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    1   /*
    2    *  Licensed to the Apache Software Foundation (ASF) under one
    3    *  or more contributor license agreements.  See the NOTICE file
    4    *  distributed with this work for additional information
    5    *  regarding copyright ownership.  The ASF licenses this file
    6    *  to you under the Apache License, Version 2.0 (the
    7    *  "License"); you may not use this file except in compliance
    8    *  with the License.  You may obtain a copy of the License at
    9    *
    10   *    http://www.apache.org/licenses/LICENSE-2.0
    11   *
    12   *  Unless required by applicable law or agreed to in writing,
    13   *  software distributed under the License is distributed on an
    14   *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
    15   *  KIND, either express or implied.  See the License for the
    16   *  specific language governing permissions and limitations
    17   *  under the License.
    18   *
    19   */
    20  package org.apache.mina.core.buffer;
    21
    22  /**
    23   * Provides utility methods to dump an {@link IoBuffer} into a hex formatted string.
    24   *
    25   * @author <a href="http://mina.apache.org">Apache MINA Project</a>
    26   */
    27  class IoBufferHexDumper {
    28
    29      /**
    30       * The high digits lookup table.
    31       */
    32      private static final byte[] highDigits;
    33
    34      /**
    35       * The low digits lookup table.
    36       */
    37      private static final byte[] lowDigits;
    38
    39      /**
    40       * Initialize lookup tables.
    41       */
    42      static {
    43          final byte[] digits = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F' };
    44
    45          int i;
    46          byte[] high = new byte[256];
    47          byte[] low = new byte[256];
    48
    49          for (i = 0; i < 256; i++) {
    50              high[i] = digits[i >>> 4];
    51              low[i] = digits[i & 0x0F];
    52          }
    53
    54          highDigits = high;
    55          lowDigits = low;
    56      }
    57
    58      /**
    59       * Dumps an {@link IoBuffer} to a hex formatted string.
    60       *
    61       * @param in the buffer to dump
    62       * @param lengthLimit the limit at which hex dumping will stop
    63       * @return a hex formatted string representation of the <i>in</i> {@link Iobuffer}.
    64       */
    65      public static String getHexdump(IoBuffer in, int lengthLimit) {
    66          if (lengthLimit == 0) {
    67              throw new IllegalArgumentException("lengthLimit: " + lengthLimit + " (expected: 1+)");
    68          }
    69
    70          boolean truncate = in.remaining() > lengthLimit;
    71          int size;
    72          if (truncate) {
    73              size = lengthLimit;
    74          } else {
    75              size = in.remaining();
    76          }
    77
    78          if (size == 0) {
    79              return "empty";
    80          }
    81
    82          StringBuilder out = new StringBuilder(size * 3 + 3);
    83
    84          int mark = in.position();
    85
    86          // fill the first
    87          int byteValue = in.get() & 0xFF;
    88          out.append((char) highDigits[byteValue]);
    89          out.append((char) lowDigits[byteValue]);
    90          size--;
    91
    92          // and the others, too
    93          for (; size > 0; size--) {
    94              out.append(' ');
    95              byteValue = in.get() & 0xFF;
    96              out.append((char) highDigits[byteValue]);
    97              out.append((char) lowDigits[byteValue]);
    98          }
    99
    100         in.position(mark);
    101
    102         if (truncate) {
    103             out.append("...");
    104         }
    105
    106         return out.toString();
    107     }
    108 }