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 struct PutBitContext {
38 uint8_t *buf, *buf_ptr, *buf_end;
43 * Initialize the PutBitContext s.
45 * @param buffer the buffer where to put bits
46 * @param buffer_size the size in bytes of buffer
48 static inline void init_put_bits(PutBitContext *s, uint8_t *buffer,
51 if (buffer_size < 0) {
56 s->size_in_bits = 8 * buffer_size;
58 s->buf_end = s->buf + buffer_size;
65 * Rebase the bit writer onto a reallocated buffer.
67 * @param buffer the buffer where to put bits
68 * @param buffer_size the size in bytes of buffer,
69 * must be larger than the previous size
71 static inline void rebase_put_bits(PutBitContext *s, uint8_t *buffer,
74 av_assert0(8*buffer_size > s->size_in_bits);
76 s->buf_end = buffer + buffer_size;
77 s->buf_ptr = buffer + (s->buf_ptr - s->buf);
79 s->size_in_bits = 8 * buffer_size;
83 * @return the total number of bits written to the bitstream.
85 static inline int put_bits_count(PutBitContext *s)
87 return (s->buf_ptr - s->buf) * 8 + 32 - s->bit_left;
91 * @return the number of bits available in the bitstream.
93 static inline int put_bits_left(PutBitContext* s)
95 return (s->buf_end - s->buf_ptr) * 8 - 32 + s->bit_left;
99 * Pad the end of the output stream with zeros.
101 static inline void flush_put_bits(PutBitContext *s)
103 #ifndef BITSTREAM_WRITER_LE
104 if (s->bit_left < 32)
105 s->bit_buf <<= s->bit_left;
107 while (s->bit_left < 32) {
108 /* XXX: should test end of buffer */
109 #ifdef BITSTREAM_WRITER_LE
110 *s->buf_ptr++ = s->bit_buf;
113 *s->buf_ptr++ = s->bit_buf >> 24;
122 #ifdef BITSTREAM_WRITER_LE
123 #define avpriv_align_put_bits align_put_bits_unsupported_here
124 #define avpriv_put_string ff_put_string_unsupported_here
125 #define avpriv_copy_bits avpriv_copy_bits_unsupported_here
128 * Pad the bitstream with zeros up to the next byte boundary.
130 void avpriv_align_put_bits(PutBitContext *s);
133 * Put the string string in the bitstream.
135 * @param terminate_string 0-terminates the written string if value is 1
137 void avpriv_put_string(PutBitContext *pb, const char *string,
138 int terminate_string);
141 * Copy the content of src to the bitstream.
143 * @param length the number of bits of src to copy
145 void avpriv_copy_bits(PutBitContext *pb, const uint8_t *src, int length);
149 * Write up to 31 bits into a bitstream.
150 * Use put_bits32 to write 32 bits.
152 static inline void put_bits(PutBitContext *s, int n, unsigned int value)
154 unsigned int bit_buf;
157 av_assert2(n <= 31 && value < (1U << n));
159 bit_buf = s->bit_buf;
160 bit_left = s->bit_left;
163 #ifdef BITSTREAM_WRITER_LE
164 bit_buf |= value << (32 - bit_left);
166 av_assert2(s->buf_ptr+3<s->buf_end);
167 AV_WL32(s->buf_ptr, bit_buf);
169 bit_buf = value >> bit_left;
175 bit_buf = (bit_buf << n) | value;
178 bit_buf <<= bit_left;
179 bit_buf |= value >> (n - bit_left);
180 av_assert2(s->buf_ptr+3<s->buf_end);
181 AV_WB32(s->buf_ptr, bit_buf);
188 s->bit_buf = bit_buf;
189 s->bit_left = bit_left;
192 static inline void put_sbits(PutBitContext *pb, int n, int32_t value)
194 av_assert2(n >= 0 && n <= 31);
196 put_bits(pb, n, av_mod_uintp2(value, n));
200 * Write exactly 32 bits into a bitstream.
202 static void av_unused put_bits32(PutBitContext *s, uint32_t value)
204 int lo = value & 0xffff;
205 int hi = value >> 16;
206 #ifdef BITSTREAM_WRITER_LE
216 * Return the pointer to the byte where the bitstream writer will put
219 static inline uint8_t *put_bits_ptr(PutBitContext *s)
225 * Skip the given number of bytes.
226 * PutBitContext must be flushed & aligned to a byte boundary before calling this.
228 static inline void skip_put_bytes(PutBitContext *s, int n)
230 av_assert2((put_bits_count(s) & 7) == 0);
231 av_assert2(s->bit_left == 32);
232 av_assert0(n <= s->buf_end - s->buf_ptr);
237 * Skip the given number of bits.
238 * Must only be used if the actual values in the bitstream do not matter.
239 * If n is 0 the behavior is undefined.
241 static inline void skip_put_bits(PutBitContext *s, int n)
244 s->buf_ptr -= 4 * (s->bit_left >> 5);
249 * Change the end of the buffer.
251 * @param size the new size in bytes of the buffer where to put bits
253 static inline void set_put_bits_buffer_size(PutBitContext *s, int size)
255 av_assert0(size <= INT_MAX/8 - 32);
256 s->buf_end = s->buf + size;
257 s->size_in_bits = 8*size;
260 #endif /* AVCODEC_PUT_BITS_H */