VILLASnode/lib/nodes/shmem.c

/** Node-type for shared memory communication.
 *
 * @file
 * @author Georg Martin Reinke <georg.reinke@rwth-aachen.de>
 * @copyright 2017, 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/>.
 *********************************************************************************/

#include <fcntl.h>
#include <pthread.h>
#include <string.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <unistd.h>

#include "kernel/kernel.h"
#include "log.h"
#include "shmem.h"
#include "nodes/shmem.h"
#include "plugin.h"
#include "timing.h"
#include "utils.h"

int shmem_parse(struct node *n, config_setting_t *cfg)
{
	struct shmem *shm = n->_vd;

	if (!config_setting_lookup_string(cfg, "out_name", &shm->out_name))
		cerror(cfg, "Missing shared memory output queue name");

	if (!config_setting_lookup_string(cfg, "in_name", &shm->in_name))
		cerror(cfg, "Missing shared memory input queue name");

	if (!config_setting_lookup_int(cfg, "queuelen", &shm->conf.queuelen))
		shm->conf.queuelen = DEFAULT_SHMEM_QUEUELEN;

	if (!config_setting_lookup_int(cfg, "samplelen", &shm->conf.samplelen))
		shm->conf.samplelen = DEFAULT_SHMEM_SAMPLELEN;

	if (!config_setting_lookup_bool(cfg, "polling", &shm->conf.polling))
		shm->conf.polling = false;

	config_setting_t *exec_cfg = config_setting_lookup(cfg, "exec");
	if (!exec_cfg)
		shm->exec = NULL;
	else {
		if (!config_setting_is_array(exec_cfg))
			cerror(exec_cfg, "Invalid format for exec");

		shm->exec = alloc(sizeof(char *) * (config_setting_length(exec_cfg) + 1));

		int i;
		for (i = 0; i < config_setting_length(exec_cfg); i++) {
			const char *elm = config_setting_get_string_elem(exec_cfg, i);
			if (!elm)
				cerror(exec_cfg, "Invalid format for exec");

			shm->exec[i] = strdup(elm);
		}

		shm->exec[i] = NULL;
	}

	return 0;
}

int shmem_open(struct node *n)
{
	struct shmem *shm = n->_vd;
	int ret;

	if (shm->exec) {
		ret = spawn(shm->exec[0], shm->exec);
		if (!ret)
			serror("Failed to spawn external program");
	}

	ret = shmem_int_open(shm->out_name, shm->in_name, &shm->intf, &shm->conf);
	if (ret < 0)
		serror("Opening shared memory interface failed");

	return 0;
}

int shmem_close(struct node *n)
{
	struct shmem* shm = n->_vd;

	return shmem_int_close(&shm->intf);
}

int shmem_read(struct node *n, struct sample *smps[], unsigned cnt)
{
	struct shmem *shm = n->_vd;
	int recv;
	struct sample *shared_smps[cnt];

	recv = shmem_int_read(&shm->intf, shared_smps, cnt);
	if (recv < 0)
		/* This can only really mean that the other process has exited, so close
		 * the interface to make sure the shared memory object is unlinked */
		shmem_int_close(&shm->intf);

	if (recv <= 0)
		return recv;

	sample_copy_many(smps, shared_smps, recv);
	sample_put_many(shared_smps, recv);

	struct timespec ts_recv = time_now();

	for (int i = 0; i < recv; i++)
		smps[i]->ts.received = ts_recv;

	return recv;
}

int shmem_write(struct node *n, struct sample *smps[], unsigned cnt)
{
	struct shmem *shm = n->_vd;
	struct sample *shared_smps[cnt]; /* Samples need to be copied to the shared pool first */
	int avail, pushed, len;

	avail = sample_alloc(&shm->intf.write.shared->pool, shared_smps, cnt);
	if (avail != cnt)
		warn("Pool underrun for shmem node %s", shm->out_name);

	for (int i = 0; i < avail; i++) {
		/* Since the node isn't in shared memory, the source can't be accessed */
		shared_smps[i]->source = NULL;
		shared_smps[i]->sequence = smps[i]->sequence;
		shared_smps[i]->ts = smps[i]->ts;

		len = MIN(smps[i]->length, shared_smps[i]->capacity);
		if (len != smps[i]->length)
			warn("Losing data because of sample capacity mismatch in node %s", node_name(n));

		memcpy(shared_smps[i]->data, smps[i]->data, SAMPLE_DATA_LEN(len));

		shared_smps[i]->length = len;
	}

	pushed = shmem_int_write(&shm->intf, shared_smps, avail);
	if (pushed != avail)
		warn("Outgoing queue overrun for node %s", node_name(n));

	return pushed;
}

char * shmem_print(struct node *n)
{
	struct shmem *shm = n->_vd;
	char *buf = NULL;

	strcatf(&buf, "out_name=%s, in_name=%s, queuelen=%d, samplelen=%d, polling=%s",
		shm->out_name, shm->in_name, shm->conf.queuelen, shm->conf.samplelen, shm->conf.polling ? "yes" : "no");

	if (shm->exec) {
		strcatf(&buf, ", exec='");

		for (int i = 0; shm->exec[i]; i++)
			strcatf(&buf, shm->exec[i+1] ? "%s " : "%s", shm->exec[i]);

		strcatf(&buf, "'");
	}

	return buf;
};

static struct plugin p = {
	.name = "shmem",
	.description = "POSIX shared memory interface with external processes",
	.type = PLUGIN_TYPE_NODE,
	.node = {
		.vectorize = 0,
		.size = sizeof(struct shmem),
		.parse = shmem_parse,
		.print = shmem_print,
		.start = shmem_open,
		.stop = shmem_close,
		.read = shmem_read,
		.write = shmem_write,
		.instances = LIST_INIT(),
	}
};

REGISTER_PLUGIN(&p)