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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/
 */

/*
 * Source:
 * http://gee.cs.oswego.edu/cgi-bin/viewcvs.cgi/jsr166/src/jsr166e/extra/AtomicDoubleArray.java?revision=1.5
 * (Modified to adapt to guava coding conventions and
 * to use AtomicLongArray instead of sun.misc.Unsafe)
 */

package com.google.common.util.concurrent;

import static com.google.common.base.Preconditions.checkNotNull;
import static java.lang.Double.doubleToRawLongBits;
import static java.lang.Double.longBitsToDouble;

import com.google.common.annotations.GwtIncompatible;
import com.google.common.annotations.J2ktIncompatible;
import com.google.common.primitives.ImmutableLongArray;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import java.util.concurrent.atomic.AtomicLongArray;
import java.util.function.DoubleBinaryOperator;
import java.util.function.DoubleUnaryOperator;

/**
 * A {@code double} array in which elements may be updated atomically. See the {@link
 * java.util.concurrent.atomic} package specification for description of the properties of atomic
 * variables.
 *
 * 

This class compares primitive {@code double} values in methods such as * {@link #compareAndSet} by comparing their bitwise representation using {@link * Double#doubleToRawLongBits}, which differs from both the primitive double {@code ==} operator and * from {@link Double#equals}, as if implemented by: * *

{@code
 * static boolean bitEquals(double x, double y) {
 *   long xBits = Double.doubleToRawLongBits(x);
 *   long yBits = Double.doubleToRawLongBits(y);
 *   return xBits == yBits;
 * }
 * }
* * @author Doug Lea * @author Martin Buchholz * @since 11.0 */ @GwtIncompatible @J2ktIncompatible @ElementTypesAreNonnullByDefault public class AtomicDoubleArray implements java.io.Serializable { private static final long serialVersionUID = 0L; // Making this non-final is the lesser evil according to Effective // Java 2nd Edition Item 76: Write readObject methods defensively. private transient AtomicLongArray longs; /** * Creates a new {@code AtomicDoubleArray} of the given length, with all elements initially zero. * * @param length the length of the array */ public AtomicDoubleArray(int length) { this.longs = new AtomicLongArray(length); } /** * Creates a new {@code AtomicDoubleArray} with the same length as, and all elements copied from, * the given array. * * @param array the array to copy elements from * @throws NullPointerException if array is null */ public AtomicDoubleArray(double[] array) { int len = array.length; long[] longArray = new long[len]; for (int i = 0; i < len; i++) { longArray[i] = doubleToRawLongBits(array[i]); } this.longs = new AtomicLongArray(longArray); } /** * Returns the length of the array. * * @return the length of the array */ public final int length() { return longs.length(); } /** * Gets the current value at position {@code i}. * * @param i the index * @return the current value */ public final double get(int i) { return longBitsToDouble(longs.get(i)); } /** * Atomically sets the element at position {@code i} to the given value. * * @param i the index * @param newValue the new value */ public final void set(int i, double newValue) { long next = doubleToRawLongBits(newValue); longs.set(i, next); } /** * Eventually sets the element at position {@code i} to the given value. * * @param i the index * @param newValue the new value */ public final void lazySet(int i, double newValue) { long next = doubleToRawLongBits(newValue); longs.lazySet(i, next); } /** * Atomically sets the element at position {@code i} to the given value and returns the old value. * * @param i the index * @param newValue the new value * @return the previous value */ public final double getAndSet(int i, double newValue) { long next = doubleToRawLongBits(newValue); return longBitsToDouble(longs.getAndSet(i, next)); } /** * Atomically sets the element at position {@code i} to the given updated value if the current * value is bitwise equal to the expected value. * * @param i the index * @param expect the expected value * @param update the new value * @return true if successful. False return indicates that the actual value was not equal to the * expected value. */ public final boolean compareAndSet(int i, double expect, double update) { return longs.compareAndSet(i, doubleToRawLongBits(expect), doubleToRawLongBits(update)); } /** * Atomically sets the element at position {@code i} to the given updated value if the current * value is bitwise equal to the expected value. * *

May * fail spuriously and does not provide ordering guarantees, so is only rarely an appropriate * alternative to {@code compareAndSet}. * * @param i the index * @param expect the expected value * @param update the new value * @return true if successful */ public final boolean weakCompareAndSet(int i, double expect, double update) { return longs.weakCompareAndSet(i, doubleToRawLongBits(expect), doubleToRawLongBits(update)); } /** * Atomically adds the given value to the element at index {@code i}. * * @param i the index * @param delta the value to add * @return the previous value */ @CanIgnoreReturnValue public final double getAndAdd(int i, double delta) { return getAndAccumulate(i, delta, Double::sum); } /** * Atomically adds the given value to the element at index {@code i}. * * @param i the index * @param delta the value to add * @return the updated value */ @CanIgnoreReturnValue public double addAndGet(int i, double delta) { return accumulateAndGet(i, delta, Double::sum); } /** * Atomically updates the element at index {@code i} with the results of applying the given * function to the current and given values. * * @param i the index to update * @param x the update value * @param accumulatorFunction the accumulator function * @return the previous value * @since 31.1 */ @CanIgnoreReturnValue public final double getAndAccumulate(int i, double x, DoubleBinaryOperator accumulatorFunction) { checkNotNull(accumulatorFunction); return getAndUpdate(i, oldValue -> accumulatorFunction.applyAsDouble(oldValue, x)); } /** * Atomically updates the element at index {@code i} with the results of applying the given * function to the current and given values. * * @param i the index to update * @param x the update value * @param accumulatorFunction the accumulator function * @return the updated value * @since 31.1 */ @CanIgnoreReturnValue public final double accumulateAndGet(int i, double x, DoubleBinaryOperator accumulatorFunction) { checkNotNull(accumulatorFunction); return updateAndGet(i, oldValue -> accumulatorFunction.applyAsDouble(oldValue, x)); } /** * Atomically updates the element at index {@code i} with the results of applying the given * function to the current value. * * @param i the index to update * @param updaterFunction the update function * @return the previous value * @since 31.1 */ @CanIgnoreReturnValue public final double getAndUpdate(int i, DoubleUnaryOperator updaterFunction) { while (true) { long current = longs.get(i); double currentVal = longBitsToDouble(current); double nextVal = updaterFunction.applyAsDouble(currentVal); long next = doubleToRawLongBits(nextVal); if (longs.compareAndSet(i, current, next)) { return currentVal; } } } /** * Atomically updates the element at index {@code i} with the results of applying the given * function to the current value. * * @param i the index to update * @param updaterFunction the update function * @return the updated value * @since 31.1 */ @CanIgnoreReturnValue public final double updateAndGet(int i, DoubleUnaryOperator updaterFunction) { while (true) { long current = longs.get(i); double currentVal = longBitsToDouble(current); double nextVal = updaterFunction.applyAsDouble(currentVal); long next = doubleToRawLongBits(nextVal); if (longs.compareAndSet(i, current, next)) { return nextVal; } } } /** * Returns the String representation of the current values of array. * * @return the String representation of the current values of array */ @Override public String toString() { int iMax = length() - 1; if (iMax == -1) { return "[]"; } // Double.toString(Math.PI).length() == 17 StringBuilder b = new StringBuilder((17 + 2) * (iMax + 1)); b.append('['); for (int i = 0; ; i++) { b.append(longBitsToDouble(longs.get(i))); if (i == iMax) { return b.append(']').toString(); } b.append(',').append(' '); } } /** * Saves the state to a stream (that is, serializes it). * * @serialData The length of the array is emitted (int), followed by all of its elements (each a * {@code double}) in the proper order. */ private void writeObject(java.io.ObjectOutputStream s) throws java.io.IOException { s.defaultWriteObject(); // Write out array length int length = length(); s.writeInt(length); // Write out all elements in the proper order. for (int i = 0; i < length; i++) { s.writeDouble(get(i)); } } /** Reconstitutes the instance from a stream (that is, deserializes it). */ private void readObject(java.io.ObjectInputStream s) throws java.io.IOException, ClassNotFoundException { s.defaultReadObject(); int length = s.readInt(); ImmutableLongArray.Builder builder = ImmutableLongArray.builder(); for (int i = 0; i < length; i++) { builder.add(doubleToRawLongBits(s.readDouble())); } this.longs = new AtomicLongArray(builder.build().toArray()); } }





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