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"
37 // TODO: Benchmark and optionally enable on other 64-bit architectures.
38 typedef uint64_t BitBuf;
39 #define AV_WBBUF AV_WB64
40 #define AV_WLBUF AV_WL64
42 typedef uint32_t BitBuf;
43 #define AV_WBBUF AV_WB32
44 #define AV_WLBUF AV_WL32
47 static const int BUF_BITS = 8 * sizeof(BitBuf);
49 typedef struct PutBitContext {
52 uint8_t *buf, *buf_ptr, *buf_end;
57 * Initialize the PutBitContext s.
59 * @param buffer the buffer where to put bits
60 * @param buffer_size the size in bytes of buffer
62 static inline void init_put_bits(PutBitContext *s, uint8_t *buffer,
65 if (buffer_size < 0) {
70 s->size_in_bits = 8 * buffer_size;
72 s->buf_end = s->buf + buffer_size;
74 s->bit_left = BUF_BITS;
79 * @return the total number of bits written to the bitstream.
81 static inline int put_bits_count(PutBitContext *s)
83 return (s->buf_ptr - s->buf) * 8 + BUF_BITS - s->bit_left;
87 * Rebase the bit writer onto a reallocated buffer.
89 * @param buffer the buffer where to put bits
90 * @param buffer_size the size in bytes of buffer,
91 * must be large enough to hold everything written so far
93 static inline void rebase_put_bits(PutBitContext *s, uint8_t *buffer,
96 av_assert0(8*buffer_size >= put_bits_count(s));
98 s->buf_end = buffer + buffer_size;
99 s->buf_ptr = buffer + (s->buf_ptr - s->buf);
101 s->size_in_bits = 8 * buffer_size;
105 * @return the number of bits available in the bitstream.
107 static inline int put_bits_left(PutBitContext* s)
109 return (s->buf_end - s->buf_ptr) * 8 - BUF_BITS + s->bit_left;
113 * Pad the end of the output stream with zeros.
115 static inline void flush_put_bits(PutBitContext *s)
117 #ifndef BITSTREAM_WRITER_LE
118 if (s->bit_left < BUF_BITS)
119 s->bit_buf <<= s->bit_left;
121 while (s->bit_left < BUF_BITS) {
122 av_assert0(s->buf_ptr < s->buf_end);
123 #ifdef BITSTREAM_WRITER_LE
124 *s->buf_ptr++ = s->bit_buf;
127 *s->buf_ptr++ = s->bit_buf >> (BUF_BITS - 8);
132 s->bit_left = BUF_BITS;
136 static inline void flush_put_bits_le(PutBitContext *s)
138 while (s->bit_left < BUF_BITS) {
139 av_assert0(s->buf_ptr < s->buf_end);
140 *s->buf_ptr++ = s->bit_buf;
144 s->bit_left = BUF_BITS;
148 #ifdef BITSTREAM_WRITER_LE
149 #define avpriv_align_put_bits align_put_bits_unsupported_here
150 #define avpriv_put_string ff_put_string_unsupported_here
151 #define avpriv_copy_bits avpriv_copy_bits_unsupported_here
154 * Pad the bitstream with zeros up to the next byte boundary.
156 void avpriv_align_put_bits(PutBitContext *s);
159 * Put the string string in the bitstream.
161 * @param terminate_string 0-terminates the written string if value is 1
163 void avpriv_put_string(PutBitContext *pb, const char *string,
164 int terminate_string);
167 * Copy the content of src to the bitstream.
169 * @param length the number of bits of src to copy
171 void avpriv_copy_bits(PutBitContext *pb, const uint8_t *src, int length);
174 static inline void put_bits_no_assert(PutBitContext *s, int n, BitBuf value)
179 bit_buf = s->bit_buf;
180 bit_left = s->bit_left;
183 #ifdef BITSTREAM_WRITER_LE
184 bit_buf |= value << (BUF_BITS - bit_left);
186 if (s->buf_end - s->buf_ptr >= sizeof(BitBuf)) {
187 AV_WLBUF(s->buf_ptr, bit_buf);
188 s->buf_ptr += sizeof(BitBuf);
190 av_log(NULL, AV_LOG_ERROR, "Internal error, put_bits buffer too small\n");
193 bit_buf = value >> bit_left;
194 bit_left += BUF_BITS;
199 bit_buf = (bit_buf << n) | value;
202 bit_buf <<= bit_left;
203 bit_buf |= value >> (n - bit_left);
204 if (s->buf_end - s->buf_ptr >= sizeof(BitBuf)) {
205 AV_WBBUF(s->buf_ptr, bit_buf);
206 s->buf_ptr += sizeof(BitBuf);
208 av_log(NULL, AV_LOG_ERROR, "Internal error, put_bits buffer too small\n");
211 bit_left += BUF_BITS - n;
216 s->bit_buf = bit_buf;
217 s->bit_left = bit_left;
221 * Write up to 31 bits into a bitstream.
222 * Use put_bits32 to write 32 bits.
224 static inline void put_bits(PutBitContext *s, int n, BitBuf value)
226 av_assert2(n <= 31 && value < (1UL << n));
227 put_bits_no_assert(s, n, value);
230 static inline void put_bits_le(PutBitContext *s, int n, BitBuf value)
235 av_assert2(n <= 31 && value < (1UL << n));
237 bit_buf = s->bit_buf;
238 bit_left = s->bit_left;
240 bit_buf |= value << (BUF_BITS - bit_left);
242 if (s->buf_end - s->buf_ptr >= sizeof(BitBuf)) {
243 AV_WLBUF(s->buf_ptr, bit_buf);
244 s->buf_ptr += sizeof(BitBuf);
246 av_log(NULL, AV_LOG_ERROR, "Internal error, put_bits buffer too small\n");
249 bit_buf = value >> bit_left;
250 bit_left += BUF_BITS;
254 s->bit_buf = bit_buf;
255 s->bit_left = bit_left;
258 static inline void put_sbits(PutBitContext *pb, int n, int32_t value)
260 av_assert2(n >= 0 && n <= 31);
262 put_bits(pb, n, av_mod_uintp2(value, n));
266 * Write exactly 32 bits into a bitstream.
268 static void av_unused put_bits32(PutBitContext *s, uint32_t value)
274 put_bits_no_assert(s, 32, value);
278 bit_buf = s->bit_buf;
279 bit_left = s->bit_left;
281 #ifdef BITSTREAM_WRITER_LE
282 bit_buf |= (BitBuf)value << (BUF_BITS - bit_left);
283 if (s->buf_end - s->buf_ptr >= sizeof(BitBuf)) {
284 AV_WLBUF(s->buf_ptr, bit_buf);
285 s->buf_ptr += sizeof(BitBuf);
287 av_log(NULL, AV_LOG_ERROR, "Internal error, put_bits buffer too small\n");
290 bit_buf = (uint64_t)value >> bit_left;
292 bit_buf = (uint64_t)bit_buf << bit_left;
293 bit_buf |= (BitBuf)value >> (BUF_BITS - bit_left);
294 if (s->buf_end - s->buf_ptr >= sizeof(BitBuf)) {
295 AV_WBBUF(s->buf_ptr, bit_buf);
296 s->buf_ptr += sizeof(BitBuf);
298 av_log(NULL, AV_LOG_ERROR, "Internal error, put_bits buffer too small\n");
304 s->bit_buf = bit_buf;
305 s->bit_left = bit_left;
309 * Write up to 64 bits into a bitstream.
311 static inline void put_bits64(PutBitContext *s, int n, uint64_t value)
313 av_assert2((n == 64) || (n < 64 && value < (UINT64_C(1) << n)));
316 put_bits(s, n, value);
318 put_bits32(s, value);
320 uint32_t lo = value & 0xffffffff;
321 uint32_t hi = value >> 32;
322 #ifdef BITSTREAM_WRITER_LE
324 put_bits(s, n - 32, hi);
326 put_bits(s, n - 32, hi);
330 uint32_t lo = value & 0xffffffff;
331 uint32_t hi = value >> 32;
332 #ifdef BITSTREAM_WRITER_LE
344 * Return the pointer to the byte where the bitstream writer will put
347 static inline uint8_t *put_bits_ptr(PutBitContext *s)
353 * Skip the given number of bytes.
354 * PutBitContext must be flushed & aligned to a byte boundary before calling this.
356 static inline void skip_put_bytes(PutBitContext *s, int n)
358 av_assert2((put_bits_count(s) & 7) == 0);
359 av_assert2(s->bit_left == BUF_BITS);
360 av_assert0(n <= s->buf_end - s->buf_ptr);
365 * Skip the given number of bits.
366 * Must only be used if the actual values in the bitstream do not matter.
367 * If n is < 0 the behavior is undefined.
369 static inline void skip_put_bits(PutBitContext *s, int n)
371 unsigned bits = BUF_BITS - s->bit_left + n;
372 s->buf_ptr += sizeof(BitBuf) * (bits / BUF_BITS);
373 s->bit_left = BUF_BITS - (bits & (BUF_BITS - 1));
377 * Change the end of the buffer.
379 * @param size the new size in bytes of the buffer where to put bits
381 static inline void set_put_bits_buffer_size(PutBitContext *s, int size)
383 av_assert0(size <= INT_MAX/8 - BUF_BITS);
384 s->buf_end = s->buf + size;
385 s->size_in_bits = 8*size;
391 #endif /* AVCODEC_PUT_BITS_H */