package com.example.blu.toys.ble.agreement;

import java.io.UnsupportedEncodingException;
import java.nio.charset.Charset;

public class HexStringUtils {

 private static final char[] DIGITS_HEX = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F' };

 protected static char[] encodeHex(byte[] data) {
  int l = data.length;
  char[] out = new char[l << 1];
  for (int i = 0, j = 0; i < l; i++) {
   out[j++] = DIGITS_HEX[(0xF0 & data[i]) >>> 4];
   out[j++] = DIGITS_HEX[0x0F & data[i]];
  }
  return out;
 }

 protected static byte[] decodeHex(char[] data) {
  int len = data.length;
  if ((len & 0x01) != 0) {
   throw new RuntimeException("字符个数应该为偶数");
  }
  byte[] out = new byte[len >> 1];
  for (int i = 0, j = 0; j < len; i++) {
   int f = toDigit(data[j], j) << 4;
   j++;
   f |= toDigit(data[j], j);
   j++;
   out[i] = (byte) (f & 0xFF);
  }
  return out;
 }

 protected static int toDigit(char ch, int index) {
  int digit = Character.digit(ch, 16);
  if (digit == -1) {
   throw new RuntimeException("Illegal hexadecimal character " + ch + " at index " + index);
  }
  return digit;
 }

 public static String toHexString(byte[] bs) {
  return new String(encodeHex(bs));
 }

 public static byte[] hexString2Bytes(String hex) {
  return decodeHex(hex.toCharArray());
 }

 public static byte[] chars2Bytes(char[] bs) {
  return decodeHex(bs);
 }

}