Util.java

/*
 * Java OTR library Copyright (C) 2008-2009 Ian Goldberg, Muhaimeen Ashraf,
 * Andrew Chung, Can Tang
 *
 * This library is free software; you can redistribute it and/or modify it under
 * the terms of version 2.1 of the GNU Lesser General Public License as
 * published by the Free Software Foundation.
 *
 * This library 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 Lesser General Public License for more
 * details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this library; if not, write to the Free Software Foundation, Inc.,
 * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 */

package net.java.otr4j.crypto;

public class Util {
    public static boolean arrayEquals(byte[] b1, byte[] b2) {
        if (b1 == null || b2 == null || b1.length != b2.length) {
            return false;
        }
        for (int i = 0; i < b1.length; i++) {
            if (b1[i] != b2[i]) {
                return false;
            }
        }
        return true;
    }

    public static void checkBytes(String s, byte[] bytes) {
        String hexString = new String();
        for (int i = 0; i < bytes.length; i++) {
            hexString += Integer.toHexString((bytes[i] >>> 4) & 0x0F);
            hexString += Integer.toHexString(0x0F & bytes[i]);
        }
        System.out.println(s + ": " + hexString);
    }

    static void writeInt(byte[] dst, int index, int src) {
        dst[index] = (byte) ((src >> 24) & 0xff);
        dst[index + 1] = (byte) ((src >> 16) & 0xff);
        dst[index + 2] = (byte) ((src >> 8) & 0xff);
        dst[index + 3] = (byte) (src & 0xff);
    }

    static int readInt(byte[] src, int index) {
        int ret = ((int) src[index] << 24) | ((int) (src[index + 1] << 16) & 0xff0000)
                  | ((int) (src[index + 2] << 8) & 0xff00) | ((int) src[index + 3] & 0xff);
        return ret;
    }

    static byte[] hexStringToBytes(String s) {
        byte[] sbytes = s.getBytes();
        if (sbytes.length % 2 != 0)
            return null;
        byte[] ret = new byte[sbytes.length / 2];
        for (int i = 0; i < ret.length; i++) {
            if (sbytes[2 * i] >= 'A' && sbytes[2 * i] <= 'F') {
                ret[i] = (byte) ((sbytes[2 * i] - ('A' - 10)) << 4);
            } else if (sbytes[2 * i] >= 'a' && sbytes[2 * i] <= 'f') {
                ret[i] = (byte) ((sbytes[2 * i] - ('a' - 10)) << 4);
            } else {
                ret[i] = (byte) ((sbytes[2 * i] - '0') << 4);
            }
            if (sbytes[2 * i + 1] >= 'A' && sbytes[2 * i + 1] <= 'F') {
                ret[i] |= (byte) (sbytes[2 * i + 1] - ('A' - 10));
            } else if (sbytes[2 * i + 1] >= 'a' && sbytes[2 * i + 1] <= 'f') {
                ret[i] |= (byte) (sbytes[2 * i + 1] - ('a' - 10));
            } else {
                ret[i] |= (byte) (sbytes[2 * i + 1] - '0');
            }
        }
        return ret;
    }

    static String bytesToHexString(byte[] mpi) {
        byte[] hex = new byte[2 * mpi.length];
        for (int i = 0; i < mpi.length; i++) {
            int num = (int) (mpi[i] >> 4 & 0xf);
            if (num <= 9) {
                hex[2 * i] = (byte) ('0' + num);
            } else {
                hex[2 * i] = (byte) ('A' + num - 10);
            }
            num = (int) (mpi[i] & 0xf);
            if (num <= 9) {
                hex[2 * i + 1] = (byte) ('0' + num);
            } else {
                hex[2 * i + 1] = (byte) ('A' + num - 10);
            }

        }
        return new String(hex);
    }

}