| 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 | #include <assert.h> |
| 32 | |
| 33 | #include "libavutil/intreadwrite.h" |
| 34 | #include "libavutil/avassert.h" |
| 35 | |
| 36 | typedef struct PutBitContext { |
| 37 | uint32_t bit_buf; |
| 38 | int bit_left; |
| 39 | uint8_t *buf, *buf_ptr, *buf_end; |
| 40 | int size_in_bits; |
| 41 | } PutBitContext; |
| 42 | |
| 43 | /** |
| 44 | * Initialize the PutBitContext s. |
| 45 | * |
| 46 | * @param buffer the buffer where to put bits |
| 47 | * @param buffer_size the size in bytes of buffer |
| 48 | */ |
| 49 | static inline void init_put_bits(PutBitContext *s, uint8_t *buffer, |
| 50 | int buffer_size) |
| 51 | { |
| 52 | if (buffer_size < 0) { |
| 53 | buffer_size = 0; |
| 54 | buffer = NULL; |
| 55 | } |
| 56 | |
| 57 | s->size_in_bits = 8 * buffer_size; |
| 58 | s->buf = buffer; |
| 59 | s->buf_end = s->buf + buffer_size; |
| 60 | s->buf_ptr = s->buf; |
| 61 | s->bit_left = 32; |
| 62 | s->bit_buf = 0; |
| 63 | } |
| 64 | |
| 65 | /** |
| 66 | * @return the total number of bits written to the bitstream. |
| 67 | */ |
| 68 | static inline int put_bits_count(PutBitContext *s) |
| 69 | { |
| 70 | return (s->buf_ptr - s->buf) * 8 + 32 - s->bit_left; |
| 71 | } |
| 72 | |
| 73 | /** |
| 74 | * @return the number of bits available in the bitstream. |
| 75 | */ |
| 76 | static inline int put_bits_left(PutBitContext* s) |
| 77 | { |
| 78 | return (s->buf_end - s->buf_ptr) * 8 - 32 + s->bit_left; |
| 79 | } |
| 80 | |
| 81 | /** |
| 82 | * Pad the end of the output stream with zeros. |
| 83 | */ |
| 84 | static inline void flush_put_bits(PutBitContext *s) |
| 85 | { |
| 86 | #ifndef BITSTREAM_WRITER_LE |
| 87 | if (s->bit_left < 32) |
| 88 | s->bit_buf <<= s->bit_left; |
| 89 | #endif |
| 90 | while (s->bit_left < 32) { |
| 91 | /* XXX: should test end of buffer */ |
| 92 | #ifdef BITSTREAM_WRITER_LE |
| 93 | *s->buf_ptr++ = s->bit_buf; |
| 94 | s->bit_buf >>= 8; |
| 95 | #else |
| 96 | *s->buf_ptr++ = s->bit_buf >> 24; |
| 97 | s->bit_buf <<= 8; |
| 98 | #endif |
| 99 | s->bit_left += 8; |
| 100 | } |
| 101 | s->bit_left = 32; |
| 102 | s->bit_buf = 0; |
| 103 | } |
| 104 | |
| 105 | #ifdef BITSTREAM_WRITER_LE |
| 106 | #define avpriv_align_put_bits align_put_bits_unsupported_here |
| 107 | #define avpriv_put_string ff_put_string_unsupported_here |
| 108 | #define avpriv_copy_bits avpriv_copy_bits_unsupported_here |
| 109 | #else |
| 110 | /** |
| 111 | * Pad the bitstream with zeros up to the next byte boundary. |
| 112 | */ |
| 113 | void avpriv_align_put_bits(PutBitContext *s); |
| 114 | |
| 115 | /** |
| 116 | * Put the string string in the bitstream. |
| 117 | * |
| 118 | * @param terminate_string 0-terminates the written string if value is 1 |
| 119 | */ |
| 120 | void avpriv_put_string(PutBitContext *pb, const char *string, |
| 121 | int terminate_string); |
| 122 | |
| 123 | /** |
| 124 | * Copy the content of src to the bitstream. |
| 125 | * |
| 126 | * @param length the number of bits of src to copy |
| 127 | */ |
| 128 | void avpriv_copy_bits(PutBitContext *pb, const uint8_t *src, int length); |
| 129 | #endif |
| 130 | |
| 131 | /** |
| 132 | * Write up to 31 bits into a bitstream. |
| 133 | * Use put_bits32 to write 32 bits. |
| 134 | */ |
| 135 | static inline void put_bits(PutBitContext *s, int n, unsigned int value) |
| 136 | { |
| 137 | unsigned int bit_buf; |
| 138 | int bit_left; |
| 139 | |
| 140 | av_assert2(n <= 31 && value < (1U << n)); |
| 141 | |
| 142 | bit_buf = s->bit_buf; |
| 143 | bit_left = s->bit_left; |
| 144 | |
| 145 | /* XXX: optimize */ |
| 146 | #ifdef BITSTREAM_WRITER_LE |
| 147 | bit_buf |= value << (32 - bit_left); |
| 148 | if (n >= bit_left) { |
| 149 | av_assert2(s->buf_ptr+3<s->buf_end); |
| 150 | AV_WL32(s->buf_ptr, bit_buf); |
| 151 | s->buf_ptr += 4; |
| 152 | bit_buf = (bit_left == 32) ? 0 : value >> bit_left; |
| 153 | bit_left += 32; |
| 154 | } |
| 155 | bit_left -= n; |
| 156 | #else |
| 157 | if (n < bit_left) { |
| 158 | bit_buf = (bit_buf << n) | value; |
| 159 | bit_left -= n; |
| 160 | } else { |
| 161 | bit_buf <<= bit_left; |
| 162 | bit_buf |= value >> (n - bit_left); |
| 163 | av_assert2(s->buf_ptr+3<s->buf_end); |
| 164 | AV_WB32(s->buf_ptr, bit_buf); |
| 165 | s->buf_ptr += 4; |
| 166 | bit_left += 32 - n; |
| 167 | bit_buf = value; |
| 168 | } |
| 169 | #endif |
| 170 | |
| 171 | s->bit_buf = bit_buf; |
| 172 | s->bit_left = bit_left; |
| 173 | } |
| 174 | |
| 175 | static inline void put_sbits(PutBitContext *pb, int n, int32_t value) |
| 176 | { |
| 177 | av_assert2(n >= 0 && n <= 31); |
| 178 | |
| 179 | put_bits(pb, n, value & ((1 << n) - 1)); |
| 180 | } |
| 181 | |
| 182 | /** |
| 183 | * Write exactly 32 bits into a bitstream. |
| 184 | */ |
| 185 | static void av_unused put_bits32(PutBitContext *s, uint32_t value) |
| 186 | { |
| 187 | int lo = value & 0xffff; |
| 188 | int hi = value >> 16; |
| 189 | #ifdef BITSTREAM_WRITER_LE |
| 190 | put_bits(s, 16, lo); |
| 191 | put_bits(s, 16, hi); |
| 192 | #else |
| 193 | put_bits(s, 16, hi); |
| 194 | put_bits(s, 16, lo); |
| 195 | #endif |
| 196 | } |
| 197 | |
| 198 | /** |
| 199 | * Return the pointer to the byte where the bitstream writer will put |
| 200 | * the next bit. |
| 201 | */ |
| 202 | static inline uint8_t *put_bits_ptr(PutBitContext *s) |
| 203 | { |
| 204 | return s->buf_ptr; |
| 205 | } |
| 206 | |
| 207 | /** |
| 208 | * Skip the given number of bytes. |
| 209 | * PutBitContext must be flushed & aligned to a byte boundary before calling this. |
| 210 | */ |
| 211 | static inline void skip_put_bytes(PutBitContext *s, int n) |
| 212 | { |
| 213 | av_assert2((put_bits_count(s) & 7) == 0); |
| 214 | av_assert2(s->bit_left == 32); |
| 215 | s->buf_ptr += n; |
| 216 | } |
| 217 | |
| 218 | /** |
| 219 | * Skip the given number of bits. |
| 220 | * Must only be used if the actual values in the bitstream do not matter. |
| 221 | * If n is 0 the behavior is undefined. |
| 222 | */ |
| 223 | static inline void skip_put_bits(PutBitContext *s, int n) |
| 224 | { |
| 225 | s->bit_left -= n; |
| 226 | s->buf_ptr -= 4 * (s->bit_left >> 5); |
| 227 | s->bit_left &= 31; |
| 228 | } |
| 229 | |
| 230 | /** |
| 231 | * Change the end of the buffer. |
| 232 | * |
| 233 | * @param size the new size in bytes of the buffer where to put bits |
| 234 | */ |
| 235 | static inline void set_put_bits_buffer_size(PutBitContext *s, int size) |
| 236 | { |
| 237 | s->buf_end = s->buf + size; |
| 238 | } |
| 239 | |
| 240 | #endif /* AVCODEC_PUT_BITS_H */ |