AtomicWord.java

/*
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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.
 *
 * 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.
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package org.graalvm.api.word;

import java.util.concurrent.atomic.AtomicLong;
import java.util.concurrent.atomic.AtomicReference;

/**
 * A {@link WordBase word} value that may be updated atomically. See the
 * {@link java.util.concurrent.atomic} package specification for description of the properties of
 * atomic variables.
 *
 * Similar to {@link AtomicReference}, but for {@link WordBase word} types. A dedicated
 * implementation is necessary because Object and word types cannot be mixed.
 */
public class AtomicWord<T extends WordBase> {

    /**
     * For simplicity, we convert the word value to a long and delegate to existing atomic
     * operations.
     */
    protected final AtomicLong value;

    /**
     * Creates a new AtomicWord with initial value {@link WordFactory#zero}.
     */
    public AtomicWord() {
        value = new AtomicLong();
    }

    /**
     * Gets the current value.
     *
     * @return the current value
     */
    public final T get() {
        return WordFactory.unsigned(value.get());
    }

    /**
     * Sets to the given value.
     *
     * @param newValue the new value
     */
    public final void set(T newValue) {
        value.set(newValue.rawValue());
    }

    /**
     * Atomically sets to the given value and returns the old value.
     *
     * @param newValue the new value
     * @return the previous value
     */
    public final T getAndSet(T newValue) {
        return WordFactory.unsigned(value.getAndSet(newValue.rawValue()));
    }

    /**
     * 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(T expect, T update) {
        return value.compareAndSet(expect.rawValue(), update.rawValue());
    }
}