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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.gpio.impl;

/*
 * #%L
 * **********************************************************************
 * ORGANIZATION  :  Pi4J
 * PROJECT       :  Pi4J :: Java Library (Core)
 * FILENAME      :  GpioEventMonitorExecutorImpl.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.gpio.GpioFactory;
import com.pi4j.io.gpio.GpioPinDigitalInput;
import com.pi4j.io.gpio.GpioPinInput;
import com.pi4j.io.gpio.PinState;
import com.pi4j.io.gpio.event.PinDigitalStateChangeEvent;
import com.pi4j.io.gpio.event.PinEvent;
import com.pi4j.io.gpio.event.PinEventType;
import com.pi4j.io.gpio.event.PinListener;
import com.pi4j.io.gpio.tasks.impl.GpioEventDebounceTaskImpl;
import com.pi4j.io.gpio.tasks.impl.GpioEventDispatchTaskImpl;

import java.util.concurrent.ExecutorService;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.ScheduledFuture;
import java.util.concurrent.TimeUnit;

public class GpioEventMonitorExecutorImpl implements PinListener {
    
    private final GpioPinInput pin;
    private static ExecutorService executor;
    private static ScheduledExecutorService scheduledExecutor;
    private ScheduledFuture debounceFuture = null;
    
    public GpioEventMonitorExecutorImpl(GpioPinInput pin) {
        this.pin = pin;        
        executor = GpioFactory.getExecutorServiceFactory().getGpioEventExecutorService();
        scheduledExecutor = GpioFactory.getExecutorServiceFactory().getScheduledExecutorService();
    }
    
    @Override
    public void handlePinEvent(PinEvent event) {

        // for digital input pins, we need to enforce pin debounce event suppression
        if(pin instanceof GpioPinDigitalInput && event.getEventType() == PinEventType.DIGITAL_STATE_CHANGE){

            // cast to the digital input pin interface, get the current state from
            // the event, and determine the debounce interval for this pin state
            GpioPinDigitalInput dip = (GpioPinDigitalInput)pin;
            PinState state = ((PinDigitalStateChangeEvent) event).getState();
            int pinDebounceForState = dip.getDebounce(state);

            // if the pin has a debounce delay configured for this pin state,
            // then we will need to use the pin debounce logic to defer pin events
            if(pinDebounceForState > 0) {
                // if no existing debounce future task exists or no future task is still busy, then
                // create a new debounce future task and schedule it based on the debounce
                // interval defined for the current pin state
                if (debounceFuture == null || debounceFuture.isDone()) {
                    debounceFuture = scheduledExecutor.schedule(
                            new GpioEventDebounceTaskImpl(dip, state), pinDebounceForState, TimeUnit.MILLISECONDS);
                } else {
                    // if an existing debounce future task exists and is still busy,
                    // then exit this method effectively suppressing the current pin event
                    return;
                }
            }
        }

        // add a new pin event notification to the thread pool for *immediate* execution
        executor.execute(new GpioEventDispatchTaskImpl(pin, event));
    }
}