1/*
2 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
3 *
4 * This code is free software; you can redistribute it and/or modify it
5 * under the terms of the GNU General Public License version 2 only, as
6 * published by the Free Software Foundation.  Oracle designates this
7 * particular file as subject to the "Classpath" exception as provided
8 * by Oracle in the LICENSE file that accompanied this code.
9 *
10 * This code is distributed in the hope that it will be useful, but WITHOUT
11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
12 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
13 * version 2 for more details (a copy is included in the LICENSE file that
14 * accompanied this code).
15 *
16 * You should have received a copy of the GNU General Public License version
17 * 2 along with this work; if not, write to the Free Software Foundation,
18 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
19 *
20 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
21 * or visit www.oracle.com if you need additional information or have any
22 * questions.
23 */
24
25/*
26 * This file is available under and governed by the GNU General Public
27 * License version 2 only, as published by the Free Software Foundation.
28 * However, the following notice accompanied the original version of this
29 * file:
30 *
31 * Written by Doug Lea with assistance from members of JCP JSR-166
32 * Expert Group and released to the public domain, as explained at
33 * http://creativecommons.org/publicdomain/zero/1.0/
34 */
35
36package java.util.concurrent.atomic;
37
38import java.util.function.LongBinaryOperator;
39import java.util.function.LongUnaryOperator;
40
41/**
42 * A {@code long} array in which elements may be updated atomically.
43 * See the {@link java.util.concurrent.atomic} package specification
44 * for description of the properties of atomic variables.
45 * @since 1.5
46 * @author Doug Lea
47 */
48public class AtomicLongArray implements java.io.Serializable {
49    private static final long serialVersionUID = -2308431214976778248L;
50
51    private static final sun.misc.Unsafe U = sun.misc.Unsafe.getUnsafe();
52    private static final int ABASE;
53    private static final int ASHIFT;
54    private final long[] array;
55
56    static {
57        ABASE = U.arrayBaseOffset(long[].class);
58        int scale = U.arrayIndexScale(long[].class);
59        if ((scale & (scale - 1)) != 0)
60            throw new Error("array index scale not a power of two");
61        ASHIFT = 31 - Integer.numberOfLeadingZeros(scale);
62    }
63
64    private long checkedByteOffset(int i) {
65        if (i < 0 || i >= array.length)
66            throw new IndexOutOfBoundsException("index " + i);
67
68        return byteOffset(i);
69    }
70
71    private static long byteOffset(int i) {
72        return ((long) i << ASHIFT) + ABASE;
73    }
74
75    /**
76     * Creates a new AtomicLongArray of the given length, with all
77     * elements initially zero.
78     *
79     * @param length the length of the array
80     */
81    public AtomicLongArray(int length) {
82        array = new long[length];
83    }
84
85    /**
86     * Creates a new AtomicLongArray with the same length as, and
87     * all elements copied from, the given array.
88     *
89     * @param array the array to copy elements from
90     * @throws NullPointerException if array is null
91     */
92    public AtomicLongArray(long[] array) {
93        // Visibility guaranteed by final field guarantees
94        this.array = array.clone();
95    }
96
97    /**
98     * Returns the length of the array.
99     *
100     * @return the length of the array
101     */
102    public final int length() {
103        return array.length;
104    }
105
106    /**
107     * Gets the current value at position {@code i}.
108     *
109     * @param i the index
110     * @return the current value
111     */
112    public final long get(int i) {
113        return getRaw(checkedByteOffset(i));
114    }
115
116    private long getRaw(long offset) {
117        return U.getLongVolatile(array, offset);
118    }
119
120    /**
121     * Sets the element at position {@code i} to the given value.
122     *
123     * @param i the index
124     * @param newValue the new value
125     */
126    public final void set(int i, long newValue) {
127        U.putLongVolatile(array, checkedByteOffset(i), newValue);
128    }
129
130    /**
131     * Eventually sets the element at position {@code i} to the given value.
132     *
133     * @param i the index
134     * @param newValue the new value
135     * @since 1.6
136     */
137    public final void lazySet(int i, long newValue) {
138        U.putOrderedLong(array, checkedByteOffset(i), newValue);
139    }
140
141    /**
142     * Atomically sets the element at position {@code i} to the given value
143     * and returns the old value.
144     *
145     * @param i the index
146     * @param newValue the new value
147     * @return the previous value
148     */
149    public final long getAndSet(int i, long newValue) {
150        return U.getAndSetLong(array, checkedByteOffset(i), newValue);
151    }
152
153    /**
154     * Atomically sets the element at position {@code i} to the given
155     * updated value if the current value {@code ==} the expected value.
156     *
157     * @param i the index
158     * @param expect the expected value
159     * @param update the new value
160     * @return {@code true} if successful. False return indicates that
161     * the actual value was not equal to the expected value.
162     */
163    public final boolean compareAndSet(int i, long expect, long update) {
164        return compareAndSetRaw(checkedByteOffset(i), expect, update);
165    }
166
167    private boolean compareAndSetRaw(long offset, long expect, long update) {
168        return U.compareAndSwapLong(array, offset, expect, update);
169    }
170
171    /**
172     * Atomically sets the element at position {@code i} to the given
173     * updated value if the current value {@code ==} the expected value.
174     *
175     * <p><a href="package-summary.html#weakCompareAndSet">May fail
176     * spuriously and does not provide ordering guarantees</a>, so is
177     * only rarely an appropriate alternative to {@code compareAndSet}.
178     *
179     * @param i the index
180     * @param expect the expected value
181     * @param update the new value
182     * @return {@code true} if successful
183     */
184    public final boolean weakCompareAndSet(int i, long expect, long update) {
185        return compareAndSet(i, expect, update);
186    }
187
188    /**
189     * Atomically increments by one the element at index {@code i}.
190     *
191     * @param i the index
192     * @return the previous value
193     */
194    public final long getAndIncrement(int i) {
195        return getAndAdd(i, 1);
196    }
197
198    /**
199     * Atomically decrements by one the element at index {@code i}.
200     *
201     * @param i the index
202     * @return the previous value
203     */
204    public final long getAndDecrement(int i) {
205        return getAndAdd(i, -1);
206    }
207
208    /**
209     * Atomically adds the given value to the element at index {@code i}.
210     *
211     * @param i the index
212     * @param delta the value to add
213     * @return the previous value
214     */
215    public final long getAndAdd(int i, long delta) {
216        return U.getAndAddLong(array, checkedByteOffset(i), delta);
217    }
218
219    /**
220     * Atomically increments by one the element at index {@code i}.
221     *
222     * @param i the index
223     * @return the updated value
224     */
225    public final long incrementAndGet(int i) {
226        return getAndAdd(i, 1) + 1;
227    }
228
229    /**
230     * Atomically decrements by one the element at index {@code i}.
231     *
232     * @param i the index
233     * @return the updated value
234     */
235    public final long decrementAndGet(int i) {
236        return getAndAdd(i, -1) - 1;
237    }
238
239    /**
240     * Atomically adds the given value to the element at index {@code i}.
241     *
242     * @param i the index
243     * @param delta the value to add
244     * @return the updated value
245     */
246    public long addAndGet(int i, long delta) {
247        return getAndAdd(i, delta) + delta;
248    }
249
250    /**
251     * Atomically updates the element at index {@code i} with the results
252     * of applying the given function, returning the previous value. The
253     * function should be side-effect-free, since it may be re-applied
254     * when attempted updates fail due to contention among threads.
255     *
256     * @param i the index
257     * @param updateFunction a side-effect-free function
258     * @return the previous value
259     * @since 1.8
260     */
261    public final long getAndUpdate(int i, LongUnaryOperator updateFunction) {
262        long offset = checkedByteOffset(i);
263        long prev, next;
264        do {
265            prev = getRaw(offset);
266            next = updateFunction.applyAsLong(prev);
267        } while (!compareAndSetRaw(offset, prev, next));
268        return prev;
269    }
270
271    /**
272     * Atomically updates the element at index {@code i} with the results
273     * of applying the given function, returning the updated value. The
274     * function should be side-effect-free, since it may be re-applied
275     * when attempted updates fail due to contention among threads.
276     *
277     * @param i the index
278     * @param updateFunction a side-effect-free function
279     * @return the updated value
280     * @since 1.8
281     */
282    public final long updateAndGet(int i, LongUnaryOperator updateFunction) {
283        long offset = checkedByteOffset(i);
284        long prev, next;
285        do {
286            prev = getRaw(offset);
287            next = updateFunction.applyAsLong(prev);
288        } while (!compareAndSetRaw(offset, prev, next));
289        return next;
290    }
291
292    /**
293     * Atomically updates the element at index {@code i} with the
294     * results of applying the given function to the current and
295     * given values, returning the previous value. The function should
296     * be side-effect-free, since it may be re-applied when attempted
297     * updates fail due to contention among threads.  The function is
298     * applied with the current value at index {@code i} as its first
299     * argument, and the given update as the second argument.
300     *
301     * @param i the index
302     * @param x the update value
303     * @param accumulatorFunction a side-effect-free function of two arguments
304     * @return the previous value
305     * @since 1.8
306     */
307    public final long getAndAccumulate(int i, long x,
308                                      LongBinaryOperator accumulatorFunction) {
309        long offset = checkedByteOffset(i);
310        long prev, next;
311        do {
312            prev = getRaw(offset);
313            next = accumulatorFunction.applyAsLong(prev, x);
314        } while (!compareAndSetRaw(offset, prev, next));
315        return prev;
316    }
317
318    /**
319     * Atomically updates the element at index {@code i} with the
320     * results of applying the given function to the current and
321     * given values, returning the updated value. The function should
322     * be side-effect-free, since it may be re-applied when attempted
323     * updates fail due to contention among threads.  The function is
324     * applied with the current value at index {@code i} as its first
325     * argument, and the given update as the second argument.
326     *
327     * @param i the index
328     * @param x the update value
329     * @param accumulatorFunction a side-effect-free function of two arguments
330     * @return the updated value
331     * @since 1.8
332     */
333    public final long accumulateAndGet(int i, long x,
334                                      LongBinaryOperator accumulatorFunction) {
335        long offset = checkedByteOffset(i);
336        long prev, next;
337        do {
338            prev = getRaw(offset);
339            next = accumulatorFunction.applyAsLong(prev, x);
340        } while (!compareAndSetRaw(offset, prev, next));
341        return next;
342    }
343
344    /**
345     * Returns the String representation of the current values of array.
346     * @return the String representation of the current values of array
347     */
348    public String toString() {
349        int iMax = array.length - 1;
350        if (iMax == -1)
351            return "[]";
352
353        StringBuilder b = new StringBuilder();
354        b.append('[');
355        for (int i = 0; ; i++) {
356            b.append(getRaw(byteOffset(i)));
357            if (i == iMax)
358                return b.append(']').toString();
359            b.append(',').append(' ');
360        }
361    }
362
363}
364