From 9ac78fb347e26270ebaf5ed41e55d34065853583 Mon Sep 17 00:00:00 2001
From: Anton Khirnov <anton@khirnov.net>
Date: Thu, 16 Jun 2022 10:25:00 +0200
Subject: [PATCH] fftools: add an object pool

Allows to avoid constantly allocating and freeing objects like AVFrame
or AVPacket.
---
 fftools/objpool.c | 131 ++++++++++++++++++++++++++++++++++++++++++++++
 fftools/objpool.h |  37 +++++++++++++
 2 files changed, 168 insertions(+)
 create mode 100644 fftools/objpool.c
 create mode 100644 fftools/objpool.h

diff --git a/fftools/objpool.c b/fftools/objpool.c
new file mode 100644
index 0000000000..b1561ecd69
--- /dev/null
+++ b/fftools/objpool.c
@@ -0,0 +1,131 @@
+/*
+ * 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 <stdint.h>
+
+#include "libavcodec/packet.h"
+
+#include "libavutil/common.h"
+#include "libavutil/error.h"
+#include "libavutil/frame.h"
+#include "libavutil/mem.h"
+
+#include "objpool.h"
+
+struct ObjPool {
+    void        *pool[32];
+    unsigned int pool_count;
+
+    ObjPoolCBAlloc alloc;
+    ObjPoolCBReset reset;
+    ObjPoolCBFree  free;
+};
+
+ObjPool *objpool_alloc(ObjPoolCBAlloc cb_alloc, ObjPoolCBReset cb_reset,
+                       ObjPoolCBFree cb_free)
+{
+    ObjPool *op = av_mallocz(sizeof(*op));
+
+    if (!op)
+        return NULL;
+
+    op->alloc = cb_alloc;
+    op->reset = cb_reset;
+    op->free  = cb_free;
+
+    return op;
+}
+
+void objpool_free(ObjPool **pop)
+{
+    ObjPool *op = *pop;
+
+    if (!op)
+        return;
+
+    for (unsigned int i = 0; i < op->pool_count; i++)
+        op->free(&op->pool[i]);
+
+    av_freep(pop);
+}
+
+int  objpool_get(ObjPool *op, void **obj)
+{
+    if (op->pool_count) {
+        *obj = op->pool[--op->pool_count];
+        op->pool[op->pool_count] = NULL;
+    } else
+        *obj = op->alloc();
+
+    return *obj ? 0 : AVERROR(ENOMEM);
+}
+
+void objpool_release(ObjPool *op, void **obj)
+{
+    if (!*obj)
+        return;
+
+    op->reset(*obj);
+
+    if (op->pool_count < FF_ARRAY_ELEMS(op->pool))
+        op->pool[op->pool_count++] = *obj;
+    else
+        op->free(obj);
+
+    *obj = NULL;
+}
+
+static void *alloc_packet(void)
+{
+    return av_packet_alloc();
+}
+static void *alloc_frame(void)
+{
+    return av_frame_alloc();
+}
+
+static void reset_packet(void *obj)
+{
+    return av_packet_unref(obj);
+}
+static void reset_frame(void *obj)
+{
+    return av_frame_unref(obj);
+}
+
+static void free_packet(void **obj)
+{
+    AVPacket *pkt = *obj;
+    av_packet_free(&pkt);
+    *obj = NULL;
+}
+static void free_frame(void **obj)
+{
+    AVFrame *frame = *obj;
+    av_frame_free(&frame);
+    *obj = NULL;
+}
+
+ObjPool *objpool_alloc_packets(void)
+{
+    return objpool_alloc(alloc_packet, reset_packet, free_packet);
+}
+ObjPool *objpool_alloc_frames(void)
+{
+    return objpool_alloc(alloc_frame, reset_frame, free_frame);
+}
diff --git a/fftools/objpool.h b/fftools/objpool.h
new file mode 100644
index 0000000000..1b2aea6aca
--- /dev/null
+++ b/fftools/objpool.h
@@ -0,0 +1,37 @@
+/*
+ * 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 FFTOOLS_OBJPOOL_H
+#define FFTOOLS_OBJPOOL_H
+
+typedef struct ObjPool ObjPool;
+
+typedef void* (*ObjPoolCBAlloc)(void);
+typedef void  (*ObjPoolCBReset)(void *);
+typedef void  (*ObjPoolCBFree)(void **);
+
+void     objpool_free(ObjPool **op);
+ObjPool *objpool_alloc(ObjPoolCBAlloc cb_alloc, ObjPoolCBReset cb_reset,
+                       ObjPoolCBFree cb_free);
+ObjPool *objpool_alloc_packets(void);
+ObjPool *objpool_alloc_frames(void);
+
+int  objpool_get(ObjPool *op, void **obj);
+void objpool_release(ObjPool *op, void **obj);
+
+#endif // FFTOOLS_OBJPOOL_H