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14  * version 2 for more details (a copy is included in the LICENSE file that
15  * accompanied this code).
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17  * You should have received a copy of the GNU General Public License version
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24  */
25 package com.sun.org.apache.xml.internal.utils;
26 
27 /**
28  * This is a combination of ThreadControllerWrapper's inner class SafeThread
29  * that was introduced as a fix for CR 6607339
30  * and sun.misc.ManagedLocalsThread, a thread that has it's thread locals, and
31  * inheritable thread locals erased on construction. Except the run method,
32  * it is identical to sun.misc.ManagedLocalsThread.
33  */
34 public class SafeThread extends Thread {
35 
36     private static final jdk.internal.misc.Unsafe UNSAFE;
37     private static final long THREAD_LOCALS;
38     private static final long INHERITABLE_THREAD_LOCALS;
39 
40     private volatile boolean ran = false;
41 
SafeThread(Runnable target)42     public SafeThread(Runnable target) {
43         super(target);
44         eraseThreadLocals();
45     }
46 
SafeThread(Runnable target, String name)47     public SafeThread(Runnable target, String name) {
48         super(target, name);
49         eraseThreadLocals();
50     }
51 
SafeThread(ThreadGroup group, Runnable target, String name)52     public SafeThread(ThreadGroup group, Runnable target, String name) {
53         super(group, target, name);
54         eraseThreadLocals();
55     }
56 
run()57     public final void run() {
58         if (Thread.currentThread() != this) {
59             throw new IllegalStateException("The run() method in a"
60                     + " SafeThread cannot be called from another thread.");
61         }
62         synchronized (this) {
63             if (!ran) {
64                 ran = true;
65             } else {
66                 throw new IllegalStateException("The run() method in a"
67                         + " SafeThread cannot be called more than once.");
68             }
69         }
70         super.run();
71     }
72 
73     /**
74      * Drops all thread locals (and inherited thread locals).
75      */
eraseThreadLocals()76     public final void eraseThreadLocals() {
77         UNSAFE.putReference(this, THREAD_LOCALS, null);
78         UNSAFE.putReference(this, INHERITABLE_THREAD_LOCALS, null);
79     }
80 
81     static {
82         UNSAFE = jdk.internal.misc.Unsafe.getUnsafe();
83         Class<?> t = Thread.class;
84         try {
85             THREAD_LOCALS = UNSAFE.objectFieldOffset(t.getDeclaredField("threadLocals"));
86             INHERITABLE_THREAD_LOCALS = UNSAFE.objectFieldOffset(t.getDeclaredField("inheritableThreadLocals"));
87         } catch (Exception e) {
88             throw new Error(e);
89         }
90     }
91 
92 }
93