/*

 * 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.VarHandle;

import java.util.function.LongBinaryOperator;

import java.util.function.LongUnaryOperator;

/**

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

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

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

 * such as atomically incremented sequence numbers, and cannot be used

 * as a replacement for a {@link java.lang.Long}. However, this class

 * does extend {@code Number} to allow uniform access by tools and

 * utilities that deal with numerically-based classes.

 *

 * @since 1.5

 * @author Doug Lea

 */

public class AtomicLong extends Number implements java.io.Serializable {

    private static final long serialVersionUID = 1927816293512124184L;

    /**

     * Records whether the underlying JVM supports lockless

     * compareAndSet for longs. While the intrinsic compareAndSetLong

     * method works in either case, some constructions should be

     * handled at Java level to avoid locking user-visible locks.

     */

    static final boolean VM_SUPPORTS_LONG_CAS = VMSupportsCS8();

    /**

     * Returns whether underlying JVM supports lockless CompareAndSet

     * for longs. Called only once and cached in VM_SUPPORTS_LONG_CAS.

     */

    private static native boolean VMSupportsCS8();

    /*

     * This class intended to be implemented using VarHandles, but there

     * are unresolved cyclic startup dependencies.

     */

    private volatile long value;

    /**

     * Creates a new AtomicLong with the given initial value.

     *

     * @param initialValue the initial value

     */

    public AtomicLong(long initialValue) {

        value = initialValue;

    }

    /**

     * Creates a new AtomicLong with initial value {@code 0}.

     */

    public AtomicLong() {

    }

    /**

     * Returns the current value,

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

     *

     * @return the current value

     */

    public final long get() {

        return value;

    }

    /**

     * Sets the value to {@code newValue},

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

     *

     * @param newValue the new value

     */

    public final void set(long newValue) {

        // See JDK-8180620: Clarify VarHandle mixed-access subtleties

        U.putLongVolatile(this, VALUE, newValue);

    }

    /**

     * 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(long newValue) {

        U.putLongRelease(this, VALUE, newValue);

    }

    /**

     * 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 long getAndSet(long newValue) {

        return U.getAndSetLong(this, VALUE, newValue);

    }

    /**

     * 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(long expectedValue, long newValue) {

        return U.compareAndSetLong(this, VALUE, expectedValue, newValue);

    }

    /**

     * 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 final boolean weakCompareAndSet(long expectedValue, long newValue) {

        return U.weakCompareAndSetLongPlain(this, VALUE, expectedValue, newValue);

    }

    /**

     * 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 final boolean weakCompareAndSetPlain(long expectedValue, long newValue) {

        return U.weakCompareAndSetLongPlain(this, VALUE, expectedValue, newValue);

    }

    /**

     * Atomically increments the current value,

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

     *

     * <p>Equivalent to {@code getAndAdd(1)}.

     *

     * @return the previous value

     */

    public final long getAndIncrement() {

        return U.getAndAddLong(this, VALUE, 1L);

    }

    /**

     * Atomically decrements the current value,

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

     *

     * <p>Equivalent to {@code getAndAdd(-1)}.

     *

     * @return the previous value

     */

    public final long getAndDecrement() {

        return U.getAndAddLong(this, VALUE, -1L);

    }

    /**

     * Atomically adds the given value to the current value,

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

     *

     * @param delta the value to add

     * @return the previous value

     */

    public final long getAndAdd(long delta) {

        return U.getAndAddLong(this, VALUE, delta);

    }

    /**

     * Atomically increments the current value,

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

     *

     * <p>Equivalent to {@code addAndGet(1)}.

     *

     * @return the updated value

     */

    public final long incrementAndGet() {

        return U.getAndAddLong(this, VALUE, 1L) + 1L;

    }

    /**

     * Atomically decrements the current value,

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

     *

     * <p>Equivalent to {@code addAndGet(-1)}.

     *

     * @return the updated value

     */

    public final long decrementAndGet() {

        return U.getAndAddLong(this, VALUE, -1L) - 1L;

    }

    /**

     * Atomically adds the given value to the current value,

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

     *

     * @param delta the value to add

     * @return the updated value

     */

    public final long addAndGet(long delta) {

        return U.getAndAddLong(this, VALUE, delta) + delta;

    }

    /**

     * Atomically updates (with memory effects as specified by {@link

     * VarHandle#compareAndSet}) the current value with the results of

     * applying the given function, returning the previous value. The

     * function should be side-effect-free, since it may be re-applied

     * when attempted updates fail due to contention among threads.

     *

     * @param updateFunction a side-effect-free function

     * @return the previous value

     * @since 1.8

     */

    public final long getAndUpdate(LongUnaryOperator updateFunction) {

        long prev = get(), next = 0L;

        for (boolean haveNext = false;;) {

            if (!haveNext)

                next = updateFunction.applyAsLong(prev);

            if (weakCompareAndSetVolatile(prev, next))

                return prev;

            haveNext = (prev == (prev = get()));

        }

    }

    /**

     * Atomically updates (with memory effects as specified by {@link

     * VarHandle#compareAndSet}) the current value with the results of

     * applying the given function, returning the updated value. The

     * function should be side-effect-free, since it may be re-applied

     * when attempted updates fail due to contention among threads.

     *

     * @param updateFunction a side-effect-free function

     * @return the updated value

     * @since 1.8

     */

    public final long updateAndGet(LongUnaryOperator updateFunction) {

        long prev = get(), next = 0L;

        for (boolean haveNext = false;;) {

            if (!haveNext)

                next = updateFunction.applyAsLong(prev);

            if (weakCompareAndSetVolatile(prev, next))

                return next;

            haveNext = (prev == (prev = get()));

        }

    }

    /**

     * Atomically updates (with memory effects as specified by {@link

     * VarHandle#compareAndSet}) the current value with the results of

     * applying the given function to the current and given values,

     * returning the previous value. The function should be

     * side-effect-free, since it may be re-applied when attempted

     * updates fail due to contention among threads.  The function is

     * applied with the current value as its first argument, and the

     * given update as the second argument.

     *

     * @param x the update value

     * @param accumulatorFunction a side-effect-free function of two arguments

     * @return the previous value

     * @since 1.8

     */

    public final long getAndAccumulate(long x,

                                       LongBinaryOperator accumulatorFunction) {

        long prev = get(), next = 0L;

        for (boolean haveNext = false;;) {

            if (!haveNext)

                next = accumulatorFunction.applyAsLong(prev, x);

            if (weakCompareAndSetVolatile(prev, next))

                return prev;

            haveNext = (prev == (prev = get()));

        }

    }

    /**

     * Atomically updates (with memory effects as specified by {@link

     * VarHandle#compareAndSet}) the current value with the results of

     * applying the given function to the current and given values,

     * returning the updated value. The function should be

     * side-effect-free, since it may be re-applied when attempted

     * updates fail due to contention among threads.  The function is

     * applied with the current value as its first argument, and the

     * given update as the second argument.

     *

     * @param x the update value

     * @param accumulatorFunction a side-effect-free function of two arguments

     * @return the updated value

     * @since 1.8

     */

    public final long accumulateAndGet(long x,

                                       LongBinaryOperator accumulatorFunction) {

        long prev = get(), next = 0L;

        for (boolean haveNext = false;;) {

            if (!haveNext)

                next = accumulatorFunction.applyAsLong(prev, x);

            if (weakCompareAndSetVolatile(prev, next))

                return next;

            haveNext = (prev == (prev = get()));

        }

    }

    /**

     * Returns the String representation of the current value.

     * @return the String representation of the current value

     */

    public String toString() {

        return Long.toString(get());

    }

    /**

     * Returns the current value of this {@code AtomicLong} as an {@code int}

     * after a narrowing primitive conversion,

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

     * @jls 5.1.3 Narrowing Primitive Conversion

     */

    public int intValue() {

        return (int)get();

    }

    /**

     * Returns the current value of this {@code AtomicLong} as a {@code long},

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

     * Equivalent to {@link #get()}.

     */

    public long longValue() {

        return get();

    }

    /**

     * Returns the current value of this {@code AtomicLong} as a {@code float}

     * after a widening primitive conversion,

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

     * @jls 5.1.2 Widening Primitive Conversion

     */

    public float floatValue() {

        return (float)get();

    }

    /**

     * Returns the current value of this {@code AtomicLong} as a {@code double}

     * after a widening primitive conversion,

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

     * @jls 5.1.2 Widening Primitive Conversion

     */

    public double doubleValue() {

        return (double)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 long getPlain() {

        return U.getLong(this, VALUE);

    }

    /**

     * 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(long newValue) {

        U.putLong(this, VALUE, newValue);

    }

    /**

     * Returns the current value,

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

     *

     * @return the value

     * @since 9

     */

    public final long getOpaque() {

        return U.getLongOpaque(this, VALUE);

    }

    /**

     * 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(long newValue) {

        U.putLongOpaque(this, VALUE, newValue);

    }

    /**

     * Returns the current value,

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

     *

     * @return the value

     * @since 9

     */

    public final long getAcquire() {

        return U.getLongAcquire(this, VALUE);

    }

    /**

     * 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(long newValue) {

        U.putLongRelease(this, VALUE, newValue);

    }

    /**

     * 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 long compareAndExchange(long expectedValue, long newValue) {

        return U.compareAndExchangeLong(this, VALUE, expectedValue, newValue);

    }

    /**

     * 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