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, 1 month ago) by jsr166
Branch:	MAIN
CVS Tags:	HEAD
Log Message:	fork jdk8 maintenance branch for source and jtreg tests
#	Content
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	}