duckstation

buffer.h (11998B)

---

 /*
  * 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 <stddef.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.
      */
     size_t   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(size_t size);
 
 /**
  * Same as av_buffer_alloc(), except the returned buffer will be initialized
  * to zero.
  */
 AVBufferRef *av_buffer_allocz(size_t 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, size_t 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(const 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, size_t size);
 
 /**
  * Ensure dst refers to the same data as src.
  *
  * When *dst is already equivalent to src, do nothing. Otherwise unreference dst
  * and replace it with a new reference to src.
  *
  * @param dst Pointer to either a valid buffer reference or NULL. On success,
  *            this will point to a buffer reference equivalent to src. On
  *            failure, dst will be left untouched.
  * @param src A buffer reference to replace dst with. May be NULL, then this
  *            function is equivalent to av_buffer_unref(dst).
  * @return 0 on success
  *         AVERROR(ENOMEM) on memory allocation failure.
  */
 int av_buffer_replace(AVBufferRef **dst, const AVBufferRef *src);
 
 /**
  * @}
  */
 
 /**
  * @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(size_t size, AVBufferRef* (*alloc)(size_t 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. May be NULL, then the default allocator will be
  *              used (av_buffer_alloc()).
  * @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. May be NULL.
  * @return newly created buffer pool on success, NULL on error.
  */
 AVBufferPool *av_buffer_pool_init2(size_t size, void *opaque,
                                    AVBufferRef* (*alloc)(void *opaque, size_t 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);
 
 /**
  * Query the original opaque parameter of an allocated buffer in the pool.
  *
  * @param ref a buffer reference to a buffer returned by av_buffer_pool_get.
  * @return the opaque parameter set by the buffer allocator function of the
  *         buffer pool.
  *
  * @note the opaque parameter of ref is used by the buffer pool implementation,
  * therefore you have to use this function to access the original opaque
  * parameter of an allocated buffer.
  */
 void *av_buffer_pool_buffer_get_opaque(const AVBufferRef *ref);
 
 /**
  * @}
  */
 
 #endif /* AVUTIL_BUFFER_H */