/*

  * Licensed to the Apache Software Foundation (ASF) under one

  * or more contributor license agreements.  See the NOTICE file

  * distributed with this work for additional information

  * regarding copyright ownership.  The ASF licenses this file

  * to you under the Apache License, Version 2.0 (the

  * "License"); you may not use this file except in compliance

  * with the License.  You may obtain a copy of the License at

  *

  *   http://www.apache.org/licenses/LICENSE-2.0

  *

  * Unless required by applicable law or agreed to in writing,

  * software distributed under the License is distributed on an

  * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY

  * KIND, either express or implied.  See the License for the

  * specific language governing permissions and limitations

  * under the License.

  */

 package org.apache.myfaces.lifecycle;

 import java.math.BigInteger;

 import java.security.NoSuchAlgorithmException;

 import java.security.SecureRandom;

 import java.util.concurrent.atomic.AtomicLong;

 /**

  *

  * @author lu4242

  */

 class TokenGenerator

 {

     private final AtomicLong _count;

     public TokenGenerator()

     {

         _count = new AtomicLong(_getSeed());

     }

     private static long _getSeed()

     {

         SecureRandom rng;

         try

         {

             // try SHA1 first

             rng = SecureRandom.getInstance("SHA1PRNG");

         }

         catch (NoSuchAlgorithmException e)

         {

             // SHA1 not present, so try the default (which could potentially not be

             // cryptographically secure)

             rng = new SecureRandom();

         }

         // use 48 bits for strength and fill them in

         byte[] randomBytes = new byte[6];

         rng.nextBytes(randomBytes);

         // convert to a long

         return new BigInteger(randomBytes).longValue();

     }

     /**

      * Get the next token to be assigned to this request

      * 

      * @return

      */

     String _getNextToken()

     {

         // atomically increment the value

         long nextToken = _count.incrementAndGet();

         // convert using base 36 because it is a fast efficient subset of base-64

         return Long.toString(nextToken, 36);

     }

 }