1 /*
   2  * Copyright (c) 2013, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 
  26 package sun.misc;
  27 
  28 import java.util.concurrent.locks.ReentrantLock;
  29 
  30 /**
  31  * This class is used to prevent multiple calling of g_thread_init ().
  32  *
  33  * Since version 2.24 of GLib, calling g_thread_init () multiple times is
  34  * allowed, but for older versions it will crash. There are two ways to 
  35  * find out if g_thread_init() has been called:
  36  * g_thread_get_initialized (), but it was introduced in 2.20
  37  * g_thread_supported (), but it is a macro and cannot be loaded with dlsym.
  38  *
  39  * usage:
  40  * <pre>
  41  * lock();
  42  * if (isInitializationNeeded) {
  43  *     //call to g_thread_init();
  44  *     initFinished();
  45  * }
  46  * unlock();
  47  * </pre>
  48  */
  49 public final class GThreadHelper {
  50 
  51     private static final ReentrantLock LOCK = new ReentrantLock();
  52     private static volatile boolean isGThreadInitialized = false;
  53 
  54     static void lock() {
  55         LOCK.lock();
  56     }
  57 
  58     static void unlock() {
  59         LOCK.unlock();
  60     }
  61 
  62     /**
  63      * MUST be called under LOCK
  64      * @return {@code true} if g_thread_init() has not been called
  65      */
  66     static boolean isInitializationNeeded() {
  67         return !isGThreadInitialized;
  68     }
  69 
  70     /**
  71      * MUST be called under LOCK
  72      * Call this method only after g_thread_init() call.
  73      */
  74     static void initFinished() {
  75         isGThreadInitialized = true;
  76     }
  77 }