1 package org.apache.maven.surefire.junitcore.pc;
2
3 /*
4 * Licensed to the Apache Software Foundation (ASF) under one
5 * or more contributor license agreements. See the NOTICE file
6 * distributed with this work for additional information
7 * regarding copyright ownership. The ASF licenses this file
8 * to you under the Apache License, Version 2.0 (the
9 * "License"); you may not use this file except in compliance
10 * with the License. You may obtain a copy of the License at
11 *
12 * http://www.apache.org/licenses/LICENSE-2.0
13 *
14 * Unless required by applicable law or agreed to in writing,
15 * software distributed under the License is distributed on an
16 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
17 * KIND, either express or implied. See the License for the
18 * specific language governing permissions and limitations
19 * under the License.
20 */
21
22 import java.util.concurrent.Semaphore;
23
24 /**
25 * @author Tibor Digana (tibor17)
26 * @see Balancer
27 * @since 2.16
28 */
29 final class ThreadResourcesBalancer
30 implements Balancer
31 {
32 private final Semaphore balancer;
33
34 private final int numPermits;
35
36 /**
37 * <tt>fair</tt> set to false.
38 *
39 * @param numPermits number of permits to acquire when maintaining concurrency on tests.
40 * Must be >0 and < {@link Integer#MAX_VALUE}.
41 * @see #ThreadResourcesBalancer(int, boolean)
42 */
43 ThreadResourcesBalancer( int numPermits )
44 {
45 this( numPermits, false );
46 }
47
48 /**
49 * @param numPermits number of permits to acquire when maintaining concurrency on tests.
50 * Must be >0 and < {@link Integer#MAX_VALUE}.
51 * @param fair {@code true} guarantees the waiting schedulers to wake up in order they acquired a permit
52 * @throws IllegalArgumentException if <tt>numPermits</tt> is not positive number
53 */
54 ThreadResourcesBalancer( int numPermits, boolean fair )
55 {
56 if ( numPermits <= 0 )
57 {
58 throw new IllegalArgumentException(
59 String.format( "numPermits=%d should be positive number", numPermits ) );
60 }
61 balancer = new Semaphore( numPermits, fair );
62 this.numPermits = numPermits;
63 }
64
65 /**
66 * Acquires a permit from this balancer, blocking until one is available.
67 *
68 * @return {@code true} if current thread is <b>NOT</b> interrupted
69 * while waiting for a permit.
70 */
71 @Override
72 public boolean acquirePermit()
73 {
74 try
75 {
76 balancer.acquire();
77 return true;
78 }
79 catch ( InterruptedException e )
80 {
81 return false;
82 }
83 }
84
85 /**
86 * Releases a permit, returning it to the balancer.
87 */
88 @Override
89 public void releasePermit()
90 {
91 balancer.release();
92 }
93
94 @Override
95 public void releaseAllPermits()
96 {
97 balancer.release( numPermits );
98 }
99 }