1 files changed, 71 insertions, 0 deletions
diff --git a/bundles/org.eclipse.team.cvs.core/src/org/eclipse/team/internal/ccvs/core/syncinfo/ReentrantLock.java b/bundles/org.eclipse.team.cvs.core/src/org/eclipse/team/internal/ccvs/core/syncinfo/ReentrantLock.java
new file mode 100644
index 000000000..dae4bd4e2
--- /dev/null
+++ b/bundles/org.eclipse.team.cvs.core/src/org/eclipse/team/internal/ccvs/core/syncinfo/ReentrantLock.java
@@ -0,0 +1,71 @@
+/*******************************************************************************
+ * Copyright (c) 2002 IBM Corporation and others.
+ * All rights reserved.   This program and the accompanying materials
+ * are made available under the terms of the Common Public License v0.5
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/cpl-v05.html
+ * 
+ * Contributors:
+ * IBM - Initial implementation
+ ******************************************************************************/
+package org.eclipse.team.internal.ccvs.core.syncinfo;
+
+import org.eclipse.team.internal.ccvs.core.Policy;
+import org.eclipse.team.internal.ccvs.core.util.Assert;
+
+/**
+ * Provides a per-thread nested locking mechanism. A thread can acquire a
+ * lock and then call acquire() multiple times. Other threads that try
+ * and acquire the lock will be blocked until the first thread releases all
+ * it's nested locks.
+ */
+public class ReentrantLock {
+
+	private final static boolean DEBUG = Policy.DEBUG_THREADING;
+	private Thread thread;
+	private int nestingCount;
+	
+	public ReentrantLock() {
+		this.thread = null;
+		this.nestingCount = 0;
+	}
+	
+	public synchronized void acquire() {
+		// stop early if we've been interrupted -- don't enter the lock anew
+		Thread thisThread = Thread.currentThread();
+
+		// race for access to the lock -- does not guarantee fairness
+		if (thread != thisThread) {
+			while (nestingCount != 0) {
+				try {
+					if(DEBUG) System.out.println("["+ thisThread.getName() + "] waiting for CVS synchronizer lock");
+					wait();
+				} catch(InterruptedException e) {
+					// keep waiting for the lock
+					if(DEBUG) System.out.println("["+ thisThread.getName() + "] interrupted in CVS synchronizer lock");
+				}
+			}
+			thread = thisThread;
+			if(DEBUG) System.out.println("[" + thisThread.getName() + "] acquired CVS synchronizer lock");
+		}
+		nestingCount++;
+	}
+	
+	public synchronized void release() {
+		Thread thisThread = Thread.currentThread();
+		Assert.isLegal(thread == thisThread,
+			"Thread attempted to release a lock it did not own");
+		if (--nestingCount == 0) {
+			if(DEBUG) System.out.println("[" + thread.getName() + "] released CVS synchronizer lock");
+			thread = null;
+			notifyAll();
+		}
+	}
+	
+	public int getNestingCount() {
+		Thread thisThread = Thread.currentThread();
+		Assert.isLegal(thread == thisThread,
+			"Thread attempted to read nesting count of a lock it did not own");
+		return nestingCount;
+	}
+}