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/**
 * Copyright 2003-2016 SSHTOOLS Limited. All Rights Reserved.
 *
 * For product documentation visit https://www.sshtools.com/
 *
 * This file is part of J2SSH Maverick.
 *
 * J2SSH Maverick is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * J2SSH Maverick is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with J2SSH Maverick.  If not, see .
 */
package com.sshtools.ssh.components.jce;

import java.math.BigInteger;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

import com.sshtools.ssh.components.Digest;
import com.sshtools.util.ByteArrayWriter;

/**
 * An abstract class that implements the
 * {@link com.sshtools.ssh.components.Digest} interface to provide support for
 * JCE based digests.
 * 
 * @author Lee David Painter
 * 
 */
public class AbstractDigest implements Digest {

	MessageDigest digest;
	String jceAlgorithm;

	public AbstractDigest(String jceAlgorithm) throws NoSuchAlgorithmException {
		digest = JCEProvider.getProviderForAlgorithm(jceAlgorithm) == null ? MessageDigest
				.getInstance(jceAlgorithm) : MessageDigest
				.getInstance(jceAlgorithm,
						JCEProvider.getProviderForAlgorithm(jceAlgorithm));
	}

	public byte[] doFinal() {
		return digest.digest();
	}

	public void putBigInteger(BigInteger bi) {

		byte[] data = bi.toByteArray();
		putInt(data.length);
		putBytes(data);
	}

	public void putByte(byte b) {
		digest.update(b);
	}

	public void putBytes(byte[] data) {
		digest.update(data, 0, data.length);
	}

	public void putBytes(byte[] data, int offset, int len) {
		digest.update(data, offset, len);
	}

	public void putInt(int i) {
		putBytes(ByteArrayWriter.encodeInt(i));
	}

	public void putString(String str) {
		putInt(str.length());
		putBytes(str.getBytes());
	}

	public void reset() {
		digest.reset();
	}

	public String getProvider() {
		return digest.getProvider().getName();
	}

}