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 * @return the number of bytes output so far; may only be called
90 * when the PutBitContext is freshly initialized or flushed.
92 static inline int put_bytes_output(const PutBitContext *s)
94 av_assert2(s->bit_left == BUF_BITS);
95 return s->buf_ptr - s->buf;
99 * @param round_up When set, the number of bits written so far will be
100 * rounded up to the next byte.
101 * @return the number of bytes output so far.
103 static inline int put_bytes_count(const PutBitContext *s, int round_up)
105 return s->buf_ptr - s->buf + ((BUF_BITS - s->bit_left + (round_up ? 7 : 0)) >> 3);
109 * Rebase the bit writer onto a reallocated buffer.
111 * @param buffer the buffer where to put bits
112 * @param buffer_size the size in bytes of buffer,
113 * must be large enough to hold everything written so far
115 static inline void rebase_put_bits(PutBitContext *s, uint8_t *buffer,
118 av_assert0(8*buffer_size >= put_bits_count(s));
120 s->buf_end = buffer + buffer_size;
121 s->buf_ptr = buffer + (s->buf_ptr - s->buf);
123 s->size_in_bits = 8 * buffer_size;
127 * @return the number of bits available in the bitstream.
129 static inline int put_bits_left(PutBitContext* s)
131 return (s->buf_end - s->buf_ptr) * 8 - BUF_BITS + s->bit_left;
135 * @param round_up When set, the number of bits written will be
136 * rounded up to the next byte.
137 * @return the number of bytes left.
139 static inline int put_bytes_left(const PutBitContext *s, int round_up)
141 return s->buf_end - s->buf_ptr - ((BUF_BITS - s->bit_left + (round_up ? 7 : 0)) >> 3);
145 * Pad the end of the output stream with zeros.
147 static inline void flush_put_bits(PutBitContext *s)
149 #ifndef BITSTREAM_WRITER_LE
150 if (s->bit_left < BUF_BITS)
151 s->bit_buf <<= s->bit_left;
153 while (s->bit_left < BUF_BITS) {
154 av_assert0(s->buf_ptr < s->buf_end);
155 #ifdef BITSTREAM_WRITER_LE
156 *s->buf_ptr++ = s->bit_buf;
159 *s->buf_ptr++ = s->bit_buf >> (BUF_BITS - 8);
164 s->bit_left = BUF_BITS;
168 static inline void flush_put_bits_le(PutBitContext *s)
170 while (s->bit_left < BUF_BITS) {
171 av_assert0(s->buf_ptr < s->buf_end);
172 *s->buf_ptr++ = s->bit_buf;
176 s->bit_left = BUF_BITS;
180 #if FF_API_AVPRIV_PUT_BITS
181 void avpriv_align_put_bits(PutBitContext *s);
182 void avpriv_copy_bits(PutBitContext *pb, const uint8_t *src, int length);
185 #ifdef BITSTREAM_WRITER_LE
186 #define ff_put_string ff_put_string_unsupported_here
187 #define ff_copy_bits ff_copy_bits_unsupported_here
191 * Put the string string in the bitstream.
193 * @param terminate_string 0-terminates the written string if value is 1
195 void ff_put_string(PutBitContext *pb, const char *string,
196 int terminate_string);
199 * Copy the content of src to the bitstream.
201 * @param length the number of bits of src to copy
203 void ff_copy_bits(PutBitContext *pb, const uint8_t *src, int length);
206 static inline void put_bits_no_assert(PutBitContext *s, int n, BitBuf value)
211 bit_buf = s->bit_buf;
212 bit_left = s->bit_left;
215 #ifdef BITSTREAM_WRITER_LE
216 bit_buf |= value << (BUF_BITS - bit_left);
218 if (s->buf_end - s->buf_ptr >= sizeof(BitBuf)) {
219 AV_WLBUF(s->buf_ptr, bit_buf);
220 s->buf_ptr += sizeof(BitBuf);
222 av_log(NULL, AV_LOG_ERROR, "Internal error, put_bits buffer too small\n");
225 bit_buf = value >> bit_left;
226 bit_left += BUF_BITS;
231 bit_buf = (bit_buf << n) | value;
234 bit_buf <<= bit_left;
235 bit_buf |= value >> (n - bit_left);
236 if (s->buf_end - s->buf_ptr >= sizeof(BitBuf)) {
237 AV_WBBUF(s->buf_ptr, bit_buf);
238 s->buf_ptr += sizeof(BitBuf);
240 av_log(NULL, AV_LOG_ERROR, "Internal error, put_bits buffer too small\n");
243 bit_left += BUF_BITS - n;
248 s->bit_buf = bit_buf;
249 s->bit_left = bit_left;
253 * Write up to 31 bits into a bitstream.
254 * Use put_bits32 to write 32 bits.
256 static inline void put_bits(PutBitContext *s, int n, BitBuf value)
258 av_assert2(n <= 31 && value < (1UL << n));
259 put_bits_no_assert(s, n, value);
262 static inline void put_bits_le(PutBitContext *s, int n, BitBuf value)
267 av_assert2(n <= 31 && value < (1UL << n));
269 bit_buf = s->bit_buf;
270 bit_left = s->bit_left;
272 bit_buf |= value << (BUF_BITS - bit_left);
274 if (s->buf_end - s->buf_ptr >= sizeof(BitBuf)) {
275 AV_WLBUF(s->buf_ptr, bit_buf);
276 s->buf_ptr += sizeof(BitBuf);
278 av_log(NULL, AV_LOG_ERROR, "Internal error, put_bits buffer too small\n");
281 bit_buf = value >> bit_left;
282 bit_left += BUF_BITS;
286 s->bit_buf = bit_buf;
287 s->bit_left = bit_left;
290 static inline void put_sbits(PutBitContext *pb, int n, int32_t value)
292 av_assert2(n >= 0 && n <= 31);
294 put_bits(pb, n, av_mod_uintp2(value, n));
298 * Write exactly 32 bits into a bitstream.
300 static void av_unused put_bits32(PutBitContext *s, uint32_t value)
306 put_bits_no_assert(s, 32, value);
310 bit_buf = s->bit_buf;
311 bit_left = s->bit_left;
313 #ifdef BITSTREAM_WRITER_LE
314 bit_buf |= (BitBuf)value << (BUF_BITS - bit_left);
315 if (s->buf_end - s->buf_ptr >= sizeof(BitBuf)) {
316 AV_WLBUF(s->buf_ptr, bit_buf);
317 s->buf_ptr += sizeof(BitBuf);
319 av_log(NULL, AV_LOG_ERROR, "Internal error, put_bits buffer too small\n");
322 bit_buf = (uint64_t)value >> bit_left;
324 bit_buf = (uint64_t)bit_buf << bit_left;
325 bit_buf |= (BitBuf)value >> (BUF_BITS - bit_left);
326 if (s->buf_end - s->buf_ptr >= sizeof(BitBuf)) {
327 AV_WBBUF(s->buf_ptr, bit_buf);
328 s->buf_ptr += sizeof(BitBuf);
330 av_log(NULL, AV_LOG_ERROR, "Internal error, put_bits buffer too small\n");
336 s->bit_buf = bit_buf;
337 s->bit_left = bit_left;
341 * Write up to 64 bits into a bitstream.
343 static inline void put_bits64(PutBitContext *s, int n, uint64_t value)
345 av_assert2((n == 64) || (n < 64 && value < (UINT64_C(1) << n)));
348 put_bits(s, n, value);
350 put_bits32(s, value);
352 uint32_t lo = value & 0xffffffff;
353 uint32_t hi = value >> 32;
354 #ifdef BITSTREAM_WRITER_LE
356 put_bits(s, n - 32, hi);
358 put_bits(s, n - 32, hi);
362 uint32_t lo = value & 0xffffffff;
363 uint32_t hi = value >> 32;
364 #ifdef BITSTREAM_WRITER_LE
376 * Return the pointer to the byte where the bitstream writer will put
379 static inline uint8_t *put_bits_ptr(PutBitContext *s)
385 * Skip the given number of bytes.
386 * PutBitContext must be flushed & aligned to a byte boundary before calling this.
388 static inline void skip_put_bytes(PutBitContext *s, int n)
390 av_assert2((put_bits_count(s) & 7) == 0);
391 av_assert2(s->bit_left == BUF_BITS);
392 av_assert0(n <= s->buf_end - s->buf_ptr);
397 * Skip the given number of bits.
398 * Must only be used if the actual values in the bitstream do not matter.
399 * If n is < 0 the behavior is undefined.
401 static inline void skip_put_bits(PutBitContext *s, int n)
403 unsigned bits = BUF_BITS - s->bit_left + n;
404 s->buf_ptr += sizeof(BitBuf) * (bits / BUF_BITS);
405 s->bit_left = BUF_BITS - (bits & (BUF_BITS - 1));
409 * Change the end of the buffer.
411 * @param size the new size in bytes of the buffer where to put bits
413 static inline void set_put_bits_buffer_size(PutBitContext *s, int size)
415 av_assert0(size <= INT_MAX/8 - BUF_BITS);
416 s->buf_end = s->buf + size;
417 s->size_in_bits = 8*size;
421 * Pad the bitstream with zeros up to the next byte boundary.
423 static inline void align_put_bits(PutBitContext *s)
425 put_bits(s, s->bit_left & 7, 0);
431 #endif /* AVCODEC_PUT_BITS_H */