| /* |
| * 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; |
| |
| /** |
| * 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 Unsafe unsafe = Unsafe.getUnsafe(); |
| private static final int base = unsafe.arrayBaseOffset(int[].class); |
| private static final int shift; |
| private final int[] array; |
| |
| static { |
| int scale = unsafe.arrayIndexScale(int[].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 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 unsafe.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) { |
| unsafe.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) { |
| unsafe.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) { |
| long offset = checkedByteOffset(i); |
| while (true) { |
| int 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, int expect, int update) { |
| return compareAndSetRaw(checkedByteOffset(i), expect, update); |
| } |
| |
| private boolean compareAndSetRaw(long offset, int expect, int update) { |
| return unsafe.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>May <a href="package-summary.html#Spurious">fail spuriously</a> |
| * and does not provide ordering guarantees, 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, 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) { |
| long offset = checkedByteOffset(i); |
| while (true) { |
| int 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 int 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 int 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 final int addAndGet(int i, int delta) { |
| long offset = checkedByteOffset(i); |
| while (true) { |
| int current = getRaw(offset); |
| int 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(' '); |
| } |
| } |
| |
| } |