with zeros.
Definition: put_bits.h:110
static void skip_put_bytes(PutBitContext *s, int n)
Skip the given number of bytes.
Definition: put_bits.h:351
static void align_put_bits(PutBitContext *s)
Pad the bitstream with zeros up to the next byte boundary.
Definition: put_bits.h:386
static const unsigned code_prefix[]
Definition: qdmc.c:76
#define AV_QSORT(p, num, type, cmp)
Quicksort This sort is fast, and fully inplace but not stable and it is possible to construct input t...
Definition: qsort.h:33
const uint8_t * code
Definition: spdifenc.c:413
Definition: vlc.h:26
int table_size
Definition: vlc.h:29
int table_allocated
Definition: vlc.h:29
int bits
Definition: vlc.h:27
VLC_TYPE(* table)[2]
code, bits
Definition: vlc.h:28
uint8_t bits
Definition: bitstream.c:138
VLC_TYPE symbol
Definition: bitstream.c:139
uint32_t code
codeword, with the first bit-to-be-read in the msb (even if intended for a little-endian bitstream re...
Definition: bitstream.c:142
#define av_free(p)
#define av_malloc_array(a, b)
#define ff_dlog(a,...)
#define av_realloc_f(p, o, n)
#define avpriv_request_sample(...)
#define av_freep(p)
#define av_log(a,...)
#define src
Definition: vp8dsp.c:255
int size
const char * b
Definition: vf_curves.c:118
if(ret< 0)
Definition: vf_mcdeint.c:282
static const uint8_t offset[127][2]
Definition: vf_spp.c:107
#define INIT_VLC_USE_NEW_STATIC
Definition: vlc.h:95
#define INIT_VLC_STATIC_OVERLONG
Definition: vlc.h:96
#define VLC_TYPE
Definition: vlc.h:24
#define INIT_VLC_OUTPUT_LE
Definition: vlc.h:93
int len
uint8_t bits
Definition: vp3data.h:141