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1 | /* |
2 | * This file is part of FFmpeg. | |
3 | * | |
4 | * FFmpeg is free software; you can redistribute it and/or | |
5 | * modify it under the terms of the GNU Lesser General Public | |
6 | * License as published by the Free Software Foundation; either | |
7 | * version 2.1 of the License, or (at your option) any later version. | |
8 | * | |
9 | * FFmpeg is distributed in the hope that it will be useful, | |
10 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
11 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
12 | * Lesser General Public License for more details. | |
13 | * | |
14 | * You should have received a copy of the GNU Lesser General Public | |
15 | * License along with FFmpeg; if not, write to the Free Software | |
16 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA | |
17 | */ | |
18 | ||
19 | /** | |
20 | * @file | |
21 | * @ingroup lavu_buffer | |
22 | * refcounted data buffer API | |
23 | */ | |
24 | ||
25 | #ifndef AVUTIL_BUFFER_H | |
26 | #define AVUTIL_BUFFER_H | |
27 | ||
28 | #include <stdint.h> | |
29 | ||
30 | /** | |
31 | * @defgroup lavu_buffer AVBuffer | |
32 | * @ingroup lavu_data | |
33 | * | |
34 | * @{ | |
35 | * AVBuffer is an API for reference-counted data buffers. | |
36 | * | |
37 | * There are two core objects in this API -- AVBuffer and AVBufferRef. AVBuffer | |
38 | * represents the data buffer itself; it is opaque and not meant to be accessed | |
39 | * by the caller directly, but only through AVBufferRef. However, the caller may | |
40 | * e.g. compare two AVBuffer pointers to check whether two different references | |
41 | * are describing the same data buffer. AVBufferRef represents a single | |
42 | * reference to an AVBuffer and it is the object that may be manipulated by the | |
43 | * caller directly. | |
44 | * | |
45 | * There are two functions provided for creating a new AVBuffer with a single | |
46 | * reference -- av_buffer_alloc() to just allocate a new buffer, and | |
47 | * av_buffer_create() to wrap an existing array in an AVBuffer. From an existing | |
48 | * reference, additional references may be created with av_buffer_ref(). | |
49 | * Use av_buffer_unref() to free a reference (this will automatically free the | |
50 | * data once all the references are freed). | |
51 | * | |
52 | * The convention throughout this API and the rest of FFmpeg is such that the | |
53 | * buffer is considered writable if there exists only one reference to it (and | |
54 | * it has not been marked as read-only). The av_buffer_is_writable() function is | |
55 | * provided to check whether this is true and av_buffer_make_writable() will | |
56 | * automatically create a new writable buffer when necessary. | |
57 | * Of course nothing prevents the calling code from violating this convention, | |
58 | * however that is safe only when all the existing references are under its | |
59 | * control. | |
60 | * | |
61 | * @note Referencing and unreferencing the buffers is thread-safe and thus | |
62 | * may be done from multiple threads simultaneously without any need for | |
63 | * additional locking. | |
64 | * | |
65 | * @note Two different references to the same buffer can point to different | |
66 | * parts of the buffer (i.e. their AVBufferRef.data will not be equal). | |
67 | */ | |
68 | ||
69 | /** | |
70 | * A reference counted buffer type. It is opaque and is meant to be used through | |
71 | * references (AVBufferRef). | |
72 | */ | |
73 | typedef struct AVBuffer AVBuffer; | |
74 | ||
75 | /** | |
76 | * A reference to a data buffer. | |
77 | * | |
78 | * The size of this struct is not a part of the public ABI and it is not meant | |
79 | * to be allocated directly. | |
80 | */ | |
81 | typedef struct AVBufferRef { | |
82 | AVBuffer *buffer; | |
83 | ||
84 | /** | |
85 | * The data buffer. It is considered writable if and only if | |
86 | * this is the only reference to the buffer, in which case | |
87 | * av_buffer_is_writable() returns 1. | |
88 | */ | |
89 | uint8_t *data; | |
90 | /** | |
91 | * Size of data in bytes. | |
92 | */ | |
93 | int size; | |
94 | } AVBufferRef; | |
95 | ||
96 | /** | |
97 | * Allocate an AVBuffer of the given size using av_malloc(). | |
98 | * | |
99 | * @return an AVBufferRef of given size or NULL when out of memory | |
100 | */ | |
101 | AVBufferRef *av_buffer_alloc(int size); | |
102 | ||
103 | /** | |
104 | * Same as av_buffer_alloc(), except the returned buffer will be initialized | |
105 | * to zero. | |
106 | */ | |
107 | AVBufferRef *av_buffer_allocz(int size); | |
108 | ||
109 | /** | |
110 | * Always treat the buffer as read-only, even when it has only one | |
111 | * reference. | |
112 | */ | |
113 | #define AV_BUFFER_FLAG_READONLY (1 << 0) | |
114 | ||
115 | /** | |
116 | * Create an AVBuffer from an existing array. | |
117 | * | |
118 | * If this function is successful, data is owned by the AVBuffer. The caller may | |
119 | * only access data through the returned AVBufferRef and references derived from | |
120 | * it. | |
121 | * If this function fails, data is left untouched. | |
122 | * @param data data array | |
123 | * @param size size of data in bytes | |
124 | * @param free a callback for freeing this buffer's data | |
125 | * @param opaque parameter to be got for processing or passed to free | |
126 | * @param flags a combination of AV_BUFFER_FLAG_* | |
127 | * | |
128 | * @return an AVBufferRef referring to data on success, NULL on failure. | |
129 | */ | |
130 | AVBufferRef *av_buffer_create(uint8_t *data, int size, | |
131 | void (*free)(void *opaque, uint8_t *data), | |
132 | void *opaque, int flags); | |
133 | ||
134 | /** | |
135 | * Default free callback, which calls av_free() on the buffer data. | |
136 | * This function is meant to be passed to av_buffer_create(), not called | |
137 | * directly. | |
138 | */ | |
139 | void av_buffer_default_free(void *opaque, uint8_t *data); | |
140 | ||
141 | /** | |
142 | * Create a new reference to an AVBuffer. | |
143 | * | |
144 | * @return a new AVBufferRef referring to the same AVBuffer as buf or NULL on | |
145 | * failure. | |
146 | */ | |
147 | AVBufferRef *av_buffer_ref(AVBufferRef *buf); | |
148 | ||
149 | /** | |
150 | * Free a given reference and automatically free the buffer if there are no more | |
151 | * references to it. | |
152 | * | |
153 | * @param buf the reference to be freed. The pointer is set to NULL on return. | |
154 | */ | |
155 | void av_buffer_unref(AVBufferRef **buf); | |
156 | ||
157 | /** | |
158 | * @return 1 if the caller may write to the data referred to by buf (which is | |
159 | * true if and only if buf is the only reference to the underlying AVBuffer). | |
160 | * Return 0 otherwise. | |
161 | * A positive answer is valid until av_buffer_ref() is called on buf. | |
162 | */ | |
163 | int av_buffer_is_writable(const AVBufferRef *buf); | |
164 | ||
165 | /** | |
166 | * @return the opaque parameter set by av_buffer_create. | |
167 | */ | |
168 | void *av_buffer_get_opaque(const AVBufferRef *buf); | |
169 | ||
170 | int av_buffer_get_ref_count(const AVBufferRef *buf); | |
171 | ||
172 | /** | |
173 | * Create a writable reference from a given buffer reference, avoiding data copy | |
174 | * if possible. | |
175 | * | |
176 | * @param buf buffer reference to make writable. On success, buf is either left | |
177 | * untouched, or it is unreferenced and a new writable AVBufferRef is | |
178 | * written in its place. On failure, buf is left untouched. | |
179 | * @return 0 on success, a negative AVERROR on failure. | |
180 | */ | |
181 | int av_buffer_make_writable(AVBufferRef **buf); | |
182 | ||
183 | /** | |
184 | * Reallocate a given buffer. | |
185 | * | |
186 | * @param buf a buffer reference to reallocate. On success, buf will be | |
187 | * unreferenced and a new reference with the required size will be | |
188 | * written in its place. On failure buf will be left untouched. *buf | |
189 | * may be NULL, then a new buffer is allocated. | |
190 | * @param size required new buffer size. | |
191 | * @return 0 on success, a negative AVERROR on failure. | |
192 | * | |
193 | * @note the buffer is actually reallocated with av_realloc() only if it was | |
194 | * initially allocated through av_buffer_realloc(NULL) and there is only one | |
195 | * reference to it (i.e. the one passed to this function). In all other cases | |
196 | * a new buffer is allocated and the data is copied. | |
197 | */ | |
198 | int av_buffer_realloc(AVBufferRef **buf, int size); | |
199 | ||
200 | /** | |
201 | * @} | |
202 | */ | |
203 | ||
204 | /** | |
205 | * @defgroup lavu_bufferpool AVBufferPool | |
206 | * @ingroup lavu_data | |
207 | * | |
208 | * @{ | |
209 | * AVBufferPool is an API for a lock-free thread-safe pool of AVBuffers. | |
210 | * | |
211 | * Frequently allocating and freeing large buffers may be slow. AVBufferPool is | |
212 | * meant to solve this in cases when the caller needs a set of buffers of the | |
213 | * same size (the most obvious use case being buffers for raw video or audio | |
214 | * frames). | |
215 | * | |
216 | * At the beginning, the user must call av_buffer_pool_init() to create the | |
217 | * buffer pool. Then whenever a buffer is needed, call av_buffer_pool_get() to | |
218 | * get a reference to a new buffer, similar to av_buffer_alloc(). This new | |
219 | * reference works in all aspects the same way as the one created by | |
220 | * av_buffer_alloc(). However, when the last reference to this buffer is | |
221 | * unreferenced, it is returned to the pool instead of being freed and will be | |
222 | * reused for subsequent av_buffer_pool_get() calls. | |
223 | * | |
224 | * When the caller is done with the pool and no longer needs to allocate any new | |
225 | * buffers, av_buffer_pool_uninit() must be called to mark the pool as freeable. | |
226 | * Once all the buffers are released, it will automatically be freed. | |
227 | * | |
228 | * Allocating and releasing buffers with this API is thread-safe as long as | |
229 | * either the default alloc callback is used, or the user-supplied one is | |
230 | * thread-safe. | |
231 | */ | |
232 | ||
233 | /** | |
234 | * The buffer pool. This structure is opaque and not meant to be accessed | |
235 | * directly. It is allocated with av_buffer_pool_init() and freed with | |
236 | * av_buffer_pool_uninit(). | |
237 | */ | |
238 | typedef struct AVBufferPool AVBufferPool; | |
239 | ||
240 | /** | |
241 | * Allocate and initialize a buffer pool. | |
242 | * | |
243 | * @param size size of each buffer in this pool | |
244 | * @param alloc a function that will be used to allocate new buffers when the | |
245 | * pool is empty. May be NULL, then the default allocator will be used | |
246 | * (av_buffer_alloc()). | |
247 | * @return newly created buffer pool on success, NULL on error. | |
248 | */ | |
249 | AVBufferPool *av_buffer_pool_init(int size, AVBufferRef* (*alloc)(int size)); | |
250 | ||
251 | /** | |
252 | * Mark the pool as being available for freeing. It will actually be freed only | |
253 | * once all the allocated buffers associated with the pool are released. Thus it | |
254 | * is safe to call this function while some of the allocated buffers are still | |
255 | * in use. | |
256 | * | |
257 | * @param pool pointer to the pool to be freed. It will be set to NULL. | |
258 | * @see av_buffer_pool_can_uninit() | |
259 | */ | |
260 | void av_buffer_pool_uninit(AVBufferPool **pool); | |
261 | ||
262 | /** | |
263 | * Allocate a new AVBuffer, reusing an old buffer from the pool when available. | |
264 | * This function may be called simultaneously from multiple threads. | |
265 | * | |
266 | * @return a reference to the new buffer on success, NULL on error. | |
267 | */ | |
268 | AVBufferRef *av_buffer_pool_get(AVBufferPool *pool); | |
269 | ||
270 | /** | |
271 | * @} | |
272 | */ | |
273 | ||
274 | #endif /* AVUTIL_BUFFER_H */ |