[common] added new ringbuffer helper for metrics collection

common/include/common/ringbuffer.h

@@ -0,0 +1,32 @@
+/**
+ * Looking Glass
+ * Copyright (C) 2017-2021 The Looking Glass Authors
+ * https://looking-glass.io
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the Free
+ * Software Foundation; either version 2 of the License, or (at your option)
+ * any later version.
+ *
+ * This program 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 General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc., 59
+ * Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ */
+
+#include <stddef.h>
+
+typedef struct RingBuffer * RingBuffer;
+
+RingBuffer ringbuffer_new(int length, size_t valueSize);
+void ringbuffer_free(RingBuffer * rb);
+void ringbuffer_push(RingBuffer rb, const void * value);
+void ringbuffer_reset(RingBuffer rb);
+
+int    ringbuffer_getStart (const RingBuffer rb);
+int    ringbuffer_getCount (const RingBuffer rb);
+void * ringbuffer_getValues(const RingBuffer rb);