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2e956d9c0f
This can be useful in other places, e.g. it can replace objpool in fftools. The API is modified in the following nontrivial ways: * opaque pointers can be passed through to all user callbacks * read and write were previously separate callbacks in order to accomodate the caller wishing to write a new reference to the FIFO and keep the original one; the two callbacks are now merged into one, and a flags argument is added that allows to request such behaviour on a per-call basis * new peek and drain functions
131 lines
4.7 KiB
C
131 lines
4.7 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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#ifndef AVUTIL_CONTAINER_FIFO_H
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#define AVUTIL_CONTAINER_FIFO_H
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#include <stddef.h>
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/**
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* AVContainerFifo is a FIFO for "containers" - dynamically allocated reusable
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* structs (e.g. AVFrame or AVPacket). AVContainerFifo uses an internal pool of
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* such containers to avoid allocating and freeing them repeatedly.
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*/
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typedef struct AVContainerFifo AVContainerFifo;
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enum AVContainerFifoFlags {
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/**
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* Signal to av_container_fifo_write() that it should make a new reference
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* to data in src rather than consume its contents.
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*
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* @note you must handle this flag manually in your own fifo_transfer()
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* callback
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*/
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AV_CONTAINER_FIFO_FLAG_REF = (1 << 0),
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/**
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* This and all higher bits in flags may be set to any value by the caller
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* and are guaranteed to be passed through to the fifo_transfer() callback
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* and not be interpreted by AVContainerFifo code.
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*/
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AV_CONTAINER_FIFO_FLAG_USER = (1 << 16),
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};
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/**
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* Allocate a new AVContainerFifo for the container type defined by provided
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* callbacks.
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*
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* @param opaque user data that will be passed to the callbacks provided to this
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* function
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* @param container_alloc allocate a new container instance and return a pointer
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* to it, or NULL on failure
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* @param container_reset reset the provided container instance to a clean state
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* @param container_free free the provided container instance
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* @param fifo_transfer Transfer the contents of container src to dst.
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* @param flags currently unused
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*
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* @return newly allocated AVContainerFifo, or NULL on failure
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*/
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AVContainerFifo*
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av_container_fifo_alloc(void *opaque,
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void* (*container_alloc)(void *opaque),
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void (*container_reset)(void *opaque, void *obj),
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void (*container_free) (void *opaque, void *obj),
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int (*fifo_transfer) (void *opaque, void *dst, void *src, unsigned flags),
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unsigned flags);
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/**
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* Allocate an AVContainerFifo instance for AVFrames.
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*
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* @param flags currently unused
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*/
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AVContainerFifo *av_container_fifo_alloc_avframe(unsigned flags);
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/**
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* Free a AVContainerFifo and everything in it.
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*/
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void av_container_fifo_free(AVContainerFifo **cf);
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/**
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* Write the contents of obj to the FIFO.
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*
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* The fifo_transfer() callback previously provided to av_container_fifo_alloc()
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* will be called with obj as src in order to perform the actual transfer.
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*/
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int av_container_fifo_write(AVContainerFifo *cf, void *obj, unsigned flags);
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/**
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* Read the next available object from the FIFO into obj.
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*
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* The fifo_read() callback previously provided to av_container_fifo_alloc()
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* will be called with obj as dst in order to perform the actual transfer.
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*/
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int av_container_fifo_read(AVContainerFifo *cf, void *obj, unsigned flags);
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/**
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* Access objects stored in the FIFO without retrieving them. The
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* fifo_transfer() callback will NOT be invoked and the FIFO state will not be
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* modified.
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*
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* @param pobj Pointer to the object stored in the FIFO will be written here on
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* success. The object remains owned by the FIFO and the caller may
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* only access it as long as the FIFO is not modified.
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* @param offset Position of the object to retrieve - 0 is the next item that
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* would be read, 1 the one after, etc. Must be smaller than
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* av_container_fifo_can_read().
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*
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* @retval 0 success, a pointer was written into pobj
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* @retval AVERROR(EINVAL) invalid offset value
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*/
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int av_container_fifo_peek(AVContainerFifo *cf, void **pobj, size_t offset);
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/**
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* Discard the specified number of elements from the FIFO.
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*
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* @param nb_elems number of elements to discard, MUST NOT be larger than
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* av_fifo_can_read(f)
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*/
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void av_container_fifo_drain(AVContainerFifo *cf, size_t nb_elems);
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/**
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* @return number of objects available for reading
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*/
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size_t av_container_fifo_can_read(const AVContainerFifo *cf);
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#endif // AVCODEC_CONTAINER_FIFO_H
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