--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/jdk/src/share/classes/sun/security/krb5/internal/rcache/ReplayCache.java	Sat Dec 01 00:00:00 2007 +0000
@@ -0,0 +1,151 @@
+/*
+ * Portions Copyright 2000-2006 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.
+ */
+
+/*
+ *
+ *  (C) Copyright IBM Corp. 1999 All Rights Reserved.
+ *  Copyright 1997 The Open Group Research Institute.  All rights reserved.
+ */
+
+package sun.security.krb5.internal.rcache;
+
+import sun.security.krb5.KrbException;
+import sun.security.krb5.Config;
+import sun.security.krb5.internal.Krb5;
+import java.util.LinkedList;
+import java.util.ListIterator;
+import sun.security.krb5.internal.KerberosTime;
+
+/**
+ * This class provides an efficient caching mechanism to store the timestamp of client authenticators.
+ * The cache minimizes the memory usage by doing self-cleanup of expired items in the cache.
+ *
+ * @author Yanni Zhang
+ */
+public class ReplayCache extends LinkedList<AuthTime> {
+
+    private static final long serialVersionUID = 2997933194993803994L;
+
+    private String principal;
+    private CacheTable table;
+    private int nap = 10 * 60 * 1000; //10 minutes break
+    private boolean DEBUG = Krb5.DEBUG;
+    /**
+     * Constructs a ReplayCache for a client principal in specified <code>CacheTable</code>.
+     * @param p client principal name.
+     * @param ct CacheTable.
+     */
+    public ReplayCache (String p, CacheTable ct) {
+        principal = p;
+        table = ct;
+    }
+
+    /**
+     * Puts the authenticator timestamp into the cache in descending order.
+     * @param t <code>AuthTime</code>
+     */
+    public synchronized void put(AuthTime t, long currentTime) {
+
+        if (this.size() == 0) {
+            addFirst(t);
+        }
+        else {
+            AuthTime temp = getFirst();
+            if (temp.kerberosTime < t.kerberosTime) {
+                // in most cases, newly received authenticator has
+                // larger timestamp.
+                addFirst(t);
+            }
+            else if (temp.kerberosTime == t.kerberosTime) {
+                if (temp.cusec < t.cusec) {
+                    addFirst(t);
+                }
+            }
+            else {
+                //unless client clock being re-adjusted.
+                ListIterator<AuthTime> it = listIterator(1);
+                while (it.hasNext()) {
+                    temp = it.next();
+                    if (temp.kerberosTime < t.kerberosTime) {
+                        add(indexOf(temp), t);
+                        break;
+                        //we always put the bigger timestamp at the front.
+                    }
+                    else if (temp.kerberosTime == t.kerberosTime) {
+                        if (temp.cusec < t.cusec) {
+                            add(indexOf(temp), t);
+                            break;
+                        }
+                    }
+                }
+            }
+        }
+
+        // let us cleanup while we are here
+        long timeLimit = currentTime - KerberosTime.getDefaultSkew() * 1000L;
+        ListIterator<AuthTime> it = listIterator(0);
+        AuthTime temp = null;
+        int index = -1;
+        while (it.hasNext()) {
+            //search expired timestamps.
+            temp = it.next();
+            if (temp.kerberosTime < timeLimit) {
+                index = indexOf(temp);
+                break;
+            }
+        }
+        if (index > -1) {
+            do {
+                //remove expired timestamps from the list.
+                removeLast();
+            } while(size() > index);
+        }
+        if (DEBUG) {
+            printList();
+        }
+
+        // if there are no entries in the replay cache,
+        // remove the replay cache from the table.
+        if (this.size() == 0) {
+            table.remove(principal);
+        }
+        if (DEBUG) {
+            printList();
+        }
+    }
+
+
+    /**
+     * Printes out the debug message.
+     */
+    private void printList() {
+        Object[] total = toArray();
+        for (int i = 0; i < total.length; i++) {
+            System.out.println("object " + i + ": " + ((AuthTime)total[i]).kerberosTime + "/"
+                               + ((AuthTime)total[i]).cusec);
+        }
+    }
+
+}