FFmpeg
buffer.h
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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 <stddef.h>
29 #include <stdint.h>
30 
31 #include "version.h"
32 
33 /**
34  * @defgroup lavu_buffer AVBuffer
35  * @ingroup lavu_data
36  *
37  * @{
38  * AVBuffer is an API for reference-counted data buffers.
39  *
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
46  * caller directly.
47  *
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).
54  *
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
62  * control.
63  *
64  * @note Referencing and unreferencing the buffers is thread-safe and thus
65  * may be done from multiple threads simultaneously without any need for
66  * additional locking.
67  *
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).
70  */
71 
72 /**
73  * A reference counted buffer type. It is opaque and is meant to be used through
74  * references (AVBufferRef).
75  */
76 typedef struct AVBuffer AVBuffer;
77 
78 /**
79  * A reference to a data buffer.
80  *
81  * The size of this struct is not a part of the public ABI and it is not meant
82  * to be allocated directly.
83  */
84 typedef struct AVBufferRef {
86 
87  /**
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.
91  */
93  /**
94  * Size of data in bytes.
95  */
96 #if FF_API_BUFFER_SIZE_T
97  int size;
98 #else
99  size_t size;
100 #endif
101 } AVBufferRef;
102 
103 /**
104  * Allocate an AVBuffer of the given size using av_malloc().
105  *
106  * @return an AVBufferRef of given size or NULL when out of memory
107  */
108 #if FF_API_BUFFER_SIZE_T
110 #else
112 #endif
113 
114 /**
115  * Same as av_buffer_alloc(), except the returned buffer will be initialized
116  * to zero.
117  */
118 #if FF_API_BUFFER_SIZE_T
120 #else
122 #endif
123 
124 /**
125  * Always treat the buffer as read-only, even when it has only one
126  * reference.
127  */
128 #define AV_BUFFER_FLAG_READONLY (1 << 0)
129 
130 /**
131  * Create an AVBuffer from an existing array.
132  *
133  * If this function is successful, data is owned by the AVBuffer. The caller may
134  * only access data through the returned AVBufferRef and references derived from
135  * it.
136  * If this function fails, data is left untouched.
137  * @param data data array
138  * @param size size of data in bytes
139  * @param free a callback for freeing this buffer's data
140  * @param opaque parameter to be got for processing or passed to free
141  * @param flags a combination of AV_BUFFER_FLAG_*
142  *
143  * @return an AVBufferRef referring to data on success, NULL on failure.
144  */
145 #if FF_API_BUFFER_SIZE_T
147 #else
148 AVBufferRef *av_buffer_create(uint8_t *data, size_t size,
149 #endif
150  void (*free)(void *opaque, uint8_t *data),
151  void *opaque, int flags);
152 
153 /**
154  * Default free callback, which calls av_free() on the buffer data.
155  * This function is meant to be passed to av_buffer_create(), not called
156  * directly.
157  */
158 void av_buffer_default_free(void *opaque, uint8_t *data);
159 
160 /**
161  * Create a new reference to an AVBuffer.
162  *
163  * @return a new AVBufferRef referring to the same AVBuffer as buf or NULL on
164  * failure.
165  */
167 
168 /**
169  * Free a given reference and automatically free the buffer if there are no more
170  * references to it.
171  *
172  * @param buf the reference to be freed. The pointer is set to NULL on return.
173  */
174 void av_buffer_unref(AVBufferRef **buf);
175 
176 /**
177  * @return 1 if the caller may write to the data referred to by buf (which is
178  * true if and only if buf is the only reference to the underlying AVBuffer).
179  * Return 0 otherwise.
180  * A positive answer is valid until av_buffer_ref() is called on buf.
181  */
182 int av_buffer_is_writable(const AVBufferRef *buf);
183 
184 /**
185  * @return the opaque parameter set by av_buffer_create.
186  */
187 void *av_buffer_get_opaque(const AVBufferRef *buf);
188 
189 int av_buffer_get_ref_count(const AVBufferRef *buf);
190 
191 /**
192  * Create a writable reference from a given buffer reference, avoiding data copy
193  * if possible.
194  *
195  * @param buf buffer reference to make writable. On success, buf is either left
196  * untouched, or it is unreferenced and a new writable AVBufferRef is
197  * written in its place. On failure, buf is left untouched.
198  * @return 0 on success, a negative AVERROR on failure.
199  */
201 
202 /**
203  * Reallocate a given buffer.
204  *
205  * @param buf a buffer reference to reallocate. On success, buf will be
206  * unreferenced and a new reference with the required size will be
207  * written in its place. On failure buf will be left untouched. *buf
208  * may be NULL, then a new buffer is allocated.
209  * @param size required new buffer size.
210  * @return 0 on success, a negative AVERROR on failure.
211  *
212  * @note the buffer is actually reallocated with av_realloc() only if it was
213  * initially allocated through av_buffer_realloc(NULL) and there is only one
214  * reference to it (i.e. the one passed to this function). In all other cases
215  * a new buffer is allocated and the data is copied.
216  */
217 #if FF_API_BUFFER_SIZE_T
218 int av_buffer_realloc(AVBufferRef **buf, int size);
219 #else
220 int av_buffer_realloc(AVBufferRef **buf, size_t size);
221 #endif
222 
223 /**
224  * Ensure dst refers to the same data as src.
225  *
226  * When *dst is already equivalent to src, do nothing. Otherwise unreference dst
227  * and replace it with a new reference to src.
228  *
229  * @param dst Pointer to either a valid buffer reference or NULL. On success,
230  * this will point to a buffer reference equivalent to src. On
231  * failure, dst will be left untouched.
232  * @param src A buffer reference to replace dst with. May be NULL, then this
233  * function is equivalent to av_buffer_unref(dst).
234  * @return 0 on success
235  * AVERROR(ENOMEM) on memory allocation failure.
236  */
238 
239 /**
240  * @}
241  */
242 
243 /**
244  * @defgroup lavu_bufferpool AVBufferPool
245  * @ingroup lavu_data
246  *
247  * @{
248  * AVBufferPool is an API for a lock-free thread-safe pool of AVBuffers.
249  *
250  * Frequently allocating and freeing large buffers may be slow. AVBufferPool is
251  * meant to solve this in cases when the caller needs a set of buffers of the
252  * same size (the most obvious use case being buffers for raw video or audio
253  * frames).
254  *
255  * At the beginning, the user must call av_buffer_pool_init() to create the
256  * buffer pool. Then whenever a buffer is needed, call av_buffer_pool_get() to
257  * get a reference to a new buffer, similar to av_buffer_alloc(). This new
258  * reference works in all aspects the same way as the one created by
259  * av_buffer_alloc(). However, when the last reference to this buffer is
260  * unreferenced, it is returned to the pool instead of being freed and will be
261  * reused for subsequent av_buffer_pool_get() calls.
262  *
263  * When the caller is done with the pool and no longer needs to allocate any new
264  * buffers, av_buffer_pool_uninit() must be called to mark the pool as freeable.
265  * Once all the buffers are released, it will automatically be freed.
266  *
267  * Allocating and releasing buffers with this API is thread-safe as long as
268  * either the default alloc callback is used, or the user-supplied one is
269  * thread-safe.
270  */
271 
272 /**
273  * The buffer pool. This structure is opaque and not meant to be accessed
274  * directly. It is allocated with av_buffer_pool_init() and freed with
275  * av_buffer_pool_uninit().
276  */
277 typedef struct AVBufferPool AVBufferPool;
278 
279 /**
280  * Allocate and initialize a buffer pool.
281  *
282  * @param size size of each buffer in this pool
283  * @param alloc a function that will be used to allocate new buffers when the
284  * pool is empty. May be NULL, then the default allocator will be used
285  * (av_buffer_alloc()).
286  * @return newly created buffer pool on success, NULL on error.
287  */
288 #if FF_API_BUFFER_SIZE_T
289 AVBufferPool *av_buffer_pool_init(int size, AVBufferRef* (*alloc)(int size));
290 #else
291 AVBufferPool *av_buffer_pool_init(size_t size, AVBufferRef* (*alloc)(size_t size));
292 #endif
293 
294 /**
295  * Allocate and initialize a buffer pool with a more complex allocator.
296  *
297  * @param size size of each buffer in this pool
298  * @param opaque arbitrary user data used by the allocator
299  * @param alloc a function that will be used to allocate new buffers when the
300  * pool is empty. May be NULL, then the default allocator will be
301  * used (av_buffer_alloc()).
302  * @param pool_free a function that will be called immediately before the pool
303  * is freed. I.e. after av_buffer_pool_uninit() is called
304  * by the caller and all the frames are returned to the pool
305  * and freed. It is intended to uninitialize the user opaque
306  * data. May be NULL.
307  * @return newly created buffer pool on success, NULL on error.
308  */
309 #if FF_API_BUFFER_SIZE_T
310 AVBufferPool *av_buffer_pool_init2(int size, void *opaque,
311  AVBufferRef* (*alloc)(void *opaque, int size),
312 #else
313 AVBufferPool *av_buffer_pool_init2(size_t size, void *opaque,
314  AVBufferRef* (*alloc)(void *opaque, size_t size),
315 #endif
316  void (*pool_free)(void *opaque));
317 
318 /**
319  * Mark the pool as being available for freeing. It will actually be freed only
320  * once all the allocated buffers associated with the pool are released. Thus it
321  * is safe to call this function while some of the allocated buffers are still
322  * in use.
323  *
324  * @param pool pointer to the pool to be freed. It will be set to NULL.
325  */
327 
328 /**
329  * Allocate a new AVBuffer, reusing an old buffer from the pool when available.
330  * This function may be called simultaneously from multiple threads.
331  *
332  * @return a reference to the new buffer on success, NULL on error.
333  */
335 
336 /**
337  * Query the original opaque parameter of an allocated buffer in the pool.
338  *
339  * @param ref a buffer reference to a buffer returned by av_buffer_pool_get.
340  * @return the opaque parameter set by the buffer allocator function of the
341  * buffer pool.
342  *
343  * @note the opaque parameter of ref is used by the buffer pool implementation,
344  * therefore you have to use this function to access the original opaque
345  * parameter of an allocated buffer.
346  */
348 
349 /**
350  * @}
351  */
352 
353 #endif /* AVUTIL_BUFFER_H */
int av_buffer_make_writable(AVBufferRef **buf)
Create a writable reference from a given buffer reference, avoiding data copy if possible.
Definition: buffer.c:151
void * av_buffer_pool_buffer_get_opaque(AVBufferRef *ref)
Query the original opaque parameter of an allocated buffer in the pool.
Definition: buffer.c:398
void av_buffer_unref(AVBufferRef **buf)
Free a given reference and automatically free the buffer if there are no more references to it...
Definition: buffer.c:125
ptrdiff_t const GLvoid * data
Definition: opengl_enc.c:100
uint8_t
AVBufferRef *(* alloc)(buffer_size_t size)
ptrdiff_t size
Definition: opengl_enc.c:100
The buffer pool.
void av_buffer_default_free(void *opaque, uint8_t *data)
Default free callback, which calls av_free() on the buffer data.
Definition: buffer.c:62
#define src
Definition: vp8dsp.c:255
AVBufferRef * av_buffer_create(uint8_t *data, int size, void(*free)(void *opaque, uint8_t *data), void *opaque, int flags)
Create an AVBuffer from an existing array.
Definition: buffer.c:29
Libavutil version macros.
int av_buffer_realloc(AVBufferRef **buf, int size)
Reallocate a given buffer.
Definition: buffer.c:169
void(* pool_free)(void *opaque)
int av_buffer_is_writable(const AVBufferRef *buf)
Definition: buffer.c:133
AVBufferPool * av_buffer_pool_init2(int size, void *opaque, AVBufferRef *(*alloc)(void *opaque, int size), void(*pool_free)(void *opaque))
Allocate and initialize a buffer pool with a more complex allocator.
Definition: buffer.c:245
AVBufferRef * av_buffer_alloc(int size)
Allocate an AVBuffer of the given size using av_malloc().
Definition: buffer.c:67
uint8_t * data
The data buffer.
Definition: buffer.h:92
int av_buffer_get_ref_count(const AVBufferRef *buf)
Definition: buffer.c:146
AVBufferRef * av_buffer_allocz(int size)
Same as av_buffer_alloc(), except the returned buffer will be initialized to zero.
Definition: buffer.c:83
AVBuffer * buffer
Definition: buffer.h:85
void * av_buffer_get_opaque(const AVBufferRef *buf)
Definition: buffer.c:141
void av_buffer_pool_uninit(AVBufferPool **pool)
Mark the pool as being available for freeing.
Definition: buffer.c:308
A reference counted buffer type.
int size
Size of data in bytes.
Definition: buffer.h:97
#define flags(name, subs,...)
Definition: cbs_av1.c:561
A reference to a data buffer.
Definition: buffer.h:84
AVBufferPool * av_buffer_pool_init(int size, AVBufferRef *(*alloc)(int size))
Allocate and initialize a buffer pool.
Definition: buffer.c:266
static int ref[MAX_W *MAX_W]
Definition: jpeg2000dwt.c:107
AVBufferRef * av_buffer_ref(AVBufferRef *buf)
Create a new reference to an AVBuffer.
Definition: buffer.c:93
BufferPoolEntry * pool
AVBufferRef * av_buffer_pool_get(AVBufferPool *pool)
Allocate a new AVBuffer, reusing an old buffer from the pool when available.
Definition: buffer.c:373
int av_buffer_replace(AVBufferRef **dst, AVBufferRef *src)
Ensure dst refers to the same data as src.
Definition: buffer.c:219