1 files changed, 88 insertions, 0 deletions
diff --git a/src/javax/media/j3d/MRSWLock.java b/src/javax/media/j3d/MRSWLock.java
new file mode 100644
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+++ b/src/javax/media/j3d/MRSWLock.java
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+/*
+ * Copyright 1999-2008 Sun Microsystems, Inc.  All Rights Reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Sun designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Sun in the LICENSE file that accompanied this code.
+ *
+ * This code 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
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
+ * CA 95054 USA or visit www.sun.com if you need additional information or
+ * have any questions.
+ *
+ */
+
+package javax.media.j3d;
+
+/**
+ * Use this lock to allow multiple reads/single write synchronization.
+ * To prevent deadlock a read/writeLock call must match with a read/writeUnlock call.
+ * Write request has precedence over read request.
+ */
+
+class MRSWLock {
+
+    static boolean debug = false;
+
+    private int readCount;
+    private boolean write;
+    private int writeRequested;
+    private int lockRequested;
+
+    MRSWLock() {
+	readCount = 0;
+	write = false;
+	writeRequested = 0;
+	lockRequested = 0;
+    }
+
+    synchronized final void readLock() {
+	lockRequested++;
+	while((write == true) || (writeRequested > 0)) {
+	    try { wait(); } catch(InterruptedException e){}
+	}
+	lockRequested--;
+	readCount++;
+    }
+
+    synchronized final void readUnlock() {
+	if(readCount>0)
+	    readCount--;
+	else
+	    if(debug) System.err.println("ReadWriteLock.java : Problem! readCount is >= 0.");
+
+	if(lockRequested>0)
+	    notifyAll();
+    }
+
+    synchronized final void writeLock() {
+	lockRequested++;
+	writeRequested++;
+	while((readCount>0)||(write == true)) {
+	    try { wait(); } catch(InterruptedException e){}
+	}
+	write = true;
+	lockRequested--;
+	writeRequested--;
+    }
+
+    synchronized final void writeUnlock() {
+	write = false;
+
+	if(lockRequested>0)
+	    notifyAll();
+    }
+
+}