Anton Khirnov:
> It provides a FIFO for "container" objects like AVFrame/AVPacket and
> features an integrated FFRefStructPool-based pool to avoid allocating an
> freeing them repeatedly.
> ---
> libavcodec/container_fifo.c | 195 ++++++++++++++++++++++++++++++++++++
> libavcodec/container_fifo.h | 87 ++++++++++++++++
> 2 files changed, 282 insertions(+)
> create mode 100644 libavcodec/container_fifo.c
> create mode 100644 libavcodec/container_fifo.h
>
> diff --git a/libavcodec/container_fifo.c b/libavcodec/container_fifo.c
> new file mode 100644
> index 0000000000..86ed15627b
> --- /dev/null
> +++ b/libavcodec/container_fifo.c
> @@ -0,0 +1,195 @@
> +/*
> + * 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
> + */
> +
> +#include "libavutil/error.h"
> +#include "libavutil/fifo.h"
> +#include "libavutil/frame.h"
> +#include "libavutil/mem.h"
> +
> +#include "container_fifo.h"
> +#include "refstruct.h"
> +
> +struct ContainerFifo {
> + AVFifo *fifo;
> + FFRefStructPool *pool;
> +
> + void* (*container_alloc)(void);
> + void (*container_reset)(void *obj);
> + void (*container_free) (void *obj);
> + int (*fifo_write) (void *dst, void *src);
> + int (*fifo_read) (void *dst, void *src);
> +
> +};
> +
> +static int container_fifo_init_entry(FFRefStructOpaque opaque, void *obj)
> +{
> + ContainerFifo *cf = opaque.nc;
> + void **pobj = obj;
> +
> + *pobj = cf->container_alloc();
> + if (!*pobj)
> + return AVERROR(ENOMEM);
> +
> + return 0;
> +}
> +
> +static void container_fifo_reset_entry(FFRefStructOpaque opaque, void *obj)
> +{
> + ContainerFifo *cf = opaque.nc;
> + cf->container_reset(*(void**)obj);
> +}
> +
> +static void container_fifo_free_entry(FFRefStructOpaque opaque, void *obj)
> +{
> + ContainerFifo *cf = opaque.nc;
> + cf->container_free(*(void**)obj);
> +}
container_fifo_(init|reset|free)_entry seem unnecessary if you simply
expected the user to already provide a RefStruct-compatible callback.
> +
> +ContainerFifo*
> +ff_container_fifo_alloc(void* (*container_alloc)(void),
> + void (*container_reset)(void *obj),
> + void (*container_free) (void *obj),
> + int (*fifo_write) (void *dst, void *src),
> + int (*fifo_read) (void *dst, void *src))
> +{
> + ContainerFifo *cf;
> +
> + cf = av_mallocz(sizeof(*cf));
> + if (!cf)
> + return NULL;
> +
> + cf->container_alloc = container_alloc;
> + cf->container_reset = container_reset;
> + cf->container_free = container_free;
> + cf->fifo_write = fifo_write;
> + cf->fifo_read = fifo_read;
> +
> + cf->fifo = av_fifo_alloc2(1, sizeof(void*), AV_FIFO_FLAG_AUTO_GROW);
> + if (!cf->fifo)
> + goto fail;
> +
> + cf->pool = ff_refstruct_pool_alloc_ext(sizeof(void*), 0, cf,
> + container_fifo_init_entry,
> + container_fifo_reset_entry,
> + container_fifo_free_entry,
> + NULL);
> + if (!cf->pool)
> + goto fail;
> +
> + return cf;
> +fail:
> + ff_container_fifo_free(&cf);
> + return NULL;
> +}
> +
> +void ff_container_fifo_free(ContainerFifo **pcf)
> +{
> + ContainerFifo *cf;
> +
> + if (!*pcf)
> + return;
> +
> + cf = *pcf;
> +
> + if (cf->fifo) {
> + void *obj;
> + while (av_fifo_read(cf->fifo, &obj, 1) >= 0)
> + ff_refstruct_unref(&obj);
> + av_fifo_freep2(&cf->fifo);
> + }
> +
> + ff_refstruct_pool_uninit(&cf->pool);
> +
> + av_freep(pcf);
> +}
> +
> +int ff_container_fifo_read(ContainerFifo *cf, void *obj)
> +{
> + void **psrc;
> + int ret;
> +
> + ret = av_fifo_read(cf->fifo, &psrc, 1);
> + if (ret < 0)
> + return ret;
> +
> + ret = cf->fifo_read(obj, *psrc);
> + ff_refstruct_unref(&psrc);
> +
> + return ret;
> +}
> +
> +int ff_container_fifo_write(ContainerFifo *cf, void *obj)
> +{
> + void **pdst;
> + int ret;
> +
> + pdst = ff_refstruct_pool_get(cf->pool);
> + if (!pdst)
> + return AVERROR(ENOMEM);
> +
> + ret = cf->fifo_write(*pdst, obj);
This API design presumes that one never one to "move" an object into the
fifo. This need not be true at all (indeed, the reference from the
frame_grain frame could be directly moved; it is not used for the
decoding process).
> + if (ret < 0)
> + goto fail;
> +
> + ret = av_fifo_write(cf->fifo, &pdst, 1);
> + if (ret < 0)
> + goto fail;
> +
> + return 0;
> +fail:
> + ff_refstruct_unref(&pdst);
> + return ret;
> +}
> +
> +size_t ff_container_fifo_can_read(ContainerFifo *cf)
> +{
> + return av_fifo_can_read(cf->fifo);
> +}
> +
> +static void* frame_alloc(void)
Inconsistent placement of *
> +{
> + return av_frame_alloc();
> +}
> +
> +static void frame_reset(void *obj)
> +{
> + av_frame_unref(obj);
> +}
> +
> +static void frame_free(void *obj)
> +{
> + AVFrame *frame = obj;
> + av_frame_free(&frame);
> +}
> +
> +static int frame_ref(void *dst, void *src)
> +{
> + return av_frame_ref(dst, src);
> +}
> +
> +static int frame_move_ref(void *dst, void *src)
> +{
> + av_frame_move_ref(dst, src);
> + return 0;
> +}
> +
> +ContainerFifo *ff_container_fifo_alloc_avframe(unsigned flags)
> +{
> + return ff_container_fifo_alloc(frame_alloc, frame_reset, frame_free,
> + frame_ref, frame_move_ref);
> +}
> diff --git a/libavcodec/container_fifo.h b/libavcodec/container_fifo.h
> new file mode 100644
> index 0000000000..75a8f9e86b
> --- /dev/null
> +++ b/libavcodec/container_fifo.h
> @@ -0,0 +1,87 @@
> +/*
> + * 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
> + */
> +
> +#ifndef AVCODEC_CONTAINER_FIFO_H
> +#define AVCODEC_CONTAINER_FIFO_H
> +
> +/**
> + * ContainerFifo is a FIFO for "containers" - dynamically allocated reusable
> + * structs (e.g. AVFrame or AVPacket). ContainerFifo uses an internal pool of
> + * such containers to avoid allocating and freeing them repeatedly.
> + */
> +typedef struct ContainerFifo ContainerFifo;
> +
> +/**
> + * Allocate a new ContainerFifo for the container type defined by provided
> + * callbacks.
> + *
> + * @param container_alloc allocate a new container instance and return a
> pointer
> + * to it, or NULL on failure
> + * @param container_reset reset the provided container instance to a clean
> state
> + * @param container_free free the provided container instance
> + * @param fifo_write transfer the contents of src to dst, where src is a
> + * container instance provided to ff_container_fifo_write()
> + * @param fifo_read transfer the contents of src to dst in other cases
> + *
> + * @note fifo_read() and fifo_write() are different parameters in order to
> allow
> + * fifo_write() implementations that make a new reference in dst,
> leaving
> + * src untouched (see e.g. ff_container_fifo_alloc_avframe())
> + */
> +ContainerFifo*
> +ff_container_fifo_alloc(void* (*container_alloc)(void),
> + void (*container_reset)(void *obj),
> + void (*container_free) (void *obj),
> + int (*fifo_write) (void *dst, void *src),
> + int (*fifo_read) (void *dst, void *src));
> +
> +/**
> + * Allocate a ContainerFifo instance for AVFrames.
> + * Note that ff_container_fifo_write() will call av_frame_ref() on src,
> making a
> + * new reference in dst and leaving src untouched.
> + *
> + * @param flags unused currently
> + */
> +ContainerFifo *ff_container_fifo_alloc_avframe(unsigned flags);
> +
> +/**
> + * Free a ContainerFifo and everything in it.
> + */
> +void ff_container_fifo_free(ContainerFifo **pf);
> +
> +/**
> + * Write the contents of obj to the FIFO.
> + *
> + * The fifo_write() callback previously provided to ff_container_fifo_alloc()
> + * will be called with obj as src in order to perform the actual transfer.
> + */
> +int ff_container_fifo_write(ContainerFifo *pf, void *obj);
> +
> +/**
> + * Read the next available object from the FIFO into obj.
> + *
> + * The fifo_read() callback previously provided to ff_container_fifo_alloc()
> + * will be called with obj as dst in order to perform the actual transfer.
> + */
> +int ff_container_fifo_read(ContainerFifo *pf, void *obj);
> +
> +/**
> + * @return number of objects available for reading
> + */
> +size_t ff_container_fifo_can_read(ContainerFifo *pf);
> +
> +#endif // AVCODEC_CONTAINER_FIFO_H
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