VILLASnode/lib/hooks/decimate.c

/** Decimate hook.
 *
 * @author Steffen Vogel <stvogel@eonerc.rwth-aachen.de>
 * @copyright 2017, Institute for Automation of Complex Power Systems, EONERC
 *********************************************************************************/

/** @addtogroup hooks Hook functions
 * @{
 */

#include "hook.h"
#include "plugin.h"

struct decimate {
	int ratio;
	unsigned counter;
};

static int decimate_init(struct hook *h)
{
	struct decimate *p = h->_vd;
	
	p->counter = 0;

	return 0;
}

static int decimate_parse(struct hook *h, config_setting_t *cfg)
{
	struct decimate *p = h->_vd;
	
	if (!cfg)
		error("Missing configuration for hook: '%s'", plugin_name(h->_vt));

	if (!config_setting_lookup_int(cfg, "ratio", &p->ratio))
		cerror(cfg, "Missing setting 'ratio' for hook '%s'", plugin_name(h->_vt));

	return 0;
}

static int decimate_read(struct hook *h, struct sample *smps[], size_t *cnt)
{
	struct decimate *p = h->_vd;
	
	int i, ok;
	for (i = 0, ok = 0; i < *cnt; i++) {
		if (p->counter++ % p->ratio == 0) {
			struct sample *tmp;
			
			tmp = smps[ok];
			smps[ok++] = smps[i];
			smps[i] = tmp;
		}
	}
	
	*cnt = ok;

	return 0;
}

static struct plugin p = {
	.name		= "decimate",
	.description	= "Downsamping by integer factor",
	.type		= PLUGIN_TYPE_HOOK,
	.hook		= {
		.priority = 99,
		.init	= decimate_init,
		.parse	= decimate_parse,
		.read	= decimate_read,
		.size	= sizeof(struct decimate)
	}
};

REGISTER_PLUGIN(&p)
	
/** @} */