FFmpeg: libavcodec/put_bits.h Source File

FFmpeg
put_bits.h
Go to the documentation of this file.
1 /*
2  * copyright (c) 2004 Michael Niedermayer <michaelni@gmx.at>
3  *
4  * This file is part of FFmpeg.
5  *
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.
10  *
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.
15  *
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
19  */
20 
21 /**
22  * @file
23  * bitstream writer API
24  */
25 
26 #ifndef AVCODEC_PUT_BITS_H
27 #define AVCODEC_PUT_BITS_H
28 
29 #include <stdint.h>
30 #include <stdlib.h>
31 #include <assert.h>
32 
33 #include "libavutil/bswap.h"
34 #include "libavutil/common.h"
35 #include "libavutil/intreadwrite.h"
36 #include "libavutil/log.h"
37 #include "libavutil/avassert.h"
38 #include "mathops.h"
39 #include "config.h"
40 
41  typedef struct PutBitContext {
42   uint32_t bit_buf;
43   int bit_left;
44   uint8_t *buf, *buf_ptr, *buf_end;
45   int size_in_bits;
46 } PutBitContext;
47 
48 /**
49  * Initialize the PutBitContext s.
50  *
51  * @param buffer the buffer where to put bits
52  * @param buffer_size the size in bytes of buffer
53  */
54  static inline void init_put_bits(PutBitContext *s, uint8_t *buffer,
55  int buffer_size)
56 {
57  if (buffer_size < 0) {
58  buffer_size = 0;
59  buffer = NULL;
60  }
61 
62  s->size_in_bits = 8 * buffer_size;
63  s->buf = buffer;
64  s->buf_end = s->buf + buffer_size;
65  s->buf_ptr = s->buf;
66  s->bit_left = 32;
67  s->bit_buf = 0;
68 }
69 
70 /**
71  * @return the total number of bits written to the bitstream.
72  */
73  static inline int put_bits_count(PutBitContext *s)
74 {
75  return (s->buf_ptr - s->buf) * 8 + 32 - s->bit_left;
76 }
77 
78 /**
79  * @return the number of bits available in the bitstream.
80  */
81  static inline int put_bits_left(PutBitContext* s)
82 {
83  return (s->buf_end - s->buf_ptr) * 8 - 32 + s->bit_left;
84 }
85 
86 /**
87  * Pad the end of the output stream with zeros.
88  */
89  static inline void flush_put_bits(PutBitContext *s)
90 {
91 #ifndef BITSTREAM_WRITER_LE
92  if (s->bit_left < 32)
93  s->bit_buf <<= s->bit_left;
94 #endif
95  while (s->bit_left < 32) {
96  /* XXX: should test end of buffer */
97 #ifdef BITSTREAM_WRITER_LE
98  *s->buf_ptr++ = s->bit_buf;
99  s->bit_buf >>= 8;
100 #else
101  *s->buf_ptr++ = s->bit_buf >> 24;
102  s->bit_buf <<= 8;
103 #endif
104  s->bit_left += 8;
105  }
106  s->bit_left = 32;
107  s->bit_buf = 0;
108 }
109 
110 #ifdef BITSTREAM_WRITER_LE
111 #define avpriv_align_put_bits align_put_bits_unsupported_here
112 #define avpriv_put_string ff_put_string_unsupported_here
113 #define avpriv_copy_bits avpriv_copy_bits_unsupported_here
114 #else
115 /**
116  * Pad the bitstream with zeros up to the next byte boundary.
117  */
118 void avpriv_align_put_bits(PutBitContext *s);
119 
120 /**
121  * Put the string string in the bitstream.
122  *
123  * @param terminate_string 0-terminates the written string if value is 1
124  */
125 void avpriv_put_string(PutBitContext *pb, const char *string,
126  int terminate_string);
127 
128 /**
129  * Copy the content of src to the bitstream.
130  *
131  * @param length the number of bits of src to copy
132  */
133 void avpriv_copy_bits(PutBitContext *pb, const uint8_t *src, int length);
134 #endif
135 
136 /**
137  * Write up to 31 bits into a bitstream.
138  * Use put_bits32 to write 32 bits.
139  */
140  static inline void put_bits(PutBitContext *s, int n, unsigned int value)
141 {
142  unsigned int bit_buf;
143  int bit_left;
144 
145  av_assert2(n <= 31 && value < (1U << n));
146 
147  bit_buf = s->bit_buf;
148  bit_left = s->bit_left;
149 
150  /* XXX: optimize */
151 #ifdef BITSTREAM_WRITER_LE
152  bit_buf |= value << (32 - bit_left);
153  if (n >= bit_left) {
154  av_assert2(s->buf_ptr+3<s->buf_end);
155  AV_WL32(s->buf_ptr, bit_buf);
156  s->buf_ptr += 4;
157  bit_buf = (bit_left == 32) ? 0 : value >> bit_left;
158  bit_left += 32;
159  }
160  bit_left -= n;
161 #else
162  if (n < bit_left) {
163  bit_buf = (bit_buf << n) | value;
164  bit_left -= n;
165  } else {
166  bit_buf <<= bit_left;
167  bit_buf |= value >> (n - bit_left);
168  av_assert2(s->buf_ptr+3<s->buf_end);
169  AV_WB32(s->buf_ptr, bit_buf);
170  s->buf_ptr += 4;
171  bit_left += 32 - n;
172  bit_buf = value;
173  }
174 #endif
175 
176  s->bit_buf = bit_buf;
177  s->bit_left = bit_left;
178 }
179 
180  static inline void put_sbits(PutBitContext *pb, int n, int32_t value)
181 {
182  av_assert2(n >= 0 && n <= 31);
183 
184  put_bits(pb, n, value & ((1 << n) - 1));
185 }
186 
187 /**
188  * Write exactly 32 bits into a bitstream.
189  */
190  static void av_unused put_bits32(PutBitContext *s, uint32_t value)
191 {
192  int lo = value & 0xffff;
193  int hi = value >> 16;
194 #ifdef BITSTREAM_WRITER_LE
195  put_bits(s, 16, lo);
196  put_bits(s, 16, hi);
197 #else
198  put_bits(s, 16, hi);
199  put_bits(s, 16, lo);
200 #endif
201 }
202 
203 /**
204  * Return the pointer to the byte where the bitstream writer will put
205  * the next bit.
206  */
207  static inline uint8_t *put_bits_ptr(PutBitContext *s)
208 {
209  return s->buf_ptr;
210 }
211 
212 /**
213  * Skip the given number of bytes.
214  * PutBitContext must be flushed & aligned to a byte boundary before calling this.
215  */
216  static inline void skip_put_bytes(PutBitContext *s, int n)
217 {
218  av_assert2((put_bits_count(s) & 7) == 0);
219  av_assert2(s->bit_left == 32);
220  s->buf_ptr += n;
221 }
222 
223 /**
224  * Skip the given number of bits.
225  * Must only be used if the actual values in the bitstream do not matter.
226  * If n is 0 the behavior is undefined.
227  */
228  static inline void skip_put_bits(PutBitContext *s, int n)
229 {
230  s->bit_left -= n;
231  s->buf_ptr -= 4 * (s->bit_left >> 5);
232  s->bit_left &= 31;
233 }
234 
235 /**
236  * Change the end of the buffer.
237  *
238  * @param size the new size in bytes of the buffer where to put bits
239  */
240  static inline void set_put_bits_buffer_size(PutBitContext *s, int size)
241 {
242  s->buf_end = s->buf + size;
243 }
244 
245 #endif /* AVCODEC_PUT_BITS_H */
Generated on Sun Mar 23 2014 23:50:01 for FFmpeg by   doxygen 1.8.2

AltStyle によって変換されたページ (->オリジナル) /