mirror of
https://github.com/FFmpeg/FFmpeg.git
synced 2024-12-23 12:43:46 +02:00
lavu: add a new API for reference-counted data buffers.
This commit is contained in:
Anton Khirnov
parent
65f1d45dcc
commit
8e401dbe90
@ -11,6 +11,7 @@ HEADERS = adler32.h \
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base64.h \
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blowfish.h \
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bswap.h \
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buffer.h \
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channel_layout.h \
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common.h \
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cpu.h \
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@ -59,6 +60,7 @@ OBJS = adler32.o \
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avstring.o \
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base64.o \
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blowfish.o \
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buffer.o \
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channel_layout.o \
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cpu.o \
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crc.o \
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194
libavutil/buffer.c
Normal file
194
libavutil/buffer.c
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@ -0,0 +1,194 @@
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/*
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* This file is part of Libav.
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*
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* Libav 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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* Libav 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 Libav; 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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#include <stdint.h>
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#include <string.h>
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#include "atomic.h"
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#include "buffer_internal.h"
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#include "common.h"
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#include "mem.h"
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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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AVBufferRef *ref = NULL;
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AVBuffer *buf = NULL;
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buf = av_mallocz(sizeof(*buf));
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if (!buf)
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return NULL;
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buf->data = data;
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buf->size = size;
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buf->free = free ? free : av_buffer_default_free;
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buf->opaque = opaque;
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buf->refcount = 1;
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if (flags & AV_BUFFER_FLAG_READONLY)
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buf->flags |= BUFFER_FLAG_READONLY;
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ref = av_mallocz(sizeof(*ref));
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if (!ref) {
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av_freep(&buf);
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return NULL;
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}
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ref->buffer = buf;
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ref->data = data;
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ref->size = size;
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return ref;
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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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av_free(data);
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}
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AVBufferRef *av_buffer_alloc(int size)
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{
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AVBufferRef *ret = NULL;
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uint8_t *data = NULL;
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data = av_malloc(size);
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if (!data)
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return NULL;
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ret = av_buffer_create(data, size, av_buffer_default_free, NULL, 0);
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if (!ret)
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av_freep(&data);
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return ret;
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}
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AVBufferRef *av_buffer_allocz(int size)
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{
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AVBufferRef *ret = av_buffer_alloc(size);
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if (!ret)
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return NULL;
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memset(ret->data, 0, size);
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return ret;
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}
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AVBufferRef *av_buffer_ref(AVBufferRef *buf)
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{
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AVBufferRef *ret = av_mallocz(sizeof(*ret));
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if (!ret)
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return NULL;
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*ret = *buf;
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avpriv_atomic_int_add_and_fetch(&buf->buffer->refcount, 1);
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return ret;
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}
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void av_buffer_unref(AVBufferRef **buf)
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{
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AVBuffer *b;
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if (!buf || !*buf)
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return;
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b = (*buf)->buffer;
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av_freep(buf);
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if (!avpriv_atomic_int_add_and_fetch(&b->refcount, -1)) {
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b->free(b->opaque, b->data);
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av_freep(&b);
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}
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}
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int av_buffer_is_writable(const AVBufferRef *buf)
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{
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if (buf->buffer->flags & AV_BUFFER_FLAG_READONLY)
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return 0;
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return avpriv_atomic_int_add_and_fetch(&buf->buffer->refcount, 0) == 1;
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}
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int av_buffer_make_writable(AVBufferRef **pbuf)
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{
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AVBufferRef *newbuf, *buf = *pbuf;
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if (av_buffer_is_writable(buf))
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return 0;
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newbuf = av_buffer_alloc(buf->size);
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if (!newbuf)
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return AVERROR(ENOMEM);
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memcpy(newbuf->data, buf->data, buf->size);
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av_buffer_unref(pbuf);
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*pbuf = newbuf;
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return 0;
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}
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int av_buffer_realloc(AVBufferRef **pbuf, int size)
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{
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AVBufferRef *buf = *pbuf;
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uint8_t *tmp;
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if (!buf) {
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/* allocate a new buffer with av_realloc(), so it will be reallocatable
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* later */
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uint8_t *data = av_realloc(NULL, size);
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if (!data)
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return AVERROR(ENOMEM);
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buf = av_buffer_create(data, size, av_buffer_default_free, NULL, 0);
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if (!buf) {
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av_freep(&data);
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return AVERROR(ENOMEM);
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}
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buf->buffer->flags |= BUFFER_FLAG_REALLOCATABLE;
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*pbuf = buf;
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return 0;
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} else if (buf->size == size)
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return 0;
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if (!(buf->buffer->flags & BUFFER_FLAG_REALLOCATABLE) ||
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!av_buffer_is_writable(buf)) {
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/* cannot realloc, allocate a new reallocable buffer and copy data */
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AVBufferRef *new = NULL;
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av_buffer_realloc(&new, size);
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if (!new)
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return AVERROR(ENOMEM);
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memcpy(new->data, buf->data, FFMIN(size, buf->size));
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av_buffer_unref(pbuf);
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*pbuf = new;
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return 0;
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}
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tmp = av_realloc(buf->buffer->data, size);
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if (!tmp)
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return AVERROR(ENOMEM);
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buf->buffer->data = buf->data = tmp;
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buf->buffer->size = buf->size = size;
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return 0;
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}
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197
libavutil/buffer.h
Normal file
197
libavutil/buffer.h
Normal file
@ -0,0 +1,197 @@
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/*
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* This file is part of Libav.
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*
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* Libav 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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* Libav 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 Libav; 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 Libav 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 data
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* @param opaque parameter to be 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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* 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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#endif /* AVUTIL_BUFFER_H */
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60
libavutil/buffer_internal.h
Normal file
60
libavutil/buffer_internal.h
Normal file
@ -0,0 +1,60 @@
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/*
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* This file is part of Libav.
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*
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* Libav 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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* Libav 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
|
||||
* License along with Libav; 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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#ifndef AVUTIL_BUFFER_INTERNAL_H
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#define AVUTIL_BUFFER_INTERNAL_H
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#include <stdint.h>
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#include "buffer.h"
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/**
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* The buffer is always treated as read-only.
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*/
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#define BUFFER_FLAG_READONLY (1 << 0)
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/**
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* The buffer was av_realloc()ed, so it is reallocatable.
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*/
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#define BUFFER_FLAG_REALLOCATABLE (1 << 1)
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struct AVBuffer {
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uint8_t *data; /**< data described by this buffer */
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int size; /**< size of data in bytes */
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/**
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* number of existing AVBufferRef instances referring to this buffer
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*/
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volatile int refcount;
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/**
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* a callback for freeing the data
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*/
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void (*free)(void *opaque, uint8_t *data);
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/**
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* an opaque pointer, to be used by the freeing callback
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*/
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void *opaque;
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/**
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* A combination of BUFFER_FLAG_*
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*/
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int flags;
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};
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#endif /* AVUTIL_BUFFER_INTERNAL_H */
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