c10dd818f0b79ad35c2cf7003925028b1f39c784
[libav.git] / libavcodec / put_bits.h
1 /*
2 * copyright (c) 2004 Michael Niedermayer <michaelni@gmx.at>
3 *
4 * This file is part of Libav.
5 *
6 * Libav 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 * Libav 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 Libav; 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 #include "libavutil/bswap.h"
33 #include "libavutil/common.h"
34 #include "libavutil/intreadwrite.h"
35 #include "libavutil/log.h"
36 #include "mathops.h"
37 #include "config.h"
38
39 typedef struct PutBitContext {
40 uint32_t bit_buf;
41 int bit_left;
42 uint8_t *buf, *buf_ptr, *buf_end;
43 int size_in_bits;
44 } PutBitContext;
45
46 /**
47 * Initialize the PutBitContext s.
48 *
49 * @param buffer the buffer where to put bits
50 * @param buffer_size the size in bytes of buffer
51 */
52 static inline void init_put_bits(PutBitContext *s, uint8_t *buffer, int buffer_size)
53 {
54 if(buffer_size < 0) {
55 buffer_size = 0;
56 buffer = NULL;
57 }
58
59 s->size_in_bits= 8*buffer_size;
60 s->buf = buffer;
61 s->buf_end = s->buf + buffer_size;
62 s->buf_ptr = s->buf;
63 s->bit_left=32;
64 s->bit_buf=0;
65 }
66
67 /**
68 * @return the total number of bits written to the bitstream.
69 */
70 static inline int put_bits_count(PutBitContext *s)
71 {
72 return (s->buf_ptr - s->buf) * 8 + 32 - s->bit_left;
73 }
74
75 /**
76 * Pad the end of the output stream with zeros.
77 */
78 static inline void flush_put_bits(PutBitContext *s)
79 {
80 #ifndef BITSTREAM_WRITER_LE
81 s->bit_buf<<= s->bit_left;
82 #endif
83 while (s->bit_left < 32) {
84 /* XXX: should test end of buffer */
85 #ifdef BITSTREAM_WRITER_LE
86 *s->buf_ptr++=s->bit_buf;
87 s->bit_buf>>=8;
88 #else
89 *s->buf_ptr++=s->bit_buf >> 24;
90 s->bit_buf<<=8;
91 #endif
92 s->bit_left+=8;
93 }
94 s->bit_left=32;
95 s->bit_buf=0;
96 }
97
98 #ifdef BITSTREAM_WRITER_LE
99 #define align_put_bits align_put_bits_unsupported_here
100 #define ff_put_string ff_put_string_unsupported_here
101 #define ff_copy_bits ff_copy_bits_unsupported_here
102 #else
103 /**
104 * Pad the bitstream with zeros up to the next byte boundary.
105 */
106 void align_put_bits(PutBitContext *s);
107
108 /**
109 * Put the string string in the bitstream.
110 *
111 * @param terminate_string 0-terminates the written string if value is 1
112 */
113 void ff_put_string(PutBitContext *pb, const char *string, int terminate_string);
114
115 /**
116 * Copy the content of src to the bitstream.
117 *
118 * @param length the number of bits of src to copy
119 */
120 void ff_copy_bits(PutBitContext *pb, const uint8_t *src, int length);
121 #endif
122
123 /**
124 * Write up to 31 bits into a bitstream.
125 * Use put_bits32 to write 32 bits.
126 */
127 static inline void put_bits(PutBitContext *s, int n, unsigned int value)
128 {
129 unsigned int bit_buf;
130 int bit_left;
131
132 // printf("put_bits=%d %x\n", n, value);
133 assert(n <= 31 && value < (1U << n));
134
135 bit_buf = s->bit_buf;
136 bit_left = s->bit_left;
137
138 // printf("n=%d value=%x cnt=%d buf=%x\n", n, value, bit_cnt, bit_buf);
139 /* XXX: optimize */
140 #ifdef BITSTREAM_WRITER_LE
141 bit_buf |= value << (32 - bit_left);
142 if (n >= bit_left) {
143 AV_WL32(s->buf_ptr, bit_buf);
144 s->buf_ptr+=4;
145 bit_buf = (bit_left==32)?0:value >> bit_left;
146 bit_left+=32;
147 }
148 bit_left-=n;
149 #else
150 if (n < bit_left) {
151 bit_buf = (bit_buf<<n) | value;
152 bit_left-=n;
153 } else {
154 bit_buf<<=bit_left;
155 bit_buf |= value >> (n - bit_left);
156 AV_WB32(s->buf_ptr, bit_buf);
157 //printf("bitbuf = %08x\n", bit_buf);
158 s->buf_ptr+=4;
159 bit_left+=32 - n;
160 bit_buf = value;
161 }
162 #endif
163
164 s->bit_buf = bit_buf;
165 s->bit_left = bit_left;
166 }
167
168 static inline void put_sbits(PutBitContext *pb, int n, int32_t value)
169 {
170 assert(n >= 0 && n <= 31);
171
172 put_bits(pb, n, value & ((1<<n)-1));
173 }
174
175 /**
176 * Write exactly 32 bits into a bitstream.
177 */
178 static void av_unused put_bits32(PutBitContext *s, uint32_t value)
179 {
180 int lo = value & 0xffff;
181 int hi = value >> 16;
182 #ifdef BITSTREAM_WRITER_LE
183 put_bits(s, 16, lo);
184 put_bits(s, 16, hi);
185 #else
186 put_bits(s, 16, hi);
187 put_bits(s, 16, lo);
188 #endif
189 }
190
191 /**
192 * Return the pointer to the byte where the bitstream writer will put
193 * the next bit.
194 */
195 static inline uint8_t* put_bits_ptr(PutBitContext *s)
196 {
197 return s->buf_ptr;
198 }
199
200 /**
201 * Skip the given number of bytes.
202 * PutBitContext must be flushed & aligned to a byte boundary before calling this.
203 */
204 static inline void skip_put_bytes(PutBitContext *s, int n)
205 {
206 assert((put_bits_count(s)&7)==0);
207 assert(s->bit_left==32);
208 s->buf_ptr += n;
209 }
210
211 /**
212 * Skip the given number of bits.
213 * Must only be used if the actual values in the bitstream do not matter.
214 * If n is 0 the behavior is undefined.
215 */
216 static inline void skip_put_bits(PutBitContext *s, int n)
217 {
218 s->bit_left -= n;
219 s->buf_ptr-= 4*(s->bit_left>>5);
220 s->bit_left &= 31;
221 }
222
223 /**
224 * Change the end of the buffer.
225 *
226 * @param size the new size in bytes of the buffer where to put bits
227 */
228 static inline void set_put_bits_buffer_size(PutBitContext *s, int size)
229 {
230 s->buf_end= s->buf + size;
231 }
232
233 #endif /* AVCODEC_PUT_BITS_H */