/*

 * 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.

 */

/*

 * This file is available under and governed by the GNU General Public

 * License version 2 only, as published by the Free Software Foundation.

 * However, the following notice accompanied the original version of this

 * file:

 *

 * Written by Doug Lea with assistance from members of JCP JSR-166

 * Expert Group and released to the public domain, as explained at

 * http://creativecommons.org/publicdomain/zero/1.0/

 */

package java.util.concurrent.atomic;

import java.lang.invoke.MethodHandles;

import java.lang.invoke.VarHandle;

/**

 * A {@code boolean} value that may be updated atomically. See the

 * {@link VarHandle} specification for descriptions of the properties

 * of atomic accesses. An {@code AtomicBoolean} is used in

 * applications such as atomically updated flags, and cannot be used

 * as a replacement for a {@link java.lang.Boolean}.

 *

 * @since 1.5

 * @author Doug Lea

 */

public class AtomicBoolean implements java.io.Serializable {

    private static final long serialVersionUID = 4654671469794556979L;

    private static final VarHandle VALUE;

    static {

        try {

            MethodHandles.Lookup l = MethodHandles.lookup();

            VALUE = l.findVarHandle(AtomicBoolean.class, "value", int.class);

        } catch (ReflectiveOperationException e) {

            throw new Error(e);

        }

    }

    private volatile int value;

    /**

     * Creates a new {@code AtomicBoolean} with the given initial value.

     *

     * @param initialValue the initial value

     */

    public AtomicBoolean(boolean initialValue) {

        value = initialValue ? 1 : 0;

    }

    /**

     * Creates a new {@code AtomicBoolean} with initial value {@code false}.

     */

    public AtomicBoolean() {

    }

    /**

     * Returns the current value,

     * with memory effects as specified by {@link VarHandle#getVolatile}.

     *

     * @return the current value

     */

    public final boolean get() {

        return value != 0;

    }

    /**

     * Atomically sets the value to {@code newValue}

     * if the current value {@code == expectedValue},

     * with memory effects as specified by {@link VarHandle#compareAndSet}.

     *

     * @param expectedValue the expected value

     * @param newValue the new value

     * @return {@code true} if successful. False return indicates that

     * the actual value was not equal to the expected value.

     */

    public final boolean compareAndSet(boolean expectedValue, boolean newValue) {

        return VALUE.compareAndSet(this,

                                   (expectedValue ? 1 : 0),

                                   (newValue ? 1 : 0));

    }

    /**

     * Possibly atomically sets the value to {@code newValue}

     * if the current value {@code == expectedValue},

     * with memory effects as specified by {@link VarHandle#weakCompareAndSetPlain}.

     *

     * @deprecated This method has plain memory effects but the method

     * name implies volatile memory effects (see methods such as

     * {@link #compareAndExchange} and {@link #compareAndSet}).  To avoid

     * confusion over plain or volatile memory effects it is recommended that

     * the method {@link #weakCompareAndSetPlain} be used instead.

     *

     * @param expectedValue the expected value

     * @param newValue the new value

     * @return {@code true} if successful

     * @see #weakCompareAndSetPlain

     */

    @Deprecated(since="9")

    public boolean weakCompareAndSet(boolean expectedValue, boolean newValue) {

        return VALUE.weakCompareAndSetPlain(this,

                                            (expectedValue ? 1 : 0),

                                            (newValue ? 1 : 0));

    }

    /**

     * Possibly atomically sets the value to {@code newValue}

     * if the current value {@code == expectedValue},

     * with memory effects as specified by {@link VarHandle#weakCompareAndSetPlain}.

     *

     * @param expectedValue the expected value

     * @param newValue the new value

     * @return {@code true} if successful

     * @since 9

     */

    public boolean weakCompareAndSetPlain(boolean expectedValue, boolean newValue) {

        return VALUE.weakCompareAndSetPlain(this,

                                            (expectedValue ? 1 : 0),

                                            (newValue ? 1 : 0));

    }

    /**

     * Sets the value to {@code newValue},

     * with memory effects as specified by {@link VarHandle#setVolatile}.

     *

     * @param newValue the new value

     */

    public final void set(boolean newValue) {

        value = newValue ? 1 : 0;

    }

    /**

     * Sets the value to {@code newValue},

     * with memory effects as specified by {@link VarHandle#setRelease}.

     *

     * @param newValue the new value

     * @since 1.6

     */

    public final void lazySet(boolean newValue) {

        VALUE.setRelease(this, (newValue ? 1 : 0));

    }

    /**

     * Atomically sets the value to {@code newValue} and returns the old value,

     * with memory effects as specified by {@link VarHandle#getAndSet}.

     *

     * @param newValue the new value

     * @return the previous value

     */

    public final boolean getAndSet(boolean newValue) {

        return (int)VALUE.getAndSet(this, (newValue ? 1 : 0)) != 0;

    }

    /**

     * Returns the String representation of the current value.

     * @return the String representation of the current value

     */

    public String toString() {

        return Boolean.toString(get());

    }

    // jdk9

    /**

     * Returns the current value, with memory semantics of reading as

     * if the variable was declared non-{@code volatile}.

     *

     * @return the value

     * @since 9

     */

    public final boolean getPlain() {

        return (int)VALUE.get(this) != 0;

    }

    /**

     * Sets the value to {@code newValue}, with memory semantics

     * of setting as if the variable was declared non-{@code volatile}

     * and non-{@code final}.

     *

     * @param newValue the new value

     * @since 9

     */

    public final void setPlain(boolean newValue) {

        VALUE.set(this, newValue ? 1 : 0);

    }

    /**

     * Returns the current value,

     * with memory effects as specified by {@link VarHandle#getOpaque}.

     *

     * @return the value

     * @since 9

     */

    public final boolean getOpaque() {

        return (int)VALUE.getOpaque(this) != 0;

    }

    /**

     * Sets the value to {@code newValue},

     * with memory effects as specified by {@link VarHandle#setOpaque}.

     *

     * @param newValue the new value

     * @since 9

     */

    public final void setOpaque(boolean newValue) {

        VALUE.setOpaque(this, newValue ? 1 : 0);

    }

    /**

     * Returns the current value,

     * with memory effects as specified by {@link VarHandle#getAcquire}.

     *

     * @return the value

     * @since 9

     */

    public final boolean getAcquire() {

        return (int)VALUE.getAcquire(this) != 0;

    }

    /**

     * Sets the value to {@code newValue},

     * with memory effects as specified by {@link VarHandle#setRelease}.

     *

     * @param newValue the new value

     * @since 9

     */

    public final void setRelease(boolean newValue) {

        VALUE.setRelease(this, newValue ? 1 : 0);

    }

    /**

     * Atomically sets the value to {@code newValue} if the current value,

     * referred to as the <em>witness value</em>, {@code == expectedValue},

     * with memory effects as specified by

     * {@link VarHandle#compareAndExchange}.

     *

     * @param expectedValue the expected value

     * @param newValue the new value

     * @return the witness value, which will be the same as the

     * expected value if successful

     * @since 9

     */

    public final boolean compareAndExchange(boolean expectedValue, boolean newValue) {

        return (int)VALUE.compareAndExchange(this,

                                             (expectedValue ? 1 : 0),

                                             (newValue ? 1 : 0)) != 0;

    }

    /**

     * Atomically sets the value to {@code newValue} if the current value,

     * referred to as the <em>witness value</em>, {@code == expectedValue},

     * with memory effects as specified by

     * {@link VarHandle#compareAndExchangeAcquire}.

     *

     * @param expectedValue the expected value

     * @param newValue the new value

     * @return the witness value, which will be the same as the

     * expected value if successful

     * @since 9

     */

    public final boolean compareAndExchangeAcquire(boolean expectedValue, boolean newValue) {

        return (int)VALUE.compareAndExchangeAcquire(this,

                                                    (expectedValue ? 1 : 0),

                                                    (newValue ? 1 : 0)) != 0;

    }

    /**

     * Atomically sets the value to {@code newValue} if the current value,

     * referred to as the <em>witness value</em>, {@code == expectedValue},

     * with memory effects as specified by

     * {@link VarHandle#compareAndExchangeRelease}.

     *

     * @param expectedValue the expected value

     * @param newValue the new value

     * @return the witness value, which will be the same as the

     * expected value if successful

     * @since 9

     */

    public final boolean compareAndExchangeRelease(boolean expectedValue, boolean newValue) {

        return (int)VALUE.compareAndExchangeRelease(this,

                                                    (expectedValue ? 1 : 0),

                                                    (newValue ? 1 : 0)) != 0;

    }

    /**

     * Possibly atomically sets the value to {@code newValue} if the current

     * value {@code == expectedValue},

     * with memory effects as specified by

     * {@link VarHandle#weakCompareAndSet}.

     *

     * @param expectedValue the expected value

     * @param newValue the new value

     * @return {@code true} if successful

     * @since 9

     */

    public final boolean weakCompareAndSetVolatile(boolean expectedValue, boolean newValue) {

        return VALUE.weakCompareAndSet(this,

                                       (expectedValue ? 1 : 0),

                                       (newValue ? 1 : 0));

    }

    /**

     * Possibly atomically sets the value to {@code newValue} if the current

     * value {@code == expectedValue},

     * with memory effects as specified by

     * {@link VarHandle#weakCompareAndSetAcquire}.

     *

     * @param expectedValue the expected value

     * @param newValue the new value

     * @return {@code true} if successful

     * @since 9

     */

    public final boolean weakCompareAndSetAcquire(boolean expectedValue, boolean newValue) {

        return VALUE.weakCompareAndSetAcquire(this,

                                              (expectedValue ? 1 : 0),

                                              (newValue ? 1 : 0));

    }

    /**

     * Possibly atomically sets the value to {@code newValue} if the current

     * value {@code == expectedValue},

     * with memory effects as specified by

     * {@link VarHandle#weakCompareAndSetRelease}.

     *

     * @param expectedValue the expected value

     * @param newValue the new value

     * @return {@code true} if successful

     * @since 9

     */

    public final boolean weakCompareAndSetRelease(boolean expectedValue, boolean newValue) {

        return VALUE.weakCompareAndSetRelease(this,

                                              (expectedValue ? 1 : 0),

                                              (newValue ? 1 : 0));

    }

}