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/*

 * 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 

/**

 * @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));

/**

 * 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.

 * @see av_buffer_pool_can_uninit()

 */

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 */