src/share/classes/java/util/concurrent/atomic/AtomicReferenceArray.java

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*** 49,76 **** public class AtomicReferenceArray<E> implements java.io.Serializable { private static final long serialVersionUID = -6209656149925076980L; private static final Unsafe unsafe = Unsafe.getUnsafe(); private static final int base = unsafe.arrayBaseOffset(Object[].class); ! private static final int scale = unsafe.arrayIndexScale(Object[].class); private final Object[] array; ! private long rawIndex(int i) { if (i < 0 || i >= array.length) throw new IndexOutOfBoundsException("index " + i); ! return base + (long) i * scale; } /** ! * Creates a new AtomicReferenceArray of given length. * @param length the length of the array */ public AtomicReferenceArray(int length) { array = new Object[length]; - // must perform at least one volatile write to conform to JMM - if (length > 0) - unsafe.putObjectVolatile(array, rawIndex(0), null); } /** * Creates a new AtomicReferenceArray with the same length as, and * all elements copied from, the given array. --- 49,87 ---- public class AtomicReferenceArray<E> implements java.io.Serializable { private static final long serialVersionUID = -6209656149925076980L; private static final Unsafe unsafe = Unsafe.getUnsafe(); private static final int base = unsafe.arrayBaseOffset(Object[].class); ! private static final int shift; private final Object[] array; ! static { ! int scale = unsafe.arrayIndexScale(Object[].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 AtomicReferenceArray of the given length, with all ! * elements initially zero. ! * * @param length the length of the array */ public AtomicReferenceArray(int length) { array = new Object[length]; } /** * Creates a new AtomicReferenceArray with the same length as, and * all elements copied from, the given array.
*** 77,99 **** * * @param array the array to copy elements from * @throws NullPointerException if array is null */ public AtomicReferenceArray(E[] array) { ! if (array == null) ! throw new NullPointerException(); ! int length = array.length; ! this.array = new Object[length]; ! if (length > 0) { ! int last = length-1; ! for (int i = 0; i < last; ++i) ! this.array[i] = array[i]; ! // Do the last write as volatile ! E e = array[last]; ! unsafe.putObjectVolatile(this.array, rawIndex(last), e); } - } /** * Returns the length of the array. * * @return the length of the array --- 88,100 ---- * * @param array the array to copy elements from * @throws NullPointerException if array is null */ public AtomicReferenceArray(E[] array) { ! // Visibility guaranteed by final field guarantees ! this.array = array.clone(); } /** * Returns the length of the array. * * @return the length of the array
*** 107,127 **** * * @param i the index * @return the current value */ public final E get(int i) { ! return (E) unsafe.getObjectVolatile(array, rawIndex(i)); } /** * 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, E newValue) { ! unsafe.putObjectVolatile(array, rawIndex(i), newValue); } /** * Eventually sets the element at position {@code i} to the given value. * --- 108,132 ---- * * @param i the index * @return the current value */ public final E get(int i) { ! return getRaw(checkedByteOffset(i)); } + private E getRaw(long offset) { + return (E) unsafe.getObjectVolatile(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, E newValue) { ! unsafe.putObjectVolatile(array, checkedByteOffset(i), newValue); } /** * Eventually sets the element at position {@code i} to the given value. *
*** 128,138 **** * @param i the index * @param newValue the new value * @since 1.6 */ public final void lazySet(int i, E newValue) { ! unsafe.putOrderedObject(array, rawIndex(i), newValue); } /** * Atomically sets the element at position {@code i} to the given --- 133,143 ---- * @param i the index * @param newValue the new value * @since 1.6 */ public final void lazySet(int i, E newValue) { ! unsafe.putOrderedObject(array, checkedByteOffset(i), newValue); } /** * Atomically sets the element at position {@code i} to the given
*** 141,171 **** * @param i the index * @param newValue the new value * @return the previous value */ public final E getAndSet(int i, E newValue) { while (true) { ! E current = get(i); ! if (compareAndSet(i, 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, E expect, E update) { ! return unsafe.compareAndSwapObject(array, rawIndex(i), ! 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> --- 146,181 ---- * @param i the index * @param newValue the new value * @return the previous value */ public final E getAndSet(int i, E newValue) { + long offset = checkedByteOffset(i); while (true) { ! E current = (E) 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, E expect, E update) { ! return compareAndSetRaw(checkedByteOffset(i), expect, update); } + private boolean compareAndSetRaw(long offset, E expect, E update) { + return unsafe.compareAndSwapObject(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>
*** 181,194 **** return compareAndSet(i, expect, update); } /** * Returns the String representation of the current values of array. ! * @return the String representation of the current values of array. */ public String toString() { ! if (array.length > 0) // force volatile read ! get(0); ! return Arrays.toString(array); } } --- 191,213 ---- return compareAndSet(i, expect, update); } /** * 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(' '); } + } }