--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/src/java.base/share/classes/java/util/concurrent/atomic/AtomicReference.java Tue Sep 12 19:03:39 2017 +0200
@@ -0,0 +1,440 @@
+/*
+ * 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;
+import java.util.function.BinaryOperator;
+import java.util.function.UnaryOperator;
+
+/**
+ * An object reference that may be updated atomically. See the {@link
+ * VarHandle} specification for descriptions of the properties of
+ * atomic accesses.
+ * @since 1.5
+ * @author Doug Lea
+ * @param <V> The type of object referred to by this reference
+ */
+public class AtomicReference<V> implements java.io.Serializable {
+ private static final long serialVersionUID = -1848883965231344442L;
+ private static final VarHandle VALUE;
+ static {
+ try {
+ MethodHandles.Lookup l = MethodHandles.lookup();
+ VALUE = l.findVarHandle(AtomicReference.class, "value", Object.class);
+ } catch (ReflectiveOperationException e) {
+ throw new Error(e);
+ }
+ }
+
+ private volatile V value;
+
+ /**
+ * Creates a new AtomicReference with the given initial value.
+ *
+ * @param initialValue the initial value
+ */
+ public AtomicReference(V initialValue) {
+ value = initialValue;
+ }
+
+ /**
+ * Creates a new AtomicReference with null initial value.
+ */
+ public AtomicReference() {
+ }
+
+ /**
+ * Returns the current value,
+ * with memory effects as specified by {@link VarHandle#getVolatile}.
+ *
+ * @return the current value
+ */
+ public final V 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(V newValue) {
+ 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(V newValue) {
+ VALUE.setRelease(this, 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(V expectedValue, V newValue) {
+ return VALUE.compareAndSet(this, 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(V expectedValue, V newValue) {
+ return VALUE.weakCompareAndSetPlain(this, 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(V expectedValue, V newValue) {
+ return VALUE.weakCompareAndSetPlain(this, expectedValue, 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
+ */
+ @SuppressWarnings("unchecked")
+ public final V getAndSet(V newValue) {
+ return (V)VALUE.getAndSet(this, newValue);
+ }
+
+ /**
+ * 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 V getAndUpdate(UnaryOperator<V> updateFunction) {
+ V prev = get(), next = null;
+ for (boolean haveNext = false;;) {
+ if (!haveNext)
+ next = updateFunction.apply(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 V updateAndGet(UnaryOperator<V> updateFunction) {
+ V prev = get(), next = null;
+ for (boolean haveNext = false;;) {
+ if (!haveNext)
+ next = updateFunction.apply(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 V getAndAccumulate(V x,
+ BinaryOperator<V> accumulatorFunction) {
+ V prev = get(), next = null;
+ for (boolean haveNext = false;;) {
+ if (!haveNext)
+ next = accumulatorFunction.apply(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 V accumulateAndGet(V x,
+ BinaryOperator<V> accumulatorFunction) {
+ V prev = get(), next = null;
+ for (boolean haveNext = false;;) {
+ if (!haveNext)
+ next = accumulatorFunction.apply(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 String.valueOf(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 V getPlain() {
+ return (V)VALUE.get(this);
+ }
+
+ /**
+ * 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(V newValue) {
+ VALUE.set(this, newValue);
+ }
+
+ /**
+ * Returns the current value,
+ * with memory effects as specified by {@link VarHandle#getOpaque}.
+ *
+ * @return the value
+ * @since 9
+ */
+ public final V getOpaque() {
+ return (V)VALUE.getOpaque(this);
+ }
+
+ /**
+ * 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(V newValue) {
+ VALUE.setOpaque(this, newValue);
+ }
+
+ /**
+ * Returns the current value,
+ * with memory effects as specified by {@link VarHandle#getAcquire}.
+ *
+ * @return the value
+ * @since 9
+ */
+ public final V getAcquire() {
+ return (V)VALUE.getAcquire(this);
+ }
+
+ /**
+ * 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(V newValue) {
+ VALUE.setRelease(this, 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 V compareAndExchange(V expectedValue, V newValue) {
+ return (V)VALUE.compareAndExchange(this, 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
+ * @since 9
+ */
+ public final V compareAndExchangeAcquire(V expectedValue, V newValue) {
+ return (V)VALUE.compareAndExchangeAcquire(this, 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#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 V compareAndExchangeRelease(V expectedValue, V newValue) {
+ return (V)VALUE.compareAndExchangeRelease(this, 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(V expectedValue, V newValue) {
+ return VALUE.weakCompareAndSet(this, 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(V expectedValue, V newValue) {
+ return VALUE.weakCompareAndSetAcquire(this, 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(V expectedValue, V newValue) {
+ return VALUE.weakCompareAndSetRelease(this, expectedValue, newValue);
+ }
+
+}