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"
36 typedef struct PutBitContext {
39 uint8_t *buf, *buf_ptr, *buf_end;
44 * Initialize the PutBitContext s.
46 * @param buffer the buffer where to put bits
47 * @param buffer_size the size in bytes of buffer
49 static inline void init_put_bits(PutBitContext *s, uint8_t *buffer,
52 if (buffer_size < 0) {
57 s->size_in_bits = 8 * buffer_size;
59 s->buf_end = s->buf + buffer_size;
66 * Rebase the bit writer onto a reallocated buffer.
68 * @param buffer the buffer where to put bits
69 * @param buffer_size the size in bytes of buffer,
70 * must be larger than the previous size
72 static inline void rebase_put_bits(PutBitContext *s, uint8_t *buffer,
75 av_assert0(8*buffer_size > s->size_in_bits);
77 s->buf_end = buffer + buffer_size;
78 s->buf_ptr = buffer + (s->buf_ptr - s->buf);
80 s->size_in_bits = 8 * buffer_size;
84 * @return the total number of bits written to the bitstream.
86 static inline int put_bits_count(PutBitContext *s)
88 return (s->buf_ptr - s->buf) * 8 + 32 - s->bit_left;
92 * @return the number of bits available in the bitstream.
94 static inline int put_bits_left(PutBitContext* s)
96 return (s->buf_end - s->buf_ptr) * 8 - 32 + s->bit_left;
100 * Pad the end of the output stream with zeros.
102 static inline void flush_put_bits(PutBitContext *s)
104 #ifndef BITSTREAM_WRITER_LE
105 if (s->bit_left < 32)
106 s->bit_buf <<= s->bit_left;
108 while (s->bit_left < 32) {
109 /* XXX: should test end of buffer */
110 #ifdef BITSTREAM_WRITER_LE
111 *s->buf_ptr++ = s->bit_buf;
114 *s->buf_ptr++ = s->bit_buf >> 24;
123 #ifdef BITSTREAM_WRITER_LE
124 #define avpriv_align_put_bits align_put_bits_unsupported_here
125 #define avpriv_put_string ff_put_string_unsupported_here
126 #define avpriv_copy_bits avpriv_copy_bits_unsupported_here
129 * Pad the bitstream with zeros up to the next byte boundary.
131 void avpriv_align_put_bits(PutBitContext *s);
134 * Put the string string in the bitstream.
136 * @param terminate_string 0-terminates the written string if value is 1
138 void avpriv_put_string(PutBitContext *pb, const char *string,
139 int terminate_string);
142 * Copy the content of src to the bitstream.
144 * @param length the number of bits of src to copy
146 void avpriv_copy_bits(PutBitContext *pb, const uint8_t *src, int length);
150 * Write up to 31 bits into a bitstream.
151 * Use put_bits32 to write 32 bits.
153 static inline void put_bits(PutBitContext *s, int n, unsigned int value)
155 unsigned int bit_buf;
158 av_assert2(n <= 31 && value < (1U << n));
160 bit_buf = s->bit_buf;
161 bit_left = s->bit_left;
164 #ifdef BITSTREAM_WRITER_LE
165 bit_buf |= value << (32 - bit_left);
167 av_assert2(s->buf_ptr+3<s->buf_end);
168 AV_WL32(s->buf_ptr, bit_buf);
170 bit_buf = (bit_left == 32) ? 0 : value >> bit_left;
176 bit_buf = (bit_buf << n) | value;
179 bit_buf <<= bit_left;
180 bit_buf |= value >> (n - bit_left);
181 av_assert2(s->buf_ptr+3<s->buf_end);
182 AV_WB32(s->buf_ptr, bit_buf);
189 s->bit_buf = bit_buf;
190 s->bit_left = bit_left;
193 static inline void put_sbits(PutBitContext *pb, int n, int32_t value)
195 av_assert2(n >= 0 && n <= 31);
197 put_bits(pb, n, value & ((1 << n) - 1));
201 * Write exactly 32 bits into a bitstream.
203 static void av_unused put_bits32(PutBitContext *s, uint32_t value)
205 int lo = value & 0xffff;
206 int hi = value >> 16;
207 #ifdef BITSTREAM_WRITER_LE
217 * Return the pointer to the byte where the bitstream writer will put
220 static inline uint8_t *put_bits_ptr(PutBitContext *s)
226 * Skip the given number of bytes.
227 * PutBitContext must be flushed & aligned to a byte boundary before calling this.
229 static inline void skip_put_bytes(PutBitContext *s, int n)
231 av_assert2((put_bits_count(s) & 7) == 0);
232 av_assert2(s->bit_left == 32);
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 s->buf_end = s->buf + size;
258 #endif /* AVCODEC_PUT_BITS_H */