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.EnumSet;
  import java.util.concurrent.Callable;
  import java.util.concurrent.ExecutionException;
  import com.scurrilous.circe.Hash;
  import com.scurrilous.circe.HashParameters;
  import com.scurrilous.circe.HashSupport;
  
  /**
   * Interface implemented by hash function caches.
   */
  public interface HashCache {
  
      /**
       * Requests a cached hash function with the given parameters and required
       * support flags. If no matching function is cached, the given loader is
       * called to obtain one to cache.
       * 
       * @param params the hash algorithm parameters
       * @param required the required hash support flags
       * @param loader a cache loader that creates the function if not cached
       * @return a hash with the given parameters and support flags
       * @throws ExecutionException if the loader throws an exception
       */
      Hash get(HashParameters params, EnumSet<HashSupport> required, Callable<Hash> loader)
              throws ExecutionException;
  }
  