Convert 4 hex digits to an int, and return the number of converted bytes.

  
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 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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
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 * 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.
 */

import java.io.ByteArrayOutputStream;

/**
 * Library of utility methods useful in dealing with converting byte arrays to
 * and from strings of hexadecimal digits.
 * 
 * @author Craig R. McClanahan
 */

public final class HexUtils {
  // Code from Ajp11, from Apache's JServ

  // Table for HEX to DEC byte translation
  public static final int[] DEC = { -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
      -1, -1, -1, -1, -1, -1, -1, -1, -1, 00, 01, 02, 03, 04, 05, 06, 07, 8, 9, -1, -1, -1, -1, -1,
      -1, -1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1,
      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
      -1, -1, -1, -1, -1, -1, -1, -1, -1, };





  /**
   * Convert 4 hex digits to an int, and return the number of converted bytes.
   * 
   * @param hex
   *          Byte array containing exactly four hexadecimal digits
   * 
   * @exception IllegalArgumentException
   *              if an invalid hexadecimal digit is included
   */
  public static int convert2Int(byte[] hex) {
    // Code from Ajp11, from Apache's JServ

    // assert b.length==4
    // assert valid data
    int len;
    if (hex.length < 4)
      return 0;
    if (DEC[hex[0]] < 0)
      throw new IllegalArgumentException("hexUtil.bad");
    len = DEC[hex[0]];
    len = len << 4;
    if (DEC[hex[1]] < 0)
      throw new IllegalArgumentException("hexUtil.bad");
    len += DEC[hex[1]];
    len = len << 4;
    if (DEC[hex[2]] < 0)
      throw new IllegalArgumentException("hexUtil.bad");
    len += DEC[hex[2]];
    len = len << 4;
    if (DEC[hex[3]] < 0)
      throw new IllegalArgumentException("hexUtil.bad");
    len += DEC[hex[3]];
    return len;
  }

}

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Convert 4 hex digits to an int, and return the number of converted bytes. : Byte Read Write « File Input Output « Java

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