/*

 * Copyright (c) 1998, 2016, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code 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

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

package sun.misc;

import java.util.Objects;

/**

 * This class provides ANSI/ISO C signal support. A Java program can register

 * signal handlers for the current process. There are two restrictions:

 * <ul>

 * <li>

 * Java code cannot register a handler for signals that are already used

 * by the Java VM implementation. The <code>Signal.handle</code>

 * function raises an <code>IllegalArgumentException</code> if such an attempt

 * is made.

 * <li>

 * When <code>Signal.handle</code> is called, the VM internally registers a

 * special C signal handler. There is no way to force the Java signal handler

 * to run synchronously before the C signal handler returns. Instead, when the

 * VM receives a signal, the special C signal handler creates a new thread

 * (at priority <code>Thread.MAX_PRIORITY</code>) to

 * run the registered Java signal handler. The C signal handler immediately

 * returns. Note that because the Java signal handler runs in a newly created

 * thread, it may not actually be executed until some time after the C signal

 * handler returns.

 * </ul>

 * <p>

 * Signal objects are created based on their names. For example:

 * <blockquote><pre>

 * new Signal("INT");

 * </pre></blockquote>

 * constructs a signal object corresponding to <code>SIGINT</code>, which is

 * typically produced when the user presses <code>Ctrl-C</code> at the command line.

 * The <code>Signal</code> constructor throws <code>IllegalArgumentException</code>

 * when it is passed an unknown signal.

 * <p>

 * This is an example of how Java code handles <code>SIGINT</code>:

 * <blockquote><pre>

 * SignalHandler handler = new SignalHandler () {

 *     public void handle(Signal sig) {

 *       ... // handle SIGINT

 *     }

 * };

 * Signal.handle(new Signal("INT"), handler);

 * </pre></blockquote>

 *

 * @author   Sheng Liang

 * @author   Bill Shannon

 * @see     sun.misc.SignalHandler

 * @since    1.2

 */

public final class Signal {

    // Delegate to jdk.internal.misc.Signal.

    private final jdk.internal.misc.Signal iSignal;

    /* Returns the signal number */

    public int getNumber() {

        return iSignal.getNumber();

    }

    /**

     * Returns the signal name.

     *

     * @return the name of the signal.

     * @see sun.misc.Signal#Signal(String name)

     */

    public String getName() {

        return iSignal.getName();

    }

    /**

     * Compares the equality of two <code>Signal</code> objects.

     *

     * @param other the object to compare with.

     * @return whether two <code>Signal</code> objects are equal.

     */

    public boolean equals(Object other) {

        if (this == other) {

            return true;

        }

        if (other == null || !(other instanceof Signal)) {

            return false;

        }

        Signal other1 = (Signal)other;

        return iSignal.equals(other1.iSignal);

    }

    /**

     * Returns a hashcode for this Signal.

     *

     * @return  a hash code value for this object.

     */

    public int hashCode() {

        return getNumber();

    }

    /**

     * Returns a string representation of this signal. For example, "SIGINT"

     * for an object constructed using <code>new Signal ("INT")</code>.

     *

     * @return a string representation of the signal

     */

    public String toString() {

        return iSignal.toString();

    }

    /**

     * Constructs a signal from its name.

     *

     * @param name the name of the signal.

     * @exception IllegalArgumentException unknown signal

     * @see sun.misc.Signal#getName()

     */

    public Signal(String name) {

        iSignal = new jdk.internal.misc.Signal(name);

    }

    /**

     * Registers a signal handler.

     *

     * @param sig a signal

     * @param handler the handler to be registered with the given signal.

     * @return the old handler

     * @exception IllegalArgumentException the signal is in use by the VM

     * @see sun.misc.Signal#raise(Signal sig)

     * @see sun.misc.SignalHandler

     * @see sun.misc.SignalHandler#SIG_DFL

     * @see sun.misc.SignalHandler#SIG_IGN

     */

    public static synchronized SignalHandler handle(Signal sig,

                                                    SignalHandler handler)

        throws IllegalArgumentException {

        jdk.internal.misc.Signal.Handler oldHandler = jdk.internal.misc.Signal.handle(sig.iSignal,

                InternalMiscHandler.of(sig, handler));

        return SunMiscHandler.of(sig.iSignal, oldHandler);

    }

    /**

     * Raises a signal in the current process.

     *

     * @param sig a signal

     * @see sun.misc.Signal#handle(Signal sig, SignalHandler handler)

     */

    public static void raise(Signal sig) throws IllegalArgumentException {

        jdk.internal.misc.Signal.raise(sig.iSignal);

    }

    /*

     * Wrapper class to proxy a SignalHandler to a jdk.internal.misc.Signal.Handler.

     */

    static final class InternalMiscHandler implements jdk.internal.misc.Signal.Handler {

        private final SignalHandler handler;

        private final Signal signal;

        static jdk.internal.misc.Signal.Handler of(Signal signal, SignalHandler handler) {

            if (handler == SignalHandler.SIG_DFL) {

                return jdk.internal.misc.Signal.Handler.SIG_DFL;

            } else if (handler == SignalHandler.SIG_IGN) {

                return jdk.internal.misc.Signal.Handler.SIG_IGN;

            } else if (handler instanceof SunMiscHandler) {

                return ((SunMiscHandler)handler).iHandler;

            } else {

                return new InternalMiscHandler(signal, handler);

            }

        }

        private InternalMiscHandler(Signal signal, SignalHandler handler) {

            this.handler = handler;

            this.signal = signal;

        }

        @Override

        public void handle(jdk.internal.misc.Signal ignore) {

            handler.handle(signal);

        }

    }

    /*

     * Wrapper class to proxy a jdk.internal.misc.Signal.Handler to a SignalHandler.

     */

    static final class SunMiscHandler implements SignalHandler {

        private final jdk.internal.misc.Signal iSignal;

        private final jdk.internal.misc.Signal.Handler iHandler;

        static SignalHandler of(jdk.internal.misc.Signal signal, jdk.internal.misc.Signal.Handler handler) {

            if (handler == jdk.internal.misc.Signal.Handler.SIG_DFL) {

                return SignalHandler.SIG_DFL;

            } else if (handler == jdk.internal.misc.Signal.Handler.SIG_IGN) {

                return SignalHandler.SIG_IGN;

            } else if (handler instanceof InternalMiscHandler) {

                return ((InternalMiscHandler) handler).handler;

            } else {

                return new SunMiscHandler(signal, handler);

            }

        }

        SunMiscHandler(jdk.internal.misc.Signal iSignal, jdk.internal.misc.Signal.Handler iHandler) {

            this.iSignal = iSignal;

            this.iHandler = iHandler;

        }

        @Override

        public void handle(Signal sig) {

            iHandler.handle(iSignal);

        }

        public String toString() {

            return iHandler.toString();

        }

    }

}