/*
    * 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;
  
  import java.nio.charset.Charset;
  import java.nio.charset.CharsetDecoder;
  import java.nio.charset.CharsetEncoder;
  import java.nio.charset.CodingErrorAction;
  import java.util.IdentityHashMap;
  import java.util.Map;
  
  /**
   * A utility class that provides various common operations and constants
   * related with {@link Charset} and its relevant classes.
   */
  public final class CharsetUtil {
  
      /**
       * 16-bit UTF (UCS Transformation Format) whose byte order is identified by
       * an optional byte-order mark
       */
      public static final Charset UTF_16 = Charset.forName("UTF-16");
  
      /**
       * 16-bit UTF (UCS Transformation Format) whose byte order is big-endian
       */
      public static final Charset UTF_16BE = Charset.forName("UTF-16BE");
  
      /**
       * 16-bit UTF (UCS Transformation Format) whose byte order is little-endian
       */
      public static final Charset UTF_16LE = Charset.forName("UTF-16LE");
  
      /**
       * 8-bit UTF (UCS Transformation Format)
       */
      public static final Charset UTF_8 = Charset.forName("UTF-8");
  
      /**
       * ISO Latin Alphabet No. 1, as known as <tt>ISO-LATIN-1</tt>
       */
      public static final Charset ISO_8859_1 = Charset.forName("ISO-8859-1");
  
      /**
       * 7-bit ASCII, as known as ISO646-US or the Basic Latin block of the
       * Unicode character set
       */
      public static final Charset US_ASCII = Charset.forName("US-ASCII");
  
      private static final ThreadLocal<Map<Charset, CharsetEncoder>> encoders =
          new ThreadLocal<Map<Charset, CharsetEncoder>>() {
              @Override
              protected Map<Charset, CharsetEncoder> initialValue() {
                  return new IdentityHashMap<Charset, CharsetEncoder>();
              }
          };
  
      private static final ThreadLocal<Map<Charset, CharsetDecoder>> decoders =
          new ThreadLocal<Map<Charset, CharsetDecoder>>() {
              @Override
              protected Map<Charset, CharsetDecoder> initialValue() {
                  return new IdentityHashMap<Charset, CharsetDecoder>();
              }
          };
  
      /**
       * Returns a cached thread-local {@link CharsetEncoder} for the specified
       * <tt>charset</tt>.
       */
      public static CharsetEncoder getEncoder(Charset charset) {
          if (charset == null) {
              throw new NullPointerException("charset");
          }
  
          Map<Charset, CharsetEncoder> map = encoders.get();
          CharsetEncoder e = map.get(charset);
          if (e != null) {
              e.reset();
              e.onMalformedInput(CodingErrorAction.REPLACE);
              e.onUnmappableCharacter(CodingErrorAction.REPLACE);
              return e;
          }
  
          e = charset.newEncoder();
          e.onMalformedInput(CodingErrorAction.REPLACE);
          e.onUnmappableCharacter(CodingErrorAction.REPLACE);
         map.put(charset, e);
         return e;
     }
 
     /**
      * Returns a cached thread-local {@link CharsetDecoder} for the specified
      * <tt>charset</tt>.
      */
     public static CharsetDecoder getDecoder(Charset charset) {
         if (charset == null) {
             throw new NullPointerException("charset");
         }
 
         Map<Charset, CharsetDecoder> map = decoders.get();
         CharsetDecoder d = map.get(charset);
         if (d != null) {
             d.reset();
             d.onMalformedInput(CodingErrorAction.REPLACE);
             d.onUnmappableCharacter(CodingErrorAction.REPLACE);
             return d;
         }
 
         d = charset.newDecoder();
         d.onMalformedInput(CodingErrorAction.REPLACE);
         d.onUnmappableCharacter(CodingErrorAction.REPLACE);
         map.put(charset, d);
         return d;
     }
 
     private CharsetUtil() {
         // Unused
     }
 }