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This bundle wraps Pi4j (http://pi4j.com) that wraps the native code Wiring Pi (http://wiringpi.com). It wraps these libraries to make them OSGi friendly and allow them to work together with the OSGi enRoute IoT circuit library (osgi.enroute.iot.circuit). The bundle will first use Pi4J to detect on what hardware it runs. If it runs on an appropriate type, it will register a component that can be configured with Metatype. The Metatype defines a full blown configuration template for all the Pi's functions. The GPIO's are registered as components for the circuit. Regardless of the success of the configuration, this bundle will also register a GpioController service, which is the main Pi4J class.

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package com.pi4j.io.i2c.impl;

/*
 * #%L
 * **********************************************************************
 * ORGANIZATION  :  Pi4J
 * PROJECT       :  Pi4J :: Java Library (Core)
 * FILENAME      :  I2CBusImplBananaPi.java  
 * 
 * This file is part of the Pi4J project. More information about 
 * this project can be found here:  http://www.pi4j.com/
 * **********************************************************************
 * %%
 * Copyright (C) 2012 - 2015 Pi4J
 * %%
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation, either version 3 of the
 * License, or (at your option) 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 Lesser Public License for more details.
 * 
 * You should have received a copy of the GNU General Lesser Public
 * License along with this program.  If not, see
 * .
 * #L%
 */

import com.pi4j.io.i2c.I2CBus;
import com.pi4j.jni.I2C;

import java.io.IOException;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

/**
 * This is implementation of i2c bus. This class keeps underlying linux file descriptor of
 * particular bus. As all reads and writes from/to i2c bus are blocked I/Os current implementation uses only 
 * one file per bus for all devices. Device implementations use this class file handle.
 * 
 * @author Daniel Sendula
 *
 */
public class I2CBusImplBananaPi extends I2CBusImpl {

    /** Singleton instance of bus 0 */
    private static I2CBus bus0 = null;

    /** Singleton instance of bus 1 */
    private static I2CBus bus1 = null;

    /** Singleton instance of bus 1 */
    private static I2CBus bus2 = null;

    /** Singleton instance of bus 1 */
    private static I2CBus bus3 = null;

    /** 
     * to lock the creation/destruction of the bus singletons
     */
    private final static Lock lock = new ReentrantLock(true);

    /**
     * Factory method that returns bus implementation.
     * 
     * @param busNumber bus number
     * @return appropriate bus implementation
     * @throws IOException thrown in case there is a problem opening bus file or bus number is not 0 or 1.
     */
    public static I2CBus getBus(int busNumber) throws IOException {
        I2CBus bus;
        lock.lock();
        if (busNumber == 0) {
            bus = bus0;
            if (bus == null) {
                bus = new I2CBusImplBananaPi("/dev/i2c-0");
                bus0 = bus;
            }
        } else if (busNumber == 1) {
            bus = bus1;
            if (bus == null) {
                bus = new I2CBusImplBananaPi("/dev/i2c-1");
                bus1 = bus;
            }
        } else if (busNumber == 2) {
            bus = bus2;
            if (bus == null) {
                bus = new I2CBusImplBananaPi("/dev/i2c-2");
                bus2 = bus;
            }
        } else if (busNumber == 3) {
            bus = bus3;
            if (bus == null) {
                bus = new I2CBusImplBananaPi("/dev/i2c-3");
                bus3 = bus;
            }
        } else {
            throw new IOException("Unknown bus number " + busNumber);
        }
        lock.unlock();
        return bus;
    }

    /**
     * Constructor of i2c bus implementation.
     * 
     * @param filename file name of device to be opened.
     * 
     * @throws IOException thrown in case that file cannot be opened
     */
    public I2CBusImplBananaPi(String filename) throws IOException {
        super(filename);
    }

    /**
     * Closes this i2c bus
     *
     * @throws IOException never in this implementation
     */
    @Override
    public void close() throws IOException {
        lock.lock();
        I2C.i2cClose(fd);
        /* after closing the fd, we must "forget" the singleton bus instance, otherwise further request to this bus will
         * always fail
         */
        if (this == bus0) {
            bus0 = null;
        } else if (this == bus1) {
            bus1 = null;
        } else if (this == bus2) {
            bus2 = null;
        } else if (this == bus3) {
            bus3 = null;
        }
        lock.unlock();
    }
}