src/share/classes/java/util/concurrent/atomic/AtomicReferenceArray.java
Print this page
*** 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(' ');
}
+ }
}