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