hook: added new averaging hook

lib/hooks/CMakeLists.txt

@@ -34,6 +34,7 @@ set(HOOK_SRC
     scale.c
     fix.c
     cast.c
+    average.c
 )
 
 if(WITH_IO)

lib/hooks/average.c

@@ -0,0 +1,108 @@
+/** Average hook.
+ *
+ * @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)
+ *
+ * VILLASnode
+ *
+ * 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/>.
+ *********************************************************************************/
+
+/** @addtogroup hooks Hook functions
+ * @{
+ */
+
+#include <string.h>
+
+#include <villas/hook.h>
+#include <villas/plugin.h>
+#include <villas/sample.h>
+
+struct average {
+	int mask;
+	int offset;
+};
+
+static int average_parse(struct hook *h, json_t *cfg)
+{
+	struct average *p = (struct average *) h->_vd;
+
+	int ret;
+	json_error_t err;
+
+	ret = json_unpack_ex(cfg, &err, 0, "{ s: i, s: i }",
+		"offset", &p->offset,
+		"mask", &p->mask
+	);
+	if (ret)
+		jerror(&err, "Failed to parse configuration of hook '%s'", hook_type_name(h->_vt));
+
+	return 0;
+}
+
+static int average_process(struct hook *h, struct sample *smps[], unsigned *cnt)
+{
+	struct average *p = (struct average *) h->_vd;
+
+	for (int i = 0; i < *cnt; i++) {
+		struct sample *smp = smps[i];
+		double sum = 0;
+		int n = 0;
+
+		for (int k = 0; k < smp->length; k++) {
+			if (!(p->mask & (1 << k)))
+				continue;
+
+			switch (sample_format(smps[i], k)) {
+				case SIGNAL_TYPE_INTEGER:
+					sum += smp->data[k].i;
+					break;
+
+				case SIGNAL_TYPE_FLOAT:
+					sum += smp->data[k].f;
+					break;
+
+				case SIGNAL_TYPE_AUTO:
+				case SIGNAL_TYPE_INVALID:
+				case SIGNAL_TYPE_COMPLEX:
+				case SIGNAL_TYPE_BOOLEAN:
+					return -1; /* not supported */
+			}
+
+			n++;
+		}
+
+		smp->data[p->offset].f = sum / n;
+	}
+
+	return 0;
+}
+
+static struct plugin p = {
+	.name		= "average",
+	.description	= "Calculate average over some signals",
+	.type		= PLUGIN_TYPE_HOOK,
+	.hook		= {
+		.flags		= HOOK_PATH | HOOK_NODE_READ | HOOK_NODE_WRITE,
+		.priority	= 99,
+		.parse		= average_parse,
+		.process	= average_process,
+		.size		= sizeof(struct average)
+	}
+};
+
+REGISTER_PLUGIN(&p)
+
+/** @} */