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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:
    *
    *   https://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 io.netty.util;
  
  import io.netty.util.internal.InternalThreadLocalMap;
  import static io.netty.util.internal.ObjectUtil.checkNotNull;
  
  import java.nio.charset.Charset;
  import java.nio.charset.CharsetDecoder;
  import java.nio.charset.CharsetEncoder;
  import java.nio.charset.CodingErrorAction;
  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 Charset[] CHARSETS = new Charset[]
              { UTF_16, UTF_16BE, UTF_16LE, UTF_8, ISO_8859_1, US_ASCII };
  
      public static Charset[] values() {
          return CHARSETS;
      }
  
      /**
       * @deprecated Use {@link #encoder(Charset)}.
       */
      @Deprecated
      public static CharsetEncoder getEncoder(Charset charset) {
          return encoder(charset);
      }
  
      /**
       * Returns a new {@link CharsetEncoder} for the {@link Charset} with specified error actions.
       *
       * @param charset The specified charset
       * @param malformedInputAction The encoder's action for malformed-input errors
       * @param unmappableCharacterAction The encoder's action for unmappable-character errors
       * @return The encoder for the specified {@code charset}
       */
      public static CharsetEncoder encoder(Charset charset, CodingErrorAction malformedInputAction,
                                           CodingErrorAction unmappableCharacterAction) {
          checkNotNull(charset, "charset");
          CharsetEncoder e = charset.newEncoder();
          e.onMalformedInput(malformedInputAction).onUnmappableCharacter(unmappableCharacterAction);
          return e;
      }
  
      /**
       * Returns a new {@link CharsetEncoder} for the {@link Charset} with the specified error action.
       *
       * @param charset The specified charset
      * @param codingErrorAction The encoder's action for malformed-input and unmappable-character errors
      * @return The encoder for the specified {@code charset}
      */
     public static CharsetEncoder encoder(Charset charset, CodingErrorAction codingErrorAction) {
         return encoder(charset, codingErrorAction, codingErrorAction);
     }
 
     /**
      * Returns a cached thread-local {@link CharsetEncoder} for the specified {@link Charset}.
      *
      * @param charset The specified charset
      * @return The encoder for the specified {@code charset}
      */
     public static CharsetEncoder encoder(Charset charset) {
         checkNotNull(charset, "charset");
 
         Map<Charset, CharsetEncoder> map = InternalThreadLocalMap.get().charsetEncoderCache();
         CharsetEncoder e = map.get(charset);
         if (e != null) {
             e.reset().onMalformedInput(CodingErrorAction.REPLACE).onUnmappableCharacter(CodingErrorAction.REPLACE);
             return e;
         }
 
         e = encoder(charset, CodingErrorAction.REPLACE, CodingErrorAction.REPLACE);
         map.put(charset, e);
         return e;
     }
 
     /**
      * @deprecated Use {@link #decoder(Charset)}.
      */
     @Deprecated
     public static CharsetDecoder getDecoder(Charset charset) {
         return decoder(charset);
     }
 
     /**
      * Returns a new {@link CharsetDecoder} for the {@link Charset} with specified error actions.
      *
      * @param charset The specified charset
      * @param malformedInputAction The decoder's action for malformed-input errors
      * @param unmappableCharacterAction The decoder's action for unmappable-character errors
      * @return The decoder for the specified {@code charset}
      */
     public static CharsetDecoder decoder(Charset charset, CodingErrorAction malformedInputAction,
                                          CodingErrorAction unmappableCharacterAction) {
         checkNotNull(charset, "charset");
         CharsetDecoder d = charset.newDecoder();
         d.onMalformedInput(malformedInputAction).onUnmappableCharacter(unmappableCharacterAction);
         return d;
     }
 
     /**
      * Returns a new {@link CharsetDecoder} for the {@link Charset} with the specified error action.
      *
      * @param charset The specified charset
      * @param codingErrorAction The decoder's action for malformed-input and unmappable-character errors
      * @return The decoder for the specified {@code charset}
      */
     public static CharsetDecoder decoder(Charset charset, CodingErrorAction codingErrorAction) {
         return decoder(charset, codingErrorAction, codingErrorAction);
     }
 
     /**
      * Returns a cached thread-local {@link CharsetDecoder} for the specified {@link Charset}.
      *
      * @param charset The specified charset
      * @return The decoder for the specified {@code charset}
      */
     public static CharsetDecoder decoder(Charset charset) {
         checkNotNull(charset, "charset");
 
         Map<Charset, CharsetDecoder> map = InternalThreadLocalMap.get().charsetDecoderCache();
         CharsetDecoder d = map.get(charset);
         if (d != null) {
             d.reset().onMalformedInput(CodingErrorAction.REPLACE).onUnmappableCharacter(CodingErrorAction.REPLACE);
             return d;
         }
 
         d = decoder(charset, CodingErrorAction.REPLACE, CodingErrorAction.REPLACE);
         map.put(charset, d);
         return d;
     }
 
     private CharsetUtil() { }
 }