/* * This file is part of FFmpeg. * * FFmpeg is free software; you can redistribute it and/or * modify it under the terms of the GNU Lesser General Public * License as published by the Free Software Foundation; either * version 2.1 of the License, or (at your option) any later version. * * FFmpeg is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU * Lesser General Public License for more details. * * You should have received a copy of the GNU Lesser General Public * License along with FFmpeg; if not, write to the Free Software * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA */ /** * @file * @ingroup lavu_buffer * refcounted data buffer API */ #ifndef AVUTIL_BUFFER_H#define AVUTIL_BUFFER_H #include <stdint.h> /** * @defgroup lavu_buffer AVBuffer * @ingroup lavu_data * * @{ * AVBuffer is an API for reference-counted data buffers. * * There are two core objects in this API -- AVBuffer and AVBufferRef. AVBuffer * represents the data buffer itself; it is opaque and not meant to be accessed * by the caller directly, but only through AVBufferRef. However, the caller may * e.g. compare two AVBuffer pointers to check whether two different references * are describing the same data buffer. AVBufferRef represents a single * reference to an AVBuffer and it is the object that may be manipulated by the * caller directly. * * There are two functions provided for creating a new AVBuffer with a single * reference -- av_buffer_alloc() to just allocate a new buffer, and * av_buffer_create() to wrap an existing array in an AVBuffer. From an existing * reference, additional references may be created with av_buffer_ref(). * Use av_buffer_unref() to free a reference (this will automatically free the * data once all the references are freed). * * The convention throughout this API and the rest of FFmpeg is such that the * buffer is considered writable if there exists only one reference to it (and * it has not been marked as read-only). The av_buffer_is_writable() function is * provided to check whether this is true and av_buffer_make_writable() will * automatically create a new writable buffer when necessary. * Of course nothing prevents the calling code from violating this convention, * however that is safe only when all the existing references are under its * control. * * @note Referencing and unreferencing the buffers is thread-safe and thus * may be done from multiple threads simultaneously without any need for * additional locking. * * @note Two different references to the same buffer can point to different * parts of the buffer (i.e. their AVBufferRef.data will not be equal). */ /** * A reference counted buffer type. It is opaque and is meant to be used through * references (AVBufferRef). */typedef struct AVBuffer AVBuffer; /** * A reference to a data buffer. * * The size of this struct is not a part of the public ABI and it is not meant * to be allocated directly. */typedef struct AVBufferRef {    AVBuffer *buffer;     /**     * The data buffer. It is considered writable if and only if     * this is the only reference to the buffer, in which case     * av_buffer_is_writable() returns 1.     */    uint8_t *data;    /**     * Size of data in bytes.     */    int      size;} AVBufferRef; /** * Allocate an AVBuffer of the given size using av_malloc(). * * @return an AVBufferRef of given size or NULL when out of memory */AVBufferRef *av_buffer_alloc(int size); /** * Same as av_buffer_alloc(), except the returned buffer will be initialized * to zero. */AVBufferRef *av_buffer_allocz(int size); /** * Always treat the buffer as read-only, even when it has only one * reference. */#define AV_BUFFER_FLAG_READONLY (1 << 0) /** * Create an AVBuffer from an existing array. * * If this function is successful, data is owned by the AVBuffer. The caller may * only access data through the returned AVBufferRef and references derived from * it. * If this function fails, data is left untouched. * @param data   data array * @param size   size of data in bytes * @param free   a callback for freeing this buffer's data * @param opaque parameter to be got for processing or passed to free * @param flags  a combination of AV_BUFFER_FLAG_* * * @return an AVBufferRef referring to data on success, NULL on failure. */AVBufferRef *av_buffer_create(uint8_t *data, int size,                              void (*free)(void *opaque, uint8_t *data),                              void *opaque, int flags); /** * Default free callback, which calls av_free() on the buffer data. * This function is meant to be passed to av_buffer_create(), not called * directly. */void av_buffer_default_free(void *opaque, uint8_t *data); /** * Create a new reference to an AVBuffer. * * @return a new AVBufferRef referring to the same AVBuffer as buf or NULL on * failure. */AVBufferRef *av_buffer_ref(AVBufferRef *buf); /** * Free a given reference and automatically free the buffer if there are no more * references to it. * * @param buf the reference to be freed. The pointer is set to NULL on return. */void av_buffer_unref(AVBufferRef **buf); /** * @return 1 if the caller may write to the data referred to by buf (which is * true if and only if buf is the only reference to the underlying AVBuffer). * Return 0 otherwise. * A positive answer is valid until av_buffer_ref() is called on buf. */int av_buffer_is_writable(const AVBufferRef *buf); /** * @return the opaque parameter set by av_buffer_create. */void *av_buffer_get_opaque(const AVBufferRef *buf); int av_buffer_get_ref_count(const AVBufferRef *buf); /** * Create a writable reference from a given buffer reference, avoiding data copy * if possible. * * @param buf buffer reference to make writable. On success, buf is either left *            untouched, or it is unreferenced and a new writable AVBufferRef is *            written in its place. On failure, buf is left untouched. * @return 0 on success, a negative AVERROR on failure. */int av_buffer_make_writable(AVBufferRef **buf); /** * Reallocate a given buffer. * * @param buf  a buffer reference to reallocate. On success, buf will be *             unreferenced and a new reference with the required size will be *             written in its place. On failure buf will be left untouched. *buf *             may be NULL, then a new buffer is allocated. * @param size required new buffer size. * @return 0 on success, a negative AVERROR on failure. * * @note the buffer is actually reallocated with av_realloc() only if it was * initially allocated through av_buffer_realloc(NULL) and there is only one * reference to it (i.e. the one passed to this function). In all other cases * a new buffer is allocated and the data is copied. */int av_buffer_realloc(AVBufferRef **buf, int size); /** * @} */ /** * @defgroup lavu_bufferpool AVBufferPool * @ingroup lavu_data * * @{ * AVBufferPool is an API for a lock-free thread-safe pool of AVBuffers. * * Frequently allocating and freeing large buffers may be slow. AVBufferPool is * meant to solve this in cases when the caller needs a set of buffers of the * same size (the most obvious use case being buffers for raw video or audio * frames). * * At the beginning, the user must call av_buffer_pool_init() to create the * buffer pool. Then whenever a buffer is needed, call av_buffer_pool_get() to * get a reference to a new buffer, similar to av_buffer_alloc(). This new * reference works in all aspects the same way as the one created by * av_buffer_alloc(). However, when the last reference to this buffer is * unreferenced, it is returned to the pool instead of being freed and will be * reused for subsequent av_buffer_pool_get() calls. * * When the caller is done with the pool and no longer needs to allocate any new * buffers, av_buffer_pool_uninit() must be called to mark the pool as freeable. * Once all the buffers are released, it will automatically be freed. * * Allocating and releasing buffers with this API is thread-safe as long as * either the default alloc callback is used, or the user-supplied one is * thread-safe. */ /** * The buffer pool. This structure is opaque and not meant to be accessed * directly. It is allocated with av_buffer_pool_init() and freed with * av_buffer_pool_uninit(). */typedef struct AVBufferPool AVBufferPool; /** * Allocate and initialize a buffer pool. * * @param size size of each buffer in this pool * @param alloc a function that will be used to allocate new buffers when the * pool is empty. May be NULL, then the default allocator will be used * (av_buffer_alloc()). * @return newly created buffer pool on success, NULL on error. */AVBufferPool *av_buffer_pool_init(int size, AVBufferRef* (*alloc)(int size)); /** * Allocate and initialize a buffer pool with a more complex allocator. * * @param size size of each buffer in this pool * @param opaque arbitrary user data used by the allocator * @param alloc a function that will be used to allocate new buffers when the *              pool is empty. * @param pool_free a function that will be called immediately before the pool *                  is freed. I.e. after av_buffer_pool_uninit() is called *                  by the caller and all the frames are returned to the pool *                  and freed. It is intended to uninitialize the user opaque *                  data. * @return newly created buffer pool on success, NULL on error. */AVBufferPool *av_buffer_pool_init2(int size, void *opaque,                                   AVBufferRef* (*alloc)(void *opaque, int size),                                   void (*pool_free)(void *opaque)); /** * Mark the pool as being available for freeing. It will actually be freed only * once all the allocated buffers associated with the pool are released. Thus it * is safe to call this function while some of the allocated buffers are still * in use. * * @param pool pointer to the pool to be freed. It will be set to NULL. */void av_buffer_pool_uninit(AVBufferPool **pool); /** * Allocate a new AVBuffer, reusing an old buffer from the pool when available. * This function may be called simultaneously from multiple threads. * * @return a reference to the new buffer on success, NULL on error. */AVBufferRef *av_buffer_pool_get(AVBufferPool *pool); /** * @} */ #endif /* AVUTIL_BUFFER_H */