org.obp.nmea.NmeaDeviceFinder.java Source code

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Here is the source code for org.obp.nmea.NmeaDeviceFinder.java

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/*
 * Copyright 2013-2014 MARSEC-XL International Limited
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.obp.nmea;

import jssc.SerialPortList;
import org.apache.log4j.Logger;
import org.obp.serial.ZeroBytesReadException;
import org.springframework.stereotype.Service;

import java.util.*;

/**
 * Created by Robert Jaremczak
 * Date: 2013-12-5
 */

@Service
public class NmeaDeviceFinder {
    public static final int MESSAGES_TO_READ = 10;

    private static Logger logger = Logger.getLogger(NmeaDeviceFinder.class);

    private boolean listenAndValidate(String portName, Set<String> requiredMessages) throws Exception {
        try {
            Set<String> remaining = new HashSet<>(requiredMessages);
            try (NmeaDevice device = NmeaDevice.createAndOpen(portName)) {
                if (device.isOpened()) {
                    NmeaBufferedReader reader = device.getReader();
                    for (int i = 0; i < MESSAGES_TO_READ; i++) {
                        NmeaLine line = reader.fetchLine();
                        if (line != null) {
                            remaining.remove(line.getName());
                            if (remaining.isEmpty()) {
                                logger.debug("all required messages found");
                                return true;
                            }
                        } else {
                            logger.debug("failed to read line");
                            return false;
                        }
                    }
                }
            }
            logger.debug("following messages not found: " + remaining);
            return false;
        } catch (ZeroBytesReadException e) {
            logger.warn("failed to read from port " + portName);
            return false;
        } catch (Exception e) {
            logger.error("error auto-sensing port " + portName, e);
            return false;
        }
    }

    /**
     * synchronized on purpose, to avoid possible race conditions
     */
    public synchronized NmeaDevice findAndOpen(String deviceUri) throws Exception {
        String[] tokens = deviceUri.split(" ");
        if (tokens.length == 1) {
            return NmeaDevice.createAndOpen(tokens[0]);
        }

        String devicePrefix = tokens[0];
        Set<String> requiredMessages = new HashSet<>(Arrays.asList(tokens).subList(1, tokens.length));
        logger.info(
                "finding NMEA device starting with " + devicePrefix + " supporting " + requiredMessages + " ...");

        List<String> portNames = findMatchingIdentifiers(devicePrefix);
        if (!portNames.isEmpty()) {
            for (String portName : portNames) {
                logger.debug("checking device " + portName);
                if (listenAndValidate(portName, requiredMessages)) {
                    logger.info("found " + portName);
                    return NmeaDevice.createAndOpen(portName);
                }
            }
        }

        logger.error("matching device not found");
        return null;
    }

    private List<String> findMatchingIdentifiers(String namePrefix) {
        List<String> matches = new ArrayList<>();
        for (String portName : SerialPortList.getPortNames()) {
            if (portName.startsWith(namePrefix)) {
                matches.add(portName);
            }
        }
        return matches;
    }

}