use soft refs for keyword intern table

1 files changed, 13 insertions, 3 deletions

diff --git a/src/jvm/clojure/lang/Keyword.java b/src/jvm/clojure/lang/Keyword.java
index ac080923..75adcdd7 100644
--- a/src/jvm/clojure/lang/Keyword.java
+++ b/src/jvm/clojure/lang/Keyword.java
@@ -15,18 +15,28 @@ package clojure.lang;
 import java.io.ObjectStreamException;
 import java.io.Serializable;
 import java.util.concurrent.ConcurrentHashMap;
+import java.lang.ref.ReferenceQueue;
+import java.lang.ref.SoftReference;
 
 
 public final class Keyword implements IFn, Comparable, Named, Serializable {
 
-private static ConcurrentHashMap<Symbol, Keyword> table = new ConcurrentHashMap();
+private static ConcurrentHashMap<Symbol, SoftReference<Keyword>> table = new ConcurrentHashMap();
+static final ReferenceQueue rq = new ReferenceQueue();
 public final Symbol sym;
 final int hash;
 
 public static Keyword intern(Symbol sym){
+	Util.clearCache(rq, table);
 	Keyword k = new Keyword(sym);
-	Keyword existingk = table.putIfAbsent(sym, k);
-	return existingk == null ? k : existingk;
+	SoftReference<Keyword> existingRef = table.putIfAbsent(sym, new SoftReference<Keyword>(k,rq));
+	if(existingRef == null)
+		return k;
+	Keyword existingk = existingRef.get();
+	if(existingk != null)
+		return existingk;
+	//entry died in the interim, do over
+	return intern(sym);
 }
 
 public static Keyword intern(String ns, String name){