| 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 <stdint.h> |
| 29 | |
| 30 | /** |
| 31 | * @defgroup lavu_buffer AVBuffer |
| 32 | * @ingroup lavu_data |
| 33 | * |
| 34 | * @{ |
| 35 | * AVBuffer is an API for reference-counted data buffers. |
| 36 | * |
| 37 | * There are two core objects in this API -- AVBuffer and AVBufferRef. AVBuffer |
| 38 | * represents the data buffer itself; it is opaque and not meant to be accessed |
| 39 | * by the caller directly, but only through AVBufferRef. However, the caller may |
| 40 | * e.g. compare two AVBuffer pointers to check whether two different references |
| 41 | * are describing the same data buffer. AVBufferRef represents a single |
| 42 | * reference to an AVBuffer and it is the object that may be manipulated by the |
| 43 | * caller directly. |
| 44 | * |
| 45 | * There are two functions provided for creating a new AVBuffer with a single |
| 46 | * reference -- av_buffer_alloc() to just allocate a new buffer, and |
| 47 | * av_buffer_create() to wrap an existing array in an AVBuffer. From an existing |
| 48 | * reference, additional references may be created with av_buffer_ref(). |
| 49 | * Use av_buffer_unref() to free a reference (this will automatically free the |
| 50 | * data once all the references are freed). |
| 51 | * |
| 52 | * The convention throughout this API and the rest of FFmpeg is such that the |
| 53 | * buffer is considered writable if there exists only one reference to it (and |
| 54 | * it has not been marked as read-only). The av_buffer_is_writable() function is |
| 55 | * provided to check whether this is true and av_buffer_make_writable() will |
| 56 | * automatically create a new writable buffer when necessary. |
| 57 | * Of course nothing prevents the calling code from violating this convention, |
| 58 | * however that is safe only when all the existing references are under its |
| 59 | * control. |
| 60 | * |
| 61 | * @note Referencing and unreferencing the buffers is thread-safe and thus |
| 62 | * may be done from multiple threads simultaneously without any need for |
| 63 | * additional locking. |
| 64 | * |
| 65 | * @note Two different references to the same buffer can point to different |
| 66 | * parts of the buffer (i.e. their AVBufferRef.data will not be equal). |
| 67 | */ |
| 68 | |
| 69 | /** |
| 70 | * A reference counted buffer type. It is opaque and is meant to be used through |
| 71 | * references (AVBufferRef). |
| 72 | */ |
| 73 | typedef struct AVBuffer AVBuffer; |
| 74 | |
| 75 | /** |
| 76 | * A reference to a data buffer. |
| 77 | * |
| 78 | * The size of this struct is not a part of the public ABI and it is not meant |
| 79 | * to be allocated directly. |
| 80 | */ |
| 81 | typedef struct AVBufferRef { |
| 82 | AVBuffer *buffer; |
| 83 | |
| 84 | /** |
| 85 | * The data buffer. It is considered writable if and only if |
| 86 | * this is the only reference to the buffer, in which case |
| 87 | * av_buffer_is_writable() returns 1. |
| 88 | */ |
| 89 | uint8_t *data; |
| 90 | /** |
| 91 | * Size of data in bytes. |
| 92 | */ |
| 93 | int size; |
| 94 | } AVBufferRef; |
| 95 | |
| 96 | /** |
| 97 | * Allocate an AVBuffer of the given size using av_malloc(). |
| 98 | * |
| 99 | * @return an AVBufferRef of given size or NULL when out of memory |
| 100 | */ |
| 101 | AVBufferRef *av_buffer_alloc(int size); |
| 102 | |
| 103 | /** |
| 104 | * Same as av_buffer_alloc(), except the returned buffer will be initialized |
| 105 | * to zero. |
| 106 | */ |
| 107 | AVBufferRef *av_buffer_allocz(int size); |
| 108 | |
| 109 | /** |
| 110 | * Always treat the buffer as read-only, even when it has only one |
| 111 | * reference. |
| 112 | */ |
| 113 | #define AV_BUFFER_FLAG_READONLY (1 << 0) |
| 114 | |
| 115 | /** |
| 116 | * Create an AVBuffer from an existing array. |
| 117 | * |
| 118 | * If this function is successful, data is owned by the AVBuffer. The caller may |
| 119 | * only access data through the returned AVBufferRef and references derived from |
| 120 | * it. |
| 121 | * If this function fails, data is left untouched. |
| 122 | * @param data data array |
| 123 | * @param size size of data in bytes |
| 124 | * @param free a callback for freeing this buffer's data |
| 125 | * @param opaque parameter to be got for processing or passed to free |
| 126 | * @param flags a combination of AV_BUFFER_FLAG_* |
| 127 | * |
| 128 | * @return an AVBufferRef referring to data on success, NULL on failure. |
| 129 | */ |
| 130 | AVBufferRef *av_buffer_create(uint8_t *data, int size, |
| 131 | void (*free)(void *opaque, uint8_t *data), |
| 132 | void *opaque, int flags); |
| 133 | |
| 134 | /** |
| 135 | * Default free callback, which calls av_free() on the buffer data. |
| 136 | * This function is meant to be passed to av_buffer_create(), not called |
| 137 | * directly. |
| 138 | */ |
| 139 | void av_buffer_default_free(void *opaque, uint8_t *data); |
| 140 | |
| 141 | /** |
| 142 | * Create a new reference to an AVBuffer. |
| 143 | * |
| 144 | * @return a new AVBufferRef referring to the same AVBuffer as buf or NULL on |
| 145 | * failure. |
| 146 | */ |
| 147 | AVBufferRef *av_buffer_ref(AVBufferRef *buf); |
| 148 | |
| 149 | /** |
| 150 | * Free a given reference and automatically free the buffer if there are no more |
| 151 | * references to it. |
| 152 | * |
| 153 | * @param buf the reference to be freed. The pointer is set to NULL on return. |
| 154 | */ |
| 155 | void av_buffer_unref(AVBufferRef **buf); |
| 156 | |
| 157 | /** |
| 158 | * @return 1 if the caller may write to the data referred to by buf (which is |
| 159 | * true if and only if buf is the only reference to the underlying AVBuffer). |
| 160 | * Return 0 otherwise. |
| 161 | * A positive answer is valid until av_buffer_ref() is called on buf. |
| 162 | */ |
| 163 | int av_buffer_is_writable(const AVBufferRef *buf); |
| 164 | |
| 165 | /** |
| 166 | * @return the opaque parameter set by av_buffer_create. |
| 167 | */ |
| 168 | void *av_buffer_get_opaque(const AVBufferRef *buf); |
| 169 | |
| 170 | int av_buffer_get_ref_count(const AVBufferRef *buf); |
| 171 | |
| 172 | /** |
| 173 | * Create a writable reference from a given buffer reference, avoiding data copy |
| 174 | * if possible. |
| 175 | * |
| 176 | * @param buf buffer reference to make writable. On success, buf is either left |
| 177 | * untouched, or it is unreferenced and a new writable AVBufferRef is |
| 178 | * written in its place. On failure, buf is left untouched. |
| 179 | * @return 0 on success, a negative AVERROR on failure. |
| 180 | */ |
| 181 | int av_buffer_make_writable(AVBufferRef **buf); |
| 182 | |
| 183 | /** |
| 184 | * Reallocate a given buffer. |
| 185 | * |
| 186 | * @param buf a buffer reference to reallocate. On success, buf will be |
| 187 | * unreferenced and a new reference with the required size will be |
| 188 | * written in its place. On failure buf will be left untouched. *buf |
| 189 | * may be NULL, then a new buffer is allocated. |
| 190 | * @param size required new buffer size. |
| 191 | * @return 0 on success, a negative AVERROR on failure. |
| 192 | * |
| 193 | * @note the buffer is actually reallocated with av_realloc() only if it was |
| 194 | * initially allocated through av_buffer_realloc(NULL) and there is only one |
| 195 | * reference to it (i.e. the one passed to this function). In all other cases |
| 196 | * a new buffer is allocated and the data is copied. |
| 197 | */ |
| 198 | int av_buffer_realloc(AVBufferRef **buf, int size); |
| 199 | |
| 200 | /** |
| 201 | * @} |
| 202 | */ |
| 203 | |
| 204 | /** |
| 205 | * @defgroup lavu_bufferpool AVBufferPool |
| 206 | * @ingroup lavu_data |
| 207 | * |
| 208 | * @{ |
| 209 | * AVBufferPool is an API for a lock-free thread-safe pool of AVBuffers. |
| 210 | * |
| 211 | * Frequently allocating and freeing large buffers may be slow. AVBufferPool is |
| 212 | * meant to solve this in cases when the caller needs a set of buffers of the |
| 213 | * same size (the most obvious use case being buffers for raw video or audio |
| 214 | * frames). |
| 215 | * |
| 216 | * At the beginning, the user must call av_buffer_pool_init() to create the |
| 217 | * buffer pool. Then whenever a buffer is needed, call av_buffer_pool_get() to |
| 218 | * get a reference to a new buffer, similar to av_buffer_alloc(). This new |
| 219 | * reference works in all aspects the same way as the one created by |
| 220 | * av_buffer_alloc(). However, when the last reference to this buffer is |
| 221 | * unreferenced, it is returned to the pool instead of being freed and will be |
| 222 | * reused for subsequent av_buffer_pool_get() calls. |
| 223 | * |
| 224 | * When the caller is done with the pool and no longer needs to allocate any new |
| 225 | * buffers, av_buffer_pool_uninit() must be called to mark the pool as freeable. |
| 226 | * Once all the buffers are released, it will automatically be freed. |
| 227 | * |
| 228 | * Allocating and releasing buffers with this API is thread-safe as long as |
| 229 | * either the default alloc callback is used, or the user-supplied one is |
| 230 | * thread-safe. |
| 231 | */ |
| 232 | |
| 233 | /** |
| 234 | * The buffer pool. This structure is opaque and not meant to be accessed |
| 235 | * directly. It is allocated with av_buffer_pool_init() and freed with |
| 236 | * av_buffer_pool_uninit(). |
| 237 | */ |
| 238 | typedef struct AVBufferPool AVBufferPool; |
| 239 | |
| 240 | /** |
| 241 | * Allocate and initialize a buffer pool. |
| 242 | * |
| 243 | * @param size size of each buffer in this pool |
| 244 | * @param alloc a function that will be used to allocate new buffers when the |
| 245 | * pool is empty. May be NULL, then the default allocator will be used |
| 246 | * (av_buffer_alloc()). |
| 247 | * @return newly created buffer pool on success, NULL on error. |
| 248 | */ |
| 249 | AVBufferPool *av_buffer_pool_init(int size, AVBufferRef* (*alloc)(int size)); |
| 250 | |
| 251 | /** |
| 252 | * Mark the pool as being available for freeing. It will actually be freed only |
| 253 | * once all the allocated buffers associated with the pool are released. Thus it |
| 254 | * is safe to call this function while some of the allocated buffers are still |
| 255 | * in use. |
| 256 | * |
| 257 | * @param pool pointer to the pool to be freed. It will be set to NULL. |
| 258 | * @see av_buffer_pool_can_uninit() |
| 259 | */ |
| 260 | void av_buffer_pool_uninit(AVBufferPool **pool); |
| 261 | |
| 262 | /** |
| 263 | * Allocate a new AVBuffer, reusing an old buffer from the pool when available. |
| 264 | * This function may be called simultaneously from multiple threads. |
| 265 | * |
| 266 | * @return a reference to the new buffer on success, NULL on error. |
| 267 | */ |
| 268 | AVBufferRef *av_buffer_pool_get(AVBufferPool *pool); |
| 269 | |
| 270 | /** |
| 271 | * @} |
| 272 | */ |
| 273 | |
| 274 | #endif /* AVUTIL_BUFFER_H */ |