2 * copyright (c) 2004 Michael Niedermayer <michaelni@gmx.at>
4 * This file is part of FFmpeg.
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.
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.
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
23 * bitstream writer API
26 #ifndef AVCODEC_PUT_BITS_H
27 #define AVCODEC_PUT_BITS_H
33 #include "libavutil/intreadwrite.h"
34 #include "libavutil/avassert.h"
39 // TODO: Benchmark and optionally enable on other 64-bit architectures.
40 typedef uint64_t BitBuf;
41 #define AV_WBBUF AV_WB64
42 #define AV_WLBUF AV_WL64
44 typedef uint32_t BitBuf;
45 #define AV_WBBUF AV_WB32
46 #define AV_WLBUF AV_WL32
49 static const int BUF_BITS = 8 * sizeof(BitBuf);
51 typedef struct PutBitContext {
54 uint8_t *buf, *buf_ptr, *buf_end;
59 * Initialize the PutBitContext s.
61 * @param buffer the buffer where to put bits
62 * @param buffer_size the size in bytes of buffer
64 static inline void init_put_bits(PutBitContext *s, uint8_t *buffer,
67 if (buffer_size < 0) {
72 s->size_in_bits = 8 * buffer_size;
74 s->buf_end = s->buf + buffer_size;
76 s->bit_left = BUF_BITS;
81 * @return the total number of bits written to the bitstream.
83 static inline int put_bits_count(PutBitContext *s)
85 return (s->buf_ptr - s->buf) * 8 + BUF_BITS - s->bit_left;
89 * Rebase the bit writer onto a reallocated buffer.
91 * @param buffer the buffer where to put bits
92 * @param buffer_size the size in bytes of buffer,
93 * must be large enough to hold everything written so far
95 static inline void rebase_put_bits(PutBitContext *s, uint8_t *buffer,
98 av_assert0(8*buffer_size >= put_bits_count(s));
100 s->buf_end = buffer + buffer_size;
101 s->buf_ptr = buffer + (s->buf_ptr - s->buf);
103 s->size_in_bits = 8 * buffer_size;
107 * @return the number of bits available in the bitstream.
109 static inline int put_bits_left(PutBitContext* s)
111 return (s->buf_end - s->buf_ptr) * 8 - BUF_BITS + s->bit_left;
115 * Pad the end of the output stream with zeros.
117 static inline void flush_put_bits(PutBitContext *s)
119 #ifndef BITSTREAM_WRITER_LE
120 if (s->bit_left < BUF_BITS)
121 s->bit_buf <<= s->bit_left;
123 while (s->bit_left < BUF_BITS) {
124 av_assert0(s->buf_ptr < s->buf_end);
125 #ifdef BITSTREAM_WRITER_LE
126 *s->buf_ptr++ = s->bit_buf;
129 *s->buf_ptr++ = s->bit_buf >> (BUF_BITS - 8);
134 s->bit_left = BUF_BITS;
138 static inline void flush_put_bits_le(PutBitContext *s)
140 while (s->bit_left < BUF_BITS) {
141 av_assert0(s->buf_ptr < s->buf_end);
142 *s->buf_ptr++ = s->bit_buf;
146 s->bit_left = BUF_BITS;
150 #if FF_API_AVPRIV_PUT_BITS
151 void avpriv_align_put_bits(PutBitContext *s);
152 void avpriv_copy_bits(PutBitContext *pb, const uint8_t *src, int length);
155 #ifdef BITSTREAM_WRITER_LE
156 #define ff_put_string ff_put_string_unsupported_here
157 #define ff_copy_bits ff_copy_bits_unsupported_here
161 * Put the string string in the bitstream.
163 * @param terminate_string 0-terminates the written string if value is 1
165 void ff_put_string(PutBitContext *pb, const char *string,
166 int terminate_string);
169 * Copy the content of src to the bitstream.
171 * @param length the number of bits of src to copy
173 void ff_copy_bits(PutBitContext *pb, const uint8_t *src, int length);
176 static inline void put_bits_no_assert(PutBitContext *s, int n, BitBuf value)
181 bit_buf = s->bit_buf;
182 bit_left = s->bit_left;
185 #ifdef BITSTREAM_WRITER_LE
186 bit_buf |= value << (BUF_BITS - bit_left);
188 if (s->buf_end - s->buf_ptr >= sizeof(BitBuf)) {
189 AV_WLBUF(s->buf_ptr, bit_buf);
190 s->buf_ptr += sizeof(BitBuf);
192 av_log(NULL, AV_LOG_ERROR, "Internal error, put_bits buffer too small\n");
195 bit_buf = value >> bit_left;
196 bit_left += BUF_BITS;
201 bit_buf = (bit_buf << n) | value;
204 bit_buf <<= bit_left;
205 bit_buf |= value >> (n - bit_left);
206 if (s->buf_end - s->buf_ptr >= sizeof(BitBuf)) {
207 AV_WBBUF(s->buf_ptr, bit_buf);
208 s->buf_ptr += sizeof(BitBuf);
210 av_log(NULL, AV_LOG_ERROR, "Internal error, put_bits buffer too small\n");
213 bit_left += BUF_BITS - n;
218 s->bit_buf = bit_buf;
219 s->bit_left = bit_left;
223 * Write up to 31 bits into a bitstream.
224 * Use put_bits32 to write 32 bits.
226 static inline void put_bits(PutBitContext *s, int n, BitBuf value)
228 av_assert2(n <= 31 && value < (1UL << n));
229 put_bits_no_assert(s, n, value);
232 static inline void put_bits_le(PutBitContext *s, int n, BitBuf value)
237 av_assert2(n <= 31 && value < (1UL << n));
239 bit_buf = s->bit_buf;
240 bit_left = s->bit_left;
242 bit_buf |= value << (BUF_BITS - bit_left);
244 if (s->buf_end - s->buf_ptr >= sizeof(BitBuf)) {
245 AV_WLBUF(s->buf_ptr, bit_buf);
246 s->buf_ptr += sizeof(BitBuf);
248 av_log(NULL, AV_LOG_ERROR, "Internal error, put_bits buffer too small\n");
251 bit_buf = value >> bit_left;
252 bit_left += BUF_BITS;
256 s->bit_buf = bit_buf;
257 s->bit_left = bit_left;
260 static inline void put_sbits(PutBitContext *pb, int n, int32_t value)
262 av_assert2(n >= 0 && n <= 31);
264 put_bits(pb, n, av_mod_uintp2(value, n));
268 * Write exactly 32 bits into a bitstream.
270 static void av_unused put_bits32(PutBitContext *s, uint32_t value)
276 put_bits_no_assert(s, 32, value);
280 bit_buf = s->bit_buf;
281 bit_left = s->bit_left;
283 #ifdef BITSTREAM_WRITER_LE
284 bit_buf |= (BitBuf)value << (BUF_BITS - bit_left);
285 if (s->buf_end - s->buf_ptr >= sizeof(BitBuf)) {
286 AV_WLBUF(s->buf_ptr, bit_buf);
287 s->buf_ptr += sizeof(BitBuf);
289 av_log(NULL, AV_LOG_ERROR, "Internal error, put_bits buffer too small\n");
292 bit_buf = (uint64_t)value >> bit_left;
294 bit_buf = (uint64_t)bit_buf << bit_left;
295 bit_buf |= (BitBuf)value >> (BUF_BITS - bit_left);
296 if (s->buf_end - s->buf_ptr >= sizeof(BitBuf)) {
297 AV_WBBUF(s->buf_ptr, bit_buf);
298 s->buf_ptr += sizeof(BitBuf);
300 av_log(NULL, AV_LOG_ERROR, "Internal error, put_bits buffer too small\n");
306 s->bit_buf = bit_buf;
307 s->bit_left = bit_left;
311 * Write up to 64 bits into a bitstream.
313 static inline void put_bits64(PutBitContext *s, int n, uint64_t value)
315 av_assert2((n == 64) || (n < 64 && value < (UINT64_C(1) << n)));
318 put_bits(s, n, value);
320 put_bits32(s, value);
322 uint32_t lo = value & 0xffffffff;
323 uint32_t hi = value >> 32;
324 #ifdef BITSTREAM_WRITER_LE
326 put_bits(s, n - 32, hi);
328 put_bits(s, n - 32, hi);
332 uint32_t lo = value & 0xffffffff;
333 uint32_t hi = value >> 32;
334 #ifdef BITSTREAM_WRITER_LE
346 * Return the pointer to the byte where the bitstream writer will put
349 static inline uint8_t *put_bits_ptr(PutBitContext *s)
355 * Skip the given number of bytes.
356 * PutBitContext must be flushed & aligned to a byte boundary before calling this.
358 static inline void skip_put_bytes(PutBitContext *s, int n)
360 av_assert2((put_bits_count(s) & 7) == 0);
361 av_assert2(s->bit_left == BUF_BITS);
362 av_assert0(n <= s->buf_end - s->buf_ptr);
367 * Skip the given number of bits.
368 * Must only be used if the actual values in the bitstream do not matter.
369 * If n is < 0 the behavior is undefined.
371 static inline void skip_put_bits(PutBitContext *s, int n)
373 unsigned bits = BUF_BITS - s->bit_left + n;
374 s->buf_ptr += sizeof(BitBuf) * (bits / BUF_BITS);
375 s->bit_left = BUF_BITS - (bits & (BUF_BITS - 1));
379 * Change the end of the buffer.
381 * @param size the new size in bytes of the buffer where to put bits
383 static inline void set_put_bits_buffer_size(PutBitContext *s, int size)
385 av_assert0(size <= INT_MAX/8 - BUF_BITS);
386 s->buf_end = s->buf + size;
387 s->size_in_bits = 8*size;
391 * Pad the bitstream with zeros up to the next byte boundary.
393 static inline void align_put_bits(PutBitContext *s)
395 put_bits(s, s->bit_left & 7, 0);
401 #endif /* AVCODEC_PUT_BITS_H */