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/**
32 * @defgroup lavu_buffer AVBuffer
33 * @ingroup lavu_data
34 *
35 * @{
36 * AVBuffer is an API for reference-counted data buffers.
37 *
38 * There are two core objects in this API -- AVBuffer and AVBufferRef. AVBuffer
39 * represents the data buffer itself; it is opaque and not meant to be accessed
40 * by the caller directly, but only through AVBufferRef. However, the caller may
41 * e.g. compare two AVBuffer pointers to check whether two different references
42 * are describing the same data buffer. AVBufferRef represents a single
43 * reference to an AVBuffer and it is the object that may be manipulated by the
44 * caller directly.
45 *
46 * There are two functions provided for creating a new AVBuffer with a single
47 * reference -- av_buffer_alloc() to just allocate a new buffer, and
48 * av_buffer_create() to wrap an existing array in an AVBuffer. From an existing
49 * reference, additional references may be created with av_buffer_ref().
50 * Use av_buffer_unref() to free a reference (this will automatically free the
51 * data once all the references are freed).
52 *
53 * The convention throughout this API and the rest of FFmpeg is such that the
54 * buffer is considered writable if there exists only one reference to it (and
55 * it has not been marked as read-only). The av_buffer_is_writable() function is
56 * provided to check whether this is true and av_buffer_make_writable() will
57 * automatically create a new writable buffer when necessary.
58 * Of course nothing prevents the calling code from violating this convention,
59 * however that is safe only when all the existing references are under its
60 * control.
61 *
62 * @note Referencing and unreferencing the buffers is thread-safe and thus
63 * may be done from multiple threads simultaneously without any need for
64 * additional locking.
65 *
66 * @note Two different references to the same buffer can point to different
67 * parts of the buffer (i.e. their AVBufferRef.data will not be equal).
68 */
69
70/**
71 * A reference counted buffer type. It is opaque and is meant to be used through
72 * references (AVBufferRef).
73 */
74typedef struct AVBuffer AVBuffer;
75
76/**
77 * A reference to a data buffer.
78 *
79 * The size of this struct is not a part of the public ABI and it is not meant
80 * to be allocated directly.
81 */
82typedef struct AVBufferRef {
83 AVBuffer *buffer;
84
85 /**
86 * The data buffer. It is considered writable if and only if
87 * this is the only reference to the buffer, in which case
88 * av_buffer_is_writable() returns 1.
89 */
90 uint8_t *data;
91 /**
92 * Size of data in bytes.
93 */
94 size_t size;
95} AVBufferRef;
96
97/**
98 * Allocate an AVBuffer of the given size using av_malloc().
99 *
100 * @return an AVBufferRef of given size or NULL when out of memory
101 */
102AVBufferRef *av_buffer_alloc(size_t size);
103
104/**
105 * Same as av_buffer_alloc(), except the returned buffer will be initialized
106 * to zero.
107 */
108AVBufferRef *av_buffer_allocz(size_t size);
109
110/**
111 * Always treat the buffer as read-only, even when it has only one
112 * reference.
113 */
114#define AV_BUFFER_FLAG_READONLY (1 << 0)
115
116/**
117 * Create an AVBuffer from an existing array.
118 *
119 * If this function is successful, data is owned by the AVBuffer. The caller may
120 * only access data through the returned AVBufferRef and references derived from
121 * it.
122 * If this function fails, data is left untouched.
123 * @param data data array
124 * @param size size of data in bytes
125 * @param free a callback for freeing this buffer's data
126 * @param opaque parameter to be got for processing or passed to free
127 * @param flags a combination of AV_BUFFER_FLAG_*
128 *
129 * @return an AVBufferRef referring to data on success, NULL on failure.
130 */
131AVBufferRef *av_buffer_create(uint8_t *data, size_t size,
132 void (*free)(void *opaque, uint8_t *data),
133 void *opaque, int flags);
134
135/**
136 * Default free callback, which calls av_free() on the buffer data.
137 * This function is meant to be passed to av_buffer_create(), not called
138 * directly.
139 */
140void av_buffer_default_free(void *opaque, uint8_t *data);
141
142/**
143 * Create a new reference to an AVBuffer.
144 *
145 * @return a new AVBufferRef referring to the same AVBuffer as buf or NULL on
146 * failure.
147 */
148AVBufferRef *av_buffer_ref(const AVBufferRef *buf);
149
150/**
151 * Free a given reference and automatically free the buffer if there are no more
152 * references to it.
153 *
154 * @param buf the reference to be freed. The pointer is set to NULL on return.
155 */
156void av_buffer_unref(AVBufferRef **buf);
157
158/**
159 * @return 1 if the caller may write to the data referred to by buf (which is
160 * true if and only if buf is the only reference to the underlying AVBuffer).
161 * Return 0 otherwise.
162 * A positive answer is valid until av_buffer_ref() is called on buf.
163 */
164int av_buffer_is_writable(const AVBufferRef *buf);
165
166/**
167 * @return the opaque parameter set by av_buffer_create.
168 */
169void *av_buffer_get_opaque(const AVBufferRef *buf);
170
171int av_buffer_get_ref_count(const AVBufferRef *buf);
172
173/**
174 * Create a writable reference from a given buffer reference, avoiding data copy
175 * if possible.
176 *
177 * @param buf buffer reference to make writable. On success, buf is either left
178 * untouched, or it is unreferenced and a new writable AVBufferRef is
179 * written in its place. On failure, buf is left untouched.
180 * @return 0 on success, a negative AVERROR on failure.
181 */
182int av_buffer_make_writable(AVBufferRef **buf);
183
184/**
185 * Reallocate a given buffer.
186 *
187 * @param buf a buffer reference to reallocate. On success, buf will be
188 * unreferenced and a new reference with the required size will be
189 * written in its place. On failure buf will be left untouched. *buf
190 * may be NULL, then a new buffer is allocated.
191 * @param size required new buffer size.
192 * @return 0 on success, a negative AVERROR on failure.
193 *
194 * @note the buffer is actually reallocated with av_realloc() only if it was
195 * initially allocated through av_buffer_realloc(NULL) and there is only one
196 * reference to it (i.e. the one passed to this function). In all other cases
197 * a new buffer is allocated and the data is copied.
198 */
199int av_buffer_realloc(AVBufferRef **buf, size_t size);
200
201/**
202 * Ensure dst refers to the same data as src.
203 *
204 * When *dst is already equivalent to src, do nothing. Otherwise unreference dst
205 * and replace it with a new reference to src.
206 *
207 * @param dst Pointer to either a valid buffer reference or NULL. On success,
208 * this will point to a buffer reference equivalent to src. On
209 * failure, dst will be left untouched.
210 * @param src A buffer reference to replace dst with. May be NULL, then this
211 * function is equivalent to av_buffer_unref(dst).
212 * @return 0 on success
213 * AVERROR(ENOMEM) on memory allocation failure.
214 */
215int av_buffer_replace(AVBufferRef **dst, const AVBufferRef *src);
216
217/**
218 * @}
219 */
220
221/**
222 * @defgroup lavu_bufferpool AVBufferPool
223 * @ingroup lavu_data
224 *
225 * @{
226 * AVBufferPool is an API for a lock-free thread-safe pool of AVBuffers.
227 *
228 * Frequently allocating and freeing large buffers may be slow. AVBufferPool is
229 * meant to solve this in cases when the caller needs a set of buffers of the
230 * same size (the most obvious use case being buffers for raw video or audio
231 * frames).
232 *
233 * At the beginning, the user must call av_buffer_pool_init() to create the
234 * buffer pool. Then whenever a buffer is needed, call av_buffer_pool_get() to
235 * get a reference to a new buffer, similar to av_buffer_alloc(). This new
236 * reference works in all aspects the same way as the one created by
237 * av_buffer_alloc(). However, when the last reference to this buffer is
238 * unreferenced, it is returned to the pool instead of being freed and will be
239 * reused for subsequent av_buffer_pool_get() calls.
240 *
241 * When the caller is done with the pool and no longer needs to allocate any new
242 * buffers, av_buffer_pool_uninit() must be called to mark the pool as freeable.
243 * Once all the buffers are released, it will automatically be freed.
244 *
245 * Allocating and releasing buffers with this API is thread-safe as long as
246 * either the default alloc callback is used, or the user-supplied one is
247 * thread-safe.
248 */
249
250/**
251 * The buffer pool. This structure is opaque and not meant to be accessed
252 * directly. It is allocated with av_buffer_pool_init() and freed with
253 * av_buffer_pool_uninit().
254 */
255typedef struct AVBufferPool AVBufferPool;
256
257/**
258 * Allocate and initialize a buffer pool.
259 *
260 * @param size size of each buffer in this pool
261 * @param alloc a function that will be used to allocate new buffers when the
262 * pool is empty. May be NULL, then the default allocator will be used
263 * (av_buffer_alloc()).
264 * @return newly created buffer pool on success, NULL on error.
265 */
266AVBufferPool *av_buffer_pool_init(size_t size, AVBufferRef* (*alloc)(size_t size));
267
268/**
269 * Allocate and initialize a buffer pool with a more complex allocator.
270 *
271 * @param size size of each buffer in this pool
272 * @param opaque arbitrary user data used by the allocator
273 * @param alloc a function that will be used to allocate new buffers when the
274 * pool is empty. May be NULL, then the default allocator will be
275 * used (av_buffer_alloc()).
276 * @param pool_free a function that will be called immediately before the pool
277 * is freed. I.e. after av_buffer_pool_uninit() is called
278 * by the caller and all the frames are returned to the pool
279 * and freed. It is intended to uninitialize the user opaque
280 * data. May be NULL.
281 * @return newly created buffer pool on success, NULL on error.
282 */
283AVBufferPool *av_buffer_pool_init2(size_t size, void *opaque,
284 AVBufferRef* (*alloc)(void *opaque, size_t size),
285 void (*pool_free)(void *opaque));
286
287/**
288 * Mark the pool as being available for freeing. It will actually be freed only
289 * once all the allocated buffers associated with the pool are released. Thus it
290 * is safe to call this function while some of the allocated buffers are still
291 * in use.
292 *
293 * @param pool pointer to the pool to be freed. It will be set to NULL.
294 */
295void av_buffer_pool_uninit(AVBufferPool **pool);
296
297/**
298 * Allocate a new AVBuffer, reusing an old buffer from the pool when available.
299 * This function may be called simultaneously from multiple threads.
300 *
301 * @return a reference to the new buffer on success, NULL on error.
302 */
303AVBufferRef *av_buffer_pool_get(AVBufferPool *pool);
304
305/**
306 * Query the original opaque parameter of an allocated buffer in the pool.
307 *
308 * @param ref a buffer reference to a buffer returned by av_buffer_pool_get.
309 * @return the opaque parameter set by the buffer allocator function of the
310 * buffer pool.
311 *
312 * @note the opaque parameter of ref is used by the buffer pool implementation,
313 * therefore you have to use this function to access the original opaque
314 * parameter of an allocated buffer.
315 */
316void *av_buffer_pool_buffer_get_opaque(const AVBufferRef *ref);
317
318/**
319 * @}
320 */
321
322#endif /* AVUTIL_BUFFER_H */
323