package com.sandu.ximon.admin.manager.iot.rrpc.util;

/**
 * @author chenjiantian
 */
public class SupplementUtils {


    /**
     * 截取指定长度的字符串，不足以0填充前面
     * @param hex 字符串
     * @param totalBit 截取长度
     * @return 截取后的字符串
     */
    public static String suppleZero(String hex, Integer totalBit) {

        if (hex.length() > totalBit) {
            return hex.substring(0, totalBit);
        } else if (hex.length() == totalBit) {
            return hex;
        }
        totalBit = totalBit - hex.length();

        StringBuilder hexBuilder = new StringBuilder(hex);
        for (int i = 0; i < totalBit; i++) {
            hexBuilder.insert(0, "0");
        }
        hex = hexBuilder.toString();
        return hex;
    }

    /** 十六进制转换成字节数组 */
    public static byte[] hexStringToBytes(String hexString) {
        if (hexString == null || hexString.equals("")) {
            return null;
        }
        hexString = hexString.toUpperCase(); // 十六进制转大写字母
        int length = hexString.length() / 2; // 获取十六进制的长度，2个字符为一个十六进制
        char[] hexChars = hexString.toCharArray();
        byte[] d = new byte[length];
        for (int i = 0; i < length; i++) {
            int pos = i * 2;
            d[i] = (byte) (charToByte(hexChars[pos]) << 4 | charToByte(hexChars[pos + 1]));
        }
        return d;
    }

    /** char转byte */
    private static byte charToByte(char c) {
        return (byte) "0123456789ABCDEF".indexOf(c);
    }


}