001package com.pi4j.wiringpi;
002
003/*
004 * #%L
005 * **********************************************************************
006 * ORGANIZATION  :  Pi4J
007 * PROJECT       :  Pi4J :: Java Library (Core)
008 * FILENAME      :  GpioInterrupt.java
009 *
010 * This file is part of the Pi4J project. More information about
011 * this project can be found here:  https://www.pi4j.com/
012 * **********************************************************************
013 * %%
014 * Copyright (C) 2012 - 2021 Pi4J
015 * %%
016 * This program is free software: you can redistribute it and/or modify
017 * it under the terms of the GNU Lesser General Public License as
018 * published by the Free Software Foundation, either version 3 of the
019 * License, or (at your option) any later version.
020 *
021 * This program is distributed in the hope that it will be useful,
022 * but WITHOUT ANY WARRANTY; without even the implied warranty of
023 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
024 * GNU General Lesser Public License for more details.
025 *
026 * You should have received a copy of the GNU General Lesser Public
027 * License along with this program.  If not, see
028 * <http://www.gnu.org/licenses/lgpl-3.0.html>.
029 * #L%
030 */
031
032
033import com.pi4j.util.NativeLibraryLoader;
034
035import java.util.Vector;
036
037/**
038 * <p>
039 * This class provides static methods to configure the native Pi4J library to listen to GPIO
040 * interrupts and invoke callbacks into this class. Additionally, this class provides a listener
041 * registration allowing Java consumers to subscribe to GPIO pin state changes.
042 * </p>
043 *
044 * <p>
045 * Before using the Pi4J library, you need to ensure that the Java VM in configured with access to
046 * the following system libraries:
047 * <ul>
048 * <li>pi4j</li>
049 * <li>wiringPi</li>
050 * </ul>
051 * <blockquote> This library depends on the wiringPi native system library.</br> (developed by
052 * Gordon Henderson @ <a href="http://wiringpi.com/">http://wiringpi.com/</a>)
053 * </blockquote>
054 * </p>
055 *
056 * @see <a href="https://www.pi4j.com/">https://www.pi4j.com/</a>
057 * @author Robert Savage (<a
058 *         href="http://www.savagehomeautomation.com">http://www.savagehomeautomation.com</a>)
059 */
060public class GpioInterrupt {
061
062    private static Vector<GpioInterruptListener> listeners = new Vector<>();
063    private Object lock;
064
065    // private constructor
066    private GpioInterrupt()  {
067        // forbid object construction
068    }
069
070    static {
071        // Load the platform library
072        NativeLibraryLoader.load("libpi4j.so", "pi4j");
073    }
074
075    /**
076     * <p>
077     * This method is used to instruct the native code to setup a monitoring thread to monitor
078     * interrupts that represent changes to the selected GPIO pin.
079     * </p>
080     *
081     * <p>
082     * <b>The GPIO pin must first be exported before it can be monitored.</b>
083     * </p>
084     *
085     * @param pin GPIO pin number (not header pin number; not wiringPi pin number)
086     * @return A return value of a negative number represents an error. A return value of '0'
087     *         represents success and that the GPIO pin is already being monitored. A return value
088     *         of '1' represents success and that a new monitoring thread was created to handle the
089     *         requested GPIO pin number.
090     */
091    public static native int enablePinStateChangeCallback(int pin);
092
093    /**
094     * <p>
095     * This method is used to instruct the native code to stop the monitoring thread monitoring
096     * interrupts on the selected GPIO pin.
097     * </p>
098     *
099     * @param pin GPIO pin number (not header pin number; not wiringPi pin number)
100
101     * @return A return value of a negative number represents an error. A return value of '0'
102     *         represents success and that no existing monitor was previously running. A return
103     *         value of '1' represents success and that an existing monitoring thread was stopped
104     *         for the requested GPIO pin number.
105     */
106    public static native int disablePinStateChangeCallback(int pin);
107
108    /**
109     * <p>
110     * This method is provided as the callback handler for the Pi4J native library to invoke when a
111     * GPIO interrupt is detected. This method should not be called from any Java consumers. (Thus
112     * is is marked as a private method.)
113     * </p>
114     *
115     * @param pin GPIO pin number (not header pin number; not wiringPi pin number)
116     * @param state New GPIO pin state.
117     */
118    @SuppressWarnings("unchecked")
119    private static void pinStateChangeCallback(int pin, boolean state) {
120
121        Vector<GpioInterruptListener> listenersClone;
122        listenersClone = (Vector<GpioInterruptListener>) listeners.clone();
123
124        for (int i = 0; i < listenersClone.size(); i++) {
125            GpioInterruptListener listener = listenersClone.elementAt(i);
126            if(listener != null) {
127                GpioInterruptEvent event = new GpioInterruptEvent(listener, pin, state);
128                listener.pinStateChange(event);
129            }
130        }
131
132        //System.out.println("GPIO PIN [" + pin + "] = " + state);
133    }
134
135    /**
136     * <p>
137     * Java consumer code can all this method to register itself as a listener for pin state
138     * changes.
139     * </p>
140     *
141     * @see com.pi4j.wiringpi.GpioInterruptListener
142     * @see com.pi4j.wiringpi.GpioInterruptEvent
143     *
144     * @param listener A class instance that implements the GpioInterruptListener interface.
145     */
146    public static synchronized void addListener(GpioInterruptListener listener) {
147        if (!listeners.contains(listener)) {
148            listeners.addElement(listener);
149        }
150    }
151
152    /**
153     * <p>
154     * Java consumer code can all this method to unregister itself as a listener for pin state
155     * changes.
156     * </p>
157     *
158     * @see com.pi4j.wiringpi.GpioInterruptListener
159     * @see com.pi4j.wiringpi.GpioInterruptEvent
160     *
161     * @param listener A class instance that implements the GpioInterruptListener interface.
162     */
163    public static synchronized void removeListener(GpioInterruptListener listener) {
164        if (listeners.contains(listener)) {
165            listeners.removeElement(listener);
166        }
167    }
168
169
170    /**
171     * <p>
172     * Returns true if the listener is already registered for event callbacks.
173     * </p>
174     *
175     * @see com.pi4j.wiringpi.GpioInterruptListener
176     * @see com.pi4j.wiringpi.GpioInterruptEvent
177     *
178     * @param listener A class instance that implements the GpioInterruptListener interface.
179     */
180    public static synchronized boolean hasListener(GpioInterruptListener listener) {
181        return listeners.contains(listener);
182    }
183}