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  */
92  uint8_t *data;
93  /**
94  * Size of data in bytes.
95  */
96  size_t size;
97 } AVBufferRef;
98 
99 /**
100  * Allocate an AVBuffer of the given size using av_malloc().
101  *
102  * @return an AVBufferRef of given size or NULL when out of memory
103  */
105 
106 /**
107  * Same as av_buffer_alloc(), except the returned buffer will be initialized
108  * to zero.
109  */
111 
112 /**
113  * Always treat the buffer as read-only, even when it has only one
114  * reference.
115  */
116 #define AV_BUFFER_FLAG_READONLY (1 << 0)
117 
118 /**
119  * Create an AVBuffer from an existing array.
120  *
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
123  * it.
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_*
130  *
131  * @return an AVBufferRef referring to data on success, NULL on failure.
132  */
133 AVBufferRef *av_buffer_create(uint8_t *data, size_t size,
134  void (*free)(void *opaque, uint8_t *data),
135  void *opaque, int flags);
136 
137 /**
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
140  * directly.
141  */
142 void av_buffer_default_free(void *opaque, uint8_t *data);
143 
144 /**
145  * Create a new reference to an AVBuffer.
146  *
147  * @return a new AVBufferRef referring to the same AVBuffer as buf or NULL on
148  * failure.
149  */
151 
152 /**
153  * Free a given reference and automatically free the buffer if there are no more
154  * references to it.
155  *
156  * @param buf the reference to be freed. The pointer is set to NULL on return.
157  */
158 void av_buffer_unref(AVBufferRef **buf);
159 
160 /**
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.
165  */
166 int av_buffer_is_writable(const AVBufferRef *buf);
167 
168 /**
169  * @return the opaque parameter set by av_buffer_create.
170  */
171 void *av_buffer_get_opaque(const AVBufferRef *buf);
172 
173 int av_buffer_get_ref_count(const AVBufferRef *buf);
174 
175 /**
176  * Create a writable reference from a given buffer reference, avoiding data copy
177  * if possible.
178  *
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.
183  */
185 
186 /**
187  * Reallocate a given buffer.
188  *
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.
195  *
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.
200  */
201 int av_buffer_realloc(AVBufferRef **buf, size_t size);
202 
203 /**
204  * Ensure dst refers to the same data as src.
205  *
206  * When *dst is already equivalent to src, do nothing. Otherwise unreference dst
207  * and replace it with a new reference to src.
208  *
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.
216  */
218 
219 /**
220  * @}
221  */
222 
223 /**
224  * @defgroup lavu_bufferpool AVBufferPool
225  * @ingroup lavu_data
226  *
227  * @{
228  * AVBufferPool is an API for a lock-free thread-safe pool of AVBuffers.
229  *
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
233  * frames).
234  *
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.
242  *
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.
246  *
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
249  * thread-safe.
250  */
251 
252 /**
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().
256  */
257 typedef struct AVBufferPool AVBufferPool;
258 
259 /**
260  * Allocate and initialize a buffer pool.
261  *
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.
267  */
269 
270 /**
271  * Allocate and initialize a buffer pool with a more complex allocator.
272  *
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
282  * data. May be NULL.
283  * @return newly created buffer pool on success, NULL on error.
284  */
286  AVBufferRef* (*alloc)(void *opaque, size_t size),
287  void (*pool_free)(void *opaque));
288 
289 /**
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
293  * in use.
294  *
295  * @param pool pointer to the pool to be freed. It will be set to NULL.
296  */
298 
299 /**
300  * Allocate a new AVBuffer, reusing an old buffer from the pool when available.
301  * This function may be called simultaneously from multiple threads.
302  *
303  * @return a reference to the new buffer on success, NULL on error.
304  */
306 
307 /**
308  * Query the original opaque parameter of an allocated buffer in the pool.
309  *
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
312  * buffer pool.
313  *
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.
317  */
319 
320 /**
321  * @}
322  */
323 
324 #endif /* AVUTIL_BUFFER_H */
av_buffer_pool_init
AVBufferPool * av_buffer_pool_init(size_t size, AVBufferRef *(*alloc)(size_t size))
Allocate and initialize a buffer pool.
Definition: buffer.c:266
AVBufferPool
The buffer pool.
Definition: buffer_internal.h:78
AVBufferRef::data
uint8_t * data
The data buffer.
Definition: buffer.h:92
data
const char data[16]
Definition: mxf.c:142
av_buffer_pool_buffer_get_opaque
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
av_buffer_pool_init2
AVBufferPool * av_buffer_pool_init2(size_t size, void *opaque, AVBufferRef *(*alloc)(void *opaque, size_t size), void(*pool_free)(void *opaque))
Allocate and initialize a buffer pool with a more complex allocator.
Definition: buffer.c:245
AVBufferPool::opaque
void * opaque
Definition: buffer_internal.h:94
av_buffer_pool_get
AVBufferRef * av_buffer_pool_get(AVBufferPool *pool)
Allocate a new AVBuffer, reusing an old buffer from the pool when available.
Definition: buffer.c:373
av_buffer_default_free
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
AVBufferPool::pool_free
void(* pool_free)(void *opaque)
Definition: buffer_internal.h:97
av_buffer_unref
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
src
#define src
Definition: vp8dsp.c:255
av_buffer_pool_uninit
void av_buffer_pool_uninit(AVBufferPool **pool)
Mark the pool as being available for freeing.
Definition: buffer.c:308
av_buffer_create
AVBufferRef * av_buffer_create(uint8_t *data, size_t size, void(*free)(void *opaque, uint8_t *data), void *opaque, int flags)
Create an AVBuffer from an existing array.
Definition: buffer.c:29
size
int size
Definition: twinvq_data.h:10344
AVBufferPool::alloc
AVBufferRef *(* alloc)(size_t size)
Definition: buffer_internal.h:95
av_buffer_make_writable
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
av_buffer_get_ref_count
int av_buffer_get_ref_count(const AVBufferRef *buf)
Definition: buffer.c:146
AVBufferRef::buffer
AVBuffer * buffer
Definition: buffer.h:85
av_buffer_alloc
AVBufferRef * av_buffer_alloc(size_t size)
Allocate an AVBuffer of the given size using av_malloc().
Definition: buffer.c:67
AVBufferRef::size
size_t size
Size of data in bytes.
Definition: buffer.h:96
AVBuffer
A reference counted buffer type.
Definition: buffer_internal.h:34
AVBufferPool::pool
BufferPoolEntry * pool
Definition: buffer_internal.h:80
av_buffer_is_writable
int av_buffer_is_writable(const AVBufferRef *buf)
Definition: buffer.c:133
version.h
av_buffer_allocz
AVBufferRef * av_buffer_allocz(size_t size)
Same as av_buffer_alloc(), except the returned buffer will be initialized to zero.
Definition: buffer.c:83
av_buffer_replace
int av_buffer_replace(AVBufferRef **dst, AVBufferRef *src)
Ensure dst refers to the same data as src.
Definition: buffer.c:219
ref
static int ref[MAX_W *MAX_W]
Definition: jpeg2000dwt.c:107
av_buffer_ref
AVBufferRef * av_buffer_ref(AVBufferRef *buf)
Create a new reference to an AVBuffer.
Definition: buffer.c:93
av_buffer_realloc
int av_buffer_realloc(AVBufferRef **buf, size_t size)
Reallocate a given buffer.
Definition: buffer.c:169
av_buffer_get_opaque
void * av_buffer_get_opaque(const AVBufferRef *buf)
Definition: buffer.c:141
AVBufferRef
A reference to a data buffer.
Definition: buffer.h:84
flags
#define flags(name, subs,...)
Definition: cbs_av1.c:561