new 1.2 classes

1 files changed, 165 insertions, 0 deletions

diff --git a/java/lang/InheritableThreadLocal.java b/java/lang/InheritableThreadLocal.java
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+++ b/java/lang/InheritableThreadLocal.java
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+/* java.lang.InheritableThreadLocal
+   Copyright (C) 2000 Free Software Foundation, Inc.
+
+This file is part of GNU Classpath.
+
+GNU Classpath is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2, or (at your option)
+any later version.
+ 
+GNU Classpath is distributed in the hope that it will be useful, but
+WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with GNU Classpath; see the file COPYING.  If not, write to the
+Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
+02111-1307 USA.
+
+As a special exception, if you link this library with other files to
+produce an executable, this library does not by itself cause the
+resulting executable to be covered by the GNU General Public License.
+This exception does not however invalidate any other reasons why the
+executable file might be covered by the GNU General Public License. */
+
+package java.lang;
+
+import java.util.Iterator;
+import java.util.HashSet;
+import java.util.Map;
+import java.util.Set;
+import java.util.WeakHashMap;
+
+/**
+ * ThreadLocal whose value is inherited by child Threads.
+ * The value of the InheritableThreadLocal associated with the (parent) Thread
+ * on the moment that it creates a new (child) Thread is set as the value that
+ * is associated with the new (child) Thread.
+ * <p>
+ * It is possible to make the value associated with the child Thread a function
+ * of the value that is associated with the parent Thread by overriding the
+ * <code>childValue()</code> method.
+ *
+ * @since 1.2
+ * @author Mark Wielaard (mark@klomp.org)
+ */
+public class InheritableThreadLocal extends ThreadLocal {
+	
+	/**
+	 * Maps Threads to a Set of InheritableThreadLocals
+	 * (the heritage of that Thread).
+	 * Uses a WeakHashMap so if the Thread is garbage collected the reference
+	 * to that Set disappears.
+	 * Both <code>AddToHeritage</code> access and modify it so they have to
+	 * synchronize on the threadMap when they do.
+	 */
+	private static Map threadMap = new WeakHashMap();
+	
+	/**
+	 * Creates a new InheritableThreadLocal that has no values associated
+	 * with it yet.
+	 */
+	public InheritableThreadLocal() {
+		super();
+	}
+	
+	/**
+	 * Determines the value associated with a newly created child Thread
+	 * as a function of the value associated with the currently executing
+	 * (parent) Thread.
+	 * <p>
+	 * The default implementation just returns the parentValue.
+	 */
+	protected Object childValue(Object parentValue) {
+		return parentValue;
+	}
+	
+	/**
+	 * Adds this <code>InheritableThreadLocal</code> to the heritage of the
+	 * current Thread and returns the value of the <code>ThreadLocal</code>
+	 * for the Thread. The value will be either the last value that the
+	 * current Thread has set, or the childValue of the last value that the
+	 * parent Thread set before the current Thread was created, or the
+	 * initialValue of the <code>ThreadLocal</code>.
+	 *
+	 * @see ThreadLocal#get()
+	 */
+	public Object get() {
+		addToHeritage(); 
+		return super.get();
+	}
+	
+	/**
+	 * Adds this <code>InheritableThreadLocal</code> to the heritage of the
+	 * current Thread and sets the value of the <code>ThreadLocal</code>
+	 * for the Thread.
+	 *
+	 * @see ThreadLocal#set(Object)
+	 */
+	public void set(Object value) {
+		addToHeritage();
+		super.set(value);
+	}
+	
+	/**
+	 * Adds this <code>InheritableThreadLocal</code> to the heritage
+	 * of the current Thread.
+	 */
+	private void addToHeritage() {
+		Thread currentThread = Thread.currentThread();
+		Set heritage;
+		synchronized(threadMap) {
+			heritage = (Set)threadMap.get(currentThread);
+		}
+		// Note that we don't have to synchronize on the heritage Set
+		// since only this Thread (or the parent Thread when creating
+		// the heritage) ever modifies it.
+		if (heritage == null) {
+			heritage = new HashSet();
+			synchronized(threadMap) {
+				threadMap.put(currentThread, heritage);
+			}
+		}
+		heritage.add(this);
+	}
+	
+	/**
+	 * Generates the childValues of all <code>InheritableThreadLocal</code>s
+	 * that are in the heritage of the current Thread for the newly created
+	 * childThread.
+	 * Should be called from the contructor of java.lang.Thread.
+	 */
+	static void newChildThread(Thread childThread) {
+		// The currentThread is the parent of the new thread
+		Thread parentThread = Thread.currentThread();
+		
+		// Inherit all the InheritableThreadLocals of the parent thread
+		Set heritage;
+		synchronized(threadMap) {
+			heritage = (Set)threadMap.get(parentThread);
+		}
+		// Note that we don't have to synchronize on the heritage Set
+		// since only this Thread (or the parent Thread when creating
+		// the heritage) ever modifies it.
+		if (heritage != null) {
+			synchronized(threadMap) {
+				threadMap.put(childThread, new HashSet(heritage));
+			}
+			// And constructs all the new child values
+			// (has to be done now that we are executing in the parentThread)
+			Iterator it = heritage.iterator();
+			while (it.hasNext()) {
+				InheritableThreadLocal local =
+					(InheritableThreadLocal) it.next();
+				// Note that the parentValue cannot be null
+				// If it was it would not be in the heritage
+				Object parentValue = local.get(parentThread).getValue();
+				Object childValue = local.childValue(parentValue);
+				ThreadLocal.Value v = new ThreadLocal.Value(childValue);
+				local.set(childThread, v);
+			}
+		}
+	}
+}