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 package org.apidesign.impl;

 import java.nio.ByteBuffer;

 import org.apidesign.spi.security.Digestor;

 /**

  *

  * @author Jaroslav Tulach <jaroslav.tulach@apidesign.org>

  */

 public abstract class DigestorAccessor {

     private static DigestorAccessor INSTANCE;

     protected DigestorAccessor() {

         if (this.getClass().getName().equals("org.apidesign.spi.security.DigestorAccessorImpl")) {

             assert INSTANCE == null;

             INSTANCE = this;

             return;

         }

         if (this.getClass().getName().equals("org.apidesign.api.security.DigestorAccessorImpl")) {

             return;

         }

         throw new IllegalStateException();

     }

     final DigestorAccessor getDefault() {

         try {

             Class.forName(Digestor.class.getName(), true, DigestorAccessor.class.getClassLoader());

             return INSTANCE;

         } catch (ClassNotFoundException ex) {

             throw new IllegalStateException(ex);

         }

     }

     protected abstract <Data> byte[] digest(Digestor<Data> dig, Data data);

     protected abstract <Data> Data create(Digestor<Data> dig, String algorithm); 

     protected abstract <Data> void update(Digestor<Data> dig, Data data, ByteBuffer input);

     protected final <Data> byte[] defaultDigest(Digestor<Data> dig, Data data) {

         return getDefault().digest(dig, data);

     }

     protected final <Data> Data defaultCreate(Digestor<Data> dig, String algorithm) {

         return getDefault().create(dig, algorithm);

     }

     protected final <Data> void defaultUpdate(Digestor<Data> dig, Data data, ByteBuffer input) {

         getDefault().update(dig, data, input);

     }

 }