added new class for moving window buffers

common/include/villas/window.h

@@ -0,0 +1,48 @@
+/** A sliding/moving window.
+ *
+ * @file
+ * @author Steffen Vogel <stvogel@eonerc.rwth-aachen.de>
+ * @copyright 2014-2019, Institute for Automation of Complex Power Systems, EONERC
+ * @license GNU General Public License (version 3)
+ *
+ * VILLAScommon
+ *
+ * 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 3 of the License, or
+ * 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, see <http://www.gnu.org/licenses/>.
+ *********************************************************************************/
+
+#pragma once
+
+#include <sys/types.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+struct window {
+	double *data;
+
+	size_t steps;
+	size_t mask;
+	size_t pos;
+};
+
+int window_init(struct window *w, size_t steps, double init);
+
+int window_destroy(struct window *w);
+
+double window_update(struct window *w, double in);
+
+#ifdef __cplusplus
+}
+#endif

common/lib/CMakeLists.txt

@@ -48,6 +48,7 @@ add_library(villas-common SHARED
 	version.cpp
 	copyright.cpp
 	common.c
+	window.c
 )
 
 execute_process( 

common/lib/window.c

@@ -0,0 +1,61 @@
+/** A sliding/moving window.
+ *
+ * @author Steffen Vogel <stvogel@eonerc.rwth-aachen.de>
+ * @copyright 2014-2019, Institute for Automation of Complex Power Systems, EONERC
+ * @license GNU General Public License (version 3)
+ *
+ * VILLAScommon
+ *
+ * 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 3 of the License, or
+ * 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, see <http://www.gnu.org/licenses/>.
+ *********************************************************************************/
+
+#include <stdlib.h>
+
+#include <villas/window.h>
+#include <villas/utils.h>
+
+int window_init(struct window *w, size_t steps, double init)
+{
+	size_t len = LOG2_CEIL(steps);
+
+	/* Allocate memory for ciruclar history buffer */
+	w->data = alloc(len * sizeof(double));
+	if (!w->data)
+		return -1;
+
+	for (size_t i = 0; i < len; i++)
+		w->data[i] = init;
+
+	w->steps = steps;
+	w->pos = len;
+	w->mask = len - 1;
+
+	return 0;
+}
+
+int window_destroy(struct window *w)
+{
+	free(w->data);
+
+	return 0;
+}
+
+double window_update(struct window *w, double in)
+{
+	double out = w->data[(w->pos - w->steps) & w->mask];
+
+	w->data[w->pos++] = in;
+
+	return out;
+}