code: /*
   * 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
   * 
   * 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 org.apache.commons.io;
  
  import java.io.IOException;
  import java.io.OutputStream;
  
  /**
   * Dumps data in hexadecimal format.
   * <p>
   * Provides a single function to take an array of bytes and display it
   * in hexadecimal form.
   * <p>
   * Origin of code: POI.
   *
   * @author Scott Sanders
   * @author Marc Johnson
   * @version $Id: HexDump.java 736507 2009-01-22 00:52:15Z jukka $
   */
  public class HexDump {
  
      /**
       * Instances should NOT be constructed in standard programming.
       */
      public HexDump() {
          super();
      }
  
      /**
       * Dump an array of bytes to an OutputStream. The output is formatted
       * for human inspection, with a hexadecimal offset followed by the
       * hexadecimal values of the next 16 bytes of data and the printable ASCII
       * characters (if any) that those bytes represent printed per each line
       * of output.
       * <p>
       * The offset argument specifies the start offset of the data array
       * within a larger entity like a file or an incoming stream. For example,
       * if the data array contains the third kibibyte of a file, then the
       * offset argument should be set to 2048. The offset value printed
       * at the beginning of each line indicates where in that larger entity
       * the first byte on that line is located.
       * <p>
       * All bytes between the given index (inclusive) and the end of the
       * data array are dumped. 
       *
       * @param data  the byte array to be dumped
       * @param offset  offset of the byte array within a larger entity
       * @param stream  the OutputStream to which the data is to be
       *               written
       * @param index initial index into the byte array
       *
       * @throws IOException is thrown if anything goes wrong writing
       *         the data to stream
       * @throws ArrayIndexOutOfBoundsException if the index is
       *         outside the data array's bounds
       * @throws IllegalArgumentException if the output stream is null
       */
  
      public static void dump(byte[] data, long offset,
                              OutputStream stream, int index)
              throws IOException, ArrayIndexOutOfBoundsException,
              IllegalArgumentException {
          
          if ((index < 0) || (index >= data.length)) {
              throw new ArrayIndexOutOfBoundsException(
                      "illegal index: " + index + " into array of length "
                      + data.length);
          }
          if (stream == null) {
              throw new IllegalArgumentException("cannot write to nullstream");
          }
          long display_offset = offset + index;
          StringBuilder buffer = new StringBuilder(74);
  
          for (int j = index; j < data.length; j += 16) {
              int chars_read = data.length - j;
  
              if (chars_read > 16) {
                  chars_read = 16;
              }
              dump(buffer, display_offset).append(' ');
              for (int k = 0; k < 16; k++) {
                  if (k < chars_read) {
                      dump(buffer, data[k + j]);
                  } else {
                      buffer.append("  ");
                  }
                  buffer.append(' ');
              }
              for (int k = 0; k < chars_read; k++) {
                  if ((data[k + j] >= ' ') && (data[k + j] < 127)) {
                      buffer.append((char) data[k + j]);
                  } else {
                      buffer.append('.');
                  }
              }
              buffer.append(EOL);
              stream.write(buffer.toString().getBytes());
              stream.flush();
              buffer.setLength(0);
              display_offset += chars_read;
          }
      }
  
      /**
       * The line-separator (initializes to "line.separator" system property.
       */
      public static final String EOL =
              System.getProperty("line.separator");
      private static final char[] _hexcodes =
              {
                  '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
                  'A', 'B', 'C', 'D', 'E', 'F'
              };
      private static final int[] _shifts =
              {
                  28, 24, 20, 16, 12, 8, 4, 0
              };
  
      /**
       * Dump a long value into a StringBuilder.
       *
       * @param _lbuffer the StringBuilder to dump the value in
       * @param value  the long value to be dumped
       * @return StringBuilder containing the dumped value.
       */
      private static StringBuilder dump(StringBuilder _lbuffer, long value) {
          for (int j = 0; j < 8; j++) {
              _lbuffer
                      .append(_hexcodes[((int) (value >> _shifts[j])) & 15]);
          }
          return _lbuffer;
      }
  
      /**
       * Dump a byte value into a StringBuilder.
       *
       * @param _cbuffer the StringBuilder to dump the value in
       * @param value  the byte value to be dumped
       * @return StringBuilder containing the dumped value.
       */
      private static StringBuilder dump(StringBuilder _cbuffer, byte value) {
          for (int j = 0; j < 2; j++) {
              _cbuffer.append(_hexcodes[(value >> _shifts[j + 6]) & 15]);
          }
          return _cbuffer;
      }
  
  }
  