1 files changed, 159 insertions, 0 deletions
diff --git a/projects/net.wotonomy.foundation/src/main/java/net/wotonomy/foundation/NSMultiReaderLock.java b/projects/net.wotonomy.foundation/src/main/java/net/wotonomy/foundation/NSMultiReaderLock.java
new file mode 100644
index 0000000..abed576
--- /dev/null
+++ b/projects/net.wotonomy.foundation/src/main/java/net/wotonomy/foundation/NSMultiReaderLock.java
@@ -0,0 +1,159 @@
+/*
+Wotonomy: OpenStep design patterns for pure Java applications.
+Copyright (C) 2002 Israfil consulting Services Corporation
+
+This library is free software; you can redistribute it and/or
+modify it under the terms of the GNU Lesser General Public
+License as published by the Free Software Foundation; either
+version 2.1 of the License, or (at your option) any later version.
+
+This library 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
+Lesser General Public License for more details.
+
+You should have received a copy of the GNU Lesser General Public
+License along with this library; if not, see http://www.gnu.org
+
+$Id: NSMultiReaderLock.java 893 2006-02-16 13:22:23Z cgruber $
+
+*/
+
+package net.wotonomy.foundation;
+
+import EDU.oswego.cs.dl.util.concurrent.ReentrantWriterPreferenceReadWriteLock;
+
+/**
+* A Read-Write lock that allows unlimited number of calling threads to
+* acquire read locks, but only one thread to acquire a write lock.  It 
+* is also reentrant, allowing each thread to re-acquire it's lock 
+* recursively.  For that reason it is somewhat slower, as there is a 
+* hash lookup when attempting to acquire and release reader locks. Of 
+* course a writer lock is quite a bit slower than a reader lock.  A 
+* write lock is mutally exclusive with read locks, though a thread 
+* that has obtained a read-lock may be promoted to a write lock and 
+* vice versa when conditions permit.
+*
+* @author cgruber@israfil.net
+* @author $Author: cgruber $
+* @version $Revision: 893 $
+*/
+public class NSMultiReaderLock extends ReentrantWriterPreferenceReadWriteLock implements NSLocking {
+
+    NSMutableDictionary _readerSuspended = new NSMutableDictionary();
+
+    public NSMultiReaderLock() {
+    }
+
+    public void lockForReading() {
+       try {
+            readerLock_.acquire();
+        } catch (InterruptedException interruptedexception) {
+            // Null behavior, as notify() is already called
+            // by acquire();            
+            // We may want to log here.  
+        }
+    }
+
+    public void unlockForReading() {
+        readerLock_.release();
+    }
+
+    public void lock() {
+        lockForWriting();
+    }
+
+    public void lockForWriting() {
+       try {
+            writerLock_.acquire();
+        } catch (InterruptedException interruptedexception) {
+            // Null behavior, as notify() is already called
+            // by acquire();            
+            // We may want to log here.  
+        }
+    }
+
+    public void unlock() {
+        unlockForWriting();
+    }
+
+    public void unlockForWriting() {
+        writerLock_.release();
+    }
+
+    /** @see com.webobjects.foundation.NSMultiReaderLock#suspendReaderLock() */
+    public void suspendReaderLocks() {
+        Thread thisThread = Thread.currentThread();
+        Integer suspendedReaders = (Integer)_readerSuspended.get(thisThread);
+        if (suspendedReaders != null && suspendedReaders.intValue() > 0) return;
+        // logic is to override startRead / endRead and ensure that the suspension
+        // isn't improperly stopped.
+		throw new UnsupportedOperationException("Not Yet Implemented");
+    }
+
+    /** @see com.webobjects.foundation.NSMultiReaderLock#retrieveReaderLock() */
+    public void retrieveReaderLocks() {
+        Thread thisThread = Thread.currentThread();
+        Integer suspendedReaders = (Integer)_readerSuspended.get(thisThread);
+        if (suspendedReaders != null && suspendedReaders.intValue() > 0) return;
+        // logic is to override startRead / endRead and ensure that the suspension
+        // isn't improperly stopped.
+        throw new UnsupportedOperationException("Not Yet Implemented");
+    }
+
+    public boolean tryLockForWriting() {
+        try {
+            return writerLock_.attempt(0);
+        } catch (InterruptedException interruptedexception) {
+            // notify() is already called by attempt();
+            // We may want to log here.  
+            return false;
+        }
+    }
+
+    public boolean tryLockForReading() {
+        try {
+            return readerLock_.attempt(0);
+        } catch (InterruptedException interruptedexception) {
+            // notify() is already called by attempt();
+            // We may want to log here.  
+            return false;
+        }
+    }
+
+    public String toString() {
+		throw new UnsupportedOperationException("Not Yet Implemented");
+    }
+
+    protected String _padString(long l, int i) {
+		throw new UnsupportedOperationException("Not Yet Implemented");
+    }
+
+    protected String _padString(String s, int i, boolean flag) {
+		throw new UnsupportedOperationException("Not Yet Implemented");
+    }
+
+
+}
+/*
+ * $Log$
+ * Revision 1.2  2006/02/16 13:15:00  cgruber
+ * Check in all sources in eclipse-friendly maven-enabled packages.
+ *
+ * Revision 1.2  2003/08/06 23:07:52  chochos
+ * general code cleanup (mostly, removing unused imports)
+ *
+ * Revision 1.1  2002/07/14 21:56:16  mpowers
+ * Contributions from cgruber.
+ *
+ * Revision 1.2  2002/06/26 00:40:22  cgruber
+ * Add implementation, using ReentrantWriterPreferenceReadWriteLock
+ * as a base.
+ * 
+ * suspendReaderLocks and retreiveReaderLocks is the one
+ * that's likeliest to be a pain.
+ *
+ * Revision 1.1  2002/06/25 07:52:57  cgruber
+ * Add quite a few abstract classes, interfaces, and classes.  All API consistent with WebObjects, but with no implementation, nor any private or package access members from the original.
+ *
+ */