/*
* Created on Apr 13, 2004
* Created by Alon Rohter
* Copyright (C) 2004, 2005, 2006 Aelitis, All Rights Reserved.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
* This program 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 this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
*
* AELITIS, SAS au capital de 46,603.30 euros
* 8 Allee Lenotre, La Grille Royale, 78600 Le Mesnil le Roi, France.
* 
*/

package com.frostwire.torrent;

import java.nio.ByteBuffer;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

/**
 * SHA-1 hasher utility frontend.
 */
final class SHA1Hasher {

    private final MessageDigest sha1;

    /**
     * Create a new SHA1Hasher instance
     */
    public SHA1Hasher() {
        try {
            sha1 = MessageDigest.getInstance("SHA-1");
        } catch (NoSuchAlgorithmException e) {
            throw new RuntimeException(e);
        }
    }

    /**
     * Calculate the SHA-1 hash for the given bytes.
     * @param bytes data to hash
     * @return 20-byte hash
     */
    public byte[] calculateHash(byte[] bytes) {
        ByteBuffer buff = ByteBuffer.wrap(bytes);
        return calculateHash(buff);
    }

    /**
     * Calculate the SHA-1 hash for the given buffer.
     * @param buffer data to hash
     * @return 20-byte hash
     */
    public byte[] calculateHash(ByteBuffer buffer) {
        sha1.reset();
        sha1.update(buffer);
        return sha1.digest();
    }

    /**
     * Start or continue a hash calculation with the given data.
     * @param data input
     */
    public void update(byte[] data) {
        update(ByteBuffer.wrap(data));
    }

    /**
     * Start or continue a hash calculation with the given data,
     * starting at the given position, for the given length.
     * @param data input
     * @param pos start position
     * @param len length
     */
    public void update(byte[] data, int pos, int len) {
        update(ByteBuffer.wrap(data, pos, len));
    }

    /**
     * Start or continue a hash calculation with the given data.
     * @param buffer data input
     */
    public void update(ByteBuffer buffer) {
        sha1.update(buffer);
    }

    /**
     * Finish the hash calculation.
     * @return 20-byte hash
     */
    public byte[] getDigest() {
        return sha1.digest();
    }

    /**
     * Resets the hash calculation.
     */
    public void reset() {
        sha1.reset();
    }

}