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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
 * 
 * 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.google.code.yanf4j.buffer;

/**
 * Provides utility methods to dump an {@link IoBuffer} into a hex formatted string.
 * 
 * @author The Apache MINA Project ([email protected])
 * @version $Rev: 686598 $, $Date: 2008-08-17 12:58:23 +0200 (Sun, 17 Aug 2008) $
 */
class IoBufferHexDumper {

  /**
   * The high digits lookup table.
   */
  private static final byte[] highDigits;

  /**
   * The low digits lookup table.
   */
  private static final byte[] lowDigits;

  /**
   * Initialize lookup tables.
   */
  static {
    final byte[] digits =
        {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F'};

    int i;
    byte[] high = new byte[256];
    byte[] low = new byte[256];

    for (i = 0; i < 256; i++) {
      high[i] = digits[i >>> 4];
      low[i] = digits[i & 0x0F];
    }

    highDigits = high;
    lowDigits = low;
  }

  /**
   * Dumps an {@link IoBuffer} to a hex formatted string.
   * 
   * @param in the buffer to dump
   * @param lengthLimit the limit at which hex dumping will stop
   * @return a hex formatted string representation of the in {@link Iobuffer}.
   */
  public static String getHexdump(IoBuffer in, int lengthLimit) {
    if (lengthLimit == 0) {
      throw new IllegalArgumentException("lengthLimit: " + lengthLimit + " (expected: 1+)");
    }

    boolean truncate = in.remaining() > lengthLimit;
    int size;
    if (truncate) {
      size = lengthLimit;
    } else {
      size = in.remaining();
    }

    if (size == 0) {
      return "empty";
    }

    StringBuilder out = new StringBuilder(in.remaining() * 3 - 1);

    int mark = in.position();

    // fill the first
    int byteValue = in.get() & 0xFF;
    out.append((char) highDigits[byteValue]);
    out.append((char) lowDigits[byteValue]);
    size--;

    // and the others, too
    for (; size > 0; size--) {
      out.append(' ');
      byteValue = in.get() & 0xFF;
      out.append((char) highDigits[byteValue]);
      out.append((char) lowDigits[byteValue]);
    }

    in.position(mark);

    if (truncate) {
      out.append("...");
    }

    return out.toString();
  }
}