content: /*
   * Copyright 1999-2018 Alibaba Group Holding Ltd.
   *
   * 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.alibaba.druid.util;
  
  /**
   * format validation This class encodes/decodes hexadecimal data
   *
   * @author Jeffrey Rodriguez
   * @version $Id: HexBin.java,v 1.4 2007/07/19 04:38:32 ofung Exp $
   */
  public final class HexBin {
      private static final int BASE_LENGTH = 128;
      private static final int LOOKUP_LENGTH = 16;
      private static final byte[] HEX_NUMBER_TABLE = new byte[BASE_LENGTH];
      private static final char[] UPPER_CHARS = new char[LOOKUP_LENGTH];
      private static final char[] LOWER_CHARS = new char[LOOKUP_LENGTH];
  
      static {
          for (int i = 0; i < BASE_LENGTH; i++) {
              HEX_NUMBER_TABLE[i] = -1;
          }
          for (int i = '9'; i >= '0'; i--) {
              HEX_NUMBER_TABLE[i] = (byte) (i - '0');
          }
          for (int i = 'F'; i >= 'A'; i--) {
              HEX_NUMBER_TABLE[i] = (byte) (i - 'A' + 10);
          }
          for (int i = 'f'; i >= 'a'; i--) {
              HEX_NUMBER_TABLE[i] = (byte) (i - 'a' + 10);
          }
  
          for (int i = 0; i < 10; i++) {
              UPPER_CHARS[i] = (char) ('0' + i);
              LOWER_CHARS[i] = (char) ('0' + i);
          }
          for (int i = 10; i <= 15; i++) {
              UPPER_CHARS[i] = (char) ('A' + i - 10);
              LOWER_CHARS[i] = (char) ('a' + i - 10);
          }
      }
  
      public static String encode(byte[] bytes) {
          return encode(bytes, true);
      }
  
      public static String encode(byte[] bytes, boolean upperCase) {
          if (bytes == null) {
              return null;
          }
  
          final char[] chars = upperCase ? UPPER_CHARS : LOWER_CHARS;
  
          char[] hex = new char[bytes.length * 2];
          for (int i = 0; i < bytes.length; i++) {
              int b = bytes[i] & 0xFF;
              hex[i * 2] = chars[b >> 4];
              hex[i * 2 + 1] = chars[b & 0xf];
          }
          return new String(hex);
      }
  
      /**
       * Decode hex string to a byte array
       *
       * @param encoded encoded string
       * @return return array of byte to encode
       */
      public static byte[] decode(String encoded) {
          if (encoded == null) {
              return null;
          }
  
          int lengthData = encoded.length();
          if (lengthData % 2 != 0) {
              return null;
          }
  
          char[] binaryData = encoded.toCharArray();
          int lengthDecode = lengthData / 2;
          byte[] decodedData = new byte[lengthDecode];
          byte temp1, temp2;
          char tempChar;
          for (int i = 0; i < lengthDecode; i++) {
              tempChar = binaryData[i * 2];
              temp1 = (tempChar < BASE_LENGTH) ? HEX_NUMBER_TABLE[tempChar] : -1;
              if (temp1 == -1) {
                  return null;
              }
              tempChar = binaryData[i * 2 + 1];
              temp2 = (tempChar < BASE_LENGTH) ? HEX_NUMBER_TABLE[tempChar] : -1;
              if (temp2 == -1) {
                  return null;
              }
              decodedData[i] = (byte) ((temp1 << 4) | temp2);
          }
          return decodedData;
      }
  }
  