2 * This file is part of FFmpeg.
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.
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.
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
21 * @ingroup lavu_buffer
22 * refcounted data buffer API
25 #ifndef AVUTIL_BUFFER_H
26 #define AVUTIL_BUFFER_H
34 * @defgroup lavu_buffer AVBuffer
38 * AVBuffer is an API for reference-counted data buffers.
40 * There are two core objects in this API -- AVBuffer and AVBufferRef. AVBuffer
41 * represents the data buffer itself; it is opaque and not meant to be accessed
42 * by the caller directly, but only through AVBufferRef. However, the caller may
43 * e.g. compare two AVBuffer pointers to check whether two different references
44 * are describing the same data buffer. AVBufferRef represents a single
45 * reference to an AVBuffer and it is the object that may be manipulated by the
48 * There are two functions provided for creating a new AVBuffer with a single
49 * reference -- av_buffer_alloc() to just allocate a new buffer, and
50 * av_buffer_create() to wrap an existing array in an AVBuffer. From an existing
51 * reference, additional references may be created with av_buffer_ref().
52 * Use av_buffer_unref() to free a reference (this will automatically free the
53 * data once all the references are freed).
55 * The convention throughout this API and the rest of FFmpeg is such that the
56 * buffer is considered writable if there exists only one reference to it (and
57 * it has not been marked as read-only). The av_buffer_is_writable() function is
58 * provided to check whether this is true and av_buffer_make_writable() will
59 * automatically create a new writable buffer when necessary.
60 * Of course nothing prevents the calling code from violating this convention,
61 * however that is safe only when all the existing references are under its
64 * @note Referencing and unreferencing the buffers is thread-safe and thus
65 * may be done from multiple threads simultaneously without any need for
68 * @note Two different references to the same buffer can point to different
69 * parts of the buffer (i.e. their AVBufferRef.data will not be equal).
73 * A reference counted buffer type. It is opaque and is meant to be used through
74 * references (AVBufferRef).
76 typedef struct AVBuffer AVBuffer;
79 * A reference to a data buffer.
81 * The size of this struct is not a part of the public ABI and it is not meant
82 * to be allocated directly.
84 typedef struct AVBufferRef {
88 * The data buffer. It is considered writable if and only if
89 * this is the only reference to the buffer, in which case
90 * av_buffer_is_writable() returns 1.
94 * Size of data in bytes.
100 * Allocate an AVBuffer of the given size using av_malloc().
102 * @return an AVBufferRef of given size or NULL when out of memory
104 AVBufferRef *av_buffer_alloc(size_t size);
107 * Same as av_buffer_alloc(), except the returned buffer will be initialized
110 AVBufferRef *av_buffer_allocz(size_t size);
113 * Always treat the buffer as read-only, even when it has only one
116 #define AV_BUFFER_FLAG_READONLY (1 << 0)
119 * Create an AVBuffer from an existing array.
121 * If this function is successful, data is owned by the AVBuffer. The caller may
122 * only access data through the returned AVBufferRef and references derived from
124 * If this function fails, data is left untouched.
125 * @param data data array
126 * @param size size of data in bytes
127 * @param free a callback for freeing this buffer's data
128 * @param opaque parameter to be got for processing or passed to free
129 * @param flags a combination of AV_BUFFER_FLAG_*
131 * @return an AVBufferRef referring to data on success, NULL on failure.
133 AVBufferRef *av_buffer_create(uint8_t *data, size_t size,
134 void (*free)(void *opaque, uint8_t *data),
135 void *opaque, int flags);
138 * Default free callback, which calls av_free() on the buffer data.
139 * This function is meant to be passed to av_buffer_create(), not called
142 void av_buffer_default_free(void *opaque, uint8_t *data);
145 * Create a new reference to an AVBuffer.
147 * @return a new AVBufferRef referring to the same AVBuffer as buf or NULL on
150 AVBufferRef *av_buffer_ref(AVBufferRef *buf);
153 * Free a given reference and automatically free the buffer if there are no more
156 * @param buf the reference to be freed. The pointer is set to NULL on return.
158 void av_buffer_unref(AVBufferRef **buf);
161 * @return 1 if the caller may write to the data referred to by buf (which is
162 * true if and only if buf is the only reference to the underlying AVBuffer).
163 * Return 0 otherwise.
164 * A positive answer is valid until av_buffer_ref() is called on buf.
166 int av_buffer_is_writable(const AVBufferRef *buf);
169 * @return the opaque parameter set by av_buffer_create.
171 void *av_buffer_get_opaque(const AVBufferRef *buf);
173 int av_buffer_get_ref_count(const AVBufferRef *buf);
176 * Create a writable reference from a given buffer reference, avoiding data copy
179 * @param buf buffer reference to make writable. On success, buf is either left
180 * untouched, or it is unreferenced and a new writable AVBufferRef is
181 * written in its place. On failure, buf is left untouched.
182 * @return 0 on success, a negative AVERROR on failure.
184 int av_buffer_make_writable(AVBufferRef **buf);
187 * Reallocate a given buffer.
189 * @param buf a buffer reference to reallocate. On success, buf will be
190 * unreferenced and a new reference with the required size will be
191 * written in its place. On failure buf will be left untouched. *buf
192 * may be NULL, then a new buffer is allocated.
193 * @param size required new buffer size.
194 * @return 0 on success, a negative AVERROR on failure.
196 * @note the buffer is actually reallocated with av_realloc() only if it was
197 * initially allocated through av_buffer_realloc(NULL) and there is only one
198 * reference to it (i.e. the one passed to this function). In all other cases
199 * a new buffer is allocated and the data is copied.
201 int av_buffer_realloc(AVBufferRef **buf, size_t size);
204 * Ensure dst refers to the same data as src.
206 * When *dst is already equivalent to src, do nothing. Otherwise unreference dst
207 * and replace it with a new reference to src.
209 * @param dst Pointer to either a valid buffer reference or NULL. On success,
210 * this will point to a buffer reference equivalent to src. On
211 * failure, dst will be left untouched.
212 * @param src A buffer reference to replace dst with. May be NULL, then this
213 * function is equivalent to av_buffer_unref(dst).
214 * @return 0 on success
215 * AVERROR(ENOMEM) on memory allocation failure.
217 int av_buffer_replace(AVBufferRef **dst, AVBufferRef *src);
224 * @defgroup lavu_bufferpool AVBufferPool
228 * AVBufferPool is an API for a lock-free thread-safe pool of AVBuffers.
230 * Frequently allocating and freeing large buffers may be slow. AVBufferPool is
231 * meant to solve this in cases when the caller needs a set of buffers of the
232 * same size (the most obvious use case being buffers for raw video or audio
235 * At the beginning, the user must call av_buffer_pool_init() to create the
236 * buffer pool. Then whenever a buffer is needed, call av_buffer_pool_get() to
237 * get a reference to a new buffer, similar to av_buffer_alloc(). This new
238 * reference works in all aspects the same way as the one created by
239 * av_buffer_alloc(). However, when the last reference to this buffer is
240 * unreferenced, it is returned to the pool instead of being freed and will be
241 * reused for subsequent av_buffer_pool_get() calls.
243 * When the caller is done with the pool and no longer needs to allocate any new
244 * buffers, av_buffer_pool_uninit() must be called to mark the pool as freeable.
245 * Once all the buffers are released, it will automatically be freed.
247 * Allocating and releasing buffers with this API is thread-safe as long as
248 * either the default alloc callback is used, or the user-supplied one is
253 * The buffer pool. This structure is opaque and not meant to be accessed
254 * directly. It is allocated with av_buffer_pool_init() and freed with
255 * av_buffer_pool_uninit().
257 typedef struct AVBufferPool AVBufferPool;
260 * Allocate and initialize a buffer pool.
262 * @param size size of each buffer in this pool
263 * @param alloc a function that will be used to allocate new buffers when the
264 * pool is empty. May be NULL, then the default allocator will be used
265 * (av_buffer_alloc()).
266 * @return newly created buffer pool on success, NULL on error.
268 AVBufferPool *av_buffer_pool_init(size_t size, AVBufferRef* (*alloc)(size_t size));
271 * Allocate and initialize a buffer pool with a more complex allocator.
273 * @param size size of each buffer in this pool
274 * @param opaque arbitrary user data used by the allocator
275 * @param alloc a function that will be used to allocate new buffers when the
276 * pool is empty. May be NULL, then the default allocator will be
277 * used (av_buffer_alloc()).
278 * @param pool_free a function that will be called immediately before the pool
279 * is freed. I.e. after av_buffer_pool_uninit() is called
280 * by the caller and all the frames are returned to the pool
281 * and freed. It is intended to uninitialize the user opaque
283 * @return newly created buffer pool on success, NULL on error.
285 AVBufferPool *av_buffer_pool_init2(size_t size, void *opaque,
286 AVBufferRef* (*alloc)(void *opaque, size_t size),
287 void (*pool_free)(void *opaque));
290 * Mark the pool as being available for freeing. It will actually be freed only
291 * once all the allocated buffers associated with the pool are released. Thus it
292 * is safe to call this function while some of the allocated buffers are still
295 * @param pool pointer to the pool to be freed. It will be set to NULL.
297 void av_buffer_pool_uninit(AVBufferPool **pool);
300 * Allocate a new AVBuffer, reusing an old buffer from the pool when available.
301 * This function may be called simultaneously from multiple threads.
303 * @return a reference to the new buffer on success, NULL on error.
305 AVBufferRef *av_buffer_pool_get(AVBufferPool *pool);
308 * Query the original opaque parameter of an allocated buffer in the pool.
310 * @param ref a buffer reference to a buffer returned by av_buffer_pool_get.
311 * @return the opaque parameter set by the buffer allocator function of the
314 * @note the opaque parameter of ref is used by the buffer pool implementation,
315 * therefore you have to use this function to access the original opaque
316 * parameter of an allocated buffer.
318 void *av_buffer_pool_buffer_get_opaque(AVBufferRef *ref);
324 #endif /* AVUTIL_BUFFER_H */