media/ffvpx/libavcodec/put_bits.h

   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 {
  51     BitBuf bit_buf;
  52     int bit_left;
  53     uint8_t *buf, *buf_ptr, *buf_end;
  54 } PutBitContext;
  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));
 250     put_bits_no_assert(s, n, value);
 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 static inline void put_sbits63(PutBitContext *pb, int n, int64_t value)
 367 {
 368     av_assert2(n >= 0 && n < 64);
 369
 370     put_bits64(pb, n, (uint64_t)(value) & (~(UINT64_MAX << n)));
 371 }
 372
 373 /**
 374  * Return the pointer to the byte where the bitstream writer will put
 375  * the next bit.
 376  */
 377 static inline uint8_t *put_bits_ptr(PutBitContext *s)
 378 {
 379     return s->buf_ptr;
 380 }
 381
 382 /**
 383  * Skip the given number of bytes.
 384  * PutBitContext must be flushed & aligned to a byte boundary before calling this.
 385  */
 386 static inline void skip_put_bytes(PutBitContext *s, int n)
 387 {
 388     av_assert2((put_bits_count(s) & 7) == 0);
 389     av_assert2(s->bit_left == BUF_BITS);
 390     av_assert0(n <= s->buf_end - s->buf_ptr);
 391     s->buf_ptr += n;
 392 }
 393
 394 /**
 395  * Skip the given number of bits.
 396  * Must only be used if the actual values in the bitstream do not matter.
 397  * If n is < 0 the behavior is undefined.
 398  */
 399 static inline void skip_put_bits(PutBitContext *s, int n)
 400 {
 401     unsigned bits = BUF_BITS - s->bit_left + n;
 402     s->buf_ptr += sizeof(BitBuf) * (bits / BUF_BITS);
 403     s->bit_left = BUF_BITS - (bits & (BUF_BITS - 1));
 404 }
 405
 406 /**
 407  * Change the end of the buffer.
 408  *
 409  * @param size the new size in bytes of the buffer where to put bits
 410  */
 411 static inline void set_put_bits_buffer_size(PutBitContext *s, int size)
 412 {
 413     av_assert0(size <= INT_MAX/8 - BUF_BITS);
 414     s->buf_end = s->buf + size;
 415 }
 416
 417 /**
 418  * Pad the bitstream with zeros up to the next byte boundary.
 419  */
 420 static inline void align_put_bits(PutBitContext *s)
 421 {
 422     put_bits(s, s->bit_left & 7, 0);
 423 }
 424
 425 #undef AV_WBBUF
 426 #undef AV_WLBUF
 427
 428 #endif /* AVCODEC_PUT_BITS_H */