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;
56 * Initialize the PutBitContext s.
58 * @param buffer the buffer where to put bits
59 * @param buffer_size the size in bytes of buffer
61 static inline void init_put_bits(PutBitContext *s, uint8_t *buffer,
64 if (buffer_size < 0) {
70 s->buf_end = s->buf + buffer_size;
72 s->bit_left = BUF_BITS;
77 * @return the total number of bits written to the bitstream.
79 static inline int put_bits_count(PutBitContext *s)
81 return (s->buf_ptr - s->buf) * 8 + BUF_BITS - s->bit_left;
85 * @return the number of bytes output so far; may only be called
86 * when the PutBitContext is freshly initialized or flushed.
88 static inline int put_bytes_output(const PutBitContext *s)
90 av_assert2(s->bit_left == BUF_BITS);
91 return s->buf_ptr - s->buf;
95 * @param round_up When set, the number of bits written so far will be
96 * rounded up to the next byte.
97 * @return the number of bytes output so far.
99 static inline int put_bytes_count(const PutBitContext *s, int round_up)
101 return s->buf_ptr - s->buf + ((BUF_BITS - s->bit_left + (round_up ? 7 : 0)) >> 3);
105 * Rebase the bit writer onto a reallocated buffer.
107 * @param buffer the buffer where to put bits
108 * @param buffer_size the size in bytes of buffer,
109 * must be large enough to hold everything written so far
111 static inline void rebase_put_bits(PutBitContext *s, uint8_t *buffer,
114 av_assert0(8*buffer_size >= put_bits_count(s));
116 s->buf_end = buffer + buffer_size;
117 s->buf_ptr = buffer + (s->buf_ptr - s->buf);
122 * @return the number of bits available in the bitstream.
124 static inline int put_bits_left(PutBitContext* s)
126 return (s->buf_end - s->buf_ptr) * 8 - BUF_BITS + s->bit_left;
130 * @param round_up When set, the number of bits written will be
131 * rounded up to the next byte.
132 * @return the number of bytes left.
134 static inline int put_bytes_left(const PutBitContext *s, int round_up)
136 return s->buf_end - s->buf_ptr - ((BUF_BITS - s->bit_left + (round_up ? 7 : 0)) >> 3);
140 * Pad the end of the output stream with zeros.
142 static inline void flush_put_bits(PutBitContext *s)
144 #ifndef BITSTREAM_WRITER_LE
145 if (s->bit_left < BUF_BITS)
146 s->bit_buf <<= s->bit_left;
148 while (s->bit_left < BUF_BITS) {
149 av_assert0(s->buf_ptr < s->buf_end);
150 #ifdef BITSTREAM_WRITER_LE
151 *s->buf_ptr++ = s->bit_buf;
154 *s->buf_ptr++ = s->bit_buf >> (BUF_BITS - 8);
159 s->bit_left = BUF_BITS;
163 static inline void flush_put_bits_le(PutBitContext *s)
165 while (s->bit_left < BUF_BITS) {
166 av_assert0(s->buf_ptr < s->buf_end);
167 *s->buf_ptr++ = s->bit_buf;
171 s->bit_left = BUF_BITS;
175 #ifdef BITSTREAM_WRITER_LE
176 #define ff_put_string ff_put_string_unsupported_here
177 #define ff_copy_bits ff_copy_bits_unsupported_here
181 * Put the string string in the bitstream.
183 * @param terminate_string 0-terminates the written string if value is 1
185 void ff_put_string(PutBitContext *pb, const char *string,
186 int terminate_string);
189 * Copy the content of src to the bitstream.
191 * @param length the number of bits of src to copy
193 void ff_copy_bits(PutBitContext *pb, const uint8_t *src, int length);
196 static inline void put_bits_no_assert(PutBitContext *s, int n, BitBuf value)
201 bit_buf = s->bit_buf;
202 bit_left = s->bit_left;
205 #ifdef BITSTREAM_WRITER_LE
206 bit_buf |= value << (BUF_BITS - bit_left);
208 if (s->buf_end - s->buf_ptr >= sizeof(BitBuf)) {
209 AV_WLBUF(s->buf_ptr, bit_buf);
210 s->buf_ptr += sizeof(BitBuf);
212 av_log(NULL, AV_LOG_ERROR, "Internal error, put_bits buffer too small\n");
215 bit_buf = value >> bit_left;
216 bit_left += BUF_BITS;
221 bit_buf = (bit_buf << n) | value;
224 bit_buf <<= bit_left;
225 bit_buf |= value >> (n - bit_left);
226 if (s->buf_end - s->buf_ptr >= sizeof(BitBuf)) {
227 AV_WBBUF(s->buf_ptr, bit_buf);
228 s->buf_ptr += sizeof(BitBuf);
230 av_log(NULL, AV_LOG_ERROR, "Internal error, put_bits buffer too small\n");
233 bit_left += BUF_BITS - n;
238 s->bit_buf = bit_buf;
239 s->bit_left = bit_left;
243 * Write up to 31 bits into a bitstream.
244 * Use put_bits32 to write 32 bits.
246 static inline void put_bits(PutBitContext *s, int n, BitBuf value)
248 av_assert2(n <= 31 && value < (1UL << n));
249 put_bits_no_assert(s, n, value);
252 static inline void put_bits_le(PutBitContext *s, int n, BitBuf value)
257 av_assert2(n <= 31 && value < (1UL << n));
259 bit_buf = s->bit_buf;
260 bit_left = s->bit_left;
262 bit_buf |= value << (BUF_BITS - bit_left);
264 if (s->buf_end - s->buf_ptr >= sizeof(BitBuf)) {
265 AV_WLBUF(s->buf_ptr, bit_buf);
266 s->buf_ptr += sizeof(BitBuf);
268 av_log(NULL, AV_LOG_ERROR, "Internal error, put_bits buffer too small\n");
271 bit_buf = value >> bit_left;
272 bit_left += BUF_BITS;
276 s->bit_buf = bit_buf;
277 s->bit_left = bit_left;
280 static inline void put_sbits(PutBitContext *pb, int n, int32_t value)
282 av_assert2(n >= 0 && n <= 31);
284 put_bits(pb, n, av_mod_uintp2(value, n));
288 * Write exactly 32 bits into a bitstream.
290 static void av_unused put_bits32(PutBitContext *s, uint32_t value)
296 put_bits_no_assert(s, 32, value);
300 bit_buf = s->bit_buf;
301 bit_left = s->bit_left;
303 #ifdef BITSTREAM_WRITER_LE
304 bit_buf |= (BitBuf)value << (BUF_BITS - bit_left);
305 if (s->buf_end - s->buf_ptr >= sizeof(BitBuf)) {
306 AV_WLBUF(s->buf_ptr, bit_buf);
307 s->buf_ptr += sizeof(BitBuf);
309 av_log(NULL, AV_LOG_ERROR, "Internal error, put_bits buffer too small\n");
312 bit_buf = (uint64_t)value >> bit_left;
314 bit_buf = (uint64_t)bit_buf << bit_left;
315 bit_buf |= (BitBuf)value >> (BUF_BITS - bit_left);
316 if (s->buf_end - s->buf_ptr >= sizeof(BitBuf)) {
317 AV_WBBUF(s->buf_ptr, bit_buf);
318 s->buf_ptr += sizeof(BitBuf);
320 av_log(NULL, AV_LOG_ERROR, "Internal error, put_bits buffer too small\n");
326 s->bit_buf = bit_buf;
327 s->bit_left = bit_left;
331 * Write up to 64 bits into a bitstream.
333 static inline void put_bits64(PutBitContext *s, int n, uint64_t value)
335 av_assert2((n == 64) || (n < 64 && value < (UINT64_C(1) << n)));
338 put_bits(s, n, value);
340 put_bits32(s, value);
342 uint32_t lo = value & 0xffffffff;
343 uint32_t hi = value >> 32;
344 #ifdef BITSTREAM_WRITER_LE
346 put_bits(s, n - 32, hi);
348 put_bits(s, n - 32, hi);
352 uint32_t lo = value & 0xffffffff;
353 uint32_t hi = value >> 32;
354 #ifdef BITSTREAM_WRITER_LE
366 * Return the pointer to the byte where the bitstream writer will put
369 static inline uint8_t *put_bits_ptr(PutBitContext *s)
375 * Skip the given number of bytes.
376 * PutBitContext must be flushed & aligned to a byte boundary before calling this.
378 static inline void skip_put_bytes(PutBitContext *s, int n)
380 av_assert2((put_bits_count(s) & 7) == 0);
381 av_assert2(s->bit_left == BUF_BITS);
382 av_assert0(n <= s->buf_end - s->buf_ptr);
387 * Skip the given number of bits.
388 * Must only be used if the actual values in the bitstream do not matter.
389 * If n is < 0 the behavior is undefined.
391 static inline void skip_put_bits(PutBitContext *s, int n)
393 unsigned bits = BUF_BITS - s->bit_left + n;
394 s->buf_ptr += sizeof(BitBuf) * (bits / BUF_BITS);
395 s->bit_left = BUF_BITS - (bits & (BUF_BITS - 1));
399 * Change the end of the buffer.
401 * @param size the new size in bytes of the buffer where to put bits
403 static inline void set_put_bits_buffer_size(PutBitContext *s, int size)
405 av_assert0(size <= INT_MAX/8 - BUF_BITS);
406 s->buf_end = s->buf + size;
410 * Pad the bitstream with zeros up to the next byte boundary.
412 static inline void align_put_bits(PutBitContext *s)
414 put_bits(s, s->bit_left & 7, 0);
420 #endif /* AVCODEC_PUT_BITS_H */