Mercurial > hg > blitz_condensed
diff src/EDU/oswego/cs/dl/util/concurrent/SynchronizedDouble.java @ 0:3dc0c5604566
Initial checkin of blitz 2.0 fcs - no installer yet.
author | Dan Creswell <dan.creswell@gmail.com> |
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date | Sat, 21 Mar 2009 11:00:06 +0000 |
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--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/src/EDU/oswego/cs/dl/util/concurrent/SynchronizedDouble.java Sat Mar 21 11:00:06 2009 +0000 @@ -0,0 +1,171 @@ +/* + File: SynchronizedDouble.java + + Originally written by Doug Lea and released into the public domain. + This may be used for any purposes whatsoever without acknowledgment. + Thanks for the assistance and support of Sun Microsystems Labs, + and everyone contributing, testing, and using this code. + + History: + Date Who What + 19Jun1998 dl Create public version +*/ + +package EDU.oswego.cs.dl.util.concurrent; + +/** + * A class useful for offloading synch for double instance variables. + * + * <p>[<a href="http://gee.cs.oswego.edu/dl/classes/EDU/oswego/cs/dl/util/concurrent/intro.html"> Introduction to this package. </a>] + **/ + +public class SynchronizedDouble extends SynchronizedVariable implements Comparable, Cloneable { + + protected double value_; + + /** + * Make a new SynchronizedDouble with the given initial value, + * and using its own internal lock. + **/ + public SynchronizedDouble(double initialValue) { + super(); + value_ = initialValue; + } + + /** + * Make a new SynchronizedDouble with the given initial value, + * and using the supplied lock. + **/ + public SynchronizedDouble(double initialValue, Object lock) { + super(lock); + value_ = initialValue; + } + + /** + * Return the current value + **/ + public final double get() { synchronized(lock_) { return value_; } } + + /** + * Set to newValue. + * @return the old value + **/ + + public double set(double newValue) { + synchronized (lock_) { + double old = value_; + value_ = newValue; + return old; + } + } + + /** + * Set value to newValue only if it is currently assumedValue. + * @return true if successful + **/ + public boolean commit(double assumedValue, double newValue) { + synchronized(lock_) { + boolean success = (assumedValue == value_); + if (success) value_ = newValue; + return success; + } + } + + + /** + * Atomically swap values with another SynchronizedDouble. + * Uses identityHashCode to avoid deadlock when + * two SynchronizedDoubles attempt to simultaneously swap with each other. + * (Note: Ordering via identyHashCode is not strictly guaranteed + * by the language specification to return unique, orderable + * values, but in practice JVMs rely on them being unique.) + * @return the new value + **/ + + public double swap(SynchronizedDouble other) { + if (other == this) return get(); + SynchronizedDouble fst = this; + SynchronizedDouble snd = other; + if (System.identityHashCode(fst) > System.identityHashCode(snd)) { + fst = other; + snd = this; + } + synchronized(fst.lock_) { + synchronized(snd.lock_) { + fst.set(snd.set(fst.get())); + return get(); + } + } + } + + + /** + * Add amount to value (i.e., set value += amount) + * @return the new value + **/ + public double add(double amount) { + synchronized (lock_) { + return value_ += amount; + } + } + + /** + * Subtract amount from value (i.e., set value -= amount) + * @return the new value + **/ + public double subtract(double amount) { + synchronized (lock_) { + return value_ -= amount; + } + } + + /** + * Multiply value by factor (i.e., set value *= factor) + * @return the new value + **/ + public synchronized double multiply(double factor) { + synchronized (lock_) { + return value_ *= factor; + } + } + + /** + * Divide value by factor (i.e., set value /= factor) + * @return the new value + **/ + public double divide(double factor) { + synchronized (lock_) { + return value_ /= factor; + } + } + + public int compareTo(double other) { + double val = get(); + return (val < other)? -1 : (val == other)? 0 : 1; + } + + public int compareTo(SynchronizedDouble other) { + return compareTo(other.get()); + } + + public int compareTo(Object other) { + return compareTo((SynchronizedDouble)other); + } + + public boolean equals(Object other) { + if (other != null && + other instanceof SynchronizedDouble) + return get() == ((SynchronizedDouble)other).get(); + else + return false; + } + + public int hashCode() { // same hash as Double + long bits = Double.doubleToLongBits(get()); + return (int)(bits ^ (bits >> 32)); + } + + public String toString() { return String.valueOf(get()); } + +} +