[FFmpeg-devel] [PATCH 36/39] lavc: add private container FIFO API

[Anton Khirnov <anton@khirnov.net>]

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);
+}
+
+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);
+    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)
+{
+    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
-- 
2.43.0

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