From 57888a70a5a1d240517f542b7b3245086a94e0c8 Mon Sep 17 00:00:00 2001 From: jzhou Date: Wed, 28 Dec 2011 00:48:54 +0000 Subject: [PATCH 1/1] changes to MGC class library --- Robust/src/ClassLibrary/MGC/Map.java | 2 +- .../MGC/gnu/AtomicStampedReference.java | 165 ++++++++++++++++++ 2 files changed, 166 insertions(+), 1 deletion(-) create mode 100644 Robust/src/ClassLibrary/MGC/gnu/AtomicStampedReference.java diff --git a/Robust/src/ClassLibrary/MGC/Map.java b/Robust/src/ClassLibrary/MGC/Map.java index 89533565..75b69fc4 100644 --- a/Robust/src/ClassLibrary/MGC/Map.java +++ b/Robust/src/ClassLibrary/MGC/Map.java @@ -85,7 +85,7 @@ public interface Map// * * @throws UnsupportedOperationException if clear is not supported */ - //void clear(); + void clear(); /** * Returns true if this contains a mapping for the given key. diff --git a/Robust/src/ClassLibrary/MGC/gnu/AtomicStampedReference.java b/Robust/src/ClassLibrary/MGC/gnu/AtomicStampedReference.java new file mode 100644 index 00000000..529fce49 --- /dev/null +++ b/Robust/src/ClassLibrary/MGC/gnu/AtomicStampedReference.java @@ -0,0 +1,165 @@ +/* + * 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/licenses/publicdomain + */ + +//package java.util.concurrent.atomic; + +/** + * An AtomicStampedReference maintains an object reference + * along with an integer "stamp", that can be updated atomically. + * + *

Implementation note. This implementation maintains stamped + * references by creating internal objects representing "boxed" + * [reference, integer] pairs. + * + * @since 1.5 + * @author Doug Lea + * @param The type of object referred to by this reference + */ +public class AtomicStampedReference/**/ { + + private static class ReferenceIntegerPair/**/ { + private final Object/*T*/ reference; + private final int integer; + ReferenceIntegerPair(Object/*T*/ r, int i) { + reference = r; integer = i; + } + } + + private final AtomicReference/*>*/ atomicRef; + + /** + * Creates a new AtomicStampedReference with the given + * initial values. + * + * @param initialRef the initial reference + * @param initialStamp the initial stamp + */ + public AtomicStampedReference(Object/*V*/ initialRef, int initialStamp) { + atomicRef = new AtomicReference/*>*/ + (new ReferenceIntegerPair/**/(initialRef, initialStamp)); + } + + /** + * Returns the current value of the reference. + * + * @return the current value of the reference + */ + public Object/*V*/ getReference() { + return atomicRef.get().reference; + } + + /** + * Returns the current value of the stamp. + * + * @return the current value of the stamp + */ + public int getStamp() { + return atomicRef.get().integer; + } + + /** + * Returns the current values of both the reference and the stamp. + * Typical usage is int[1] holder; ref = v.get(holder); . + * + * @param stampHolder an array of size of at least one. On return, + * stampholder[0] will hold the value of the stamp. + * @return the current value of the reference + */ + public Object/*V*/ get(int[] stampHolder) { + ReferenceIntegerPair/**/ p = atomicRef.get(); + stampHolder[0] = p.integer; + return p.reference; + } + + /** + * Atomically sets the value of both the reference and stamp + * to the given update values if the + * current reference is == to the expected reference + * and the current stamp is equal to the expected stamp. + * May fail spuriously and does not provide ordering guarantees, + * so is only rarely an appropriate alternative to compareAndSet. + * + * @param expectedReference the expected value of the reference + * @param newReference the new value for the reference + * @param expectedStamp the expected value of the stamp + * @param newStamp the new value for the stamp + * @return true if successful + */ + public boolean weakCompareAndSet(Object/*V*/ expectedReference, + Object/*V*/ newReference, + int expectedStamp, + int newStamp) { + ReferenceIntegerPair/**/ current = atomicRef.get(); + return expectedReference == current.reference && + expectedStamp == current.integer && + ((newReference == current.reference && + newStamp == current.integer) || + atomicRef.weakCompareAndSet(current, + new ReferenceIntegerPair/**/(newReference, + newStamp))); + } + + /** + * Atomically sets the value of both the reference and stamp + * to the given update values if the + * current reference is == to the expected reference + * and the current stamp is equal to the expected stamp. + * + * @param expectedReference the expected value of the reference + * @param newReference the new value for the reference + * @param expectedStamp the expected value of the stamp + * @param newStamp the new value for the stamp + * @return true if successful + */ + public boolean compareAndSet(Object/*V*/ expectedReference, + Object/*V*/ newReference, + int expectedStamp, + int newStamp) { + ReferenceIntegerPair/**/ current = atomicRef.get(); + return expectedReference == current.reference && + expectedStamp == current.integer && + ((newReference == current.reference && + newStamp == current.integer) || + atomicRef.compareAndSet(current, + new ReferenceIntegerPair/**/(newReference, + newStamp))); + } + + + /** + * Unconditionally sets the value of both the reference and stamp. + * + * @param newReference the new value for the reference + * @param newStamp the new value for the stamp + */ + public void set(Object/*V*/ newReference, int newStamp) { + ReferenceIntegerPair/**/ current = atomicRef.get(); + if (newReference != current.reference || newStamp != current.integer) + atomicRef.set(new ReferenceIntegerPair/**/(newReference, newStamp)); + } + + /** + * Atomically sets the value of the stamp to the given update value + * if the current reference is == to the expected + * reference. Any given invocation of this operation may fail + * (return false) spuriously, but repeated invocation + * when the current value holds the expected value and no other + * thread is also attempting to set the value will eventually + * succeed. + * + * @param expectedReference the expected value of the reference + * @param newStamp the new value for the stamp + * @return true if successful + */ + public boolean attemptStamp(Object/*V*/ expectedReference, int newStamp) { + ReferenceIntegerPair/**/ current = atomicRef.get(); + return expectedReference == current.reference && + (newStamp == current.integer || + atomicRef.compareAndSet(current, + new ReferenceIntegerPair/**/(expectedReference, + newStamp))); + } +} -- 2.34.1