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   /*
    * Copyright 2012 The Netty Project
    *
    * The Netty Project 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.jboss.netty.util.internal;
  
  import java.util.ArrayList;
  import java.util.Formatter;
  import java.util.List;
  
  /**
   * String utility class.
   */
  public final class StringUtil {
  
      private StringUtil() {
          // Unused.
      }
  
      public static final String NEWLINE;
  
      static {
          String newLine;
  
          try {
              newLine = new Formatter().format("%n").toString();
          } catch (Exception e) {
              newLine = "\n";
          }
  
          NEWLINE = newLine;
      }
  
      /**
       * Strip an Object of it's ISO control characters.
       *
       * @param value
       *          The Object that should be stripped. This objects toString method will
       *          called and the result passed to {@link #stripControlCharacters(String)}.
       * @return {@code String}
       *          A new String instance with its hexadecimal control characters replaced
       *          by a space. Or the unmodified String if it does not contain any ISO
       *          control characters.
       */
      public static String stripControlCharacters(Object value) {
          if (value == null) {
              return null;
          }
  
          return stripControlCharacters(value.toString());
      }
  
      /**
       * Strip a String of it's ISO control characters.
       *
       * @param value
       *          The String that should be stripped.
       * @return {@code String}
       *          A new String instance with its hexadecimal control characters replaced
       *          by a space. Or the unmodified String if it does not contain any ISO
       *          control characters.
       */
      public static String stripControlCharacters(String value) {
          if (value == null) {
              return null;
          }
  
          boolean hasControlChars = false;
          for (int i = value.length() - 1; i >= 0; i --) {
              if (Character.isISOControl(value.charAt(i))) {
                  hasControlChars = true;
                  break;
              }
          }
  
          if (!hasControlChars) {
              return value;
          }
  
          StringBuilder buf = new StringBuilder(value.length());
          int i = 0;
  
          // Skip initial control characters (i.e. left trim)
          for (; i < value.length(); i ++) {
              if (!Character.isISOControl(value.charAt(i))) {
                  break;
              }
          }
 
         // Copy non control characters and substitute control characters with
         // a space.  The last control characters are trimmed.
         boolean suppressingControlChars = false;
         for (; i < value.length(); i ++) {
             if (Character.isISOControl(value.charAt(i))) {
                 suppressingControlChars = true;
                 continue;
             } else {
                 if (suppressingControlChars) {
                     suppressingControlChars = false;
                     buf.append(' ');
                 }
                 buf.append(value.charAt(i));
             }
         }
 
         return buf.toString();
     }
 
     private static final String EMPTY_STRING = "";
 
     /**
      * Splits the specified {@link String} with the specified delimiter.  This operation is a simplified and optimized
      * version of {@link String#split(String)}.
      */
     public static String[] split(String value, char delim) {
         final int end = value.length();
         final List<String> res = new ArrayList<String>();
 
         int start = 0;
         for (int i = 0; i < end; i ++) {
             if (value.charAt(i) == delim) {
                 if (start == i) {
                     res.add(EMPTY_STRING);
                 } else {
                     res.add(value.substring(start, i));
                 }
                 start = i + 1;
             }
         }
 
         if (start == 0) { // If no delimiter was found in the value
             res.add(value);
         } else {
             if (start != end) {
                 // Add the last element if it's not empty.
                 res.add(value.substring(start, end));
             } else {
                 // Truncate trailing empty elements.
                 for (int i = res.size() - 1; i >= 0; i --) {
                     if (res.get(i).length() == 0) {
                         res.remove(i);
                     } else {
                         break;
                     }
                 }
             }
         }
 
         return res.toArray(new String[res.size()]);
     }
 
     /**
      * Splits the specified {@link String} with the specified delimiter in maxParts maximum parts.
      * This operation is a simplified and optimized
      * version of {@link String#split(String, int)}.
      */
     public static String[] split(String value, char delim, int maxParts) {
         final int end = value.length();
         final List<String> res = new ArrayList<String>();
 
         int start = 0;
         int cpt = 1;
         for (int i = 0; i < end && cpt < maxParts; i ++) {
             if (value.charAt(i) == delim) {
                 if (start == i) {
                     res.add(EMPTY_STRING);
                 } else {
                     res.add(value.substring(start, i));
                 }
                 start = i + 1;
                 cpt++;
             }
         }
 
         if (start == 0) { // If no delimiter was found in the value
             res.add(value);
         } else {
             if (start != end) {
                 // Add the last element if it's not empty.
                 res.add(value.substring(start, end));
             } else {
                 // Truncate trailing empty elements.
                 for (int i = res.size() - 1; i >= 0; i --) {
                     if (res.get(i).length() == 0) {
                         res.remove(i);
                     } else {
                         break;
                     }
                 }
             }
         }
 
         return res.toArray(new String[res.size()]);
     }
 
     /**
      * Get the item after one char delim if the delim is found (else null).
      * This operation is a simplified and optimized
      * version of {@link String#split(String, int)}.
      */
     public static String substringAfter(String value, char delim) {
         int pos = value.indexOf(delim);
         if (pos >= 0) {
             return value.substring(pos + 1);
         }
         return null;
     }
 }