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 libavcodec/put_bits.h
  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 <stdlib.h>
  31 #include <assert.h>
  32 #include "libavutil/bswap.h"
  33 #include "libavutil/common.h"
  34 #include "libavutil/intreadwrite.h"
  35 #include "libavutil/log.h"
  36 #include "mathops.h"
  37
  38 //#define ALT_BITSTREAM_WRITER
  39 //#define ALIGNED_BITSTREAM_WRITER
  40
  41 /* buf and buf_end must be present and used by every alternative writer. */
  42 typedef struct PutBitContext {
  43 #ifdef ALT_BITSTREAM_WRITER
  44     uint8_t *buf, *buf_end;
  45     int index;
  46 #else
  47     uint32_t bit_buf;
  48     int bit_left;
  49     uint8_t *buf, *buf_ptr, *buf_end;
  50 #endif
  51     int size_in_bits;
  52 } PutBitContext;
  53
  54 /**
  55  * Initializes the PutBitContext s.
  56  *
  57  * @param buffer the buffer where to put bits
  58  * @param buffer_size the size in bytes of buffer
  59  */
  60 static inline void init_put_bits(PutBitContext *s, uint8_t *buffer, int buffer_size)
  61 {
  62     if(buffer_size < 0) {
  63         buffer_size = 0;
  64         buffer = NULL;
  65     }
  66
  67     s->size_in_bits= 8*buffer_size;
  68     s->buf = buffer;
  69     s->buf_end = s->buf + buffer_size;
  70 #ifdef ALT_BITSTREAM_WRITER
  71     s->index=0;
  72     ((uint32_t*)(s->buf))[0]=0;
  73 //    memset(buffer, 0, buffer_size);
  74 #else
  75     s->buf_ptr = s->buf;
  76     s->bit_left=32;
  77     s->bit_buf=0;
  78 #endif
  79 }
  80
  81 /**
  82  * Returns the total number of bits written to the bitstream.
  83  */
  84 static inline int put_bits_count(PutBitContext *s)
  85 {
  86 #ifdef ALT_BITSTREAM_WRITER
  87     return s->index;
  88 #else
  89     return (s->buf_ptr - s->buf) * 8 + 32 - s->bit_left;
  90 #endif
  91 }
  92
  93 /**
  94  * Pads the end of the output stream with zeros.
  95  */
  96 static inline void flush_put_bits(PutBitContext *s)
  97 {
  98 #ifdef ALT_BITSTREAM_WRITER
  99     align_put_bits(s);
 100 #else
 101 #ifndef BITSTREAM_WRITER_LE
 102     s->bit_buf<<= s->bit_left;
 103 #endif
 104     while (s->bit_left < 32) {
 105         /* XXX: should test end of buffer */
 106 #ifdef BITSTREAM_WRITER_LE
 107         *s->buf_ptr++=s->bit_buf;
 108         s->bit_buf>>=8;
 109 #else
 110         *s->buf_ptr++=s->bit_buf >> 24;
 111         s->bit_buf<<=8;
 112 #endif
 113         s->bit_left+=8;
 114     }
 115     s->bit_left=32;
 116     s->bit_buf=0;
 117 #endif
 118 }
 119
 120 /**
 121  * Pads the bitstream with zeros up to the next byte boundary.
 122  */
 123 void align_put_bits(PutBitContext *s);
 124
 125 /**
 126  * Puts the string s in the bitstream.
 127  *
 128  * @param terminate_string 0-terminates the written string if value is 1
 129  */
 130 void ff_put_string(PutBitContext * pbc, const char *s, int terminate_string);
 131
 132 /**
 133  * Copies the content of src to the bitstream.
 134  *
 135  * @param length the number of bits of src to copy
 136  */
 137 void ff_copy_bits(PutBitContext *pb, const uint8_t *src, int length);
 138
 139 static inline void put_bits(PutBitContext *s, int n, unsigned int value)
 140 #ifndef ALT_BITSTREAM_WRITER
 141 {
 142     unsigned int bit_buf;
 143     int bit_left;
 144
 145     //    printf("put_bits=%d %x\n", n, value);
 146     assert(n == 32 || value < (1U << n));
 147
 148     bit_buf = s->bit_buf;
 149     bit_left = s->bit_left;
 150
 151     //    printf("n=%d value=%x cnt=%d buf=%x\n", n, value, bit_cnt, bit_buf);
 152     /* XXX: optimize */
 153 #ifdef BITSTREAM_WRITER_LE
 154     bit_buf |= value << (32 - bit_left);
 155     if (n >= bit_left) {
 156 #if !HAVE_FAST_UNALIGNED
 157         if (3 & (intptr_t) s->buf_ptr) {
 158             AV_WL32(s->buf_ptr, bit_buf);
 159         } else
 160 #endif
 161         *(uint32_t *)s->buf_ptr = le2me_32(bit_buf);
 162         s->buf_ptr+=4;
 163         bit_buf = (bit_left==32)?0:value >> bit_left;
 164         bit_left+=32;
 165     }
 166     bit_left-=n;
 167 #else
 168     if (n < bit_left) {
 169         bit_buf = (bit_buf<<n) | value;
 170         bit_left-=n;
 171     } else {
 172         bit_buf<<=bit_left;
 173         bit_buf |= value >> (n - bit_left);
 174 #if !HAVE_FAST_UNALIGNED
 175         if (3 & (intptr_t) s->buf_ptr) {
 176             AV_WB32(s->buf_ptr, bit_buf);
 177         } else
 178 #endif
 179         *(uint32_t *)s->buf_ptr = be2me_32(bit_buf);
 180         //printf("bitbuf = %08x\n", bit_buf);
 181         s->buf_ptr+=4;
 182         bit_left+=32 - n;
 183         bit_buf = value;
 184     }
 185 #endif
 186
 187     s->bit_buf = bit_buf;
 188     s->bit_left = bit_left;
 189 }
 190 #else  /* ALT_BITSTREAM_WRITER defined */
 191 {
 192 #    ifdef ALIGNED_BITSTREAM_WRITER
 193 #        if ARCH_X86
 194     __asm__ volatile(
 195         "movl %0, %%ecx                 \n\t"
 196         "xorl %%eax, %%eax              \n\t"
 197         "shrdl %%cl, %1, %%eax          \n\t"
 198         "shrl %%cl, %1                  \n\t"
 199         "movl %0, %%ecx                 \n\t"
 200         "shrl $3, %%ecx                 \n\t"
 201         "andl $0xFFFFFFFC, %%ecx        \n\t"
 202         "bswapl %1                      \n\t"
 203         "orl %1, (%2, %%ecx)            \n\t"
 204         "bswapl %%eax                   \n\t"
 205         "addl %3, %0                    \n\t"
 206         "movl %%eax, 4(%2, %%ecx)       \n\t"
 207         : "=&r" (s->index), "=&r" (value)
 208         : "r" (s->buf), "r" (n), "0" (s->index), "1" (value<<(-n))
 209         : "%eax", "%ecx"
 210     );
 211 #        else
 212     int index= s->index;
 213     uint32_t *ptr= ((uint32_t *)s->buf)+(index>>5);
 214
 215     value<<= 32-n;
 216
 217     ptr[0] |= be2me_32(value>>(index&31));
 218     ptr[1]  = be2me_32(value<<(32-(index&31)));
 219 //if(n>24) printf("%d %d\n", n, value);
 220     index+= n;
 221     s->index= index;
 222 #        endif
 223 #    else //ALIGNED_BITSTREAM_WRITER
 224 #        if ARCH_X86
 225     __asm__ volatile(
 226         "movl $7, %%ecx                 \n\t"
 227         "andl %0, %%ecx                 \n\t"
 228         "addl %3, %%ecx                 \n\t"
 229         "negl %%ecx                     \n\t"
 230         "shll %%cl, %1                  \n\t"
 231         "bswapl %1                      \n\t"
 232         "movl %0, %%ecx                 \n\t"
 233         "shrl $3, %%ecx                 \n\t"
 234         "orl %1, (%%ecx, %2)            \n\t"
 235         "addl %3, %0                    \n\t"
 236         "movl $0, 4(%%ecx, %2)          \n\t"
 237         : "=&r" (s->index), "=&r" (value)
 238         : "r" (s->buf), "r" (n), "0" (s->index), "1" (value)
 239         : "%ecx"
 240     );
 241 #        else
 242     int index= s->index;
 243     uint32_t *ptr= (uint32_t*)(((uint8_t *)s->buf)+(index>>3));
 244
 245     ptr[0] |= be2me_32(value<<(32-n-(index&7) ));
 246     ptr[1] = 0;
 247 //if(n>24) printf("%d %d\n", n, value);
 248     index+= n;
 249     s->index= index;
 250 #        endif
 251 #    endif //!ALIGNED_BITSTREAM_WRITER
 252 }
 253 #endif
 254
 255 static inline void put_sbits(PutBitContext *pb, int bits, int32_t val)
 256 {
 257     assert(bits >= 0 && bits <= 31);
 258
 259     put_bits(pb, bits, val & ((1<<bits)-1));
 260 }
 261
 262 /**
 263  * Returns the pointer to the byte where the bitstream writer will put
 264  * the next bit.
 265  */
 266 static inline uint8_t* put_bits_ptr(PutBitContext *s)
 267 {
 268 #ifdef ALT_BITSTREAM_WRITER
 269         return s->buf + (s->index>>3);
 270 #else
 271         return s->buf_ptr;
 272 #endif
 273 }
 274
 275 /**
 276  * Skips the given number of bytes.
 277  * PutBitContext must be flushed & aligned to a byte boundary before calling this.
 278  */
 279 static inline void skip_put_bytes(PutBitContext *s, int n){
 280         assert((put_bits_count(s)&7)==0);
 281 #ifdef ALT_BITSTREAM_WRITER
 282         FIXME may need some cleaning of the buffer
 283         s->index += n<<3;
 284 #else
 285         assert(s->bit_left==32);
 286         s->buf_ptr += n;
 287 #endif
 288 }
 289
 290 /**
 291  * Skips the given number of bits.
 292  * Must only be used if the actual values in the bitstream do not matter.
 293  * If n is 0 the behavior is undefined.
 294  */
 295 static inline void skip_put_bits(PutBitContext *s, int n){
 296 #ifdef ALT_BITSTREAM_WRITER
 297     s->index += n;
 298 #else
 299     s->bit_left -= n;
 300     s->buf_ptr-= 4*(s->bit_left>>5);
 301     s->bit_left &= 31;
 302 #endif
 303 }
 304
 305 /**
 306  * Changes the end of the buffer.
 307  *
 308  * @param size the new size in bytes of the buffer where to put bits
 309  */
 310 static inline void set_put_bits_buffer_size(PutBitContext *s, int size){
 311     s->buf_end= s->buf + size;
 312 }
 313
 314 #endif /* AVCODEC_PUT_BITS_H */