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/*
 * 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;
import jdk.internal.misc.Unsafe;

/**
 * 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 static final Unsafe U = Unsafe.getUnsafe();
    private static final long VALUE
        = U.objectFieldOffset(AtomicLong.class, "value");

    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}.
     *
     * 

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}. * *

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}. * *

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}. * *

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 witness value, {@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 witness value, {@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 long compareAndExchangeAcquire(long expectedValue, long newValue) { return U.compareAndExchangeLongAcquire(this, VALUE, expectedValue, newValue); } /** * Atomically sets the value to {@code newValue} if the current value, * referred to as the witness value, {@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 long compareAndExchangeRelease(long expectedValue, long newValue) { return U.compareAndExchangeLongRelease(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#weakCompareAndSet}. * * @param expectedValue the expected value * @param newValue the new value * @return {@code true} if successful * @since 9 */ public final boolean weakCompareAndSetVolatile(long expectedValue, long newValue) { return U.weakCompareAndSetLong(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#weakCompareAndSetAcquire}. * * @param expectedValue the expected value * @param newValue the new value * @return {@code true} if successful * @since 9 */ public final boolean weakCompareAndSetAcquire(long expectedValue, long newValue) { return U.weakCompareAndSetLongAcquire(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#weakCompareAndSetRelease}. * * @param expectedValue the expected value * @param newValue the new value * @return {@code true} if successful * @since 9 */ public final boolean weakCompareAndSetRelease(long expectedValue, long newValue) { return U.weakCompareAndSetLongRelease(this, VALUE, expectedValue, newValue); } }





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