/*
 * Copyright (c) 2008-2014 MongoDB, 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.mongodb.util;

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

/**
 *  Misc utility helpers.  Not sure what else to call the class
 */
public class Util {

    public static String toHex( byte b[] ){
        StringBuilder sb = new StringBuilder();
        
        for ( int i=0; i<b.length; i++ ){
            String s = Integer.toHexString(0xff & b[i]);
            
            if (s.length() < 2) {
                sb.append("0");
            }
                sb.append(s);
        }
        
        return sb.toString();

    }

    /**
     *  Produce hex representation of the MD5 digest of a byte array
     *
     * @param data bytes to digest
     * @return hex string of the MD5 digest
     */
    public static String hexMD5(byte[] data) {

        try {
            MessageDigest md5 = MessageDigest.getInstance("MD5");

            md5.reset();
            md5.update(data);
            byte digest[] = md5.digest();
            
            return toHex( digest );
        } catch (NoSuchAlgorithmException e) {
            throw new RuntimeException("Error - this implementation of Java doesn't support MD5.");
        }
    }

    public static String hexMD5( ByteBuffer buf , int offset , int len ){
        byte b[] = new byte[len];
        for ( int i=0; i<len; i++ )
            b[i] = buf.get( offset + i );
        
        return hexMD5( b );
    }
}
