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
32 #include "libavutil/intreadwrite.h"
33 #include "libavutil/avassert.h"
35 typedef uint32_t BitBuf;
36 #define AV_WBBUF AV_WB32
37 #define AV_WLBUF AV_WL32
39 static const int BUF_BITS = 8 * sizeof(BitBuf);
41 typedef struct PutBitContext {
44 uint8_t *buf, *buf_ptr, *buf_end;
49 * Initialize the PutBitContext s.
51 * @param buffer the buffer where to put bits
52 * @param buffer_size the size in bytes of buffer
54 static inline void init_put_bits(PutBitContext *s, uint8_t *buffer,
57 if (buffer_size < 0) {
62 s->size_in_bits = 8 * buffer_size;
64 s->buf_end = s->buf + buffer_size;
66 s->bit_left = BUF_BITS;
71 * @return the total number of bits written to the bitstream.
73 static inline int put_bits_count(PutBitContext *s)
75 return (s->buf_ptr - s->buf) * 8 + BUF_BITS - s->bit_left;
79 * Rebase the bit writer onto a reallocated buffer.
81 * @param buffer the buffer where to put bits
82 * @param buffer_size the size in bytes of buffer,
83 * must be large enough to hold everything written so far
85 static inline void rebase_put_bits(PutBitContext *s, uint8_t *buffer,
88 av_assert0(8*buffer_size >= put_bits_count(s));
90 s->buf_end = buffer + buffer_size;
91 s->buf_ptr = buffer + (s->buf_ptr - s->buf);
93 s->size_in_bits = 8 * buffer_size;
97 * @return the number of bits available in the bitstream.
99 static inline int put_bits_left(PutBitContext* s)
101 return (s->buf_end - s->buf_ptr) * 8 - BUF_BITS + s->bit_left;
105 * Pad the end of the output stream with zeros.
107 static inline void flush_put_bits(PutBitContext *s)
109 #ifndef BITSTREAM_WRITER_LE
110 if (s->bit_left < BUF_BITS)
111 s->bit_buf <<= s->bit_left;
113 while (s->bit_left < BUF_BITS) {
114 av_assert0(s->buf_ptr < s->buf_end);
115 #ifdef BITSTREAM_WRITER_LE
116 *s->buf_ptr++ = s->bit_buf;
119 *s->buf_ptr++ = s->bit_buf >> (BUF_BITS - 8);
124 s->bit_left = BUF_BITS;
128 static inline void flush_put_bits_le(PutBitContext *s)
130 while (s->bit_left < BUF_BITS) {
131 av_assert0(s->buf_ptr < s->buf_end);
132 *s->buf_ptr++ = s->bit_buf;
136 s->bit_left = BUF_BITS;
140 #ifdef BITSTREAM_WRITER_LE
141 #define avpriv_align_put_bits align_put_bits_unsupported_here
142 #define avpriv_put_string ff_put_string_unsupported_here
143 #define avpriv_copy_bits avpriv_copy_bits_unsupported_here
146 * Pad the bitstream with zeros up to the next byte boundary.
148 void avpriv_align_put_bits(PutBitContext *s);
151 * Put the string string in the bitstream.
153 * @param terminate_string 0-terminates the written string if value is 1
155 void avpriv_put_string(PutBitContext *pb, const char *string,
156 int terminate_string);
159 * Copy the content of src to the bitstream.
161 * @param length the number of bits of src to copy
163 void avpriv_copy_bits(PutBitContext *pb, const uint8_t *src, int length);
167 * Write up to 31 bits into a bitstream.
168 * Use put_bits32 to write 32 bits.
170 static inline void put_bits(PutBitContext *s, int n, BitBuf value)
175 av_assert2(n <= 31 && value < (1UL << n));
177 bit_buf = s->bit_buf;
178 bit_left = s->bit_left;
181 #ifdef BITSTREAM_WRITER_LE
182 bit_buf |= value << (BUF_BITS - bit_left);
184 if (s->buf_end - s->buf_ptr >= sizeof(BitBuf)) {
185 AV_WLBUF(s->buf_ptr, bit_buf);
186 s->buf_ptr += sizeof(BitBuf);
188 av_log(NULL, AV_LOG_ERROR, "Internal error, put_bits buffer too small\n");
191 bit_buf = value >> bit_left;
192 bit_left += BUF_BITS;
197 bit_buf = (bit_buf << n) | value;
200 bit_buf <<= bit_left;
201 bit_buf |= value >> (n - bit_left);
202 if (s->buf_end - s->buf_ptr >= sizeof(BitBuf)) {
203 AV_WBBUF(s->buf_ptr, bit_buf);
204 s->buf_ptr += sizeof(BitBuf);
206 av_log(NULL, AV_LOG_ERROR, "Internal error, put_bits buffer too small\n");
209 bit_left += BUF_BITS - n;
214 s->bit_buf = bit_buf;
215 s->bit_left = bit_left;
218 static inline void put_bits_le(PutBitContext *s, int n, BitBuf value)
223 av_assert2(n <= 31 && value < (1UL << n));
225 bit_buf = s->bit_buf;
226 bit_left = s->bit_left;
228 bit_buf |= value << (BUF_BITS - bit_left);
230 if (s->buf_end - s->buf_ptr >= sizeof(BitBuf)) {
231 AV_WLBUF(s->buf_ptr, bit_buf);
232 s->buf_ptr += sizeof(BitBuf);
234 av_log(NULL, AV_LOG_ERROR, "Internal error, put_bits buffer too small\n");
237 bit_buf = value >> bit_left;
238 bit_left += BUF_BITS;
242 s->bit_buf = bit_buf;
243 s->bit_left = bit_left;
246 static inline void put_sbits(PutBitContext *pb, int n, int32_t value)
248 av_assert2(n >= 0 && n <= 31);
250 put_bits(pb, n, av_mod_uintp2(value, n));
254 * Write exactly 32 bits into a bitstream.
256 static void av_unused put_bits32(PutBitContext *s, uint32_t value)
261 bit_buf = s->bit_buf;
262 bit_left = s->bit_left;
264 #ifdef BITSTREAM_WRITER_LE
265 bit_buf |= (BitBuf)value << (BUF_BITS - bit_left);
266 if (s->buf_end - s->buf_ptr >= sizeof(BitBuf)) {
267 AV_WLBUF(s->buf_ptr, bit_buf);
268 s->buf_ptr += sizeof(BitBuf);
270 av_log(NULL, AV_LOG_ERROR, "Internal error, put_bits buffer too small\n");
273 bit_buf = (uint64_t)value >> bit_left;
275 bit_buf = (uint64_t)bit_buf << bit_left;
276 bit_buf |= (BitBuf)value >> (BUF_BITS - bit_left);
277 if (s->buf_end - s->buf_ptr >= sizeof(BitBuf)) {
278 AV_WBBUF(s->buf_ptr, bit_buf);
279 s->buf_ptr += sizeof(BitBuf);
281 av_log(NULL, AV_LOG_ERROR, "Internal error, put_bits buffer too small\n");
287 s->bit_buf = bit_buf;
288 s->bit_left = bit_left;
292 * Write up to 64 bits into a bitstream.
294 static inline void put_bits64(PutBitContext *s, int n, uint64_t value)
296 av_assert2((n == 64) || (n < 64 && value < (UINT64_C(1) << n)));
299 put_bits(s, n, value);
301 put_bits32(s, value);
303 uint32_t lo = value & 0xffffffff;
304 uint32_t hi = value >> 32;
305 #ifdef BITSTREAM_WRITER_LE
307 put_bits(s, n - 32, hi);
309 put_bits(s, n - 32, hi);
313 uint32_t lo = value & 0xffffffff;
314 uint32_t hi = value >> 32;
315 #ifdef BITSTREAM_WRITER_LE
327 * Return the pointer to the byte where the bitstream writer will put
330 static inline uint8_t *put_bits_ptr(PutBitContext *s)
336 * Skip the given number of bytes.
337 * PutBitContext must be flushed & aligned to a byte boundary before calling this.
339 static inline void skip_put_bytes(PutBitContext *s, int n)
341 av_assert2((put_bits_count(s) & 7) == 0);
342 av_assert2(s->bit_left == BUF_BITS);
343 av_assert0(n <= s->buf_end - s->buf_ptr);
348 * Skip the given number of bits.
349 * Must only be used if the actual values in the bitstream do not matter.
350 * If n is 0 the behavior is undefined.
352 static inline void skip_put_bits(PutBitContext *s, int n)
355 s->buf_ptr -= sizeof(BitBuf) * ((unsigned)s->bit_left / BUF_BITS);
356 s->bit_left &= (BUF_BITS - 1);
360 * Change the end of the buffer.
362 * @param size the new size in bytes of the buffer where to put bits
364 static inline void set_put_bits_buffer_size(PutBitContext *s, int size)
366 av_assert0(size <= INT_MAX/8 - BUF_BITS);
367 s->buf_end = s->buf + size;
368 s->size_in_bits = 8*size;
374 #endif /* AVCODEC_PUT_BITS_H */