1 /* |
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2 * Copyright (c) 2011, 2012, Oracle and/or its affiliates. All rights reserved. |
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
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4 * |
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5 * This code is free software; you can redistribute it and/or modify it |
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6 * under the terms of the GNU General Public License version 2 only, as |
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7 * published by the Free Software Foundation. Oracle designates this |
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8 * particular file as subject to the "Classpath" exception as provided |
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9 * by Oracle in the LICENSE file that accompanied this code. |
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10 * |
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11 * This code is distributed in the hope that it will be useful, but WITHOUT |
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12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
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13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
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14 * version 2 for more details (a copy is included in the LICENSE file that |
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15 * accompanied this code). |
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16 * |
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17 * You should have received a copy of the GNU General Public License version |
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18 * 2 along with this work; if not, write to the Free Software Foundation, |
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19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
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20 * |
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21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
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22 * or visit www.oracle.com if you need additional information or have any |
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23 * questions. |
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24 */ |
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25 |
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26 package com.apple.concurrent; |
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27 |
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28 import java.util.concurrent.*; |
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29 |
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30 /** |
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31 * Factory for {@link Executor}s and {@link ExecutorService}s backed by |
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32 * libdispatch. |
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33 * |
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34 * Access is controlled through the Dispatch.getInstance() method, because |
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35 * performed tasks occur on threads owned by libdispatch. These threads are |
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36 * not owned by any particular AppContext or have any specific context |
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37 * classloader installed. |
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38 * |
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39 * @since Java for Mac OS X 10.6 Update 2 |
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40 */ |
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41 public final class Dispatch { |
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42 /** |
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43 * The priorities of the three default asynchronous queues. |
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44 */ |
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45 public enum Priority { |
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46 LOW(-2), NORMAL(0), HIGH(2); // values from <dispatch/queue.h> |
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47 |
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48 final int nativePriority; |
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49 Priority(final int nativePriority) { this.nativePriority = nativePriority; } |
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50 }; |
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51 |
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52 final static Dispatch instance = new Dispatch(); |
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53 |
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54 /** |
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55 * Factory method returns an instnace of Dispatch if supported by the |
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56 * underlying operating system, and if the caller's security manager |
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57 * permits "canInvokeInSystemThreadGroup". |
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58 * |
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59 * @return a factory instance of Dispatch, or null if not available |
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60 */ |
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61 public static Dispatch getInstance() { |
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62 checkSecurity(); |
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63 if (!LibDispatchNative.nativeIsDispatchSupported()) return null; |
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64 |
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65 return instance; |
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66 } |
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67 |
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68 private static void checkSecurity() { |
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69 final SecurityManager security = System.getSecurityManager(); |
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70 if (security != null) security.checkPermission(new RuntimePermission("canInvokeInSystemThreadGroup")); |
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71 } |
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72 |
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73 private Dispatch() { } |
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74 |
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75 /** |
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76 * Creates an {@link Executor} that performs tasks asynchronously. The {@link Executor} |
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77 * cannot be shutdown, and enqueued {@link Runnable}s cannot be canceled. Passing null |
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78 * returns the {@link Priority.NORMAL} {@link Executor}. |
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79 * |
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80 * @param priority - the priority of the returned {@link Executor} |
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81 * @return an asynchronous {@link Executor} |
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82 */ |
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83 public Executor getAsyncExecutor(Priority priority) { |
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84 if (priority == null) priority = Priority.NORMAL; |
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85 final long nativeQueue = LibDispatchNative.nativeCreateConcurrentQueue(priority.nativePriority); |
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86 if (nativeQueue == 0L) return null; |
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87 return new LibDispatchConcurrentQueue(nativeQueue); |
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88 } |
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89 |
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90 int queueIndex = 0; |
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91 /** |
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92 * Creates an {@link ExecutorService} that performs tasks synchronously in FIFO order. |
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93 * Useful to protect a resource against concurrent modification, in lieu of a lock. |
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94 * Passing null returns an {@link ExecutorService} with a uniquely labeled queue. |
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95 * |
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96 * @param label - a label to name the queue, shown in several debugging tools |
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97 * @return a synchronous {@link ExecutorService} |
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98 */ |
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99 public ExecutorService createSerialExecutor(String label) { |
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100 if (label == null) label = ""; |
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101 if (label.length() > 256) label = label.substring(0, 256); |
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102 String queueName = "com.apple.java.concurrent."; |
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103 if ("".equals(label)) { |
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104 synchronized (this) { |
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105 queueName += queueIndex++; |
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106 } |
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107 } else { |
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108 queueName += label; |
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109 } |
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110 |
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111 final long nativeQueue = LibDispatchNative.nativeCreateSerialQueue(queueName); |
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112 if (nativeQueue == 0) return null; |
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113 return new LibDispatchSerialQueue(nativeQueue); |
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114 } |
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115 |
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116 Executor nonBlockingMainQueue = null; |
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117 /** |
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118 * Returns an {@link Executor} that performs the provided Runnables on the main queue of the process. |
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119 * Runnables submitted to this {@link Executor} will not run until the AWT is started or another native toolkit is running a CFRunLoop or NSRunLoop on the main thread. |
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120 * |
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121 * Submitting a Runnable to this {@link Executor} does not wait for the Runnable to complete. |
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122 * @return an asynchronous {@link Executor} that is backed by the main queue |
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123 */ |
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124 public synchronized Executor getNonBlockingMainQueueExecutor() { |
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125 if (nonBlockingMainQueue != null) return nonBlockingMainQueue; |
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126 return nonBlockingMainQueue = new LibDispatchMainQueue.ASync(); |
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127 } |
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128 |
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129 Executor blockingMainQueue = null; |
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130 /** |
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131 * Returns an {@link Executor} that performs the provided Runnables on the main queue of the process. |
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132 * Runnables submitted to this {@link Executor} will not run until the AWT is started or another native toolkit is running a CFRunLoop or NSRunLoop on the main thread. |
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133 * |
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134 * Submitting a Runnable to this {@link Executor} will block until the Runnable has completed. |
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135 * @return an {@link Executor} that is backed by the main queue |
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136 */ |
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137 public synchronized Executor getBlockingMainQueueExecutor() { |
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138 if (blockingMainQueue != null) return blockingMainQueue; |
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139 return blockingMainQueue = new LibDispatchMainQueue.Sync(); |
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140 } |
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141 } |
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