concurrent/atomic/AtomicLongArray.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 sun.misc.Unsafe;

/**
 * A {@code long} 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 AtomicLongArray implements java.io.Serializable {
    private static final long serialVersionUID = -2308431214976778248L;

    private static final Unsafe unsafe = Unsafe.getUnsafe();
    private static final int base = unsafe.arrayBaseOffset(long[].class);
    private static final int shift;
    private final long[] array;

    static {
        int scale = unsafe.arrayIndexScale(long[].class);
        if ((scale & (scale - 1)) != 0)
            throw new Error("data type scale not a power of two");
        shift = 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 << shift) + base;
    }

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

    /**
     * Creates a new AtomicLongArray 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 AtomicLongArray(long[] 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 long get(int i) {
        return getRaw(checkedByteOffset(i));
    }

    private long getRaw(long offset) {
        return unsafe.getLongVolatile(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, long newValue) {
        unsafe.putLongVolatile(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, long newValue) {
        unsafe.putOrderedLong(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 long getAndSet(int i, long newValue) {
        long offset = checkedByteOffset(i);
        while (true) {
            long current = getRaw(offset);
            if (compareAndSetRaw(offset, current, newValue))
                return current;
        }
    }

    /**
     * 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 true if successful. False return indicates that
     * the actual value was not equal to the expected value.
     */
    public final boolean compareAndSet(int i, long expect, long update) {
        return compareAndSetRaw(checkedByteOffset(i), expect, update);
    }

    private boolean compareAndSetRaw(long offset, long expect, long update) {
        return unsafe.compareAndSwapLong(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 true if successful
     */
    public final boolean weakCompareAndSet(int i, long expect, long 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 long 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 long 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 long getAndAdd(int i, long delta) {
        long offset = checkedByteOffset(i);
        while (true) {
            long current = getRaw(offset);
            if (compareAndSetRaw(offset, current, current + delta))
                return current;
        }
    }

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

    /**
     * Atomically decrements by one the element at index {@code i}.
     *
     * @param i the index
     * @return the updated value
     */
    public final long decrementAndGet(int i) {
        return addAndGet(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 updated value
     */
    public long addAndGet(int i, long delta) {
        long offset = checkedByteOffset(i);
        while (true) {
            long current = getRaw(offset);
            long next = current + delta;
            if (compareAndSetRaw(offset, current, 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:	1.4
Committed:	Sun Jan 18 20:17:32 2015 UTC (9 years, 4 months ago) by jsr166
Branch:	MAIN
CVS Tags:	HEAD
Changes since 1.3:	+1 -0 lines
Log Message:	exactly one blank line before and after package statements
#	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 sun.misc.Unsafe;
10
11	/**
12	* A {@code long} array in which elements may be updated atomically.
13	* See the {@link java.util.concurrent.atomic} package specification
14	* for description of the properties of atomic variables.
15	* @since 1.5
16	* @author Doug Lea
17	*/
18	public class AtomicLongArray implements java.io.Serializable {
19	private static final long serialVersionUID = -2308431214976778248L;
20
21	private static final Unsafe unsafe = Unsafe.getUnsafe();
22	private static final int base = unsafe.arrayBaseOffset(long[].class);
23	private static final int shift;
24	private final long[] array;
25
26	static {
27	int scale = unsafe.arrayIndexScale(long[].class);
28	if ((scale & (scale - 1)) != 0)
29	throw new Error("data type scale not a power of two");
30	shift = 31 - Integer.numberOfLeadingZeros(scale);
31	}
32
33	private long checkedByteOffset(int i) {
34	if (i < 0 \|\| i >= array.length)
35	throw new IndexOutOfBoundsException("index " + i);
36
37	return byteOffset(i);
38	}
39
40	private static long byteOffset(int i) {
41	return ((long) i << shift) + base;
42	}
43
44	/**
45	* Creates a new AtomicLongArray of the given length, with all
46	* elements initially zero.
47	*
48	* @param length the length of the array
49	*/
50	public AtomicLongArray(int length) {
51	array = new long[length];
52	}
53
54	/**
55	* Creates a new AtomicLongArray with the same length as, and
56	* all elements copied from, the given array.
57	*
58	* @param array the array to copy elements from
59	* @throws NullPointerException if array is null
60	*/
61	public AtomicLongArray(long[] array) {
62	// Visibility guaranteed by final field guarantees
63	this.array = array.clone();
64	}
65
66	/**
67	* Returns the length of the array.
68	*
69	* @return the length of the array
70	*/
71	public final int length() {
72	return array.length;
73	}
74
75	/**
76	* Gets the current value at position {@code i}.
77	*
78	* @param i the index
79	* @return the current value
80	*/
81	public final long get(int i) {
82	return getRaw(checkedByteOffset(i));
83	}
84
85	private long getRaw(long offset) {
86	return unsafe.getLongVolatile(array, offset);
87	}
88
89	/**
90	* Sets the element at position {@code i} to the given value.
91	*
92	* @param i the index
93	* @param newValue the new value
94	*/
95	public final void set(int i, long newValue) {
96	unsafe.putLongVolatile(array, checkedByteOffset(i), newValue);
97	}
98
99	/**
100	* Eventually sets the element at position {@code i} to the given value.
101	*
102	* @param i the index
103	* @param newValue the new value
104	* @since 1.6
105	*/
106	public final void lazySet(int i, long newValue) {
107	unsafe.putOrderedLong(array, checkedByteOffset(i), newValue);
108	}
109
110	/**
111	* Atomically sets the element at position {@code i} to the given value
112	* and returns the old value.
113	*
114	* @param i the index
115	* @param newValue the new value
116	* @return the previous value
117	*/
118	public final long getAndSet(int i, long newValue) {
119	long offset = checkedByteOffset(i);
120	while (true) {
121	long current = getRaw(offset);
122	if (compareAndSetRaw(offset, current, newValue))
123	return current;
124	}
125	}
126
127	/**
128	* Atomically sets the element at position {@code i} to the given
129	* updated value if the current value {@code ==} the expected value.
130	*
131	* @param i the index
132	* @param expect the expected value
133	* @param update the new value
134	* @return true if successful. False return indicates that
135	* the actual value was not equal to the expected value.
136	*/
137	public final boolean compareAndSet(int i, long expect, long update) {
138	return compareAndSetRaw(checkedByteOffset(i), expect, update);
139	}
140
141	private boolean compareAndSetRaw(long offset, long expect, long update) {
142	return unsafe.compareAndSwapLong(array, offset, expect, update);
143	}
144
145	/**
146	* Atomically sets the element at position {@code i} to the given
147	* updated value if the current value {@code ==} the expected value.
148	*
149	* <p><a href="package-summary.html#weakCompareAndSet">May fail
150	* spuriously and does not provide ordering guarantees</a>, so is
151	* only rarely an appropriate alternative to {@code compareAndSet}.
152	*
153	* @param i the index
154	* @param expect the expected value
155	* @param update the new value
156	* @return true if successful
157	*/
158	public final boolean weakCompareAndSet(int i, long expect, long update) {
159	return compareAndSet(i, expect, update);
160	}
161
162	/**
163	* Atomically increments by one the element at index {@code i}.
164	*
165	* @param i the index
166	* @return the previous value
167	*/
168	public final long getAndIncrement(int i) {
169	return getAndAdd(i, 1);
170	}
171
172	/**
173	* Atomically decrements by one the element at index {@code i}.
174	*
175	* @param i the index
176	* @return the previous value
177	*/
178	public final long getAndDecrement(int i) {
179	return getAndAdd(i, -1);
180	}
181
182	/**
183	* Atomically adds the given value to the element at index {@code i}.
184	*
185	* @param i the index
186	* @param delta the value to add
187	* @return the previous value
188	*/
189	public final long getAndAdd(int i, long delta) {
190	long offset = checkedByteOffset(i);
191	while (true) {
192	long current = getRaw(offset);
193	if (compareAndSetRaw(offset, current, current + delta))
194	return current;
195	}
196	}
197
198	/**
199	* Atomically increments by one the element at index {@code i}.
200	*
201	* @param i the index
202	* @return the updated value
203	*/
204	public final long incrementAndGet(int i) {
205	return addAndGet(i, 1);
206	}
207
208	/**
209	* Atomically decrements by one the element at index {@code i}.
210	*
211	* @param i the index
212	* @return the updated value
213	*/
214	public final long decrementAndGet(int i) {
215	return addAndGet(i, -1);
216	}
217
218	/**
219	* Atomically adds the given value to the element at index {@code i}.
220	*
221	* @param i the index
222	* @param delta the value to add
223	* @return the updated value
224	*/
225	public long addAndGet(int i, long delta) {
226	long offset = checkedByteOffset(i);
227	while (true) {
228	long current = getRaw(offset);
229	long next = current + delta;
230	if (compareAndSetRaw(offset, current, next))
231	return next;
232	}
233	}
234
235	/**
236	* Returns the String representation of the current values of array.
237	* @return the String representation of the current values of array
238	*/
239	public String toString() {
240	int iMax = array.length - 1;
241	if (iMax == -1)
242	return "[]";
243
244	StringBuilder b = new StringBuilder();
245	b.append('[');
246	for (int i = 0; ; i++) {
247	b.append(getRaw(byteOffset(i)));
248	if (i == iMax)
249	return b.append(']').toString();
250	b.append(',').append(' ');
251	}
252	}
253
254	}