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    1   /*
    2    * Copyright 2009 Red Hat, Inc.
    3    *
    4    * Red Hat licenses this file to you under the Apache License, version 2.0
    5    * (the "License"); you may not use this file except in compliance with the
    6    * License.  You may obtain a copy of the License at:
    7    *
    8    *    http://www.apache.org/licenses/LICENSE-2.0
    9    *
    10   * Unless required by applicable law or agreed to in writing, software
    11   * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
    12   * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
    13   * License for the specific language governing permissions and limitations
    14   * under the License.
    15   */
    16  package org.jboss.netty.util.internal;
    17
    18  import java.util.Formatter;
    19
    20  /**
    21   * String utility class.
    22   *
    23   * @author <a href="http://www.jboss.org/netty/">The Netty Project</a>
    24   * @author <a href="http://gleamynode.net/">Trustin Lee</a>
    25   * @version $Rev: 2080 $, $Date: 2010-01-26 18:04:19 +0900 (Tue, 26 Jan 2010) $
    26   */
    27  public class StringUtil {
    28
    29      private StringUtil() {
    30          // Unused.
    31      }
    32
    33      public static final String NEWLINE;
    34
    35      static {
    36          String newLine = null;
    37
    38          try {
    39              newLine = new Formatter().format("%n").toString();
    40          } catch (Exception e) {
    41              newLine = "\n";
    42          }
    43
    44          NEWLINE = newLine;
    45      }
    46
    47      /**
    48       * Strip an Object of it's ISO control characters.
    49       *
    50       * @param value
    51       *          The Object that should be stripped. This objects toString method will
    52       *          called and the result passed to {@link #stripControlCharacters(String)}.
    53       * @return {@code String}
    54       *          A new String instance with its hexadecimal control characters replaced
    55       *          by a space. Or the unmodified String if it does not contain any ISO
    56       *          control characters.
    57       */
    58      public static String stripControlCharacters(Object value) {
    59          if (value == null) {
    60              return null;
    61          }
    62
    63          return stripControlCharacters(value.toString());
    64      }
    65
    66      /**
    67       * Strip a String of it's ISO control characters.
    68       *
    69       * @param value
    70       *          The String that should be stripped.
    71       * @return {@code String}
    72       *          A new String instance with its hexadecimal control characters replaced
    73       *          by a space. Or the unmodified String if it does not contain any ISO
    74       *          control characters.
    75       */
    76      public static String stripControlCharacters(String value) {
    77          if (value == null) {
    78              return null;
    79          }
    80
    81          boolean hasControlChars = false;
    82          for (int i = value.length() - 1; i >= 0; i --) {
    83              if (Character.isISOControl(value.charAt(i))) {
    84                  hasControlChars = true;
    85                  break;
    86              }
    87          }
    88
    89          if (!hasControlChars) {
    90              return value;
    91          }
    92
    93          StringBuilder buf = new StringBuilder(value.length());
    94          int i = 0;
    95
    96          // Skip initial control characters (i.e. left trim)
    97          for (; i < value.length(); i ++) {
    98              if (!Character.isISOControl(value.charAt(i))) {
    99                  break;
    100             }
    101         }
    102
    103         // Copy non control characters and substitute control characters with
    104         // a space.  The last control characters are trimmed.
    105         boolean suppressingControlChars = false;
    106         for (; i < value.length(); i ++) {
    107             if (Character.isISOControl(value.charAt(i))) {
    108                 suppressingControlChars = true;
    109                 continue;
    110             } else {
    111                 if (suppressingControlChars) {
    112                     suppressingControlChars = false;
    113                     buf.append(' ');
    114                 }
    115                 buf.append(value.charAt(i));
    116             }
    117         }
    118
    119         return buf.toString();
    120     }
    121 }