| Clover coverage report - PLT Utilities Test Coverage (plt-20120304-r5436) |
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| Source file | Conditionals | Statements | Methods | TOTAL | |||||||||||||||
| SnapshotSynchronizedSet.java | 50% | 47.8% | 33.3% | 41.9% |
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| 1 | /*BEGIN_COPYRIGHT_BLOCK* | |
| 2 | ||
| 3 | PLT Utilities BSD License | |
| 4 | ||
| 5 | Copyright (c) 2007-2010 JavaPLT group at Rice University | |
| 6 | All rights reserved. | |
| 7 | ||
| 8 | Developed by: Java Programming Languages Team | |
| 9 | Rice University | |
| 10 | http://www.cs.rice.edu/~javaplt/ | |
| 11 | ||
| 12 | Redistribution and use in source and binary forms, with or without modification, are permitted | |
| 13 | provided that the following conditions are met: | |
| 14 | ||
| 15 | - Redistributions of source code must retain the above copyright notice, this list of conditions | |
| 16 | and the following disclaimer. | |
| 17 | - Redistributions in binary form must reproduce the above copyright notice, this list of | |
| 18 | conditions and the following disclaimer in the documentation and/or other materials provided | |
| 19 | with the distribution. | |
| 20 | - Neither the name of the JavaPLT group, Rice University, nor the names of the library's | |
| 21 | contributors may be used to endorse or promote products derived from this software without | |
| 22 | specific prior written permission. | |
| 23 | ||
| 24 | THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR | |
| 25 | IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND | |
| 26 | FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDERS AND | |
| 27 | CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL | |
| 28 | DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, | |
| 29 | DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER | |
| 30 | IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT | |
| 31 | OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. | |
| 32 | ||
| 33 | *END_COPYRIGHT_BLOCK*/ | |
| 34 | ||
| 35 | package edu.rice.cs.plt.collect; | |
| 36 | ||
| 37 | import java.io.Serializable; | |
| 38 | import java.util.*; | |
| 39 | ||
| 40 | import edu.rice.cs.plt.iter.IterUtil; | |
| 41 | import edu.rice.cs.plt.lambda.CachedThunk; | |
| 42 | import edu.rice.cs.plt.lambda.Thunk; | |
| 43 | ||
| 44 | /** | |
| 45 | * A synchronized set like {@link Collections#synchronizedSet}, but one that returns a snapshot of | |
| 46 | * the set contents on invocations of {@code iterator()}. In contrast to | |
| 47 | * {@link java.util.concurrent.CopyOnWriteArraySet}, copies are only made when needed for iteration; other | |
| 48 | * operations use locking to support concurrency. The snapshot strategy has the following advantages over | |
| 49 | * {@link Collections#synchronizedSet}: 1) Thread safety during iteration is guaranteed; 2) the set is | |
| 50 | * interchangeable with other types of sets, even in contexts that perform iteration; 3) concurrent access to | |
| 51 | * the set is not blocked during iteration; and 4) the set can be directly mutated by the iteration loop | |
| 52 | * (on the other hand, removing elements via the iterator is not supported). Note, also, that operations on | |
| 53 | * this set cannot be blocked by synchronizing on the set itself. To support these differences, the | |
| 54 | * implementation must make a copy whenever {@code iterator()} is invoked after the set has been mutated; | |
| 55 | * that copy is cached with the set (optimizing the performance of subsequent calls, but doubling the | |
| 56 | * set's memory footprint). | |
| 57 | */ | |
| 58 | public class SnapshotSynchronizedSet<E> extends DelegatingSet<E> { | |
| 59 | private final CachedThunk<Iterable<E>> _copy; | |
| 60 | ||
| 61 | 12 | public SnapshotSynchronizedSet(Set<E> delegate) { |
| 62 | 12 | super(Collections.synchronizedSet(delegate)); |
| 63 | 12 | _copy = CachedThunk.make(new Thunk<Iterable<E>>() { |
| 64 | 9 | public Iterable<E> value() { |
| 65 | 9 | synchronized(_delegate) { |
| 66 | 9 | return IterUtil.snapshot(_delegate.iterator()); |
| 67 | } | |
| 68 | } | |
| 69 | }); | |
| 70 | } | |
| 71 | ||
| 72 | /** | |
| 73 | * Discard the cached copy of the set, if it exists. This minimizes this set's memory footprint, but | |
| 74 | * forces the copy to be recalculated when {@link #iterator} is next invoked. Has no effect if | |
| 75 | * {@code iterator()} has not been invoked since the last mutating operation. | |
| 76 | */ | |
| 77 | 0 | public void discardSnapshot() { _copy.reset(); } |
| 78 | ||
| 79 | /** Reset the copy thunk if {@code changed} is {@code true}; return {@code changed}. */ | |
| 80 | 9 | private boolean reset(boolean changed) { |
| 81 | 9 | if (changed) { _copy.reset(); } |
| 82 | 9 | return changed; |
| 83 | } | |
| 84 | ||
| 85 | 9 | @Override public Iterator<E> iterator() { return _copy.value().iterator(); } |
| 86 | ||
| 87 | 0 | @Override public boolean add(E o) { return reset(_delegate.add(o)); } |
| 88 | 0 | @Override public boolean addAll(Collection<? extends E> c) { return reset(_delegate.addAll(c)); } |
| 89 | 9 | @Override public void clear() { _delegate.clear(); reset(true); } |
| 90 | 0 | @Override public boolean remove(Object o) { return reset(_delegate.remove(o)); } |
| 91 | 0 | @Override public boolean removeAll(Collection<?> c) { return reset(_delegate.removeAll(c)); } |
| 92 | 0 | @Override public boolean retainAll(Collection<?> c) { return reset(_delegate.retainAll(c)); } |
| 93 | ||
| 94 | /** Get a thunk that invokes the constructor with sets produced by the given factory. */ | |
| 95 | 0 | public static <T> Thunk<Set<T>> factory(Thunk<? extends Set<T>> delegateFactory) { |
| 96 | 0 | return new Factory<T>(delegateFactory); |
| 97 | } | |
| 98 | ||
| 99 | private static final class Factory<T> implements Thunk<Set<T>>, Serializable { | |
| 100 | private final Thunk<? extends Set<T>> _delegateFactory; | |
| 101 | 0 | private Factory(Thunk<? extends Set<T>> delegateFactory) { _delegateFactory = delegateFactory; } |
| 102 | 0 | public Set<T> value() { return new SnapshotSynchronizedSet<T>(_delegateFactory.value()); } |
| 103 | } | |
| 104 | ||
| 105 | /** Call the constructor (allows {@code T} to be inferred). */ | |
| 106 | 0 | public static <T> SnapshotSynchronizedSet<T> make(Set<T> delegate) { |
| 107 | 0 | return new SnapshotSynchronizedSet<T>(delegate); |
| 108 | } | |
| 109 | /** Call the constructor with an empty HashSet. */ | |
| 110 | 0 | public static <T> SnapshotSynchronizedSet<T> makeHash() { |
| 111 | 0 | return new SnapshotSynchronizedSet<T>(new HashSet<T>()); |
| 112 | } | |
| 113 | /** Call the constructor with an empty LinkedHashSet. */ | |
| 114 | 12 | public static <T> SnapshotSynchronizedSet<T> makeLinkedHash() { |
| 115 | 12 | return new SnapshotSynchronizedSet<T>(new LinkedHashSet<T>()); |
| 116 | } | |
| 117 | /** Call the constructor with an empty TreeSet. */ | |
| 118 | 0 | public static <T> SnapshotSynchronizedSet<T> makeTree() { |
| 119 | 0 | return new SnapshotSynchronizedSet<T>(new TreeSet<T>()); |
| 120 | } | |
| 121 | ||
| 122 | } |
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