concurrent/atomic/AtomicIntegerArray.java

/*
 * 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.IntBinaryOperator;
import java.util.function.IntUnaryOperator;

/**
 * An {@code int} 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.
 * @since 1.5
 * @author Doug Lea
 */
public class AtomicIntegerArray implements java.io.Serializable {
    private static final long serialVersionUID = 2862133569453604235L;

    private static final sun.misc.Unsafe U = sun.misc.Unsafe.getUnsafe();
    private static final int ABASE;
    private static final int ASHIFT;
    private final int[] array;

    static {
        ABASE = U.arrayBaseOffset(int[].class);
        int scale = U.arrayIndexScale(int[].class);
        if ((scale & (scale - 1)) != 0)
            throw new Error("array index scale not a power of two");
        ASHIFT = 31 - Integer.numberOfLeadingZeros(scale);
    }

    private long checkedByteOffset(int i) {
        if (i < 0 || i >= array.length)
            throw new IndexOutOfBoundsException("index " + i);

        return byteOffset(i);
    }

    private static long byteOffset(int i) {
        return ((long) i << ASHIFT) + ABASE;
    }

    /**
     * Creates a new AtomicIntegerArray of the given length, with all
     * elements initially zero.
     *
     * @param length the length of the array
     */
    public AtomicIntegerArray(int length) {
        array = new int[length];
    }

    /**
     * Creates a new AtomicIntegerArray 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 AtomicIntegerArray(int[] array) {
        // Visibility guaranteed by final field guarantees
        this.array = array.clone();
    }

    /**
     * Returns the length of the array.
     *
     * @return the length of the array
     */
    public final int length() {
        return array.length;
    }

    /**
     * Gets the current value at position {@code i}.
     *
     * @param i the index
     * @return the current value
     */
    public final int get(int i) {
        return getRaw(checkedByteOffset(i));
    }

    private int getRaw(long offset) {
        return U.getIntVolatile(array, offset);
    }

    /**
     * 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, int newValue) {
        U.putIntVolatile(array, checkedByteOffset(i), newValue);
    }

    /**
     * Eventually sets the element at position {@code i} to the given value.
     *
     * @param i the index
     * @param newValue the new value
     * @since 1.6
     */
    public final void lazySet(int i, int newValue) {
        U.putOrderedInt(array, checkedByteOffset(i), newValue);
    }

    /**
     * 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 int getAndSet(int i, int newValue) {
        return U.getAndSetInt(array, checkedByteOffset(i), newValue);
    }

    /**
     * Atomically sets the element at position {@code i} to the given
     * updated value if the current value {@code ==} the expected value.
     *
     * @param i the index
     * @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(int i, int expect, int update) {
        return compareAndSetRaw(checkedByteOffset(i), expect, update);
    }

    private boolean compareAndSetRaw(long offset, int expect, int update) {
        return U.compareAndSwapInt(array, offset, expect, update);
    }

    /**
     * Atomically sets the element at position {@code i} 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 i the index
     * @param expect the expected value
     * @param update the new value
     * @return {@code true} if successful
     */
    public final boolean weakCompareAndSet(int i, int expect, int update) {
        return compareAndSet(i, expect, update);
    }

    /**
     * Atomically increments by one the element at index {@code i}.
     *
     * @param i the index
     * @return the previous value
     */
    public final int getAndIncrement(int i) {
        return getAndAdd(i, 1);
    }

    /**
     * Atomically decrements by one the element at index {@code i}.
     *
     * @param i the index
     * @return the previous value
     */
    public final int getAndDecrement(int i) {
        return getAndAdd(i, -1);
    }

    /**
     * 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
     */
    public final int getAndAdd(int i, int delta) {
        return U.getAndAddInt(array, checkedByteOffset(i), delta);
    }

    /**
     * Atomically increments by one the element at index {@code i}.
     *
     * @param i the index
     * @return the updated value
     */
    public final int incrementAndGet(int i) {
        return getAndAdd(i, 1) + 1;
    }

    /**
     * Atomically decrements by one the element at index {@code i}.
     *
     * @param i the index
     * @return the updated value
     */
    public final int decrementAndGet(int i) {
        return getAndAdd(i, -1) - 1;
    }

    /**
     * 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
     */
    public final int addAndGet(int i, int delta) {
        return getAndAdd(i, delta) + delta;
    }

    /**
     * Atomically updates the element at index {@code i} 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 i the index
     * @param updateFunction a side-effect-free function
     * @return the previous value
     * @since 1.8
     */
    public final int getAndUpdate(int i, IntUnaryOperator updateFunction) {
        long offset = checkedByteOffset(i);
        int prev, next;
        do {
            prev = getRaw(offset);
            next = updateFunction.applyAsInt(prev);
        } while (!compareAndSetRaw(offset, prev, next));
        return prev;
    }

    /**
     * Atomically updates the element at index {@code i} 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 i the index
     * @param updateFunction a side-effect-free function
     * @return the updated value
     * @since 1.8
     */
    public final int updateAndGet(int i, IntUnaryOperator updateFunction) {
        long offset = checkedByteOffset(i);
        int prev, next;
        do {
            prev = getRaw(offset);
            next = updateFunction.applyAsInt(prev);
        } while (!compareAndSetRaw(offset, prev, next));
        return next;
    }

    /**
     * Atomically updates the element at index {@code i} 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 at index {@code i} as its first
     * argument, and the given update as the second argument.
     *
     * @param i the index
     * @param x the update value
     * @param accumulatorFunction a side-effect-free function of two arguments
     * @return the previous value
     * @since 1.8
     */
    public final int getAndAccumulate(int i, int x,
                                      IntBinaryOperator accumulatorFunction) {
        long offset = checkedByteOffset(i);
        int prev, next;
        do {
            prev = getRaw(offset);
            next = accumulatorFunction.applyAsInt(prev, x);
        } while (!compareAndSetRaw(offset, prev, next));
        return prev;
    }

    /**
     * Atomically updates the element at index {@code i} 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 at index {@code i} as its first
     * argument, and the given update as the second argument.
     *
     * @param i the index
     * @param x the update value
     * @param accumulatorFunction a side-effect-free function of two arguments
     * @return the updated value
     * @since 1.8
     */
    public final int accumulateAndGet(int i, int x,
                                      IntBinaryOperator accumulatorFunction) {
        long offset = checkedByteOffset(i);
        int prev, next;
        do {
            prev = getRaw(offset);
            next = accumulatorFunction.applyAsInt(prev, x);
        } while (!compareAndSetRaw(offset, prev, next));
        return next;
    }

    /**
     * Returns the String representation of the current values of array.
     * @return the String representation of the current values of array
     */
    public String toString() {
        int iMax = array.length - 1;
        if (iMax == -1)
            return "[]";

        StringBuilder b = new StringBuilder();
        b.append('[');
        for (int i = 0; ; i++) {
            b.append(getRaw(byteOffset(i)));
            if (i == iMax)
                return b.append(']').toString();
            b.append(',').append(' ');
        }
    }

}
Revision:	1.1
Committed:	Sat Mar 26 06:22:51 2016 UTC (8 years, 2 months ago) by jsr166
Branch:	MAIN
CVS Tags:	HEAD
Log Message:	fork jdk8 maintenance branch for source and jtreg tests
#	User	Rev	Content
1	jsr166	1.1	/*
2			* Written by Doug Lea with assistance from members of JCP JSR-166
3			* Expert Group and released to the public domain, as explained at
4			* http://creativecommons.org/publicdomain/zero/1.0/
5			*/
6
7			package java.util.concurrent.atomic;
8
9			import java.util.function.IntBinaryOperator;
10			import java.util.function.IntUnaryOperator;
11
12			/**
13			* An {@code int} array in which elements may be updated atomically.
14			* See the {@link java.util.concurrent.atomic} package
15			* specification for description of the properties of atomic
16			* variables.
17			* @since 1.5
18			* @author Doug Lea
19			*/
20			public class AtomicIntegerArray implements java.io.Serializable {
21			private static final long serialVersionUID = 2862133569453604235L;
22
23			private static final sun.misc.Unsafe U = sun.misc.Unsafe.getUnsafe();
24			private static final int ABASE;
25			private static final int ASHIFT;
26			private final int[] array;
27
28			static {
29			ABASE = U.arrayBaseOffset(int[].class);
30			int scale = U.arrayIndexScale(int[].class);
31			if ((scale & (scale - 1)) != 0)
32			throw new Error("array index scale not a power of two");
33			ASHIFT = 31 - Integer.numberOfLeadingZeros(scale);
34			}
35
36			private long checkedByteOffset(int i) {
37			if (i < 0 \|\| i >= array.length)
38			throw new IndexOutOfBoundsException("index " + i);
39
40			return byteOffset(i);
41			}
42
43			private static long byteOffset(int i) {
44			return ((long) i << ASHIFT) + ABASE;
45			}
46
47			/**
48			* Creates a new AtomicIntegerArray of the given length, with all
49			* elements initially zero.
50			*
51			* @param length the length of the array
52			*/
53			public AtomicIntegerArray(int length) {
54			array = new int[length];
55			}
56
57			/**
58			* Creates a new AtomicIntegerArray with the same length as, and
59			* all elements copied from, the given array.
60			*
61			* @param array the array to copy elements from
62			* @throws NullPointerException if array is null
63			*/
64			public AtomicIntegerArray(int[] array) {
65			// Visibility guaranteed by final field guarantees
66			this.array = array.clone();
67			}
68
69			/**
70			* Returns the length of the array.
71			*
72			* @return the length of the array
73			*/
74			public final int length() {
75			return array.length;
76			}
77
78			/**
79			* Gets the current value at position {@code i}.
80			*
81			* @param i the index
82			* @return the current value
83			*/
84			public final int get(int i) {
85			return getRaw(checkedByteOffset(i));
86			}
87
88			private int getRaw(long offset) {
89			return U.getIntVolatile(array, offset);
90			}
91
92			/**
93			* Sets the element at position {@code i} to the given value.
94			*
95			* @param i the index
96			* @param newValue the new value
97			*/
98			public final void set(int i, int newValue) {
99			U.putIntVolatile(array, checkedByteOffset(i), newValue);
100			}
101
102			/**
103			* Eventually sets the element at position {@code i} to the given value.
104			*
105			* @param i the index
106			* @param newValue the new value
107			* @since 1.6
108			*/
109			public final void lazySet(int i, int newValue) {
110			U.putOrderedInt(array, checkedByteOffset(i), newValue);
111			}
112
113			/**
114			* Atomically sets the element at position {@code i} to the given
115			* value and returns the old value.
116			*
117			* @param i the index
118			* @param newValue the new value
119			* @return the previous value
120			*/
121			public final int getAndSet(int i, int newValue) {
122			return U.getAndSetInt(array, checkedByteOffset(i), newValue);
123			}
124
125			/**
126			* Atomically sets the element at position {@code i} to the given
127			* updated value if the current value {@code ==} the expected value.
128			*
129			* @param i the index
130			* @param expect the expected value
131			* @param update the new value
132			* @return {@code true} if successful. False return indicates that
133			* the actual value was not equal to the expected value.
134			*/
135			public final boolean compareAndSet(int i, int expect, int update) {
136			return compareAndSetRaw(checkedByteOffset(i), expect, update);
137			}
138
139			private boolean compareAndSetRaw(long offset, int expect, int update) {
140			return U.compareAndSwapInt(array, offset, expect, update);
141			}
142
143			/**
144			* Atomically sets the element at position {@code i} to the given
145			* updated value if the current value {@code ==} the expected value.
146			*
147			* <p><a href="package-summary.html#weakCompareAndSet">May fail
148			* spuriously and does not provide ordering guarantees</a>, so is
149			* only rarely an appropriate alternative to {@code compareAndSet}.
150			*
151			* @param i the index
152			* @param expect the expected value
153			* @param update the new value
154			* @return {@code true} if successful
155			*/
156			public final boolean weakCompareAndSet(int i, int expect, int update) {
157			return compareAndSet(i, expect, update);
158			}
159
160			/**
161			* Atomically increments by one the element at index {@code i}.
162			*
163			* @param i the index
164			* @return the previous value
165			*/
166			public final int getAndIncrement(int i) {
167			return getAndAdd(i, 1);
168			}
169
170			/**
171			* Atomically decrements by one the element at index {@code i}.
172			*
173			* @param i the index
174			* @return the previous value
175			*/
176			public final int getAndDecrement(int i) {
177			return getAndAdd(i, -1);
178			}
179
180			/**
181			* Atomically adds the given value to the element at index {@code i}.
182			*
183			* @param i the index
184			* @param delta the value to add
185			* @return the previous value
186			*/
187			public final int getAndAdd(int i, int delta) {
188			return U.getAndAddInt(array, checkedByteOffset(i), delta);
189			}
190
191			/**
192			* Atomically increments by one the element at index {@code i}.
193			*
194			* @param i the index
195			* @return the updated value
196			*/
197			public final int incrementAndGet(int i) {
198			return getAndAdd(i, 1) + 1;
199			}
200
201			/**
202			* Atomically decrements by one the element at index {@code i}.
203			*
204			* @param i the index
205			* @return the updated value
206			*/
207			public final int decrementAndGet(int i) {
208			return getAndAdd(i, -1) - 1;
209			}
210
211			/**
212			* Atomically adds the given value to the element at index {@code i}.
213			*
214			* @param i the index
215			* @param delta the value to add
216			* @return the updated value
217			*/
218			public final int addAndGet(int i, int delta) {
219			return getAndAdd(i, delta) + delta;
220			}
221
222			/**
223			* Atomically updates the element at index {@code i} with the results
224			* of applying the given function, returning the previous value. The
225			* function should be side-effect-free, since it may be re-applied
226			* when attempted updates fail due to contention among threads.
227			*
228			* @param i the index
229			* @param updateFunction a side-effect-free function
230			* @return the previous value
231			* @since 1.8
232			*/
233			public final int getAndUpdate(int i, IntUnaryOperator updateFunction) {
234			long offset = checkedByteOffset(i);
235			int prev, next;
236			do {
237			prev = getRaw(offset);
238			next = updateFunction.applyAsInt(prev);
239			} while (!compareAndSetRaw(offset, prev, next));
240			return prev;
241			}
242
243			/**
244			* Atomically updates the element at index {@code i} with the results
245			* of applying the given function, returning the updated value. The
246			* function should be side-effect-free, since it may be re-applied
247			* when attempted updates fail due to contention among threads.
248			*
249			* @param i the index
250			* @param updateFunction a side-effect-free function
251			* @return the updated value
252			* @since 1.8
253			*/
254			public final int updateAndGet(int i, IntUnaryOperator updateFunction) {
255			long offset = checkedByteOffset(i);
256			int prev, next;
257			do {
258			prev = getRaw(offset);
259			next = updateFunction.applyAsInt(prev);
260			} while (!compareAndSetRaw(offset, prev, next));
261			return next;
262			}
263
264			/**
265			* Atomically updates the element at index {@code i} with the
266			* results of applying the given function to the current and
267			* given values, returning the previous value. The function should
268			* be side-effect-free, since it may be re-applied when attempted
269			* updates fail due to contention among threads. The function is
270			* applied with the current value at index {@code i} as its first
271			* argument, and the given update as the second argument.
272			*
273			* @param i the index
274			* @param x the update value
275			* @param accumulatorFunction a side-effect-free function of two arguments
276			* @return the previous value
277			* @since 1.8
278			*/
279			public final int getAndAccumulate(int i, int x,
280			IntBinaryOperator accumulatorFunction) {
281			long offset = checkedByteOffset(i);
282			int prev, next;
283			do {
284			prev = getRaw(offset);
285			next = accumulatorFunction.applyAsInt(prev, x);
286			} while (!compareAndSetRaw(offset, prev, next));
287			return prev;
288			}
289
290			/**
291			* Atomically updates the element at index {@code i} with the
292			* results of applying the given function to the current and
293			* given values, returning the updated value. The function should
294			* be side-effect-free, since it may be re-applied when attempted
295			* updates fail due to contention among threads. The function is
296			* applied with the current value at index {@code i} as its first
297			* argument, and the given update as the second argument.
298			*
299			* @param i the index
300			* @param x the update value
301			* @param accumulatorFunction a side-effect-free function of two arguments
302			* @return the updated value
303			* @since 1.8
304			*/
305			public final int accumulateAndGet(int i, int x,
306			IntBinaryOperator accumulatorFunction) {
307			long offset = checkedByteOffset(i);
308			int prev, next;
309			do {
310			prev = getRaw(offset);
311			next = accumulatorFunction.applyAsInt(prev, x);
312			} while (!compareAndSetRaw(offset, prev, next));
313			return next;
314			}
315
316			/**
317			* Returns the String representation of the current values of array.
318			* @return the String representation of the current values of array
319			*/
320			public String toString() {
321			int iMax = array.length - 1;
322			if (iMax == -1)
323			return "[]";
324
325			StringBuilder b = new StringBuilder();
326			b.append('[');
327			for (int i = 0; ; i++) {
328			b.append(getRaw(byteOffset(i)));
329			if (i == iMax)
330			return b.append(']').toString();
331			b.append(',').append(' ');
332			}
333			}
334
335			}