| Clover coverage report - PLT Utilities Test Coverage (plt-20120304-r5436) |
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| Source file | Conditionals | Statements | Methods | TOTAL | |||||||||||||||
| LockMap.java | 0% | 8.3% | 16.7% | 10% |
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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.concurrent; | |
| 36 | ||
| 37 | import java.util.WeakHashMap; | |
| 38 | import java.util.concurrent.locks.ReentrantLock; | |
| 39 | ||
| 40 | import edu.rice.cs.plt.tuple.IdentityWrapper; | |
| 41 | ||
| 42 | /** | |
| 43 | * A map for associating arbitrary objects with locks for the lifetime of the objects. This allows, for example, | |
| 44 | * synchronization based on the arguments to a method (the alternative of directly locking on the arguments | |
| 45 | * themselves is dangerous, because the argument objects may be used for locking in a different context; two | |
| 46 | * threads locking on the same object for unrelated purposes may lead to deadlock). Each unique key | |
| 47 | * (distinguished via {@code ==}) is associated with a different ReentrantLock. Weak references are used to | |
| 48 | * allow keys to be freely garbage-collected. | |
| 49 | */ | |
| 50 | public class LockMap<T> { | |
| 51 | ||
| 52 | private final WeakHashMap<IdentityWrapper<T>, ReentrantLock> _map; | |
| 53 | ||
| 54 | 0 | public LockMap() { _map = new WeakHashMap<IdentityWrapper<T>, ReentrantLock>(); } |
| 55 | ||
| 56 | 14 | public LockMap(int initialCapacity) { |
| 57 | 14 | _map = new WeakHashMap<IdentityWrapper<T>, ReentrantLock>(initialCapacity); |
| 58 | } | |
| 59 | ||
| 60 | /** Get the lock associated with the given value. If necessary, allocate and cache a new lock. */ | |
| 61 | 0 | public synchronized ReentrantLock get(T val) { |
| 62 | 0 | IdentityWrapper<T> key = IdentityWrapper.make(val); |
| 63 | 0 | if (!_map.containsKey(key)) { _map.put(key, new ReentrantLock()); } |
| 64 | 0 | return _map.get(key); |
| 65 | } | |
| 66 | ||
| 67 | /** | |
| 68 | * Acquire the lock associated with the given value, and return a Runnable for unlocking when the lock can | |
| 69 | * be released. Clients should generally follow this invocation with a {@code try/finally} block that | |
| 70 | * guarantees execution of the resulting runnable. | |
| 71 | * @return A Runnable for invoking {@code lock.unlock()}. If invoked incorrectly, may throw an | |
| 72 | * {@link IllegalMonitorStateException}. | |
| 73 | * @see ReentrantLock#lock | |
| 74 | * @see ReentrantLock#unlock | |
| 75 | */ | |
| 76 | 0 | public Runnable lock(T val) { |
| 77 | 0 | final ReentrantLock l = get(val); |
| 78 | 0 | Runnable result = new Unlocker(l); |
| 79 | 0 | l.lock(); |
| 80 | 0 | return result; |
| 81 | } | |
| 82 | ||
| 83 | /** | |
| 84 | * Declared out of local scope to prevent accidental ties to local variables, potentially preventing | |
| 85 | * garbage collection. | |
| 86 | */ | |
| 87 | private static class Unlocker implements Runnable { | |
| 88 | private final ReentrantLock _l; | |
| 89 | 0 | public Unlocker(ReentrantLock l) { _l = l; } |
| 90 | 0 | public void run() { _l.unlock(); } |
| 91 | } | |
| 92 | ||
| 93 | } |
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