From 254ee6f47eebfc00462c10756a92066e82cc1a96 Mon Sep 17 00:00:00 2001
From: Andrew Branson <andrew@andrewbranson.net>
Date: Tue, 21 Jun 2011 15:46:02 +0200
Subject: Initial commit

---
 source/com/c2kernel/utils/TransientCache.java | 115 ++++++++++++++++++++++++++
 1 file changed, 115 insertions(+)
 create mode 100755 source/com/c2kernel/utils/TransientCache.java

(limited to 'source/com/c2kernel/utils/TransientCache.java')

diff --git a/source/com/c2kernel/utils/TransientCache.java b/source/com/c2kernel/utils/TransientCache.java
new file mode 100755
index 0000000..b93bbd7
--- /dev/null
+++ b/source/com/c2kernel/utils/TransientCache.java
@@ -0,0 +1,115 @@
+
+package com.c2kernel.utils;
+import java.lang.ref.*;
+import java.util.*;
+/**************************************************************************
+ * TransientCache - Uses transient references to allow unused entries to be 
+ * reaped by the java garbage collector.
+ *
+ * $Revision: 1.1 $
+ * $Date: 2004/04/20 09:37:02 $
+ *
+ * Copyright (C) 2003 CERN - European Organization for Nuclear Research
+ * All rights reserved.
+ **************************************************************************/
+public abstract class TransientCache extends AbstractMap {
+    
+    private Map map = new Hashtable();
+    public synchronized Set entrySet() {
+        Map newMap;
+        Iterator iter;
+        newMap = new Hashtable();
+        iter = map.entrySet().iterator();
+        while (iter.hasNext()) {
+            Map.Entry me = (Map.Entry)iter.next();
+            Reference ref = (Reference)me.getValue();
+            Object o = ref.get();
+            if (o == null) {
+                // Delete cleared reference 
+                iter.remove();
+            } else {
+                // Copy out interior object 
+                newMap.put(me.getKey(), o);
+            }
+        }
+        // Return set of interior objects 
+        return newMap.entrySet();
+    }
+    
+    public synchronized Object put(Object key, Object value) {
+        Reference ref = makeReference(value);
+        ref = (Reference)map.put(key, ref);
+        if (ref != null)
+            return (ref.get());
+        return null;
+    }
+    
+    public abstract Reference makeReference(Object value);
+    
+    public Object remove(Object key) {
+        Iterator i = map.entrySet().iterator();
+        Entry correctEntry = null;
+        if (key == null) {
+            while (correctEntry == null && i.hasNext()) {
+                Entry e = (Entry)i.next();
+                if (e.getKey() == null)
+                    correctEntry = e;
+            }
+        } else {
+            while (correctEntry == null && i.hasNext()) {
+                Entry e = (Entry)i.next();
+                if (key.equals(e.getKey()))
+                    correctEntry = e;
+            }
+        }
+        Object oldValue = null;
+        if (correctEntry != null) {
+            Reference correctReference = (Reference)correctEntry.getValue();
+            oldValue = correctReference.get();
+            i.remove();
+        }
+        return oldValue;
+    }
+    /**
+     *
+     */
+    public void clear() {
+        map.entrySet().clear();
+    }
+    
+    private transient Set keySet = null;
+    
+    public Set keySet() {
+        if (keySet == null) {
+            keySet = new AbstractSet() {
+            public Iterator iterator() {
+                return new Iterator() {
+                private Iterator i = map.entrySet().iterator();
+
+                public boolean hasNext() {
+                    return i.hasNext();
+                }
+
+                public Object next() {
+                    return ((Entry)i.next()).getKey();
+                }
+
+                public void remove() {
+                    i.remove();
+                }
+                        };
+            }
+
+            public int size() {
+                return TransientCache.this.size();
+            }
+
+            public boolean contains(Object k) {
+                return TransientCache.this.containsKey(k);
+            }
+            };
+        }
+        return keySet;
+        }
+
+}
-- 
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