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- /*
- * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
- *
- *
- *
- *
- *
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- *
- *
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- *
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- *
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- *
- */
- /*
- *
- *
- *
- *
- *
- * 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.util.function.LongUnaryOperator;
- import java.util.function.LongBinaryOperator;
- import sun.misc.Unsafe;
- /**
- * A {@code long} value that may be updated atomically. See the
- * {@link java.util.concurrent.atomic} package specification for
- * description of the properties of atomic variables. 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;
- // setup to use Unsafe.compareAndSwapLong for updates
- private static final Unsafe unsafe = Unsafe.getUnsafe();
- private static final long valueOffset;
- /**
- * Records whether the underlying JVM supports lockless
- * compareAndSwap for longs. While the Unsafe.compareAndSwapLong
- * 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();
- static {
- try {
- valueOffset = unsafe.objectFieldOffset
- (AtomicLong.class.getDeclaredField("value"));
- } catch (Exception ex) { throw new Error(ex); }
- }
- 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() {
- }
- /**
- * Gets the current value.
- *
- * @return the current value
- */
- public final long get() {
- return value;
- }
- /**
- * Sets to the given value.
- *
- * @param newValue the new value
- */
- public final void set(long newValue) {
- value = newValue;
- }
- /**
- * Eventually sets to the given value.
- *
- * @param newValue the new value
- * @since 1.6
- */
- public final void lazySet(long newValue) {
- unsafe.putOrderedLong(this, valueOffset, newValue);
- }
- /**
- * Atomically sets to the given value and returns the old value.
- *
- * @param newValue the new value
- * @return the previous value
- */
- public final long getAndSet(long newValue) {
- return unsafe.getAndSetLong(this, valueOffset, newValue);
- }
- /**
- * Atomically sets the value to the given updated value
- * if the current value {@code ==} the expected value.
- *
- * @param expect the expected value
- * @param update 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 expect, long update) {
- return unsafe.compareAndSwapLong(this, valueOffset, expect, update);
- }
- /**
- * Atomically sets the value to the given updated value
- * if the current value {@code ==} the expected value.
- *
- * <p><a href="package-summary.html#weakCompareAndSet">May fail
- * spuriously and does not provide ordering guarantees</a>, so is
- * only rarely an appropriate alternative to {@code compareAndSet}.
- *
- * @param expect the expected value
- * @param update the new value
- * @return {@code true} if successful
- */
- public final boolean weakCompareAndSet(long expect, long update) {
- return unsafe.compareAndSwapLong(this, valueOffset, expect, update);
- }
- /**
- * Atomically increments by one the current value.
- *
- * @return the previous value
- */
- public final long getAndIncrement() {
- return unsafe.getAndAddLong(this, valueOffset, 1L);
- }
- /**
- * Atomically decrements by one the current value.
- *
- * @return the previous value
- */
- public final long getAndDecrement() {
- return unsafe.getAndAddLong(this, valueOffset, -1L);
- }
- /**
- * Atomically adds the given value to the current value.
- *
- * @param delta the value to add
- * @return the previous value
- */
- public final long getAndAdd(long delta) {
- return unsafe.getAndAddLong(this, valueOffset, delta);
- }
- /**
- * Atomically increments by one the current value.
- *
- * @return the updated value
- */
- public final long incrementAndGet() {
- return unsafe.getAndAddLong(this, valueOffset, 1L) + 1L;
- }
- /**
- * Atomically decrements by one the current value.
- *
- * @return the updated value
- */
- public final long decrementAndGet() {
- return unsafe.getAndAddLong(this, valueOffset, -1L) - 1L;
- }
- /**
- * Atomically adds the given value to the current value.
- *
- * @param delta the value to add
- * @return the updated value
- */
- public final long addAndGet(long delta) {
- return unsafe.getAndAddLong(this, valueOffset, delta) + delta;
- }
- /**
- * Atomically updates 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, next;
- do {
- prev = get();
- next = updateFunction.applyAsLong(prev);
- } while (!compareAndSet(prev, next));
- return prev;
- }
- /**
- * Atomically updates 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, next;
- do {
- prev = get();
- next = updateFunction.applyAsLong(prev);
- } while (!compareAndSet(prev, next));
- return next;
- }
- /**
- * Atomically updates 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, next;
- do {
- prev = get();
- next = accumulatorFunction.applyAsLong(prev, x);
- } while (!compareAndSet(prev, next));
- return prev;
- }
- /**
- * Atomically updates 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, next;
- do {
- prev = get();
- next = accumulatorFunction.applyAsLong(prev, x);
- } while (!compareAndSet(prev, next));
- return next;
- }
- /**
- * 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 value of this {@code AtomicLong} as an {@code int}
- * after a narrowing primitive conversion.
- * @jls 5.1.3 Narrowing Primitive Conversions
- */
- public int intValue() {
- return (int)get();
- }
- /**
- * Returns the value of this {@code AtomicLong} as a {@code long}.
- */
- public long longValue() {
- return get();
- }
- /**
- * Returns the value of this {@code AtomicLong} as a {@code float}
- * after a widening primitive conversion.
- * @jls 5.1.2 Widening Primitive Conversions
- */
- public float floatValue() {
- return (float)get();
- }
- /**
- * Returns the value of this {@code AtomicLong} as a {@code double}
- * after a widening primitive conversion.
- * @jls 5.1.2 Widening Primitive Conversions
- */
- public double doubleValue() {
- return (double)get();
- }
- }
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