content: /*******************************************************************************
   * Copyright 2014 Trevor Robinson
   * 
   * Licensed 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 com.scurrilous.circe.impl;
  
  import java.util.Iterator;
  import java.util.ServiceLoader;
  
  /**
   * Provides access to a singleton hash function cache, if an implementation is
   * available.
   */
  public final class HashCacheLoader {
  
      private static final HashCache HASH_CACHE;
  
      static {
          final Iterator<HashCache> iterator = ServiceLoader.load(HashCache.class).iterator();
          HASH_CACHE = iterator.hasNext() ? iterator.next() : null;
      }
  
      /**
       * Returns whether a hash function cache is available.
       * 
       * @return true if a cache is available, false if {@link #getCache} will
       *         throw an exception
       */
      public static boolean hasCache() {
          return HASH_CACHE != null;
      }
  
      /**
       * Returns the single hash function cache.
       * 
       * @return the single hash cache
       * @throws UnsupportedOperationException if no hash cache is available
       */
      public static HashCache getCache() {
          if (HASH_CACHE == null)
              throw new UnsupportedOperationException();
          return HASH_CACHE;
      }
  
      private HashCacheLoader() {
      }
  }
  