libavcodec/put_bits.h

   1 /*
   2  * copyright (c) 2004 Michael Niedermayer <michaelni@gmx.at>
   3  *
   4  * This file is part of Libav.
   5  *
   6  * Libav 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  * Libav 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 Libav; 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 <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 #include "config.h"
  38
  39 typedef struct PutBitContext {
  40     uint32_t bit_buf;
  41     int bit_left;
  42     uint8_t *buf, *buf_ptr, *buf_end;
  43     int size_in_bits;
  44 } PutBitContext;
  45
  46 /**
  47  * Initialize the PutBitContext s.
  48  *
  49  * @param buffer the buffer where to put bits
  50  * @param buffer_size the size in bytes of buffer
  51  */
  52 static inline void init_put_bits(PutBitContext *s, uint8_t *buffer, int buffer_size)
  53 {
  54     if(buffer_size < 0) {
  55         buffer_size = 0;
  56         buffer = NULL;
  57     }
  58
  59     s->size_in_bits= 8*buffer_size;
  60     s->buf = buffer;
  61     s->buf_end = s->buf + buffer_size;
  62     s->buf_ptr = s->buf;
  63     s->bit_left=32;
  64     s->bit_buf=0;
  65 }
  66
  67 /**
  68  * @return the total number of bits written to the bitstream.
  69  */
  70 static inline int put_bits_count(PutBitContext *s)
  71 {
  72     return (s->buf_ptr - s->buf) * 8 + 32 - s->bit_left;
  73 }
  74
  75 /**
  76  * Pad the end of the output stream with zeros.
  77  */
  78 static inline void flush_put_bits(PutBitContext *s)
  79 {
  80 #ifndef BITSTREAM_WRITER_LE
  81     s->bit_buf<<= s->bit_left;
  82 #endif
  83     while (s->bit_left < 32) {
  84         /* XXX: should test end of buffer */
  85 #ifdef BITSTREAM_WRITER_LE
  86         *s->buf_ptr++=s->bit_buf;
  87         s->bit_buf>>=8;
  88 #else
  89         *s->buf_ptr++=s->bit_buf >> 24;
  90         s->bit_buf<<=8;
  91 #endif
  92         s->bit_left+=8;
  93     }
  94     s->bit_left=32;
  95     s->bit_buf=0;
  96 }
  97
  98 #ifdef BITSTREAM_WRITER_LE
  99 #define align_put_bits align_put_bits_unsupported_here
 100 #define ff_put_string ff_put_string_unsupported_here
 101 #define ff_copy_bits ff_copy_bits_unsupported_here
 102 #else
 103 /**
 104  * Pad the bitstream with zeros up to the next byte boundary.
 105  */
 106 void align_put_bits(PutBitContext *s);
 107
 108 /**
 109  * Put the string string in the bitstream.
 110  *
 111  * @param terminate_string 0-terminates the written string if value is 1
 112  */
 113 void ff_put_string(PutBitContext *pb, const char *string, int terminate_string);
 114
 115 /**
 116  * Copy the content of src to the bitstream.
 117  *
 118  * @param length the number of bits of src to copy
 119  */
 120 void ff_copy_bits(PutBitContext *pb, const uint8_t *src, int length);
 121 #endif
 122
 123 /**
 124  * Write up to 31 bits into a bitstream.
 125  * Use put_bits32 to write 32 bits.
 126  */
 127 static inline void put_bits(PutBitContext *s, int n, unsigned int value)
 128 {
 129     unsigned int bit_buf;
 130     int bit_left;
 131
 132     //    printf("put_bits=%d %x\n", n, value);
 133     assert(n <= 31 && value < (1U << n));
 134
 135     bit_buf = s->bit_buf;
 136     bit_left = s->bit_left;
 137
 138     //    printf("n=%d value=%x cnt=%d buf=%x\n", n, value, bit_cnt, bit_buf);
 139     /* XXX: optimize */
 140 #ifdef BITSTREAM_WRITER_LE
 141     bit_buf |= value << (32 - bit_left);
 142     if (n >= bit_left) {
 143         AV_WL32(s->buf_ptr, bit_buf);
 144         s->buf_ptr+=4;
 145         bit_buf = (bit_left==32)?0:value >> bit_left;
 146         bit_left+=32;
 147     }
 148     bit_left-=n;
 149 #else
 150     if (n < bit_left) {
 151         bit_buf = (bit_buf<<n) | value;
 152         bit_left-=n;
 153     } else {
 154         bit_buf<<=bit_left;
 155         bit_buf |= value >> (n - bit_left);
 156         AV_WB32(s->buf_ptr, bit_buf);
 157         //printf("bitbuf = %08x\n", bit_buf);
 158         s->buf_ptr+=4;
 159         bit_left+=32 - n;
 160         bit_buf = value;
 161     }
 162 #endif
 163
 164     s->bit_buf = bit_buf;
 165     s->bit_left = bit_left;
 166 }
 167
 168 static inline void put_sbits(PutBitContext *pb, int n, int32_t value)
 169 {
 170     assert(n >= 0 && n <= 31);
 171
 172     put_bits(pb, n, value & ((1<<n)-1));
 173 }
 174
 175 /**
 176  * Write exactly 32 bits into a bitstream.
 177  */
 178 static void av_unused put_bits32(PutBitContext *s, uint32_t value)
 179 {
 180     int lo = value & 0xffff;
 181     int hi = value >> 16;
 182 #ifdef BITSTREAM_WRITER_LE
 183     put_bits(s, 16, lo);
 184     put_bits(s, 16, hi);
 185 #else
 186     put_bits(s, 16, hi);
 187     put_bits(s, 16, lo);
 188 #endif
 189 }
 190
 191 /**
 192  * Return the pointer to the byte where the bitstream writer will put
 193  * the next bit.
 194  */
 195 static inline uint8_t* put_bits_ptr(PutBitContext *s)
 196 {
 197         return s->buf_ptr;
 198 }
 199
 200 /**
 201  * Skip the given number of bytes.
 202  * PutBitContext must be flushed & aligned to a byte boundary before calling this.
 203  */
 204 static inline void skip_put_bytes(PutBitContext *s, int n)
 205 {
 206         assert((put_bits_count(s)&7)==0);
 207         assert(s->bit_left==32);
 208         s->buf_ptr += n;
 209 }
 210
 211 /**
 212  * Skip the given number of bits.
 213  * Must only be used if the actual values in the bitstream do not matter.
 214  * If n is 0 the behavior is undefined.
 215  */
 216 static inline void skip_put_bits(PutBitContext *s, int n)
 217 {
 218     s->bit_left -= n;
 219     s->buf_ptr-= 4*(s->bit_left>>5);
 220     s->bit_left &= 31;
 221 }
 222
 223 /**
 224  * Change the end of the buffer.
 225  *
 226  * @param size the new size in bytes of the buffer where to put bits
 227  */
 228 static inline void set_put_bits_buffer_size(PutBitContext *s, int size)
 229 {
 230     s->buf_end= s->buf + size;
 231 }
 232
 233 #endif /* AVCODEC_PUT_BITS_H */