PrimareUtils.java

/**
 * Copyright (c) 2010-2016 by the respective copyright holders.
 *
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 */
package org.openhab.binding.primare.internal.protocol;

import java.util.Arrays;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Class for Primare-specific utility functions
 *
 * @author Veli-Pekka Juslin
 * @since 1.7.0
 */
public class PrimareUtils {

    private static final Logger logger = LoggerFactory.getLogger(PrimareUtils.class);

    public static byte[] hexStringToByteArray(String s) {
        int len = s.length();
        byte[] data = new byte[len / 2];
        for (int i = 0; i < len; i += 2) {
            data[i / 2] = (byte) ((Character.digit(s.charAt(i), 16) << 4) + Character.digit(s.charAt(i + 1), 16));
        }
        return data;
    }

    public static String byteArrayToHex(byte[] a) {
        StringBuilder sb = new StringBuilder();
        for (byte b : a) {
            sb.append(String.format("%02x ", b & 0xff));
        }
        return sb.toString().trim();
    }

    public static String byteArraysToHex(byte[][] a) {
        StringBuilder sb = new StringBuilder();
        for (byte[] b : a) {
            sb.append(String.format("%s ", byteArrayToHex(b)));
        }
        return sb.toString().trim();
    }

    // DLE (0x10) requires ecaping (double DLE) before sending to device
    // Do not escape DLE at a.length-2
    public static byte[] escapeMessage(byte[] a) {
        byte[] buffer = new byte[a.length * 2];
        int target_ix = 0;

        for (int i = 0; i < a.length; i++) {
            if ((buffer[target_ix++] = a[i]) == 0x10 && (i != a.length - 2)) {
                buffer[target_ix++] = a[i];
            }
        }

        return Arrays.copyOf(buffer, target_ix);
    }

    // DLE (0x10) has been escaped (double DLE) when receiving message
    public static byte[] unescapeMessage(byte[] a) {
        byte[] buffer = new byte[a.length];
        int target_ix = 0;
        int double_dle_start = -2;
        for (int i = 0; i < a.length; i++) {
            if (a[i] == (byte) 0x10) {
                if (double_dle_start == i - 1) {
                    double_dle_start = -1;
                    continue; // skip second DLE
                } else {
                    double_dle_start = i;
                }
            }
            buffer[target_ix++] = a[i];
        }
        return Arrays.copyOf(buffer, target_ix);
    }
}