http://github.com/google/tink: Tink is a small cryptographic library that provides a safe, simple, agile and fast way to accomplish some common cryptographic tasks. 
// Copyright 2017 Google Inc.
//
// 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.google.crypto.tink;

import java.security.GeneralSecurityException;


Basic interface for wrapping a primitive.

A PrimitiveSet can be wrapped by a single primitive in order to fulfil a cryptographic task. This is done by the PrimitiveWrapper. Whenever a new primitive type is added to Tink, the user should define a new PrimitiveWrapper and register it by calling com.google.crypto.tink.Registry#registerPrimitiveWrapper. 
/**
 * Basic interface for wrapping a primitive.
 *
 * <p>A PrimitiveSet can be wrapped by a single primitive in order to fulfil a cryptographic task.
 * This is done by the PrimitiveWrapper. Whenever a new primitive type is added to Tink, the user
 * should define a new PrimitiveWrapper and register it by calling
 * {@code com.google.crypto.tink.Registry#registerPrimitiveWrapper}.
 */
public interface PrimitiveWrapper<P> {
  
Wraps a PrimitiveSet and returns a single instance. This has to be implemented when a new primitive type is added. 
/**
   * Wraps a {@code PrimitiveSet} and returns a single instance.
   *
   * This has to be implemented when a new primitive type is added. */
  P wrap(PrimitiveSet<P> set) throws GeneralSecurityException;

  
Returns the primitive class object of the primitive managed. Used for internal management. Should be implemented as return P.class; when implementing a key manager for primitive {$code P}. 
/**
   * Returns the primitive class object of the primitive managed. Used for internal management.
   * Should be implemented as {@code return P.class;} when implementing a key manager for
   * primitive {$code P}.
   */
  Class<P> getPrimitiveClass();
}