blob: 73b6bd0b148e6e6018845a0df928d8d20cef115a
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 | * Allocate and initialize a buffer pool with a more complex allocator. |
253 | * |
254 | * @param size size of each buffer in this pool |
255 | * @param opaque arbitrary user data used by the allocator |
256 | * @param alloc a function that will be used to allocate new buffers when the |
257 | * pool is empty. |
258 | * @param pool_free a function that will be called immediately before the pool |
259 | * is freed. I.e. after av_buffer_pool_uninit() is called |
260 | * by the caller and all the frames are returned to the pool |
261 | * and freed. It is intended to uninitialize the user opaque |
262 | * data. |
263 | * @return newly created buffer pool on success, NULL on error. |
264 | */ |
265 | AVBufferPool *av_buffer_pool_init2(int size, void *opaque, |
266 | AVBufferRef* (*alloc)(void *opaque, int size), |
267 | void (*pool_free)(void *opaque)); |
268 | |
269 | /** |
270 | * Mark the pool as being available for freeing. It will actually be freed only |
271 | * once all the allocated buffers associated with the pool are released. Thus it |
272 | * is safe to call this function while some of the allocated buffers are still |
273 | * in use. |
274 | * |
275 | * @param pool pointer to the pool to be freed. It will be set to NULL. |
276 | */ |
277 | void av_buffer_pool_uninit(AVBufferPool **pool); |
278 | |
279 | /** |
280 | * Allocate a new AVBuffer, reusing an old buffer from the pool when available. |
281 | * This function may be called simultaneously from multiple threads. |
282 | * |
283 | * @return a reference to the new buffer on success, NULL on error. |
284 | */ |
285 | AVBufferRef *av_buffer_pool_get(AVBufferPool *pool); |
286 | |
287 | /** |
288 | * @} |
289 | */ |
290 | |
291 | #endif /* AVUTIL_BUFFER_H */ |
292 |