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