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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);

    }

}