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 { 85 AVBuffer *buffer; 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 #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 109 AVBufferRef *av_buffer_alloc(int size); 110 #else 111 AVBufferRef *av_buffer_alloc(size_t size); 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 119 AVBufferRef *av_buffer_allocz(int size); 120 #else 121 AVBufferRef *av_buffer_allocz(size_t size); 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 146 AVBufferRef *av_buffer_create(uint8_t *data, int size, 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 */ 166 AVBufferRef *av_buffer_ref(AVBufferRef *buf); 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 */ 200 int av_buffer_make_writable(AVBufferRef **buf); 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 */ 237 int av_buffer_replace(AVBufferRef **dst, AVBufferRef *src); 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 */ 326 void av_buffer_pool_uninit(AVBufferPool **pool); 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 */ 334 AVBufferRef *av_buffer_pool_get(AVBufferPool *pool); 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 */ 347 void *av_buffer_pool_buffer_get_opaque(AVBufferRef *ref); 348 349 /** 350 * @} 351 */ 352 353 #endif /* AVUTIL_BUFFER_H */ 354