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);
154 #ifdef BITSTREAM_WRITER_LE
155 #define avpriv_put_string ff_put_string_unsupported_here
156 #define avpriv_copy_bits avpriv_copy_bits_unsupported_here
160 * Put the string string in the bitstream.
162 * @param terminate_string 0-terminates the written string if value is 1
164 void avpriv_put_string(PutBitContext *pb, const char *string,
165 int terminate_string);
168 * Copy the content of src to the bitstream.
170 * @param length the number of bits of src to copy
172 void avpriv_copy_bits(PutBitContext *pb, const uint8_t *src, int length);
175 static inline void put_bits_no_assert(PutBitContext *s, int n, BitBuf value)
180 bit_buf = s->bit_buf;
181 bit_left = s->bit_left;
184 #ifdef BITSTREAM_WRITER_LE
185 bit_buf |= value << (BUF_BITS - bit_left);
187 if (s->buf_end - s->buf_ptr >= sizeof(BitBuf)) {
188 AV_WLBUF(s->buf_ptr, bit_buf);
189 s->buf_ptr += sizeof(BitBuf);
191 av_log(NULL, AV_LOG_ERROR, "Internal error, put_bits buffer too small\n");
194 bit_buf = value >> bit_left;
195 bit_left += BUF_BITS;
200 bit_buf = (bit_buf << n) | value;
203 bit_buf <<= bit_left;
204 bit_buf |= value >> (n - bit_left);
205 if (s->buf_end - s->buf_ptr >= sizeof(BitBuf)) {
206 AV_WBBUF(s->buf_ptr, bit_buf);
207 s->buf_ptr += sizeof(BitBuf);
209 av_log(NULL, AV_LOG_ERROR, "Internal error, put_bits buffer too small\n");
212 bit_left += BUF_BITS - n;
217 s->bit_buf = bit_buf;
218 s->bit_left = bit_left;
222 * Write up to 31 bits into a bitstream.
223 * Use put_bits32 to write 32 bits.
225 static inline void put_bits(PutBitContext *s, int n, BitBuf value)
227 av_assert2(n <= 31 && value < (1UL << n));
228 put_bits_no_assert(s, n, value);
231 static inline void put_bits_le(PutBitContext *s, int n, BitBuf value)
236 av_assert2(n <= 31 && value < (1UL << n));
238 bit_buf = s->bit_buf;
239 bit_left = s->bit_left;
241 bit_buf |= value << (BUF_BITS - bit_left);
243 if (s->buf_end - s->buf_ptr >= sizeof(BitBuf)) {
244 AV_WLBUF(s->buf_ptr, bit_buf);
245 s->buf_ptr += sizeof(BitBuf);
247 av_log(NULL, AV_LOG_ERROR, "Internal error, put_bits buffer too small\n");
250 bit_buf = value >> bit_left;
251 bit_left += BUF_BITS;
255 s->bit_buf = bit_buf;
256 s->bit_left = bit_left;
259 static inline void put_sbits(PutBitContext *pb, int n, int32_t value)
261 av_assert2(n >= 0 && n <= 31);
263 put_bits(pb, n, av_mod_uintp2(value, n));
267 * Write exactly 32 bits into a bitstream.
269 static void av_unused put_bits32(PutBitContext *s, uint32_t value)
275 put_bits_no_assert(s, 32, value);
279 bit_buf = s->bit_buf;
280 bit_left = s->bit_left;
282 #ifdef BITSTREAM_WRITER_LE
283 bit_buf |= (BitBuf)value << (BUF_BITS - bit_left);
284 if (s->buf_end - s->buf_ptr >= sizeof(BitBuf)) {
285 AV_WLBUF(s->buf_ptr, bit_buf);
286 s->buf_ptr += sizeof(BitBuf);
288 av_log(NULL, AV_LOG_ERROR, "Internal error, put_bits buffer too small\n");
291 bit_buf = (uint64_t)value >> bit_left;
293 bit_buf = (uint64_t)bit_buf << bit_left;
294 bit_buf |= (BitBuf)value >> (BUF_BITS - bit_left);
295 if (s->buf_end - s->buf_ptr >= sizeof(BitBuf)) {
296 AV_WBBUF(s->buf_ptr, bit_buf);
297 s->buf_ptr += sizeof(BitBuf);
299 av_log(NULL, AV_LOG_ERROR, "Internal error, put_bits buffer too small\n");
305 s->bit_buf = bit_buf;
306 s->bit_left = bit_left;
310 * Write up to 64 bits into a bitstream.
312 static inline void put_bits64(PutBitContext *s, int n, uint64_t value)
314 av_assert2((n == 64) || (n < 64 && value < (UINT64_C(1) << n)));
317 put_bits(s, n, value);
319 put_bits32(s, value);
321 uint32_t lo = value & 0xffffffff;
322 uint32_t hi = value >> 32;
323 #ifdef BITSTREAM_WRITER_LE
325 put_bits(s, n - 32, hi);
327 put_bits(s, n - 32, hi);
331 uint32_t lo = value & 0xffffffff;
332 uint32_t hi = value >> 32;
333 #ifdef BITSTREAM_WRITER_LE
345 * Return the pointer to the byte where the bitstream writer will put
348 static inline uint8_t *put_bits_ptr(PutBitContext *s)
354 * Skip the given number of bytes.
355 * PutBitContext must be flushed & aligned to a byte boundary before calling this.
357 static inline void skip_put_bytes(PutBitContext *s, int n)
359 av_assert2((put_bits_count(s) & 7) == 0);
360 av_assert2(s->bit_left == BUF_BITS);
361 av_assert0(n <= s->buf_end - s->buf_ptr);
366 * Skip the given number of bits.
367 * Must only be used if the actual values in the bitstream do not matter.
368 * If n is < 0 the behavior is undefined.
370 static inline void skip_put_bits(PutBitContext *s, int n)
372 unsigned bits = BUF_BITS - s->bit_left + n;
373 s->buf_ptr += sizeof(BitBuf) * (bits / BUF_BITS);
374 s->bit_left = BUF_BITS - (bits & (BUF_BITS - 1));
378 * Change the end of the buffer.
380 * @param size the new size in bytes of the buffer where to put bits
382 static inline void set_put_bits_buffer_size(PutBitContext *s, int size)
384 av_assert0(size <= INT_MAX/8 - BUF_BITS);
385 s->buf_end = s->buf + size;
386 s->size_in_bits = 8*size;
390 * Pad the bitstream with zeros up to the next byte boundary.
392 static inline void align_put_bits(PutBitContext *s)
394 put_bits(s, s->bit_left & 7, 0);
400 #endif /* AVCODEC_PUT_BITS_H */