зеркало из https://github.com/mono/ikvm-fork.git
172 строки
5.1 KiB
Java
172 строки
5.1 KiB
Java
/*
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* Written by Doug Lea with assistance from members of JCP JSR-166
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* Expert Group and released to the public domain, as explained at
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* http://creativecommons.org/licenses/publicdomain
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*
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* Modified for IKVM.NET by Jeroen Frijters
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*/
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/*
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Parts Copyright (C) 2006 Jeroen Frijters
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This software is provided 'as-is', without any express or implied
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warranty. In no event will the authors be held liable for any damages
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arising from the use of this software.
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Permission is granted to anyone to use this software for any purpose,
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including commercial applications, and to alter it and redistribute it
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freely, subject to the following restrictions:
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1. The origin of this software must not be misrepresented; you must not
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claim that you wrote the original software. If you use this software
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in a product, an acknowledgment in the product documentation would be
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appreciated but is not required.
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2. Altered source versions must be plainly marked as such, and must not be
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misrepresented as being the original software.
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3. This notice may not be removed or altered from any source distribution.
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Jeroen Frijters
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jeroen@frijters.net
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*/
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package java.util.concurrent.atomic;
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import java.util.*;
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/**
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* An array of object references in which elements may be updated
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* atomically. See the {@link java.util.concurrent.atomic} package
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* specification for description of the properties of atomic
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* variables.
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* @since 1.5
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* @author Doug Lea
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* @param <E> The base class of elements held in this array
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*/
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public class AtomicReferenceArray<E> implements java.io.Serializable {
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private static final long serialVersionUID = -6209656149925076980L;
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private final Object[] array;
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/**
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* Creates a new AtomicReferenceArray of given length.
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* @param length the length of the array
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*/
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public AtomicReferenceArray(int length) {
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array = new Object[length];
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// must perform at least one volatile write to conform to JMM
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if (length > 0)
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set(0, null);
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}
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/**
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* Creates a new AtomicReferenceArray with the same length as, and
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* all elements copied from, the given array.
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*
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* @param array the array to copy elements from
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* @throws NullPointerException if array is null
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*/
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public AtomicReferenceArray(E[] array) {
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if (array == null)
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throw new NullPointerException();
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int length = array.length;
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this.array = new Object[length];
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if (length > 0) {
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int last = length-1;
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for (int i = 0; i < last; ++i)
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this.array[i] = array[i];
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// Do the last write as volatile
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E e = array[last];
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set(last, e);
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}
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}
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/**
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* Returns the length of the array.
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*
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* @return the length of the array
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*/
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public final int length() {
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return array.length;
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}
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/**
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* Gets the current value at position <tt>i</tt>.
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*
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* @param i the index
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* @return the current value
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*/
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public final native E get(int i);
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/**
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* Sets the element at position <tt>i</tt> to the given value.
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*
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* @param i the index
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* @param newValue the new value
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*/
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public final native void set(int i, E newValue);
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/**
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* Eventually sets the element at position <tt>i</tt> to the given value.
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*
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* @param i the index
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* @param newValue the new value
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* @since 1.6
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*/
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public final void lazySet(int i, E newValue) {
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set(i, newValue);
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}
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/**
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* Atomically sets the element at position <tt>i</tt> to the given
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* value and returns the old value.
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*
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* @param i the index
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* @param newValue the new value
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* @return the previous value
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*/
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public final E getAndSet(int i, E newValue) {
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while (true) {
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E current = get(i);
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if (compareAndSet(i, current, newValue))
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return current;
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}
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}
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/**
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* Atomically sets the element at position <tt>i</tt> to the given
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* updated value if the current value <tt>==</tt> the expected value.
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* @param i the index
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* @param expect the expected value
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* @param update the new value
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* @return true if successful. False return indicates that
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* the actual value was not equal to the expected value.
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*/
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public final native boolean compareAndSet(int i, E expect, E update);
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/**
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* Atomically sets the element at position <tt>i</tt> to the given
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* updated value if the current value <tt>==</tt> the expected value.
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* May fail spuriously.
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* @param i the index
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* @param expect the expected value
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* @param update the new value
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* @return true if successful.
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*/
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public final boolean weakCompareAndSet(int i, E expect, E update) {
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return compareAndSet(i, expect, update);
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}
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/**
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* Returns the String representation of the current values of array.
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* @return the String representation of the current values of array.
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*/
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public String toString() {
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if (array.length > 0) // force volatile read
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get(0);
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return Arrays.toString(array);
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}
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}
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