--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/fschmidt/db/util/Unique.java	Sun Oct 05 17:24:15 2025 -0600
@@ -0,0 +1,56 @@
+/*
+Copyright (c) 2008  Franklin Schmidt <fschmidt@gmail.com>
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.
+*/
+
+package fschmidt.db.util;
+
+import java.util.Map;
+import java.util.HashMap;
+
+
+public final class Unique<T> {
+
+	private static class Val<T> {
+		T o;
+		int count;
+	}
+
+	private Map<T,Val<T>> map = new HashMap<T,Val<T>>();
+
+	public synchronized T get(T o) {
+		Val<T> v = map.get(o);
+		if( v == null ) {
+			v = new Val<T>();
+			v.o = o;
+			map.put(o,v);
+		}
+		v.count++;
+		return v.o;
+	}
+
+	public synchronized void free(T o) {
+		Val<T> v = map.get(o);
+		if (v==null) return;
+		if( --v.count == 0 )
+			map.remove(o);
+	}
+}
+