gcc/libjava/java/nio/charset/Charset.java

/* Charset.java -- 
   Copyright (C) 2002, 2004  Free Software Foundation, Inc.

This file is part of GNU Classpath.

GNU Classpath is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.

GNU Classpath is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
General Public License for more details.

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Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
02111-1307 USA.

Linking this library statically or dynamically with other modules is
making a combined work based on this library.  Thus, the terms and
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As a special exception, the copyright holders of this library give you
permission to link this library with independent modules to produce an
executable, regardless of the license terms of these independent
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terms of your choice, provided that you also meet, for each linked
independent module, the terms and conditions of the license of that
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this exception to your version of the library, but you are not
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package java.nio.charset;

import gnu.java.nio.charset.Provider;

import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.charset.spi.CharsetProvider;
import java.util.Collections;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Locale;
import java.util.Set;
import java.util.SortedMap;
import java.util.TreeMap;

/**
 * @author Jesse Rosenstock
 * @since 1.4
 */
public abstract class Charset implements Comparable
{
  private static CharsetEncoder cachedEncoder;
  private static CharsetDecoder cachedDecoder;
 
  static
  {
    synchronized (Charset.class)
      {
        cachedEncoder = null;
        cachedDecoder = null;
      }
  }

  private final String canonicalName;
  private final String[] aliases;
  
  protected Charset (String canonicalName, String[] aliases)
  {
    checkName (canonicalName);
    if (aliases != null)
      {
        int n = aliases.length;
        for (int i = 0; i < n; ++i)
            checkName (aliases[i]);
      }

    this.canonicalName = canonicalName;
    this.aliases = aliases;
  }

  /**
   * @throws IllegalCharsetNameException  if the name is illegal
   */
  private static void checkName (String name)
  {
    int n = name.length ();

    if (n == 0)
      throw new IllegalCharsetNameException (name);

    char ch = name.charAt (0);
    if (!(('A' <= ch && ch <= 'Z')
          || ('a' <= ch && ch <= 'z')
          || ('0' <= ch && ch <= '9')))
      throw new IllegalCharsetNameException (name);

    for (int i = 1; i < n; ++i)
      {
        ch = name.charAt (i);
        if (!(('A' <= ch && ch <= 'Z')
              || ('a' <= ch && ch <= 'z')
              || ('0' <= ch && ch <= '9')
              || ch == '-' || ch == '.' || ch == ':' || ch == '_'))
          throw new IllegalCharsetNameException (name);
      }
  }

  public static boolean isSupported (String charsetName)
  {
    return charsetForName (charsetName) != null;
  }
 
  public static Charset forName (String charsetName)
  {
    Charset cs = charsetForName (charsetName);
    if (cs == null)
      throw new UnsupportedCharsetException (charsetName);
    cachedDecoder = null;
    cachedEncoder = null;
    return cs;
  }

  /**
   * Retrieves a charset for the given charset name.
   *
   * @return A charset object for the charset with the specified name, or
   *   <code>null</code> if no such charset exists.
   *
   * @throws IllegalCharsetNameException  if the name is illegal
   */
  private static Charset charsetForName (String charsetName)
  {
    checkName (charsetName);
    return provider ().charsetForName (charsetName);
  }

  public static SortedMap availableCharsets ()
  {
    TreeMap charsets = new TreeMap (String.CASE_INSENSITIVE_ORDER);

    for (Iterator i = provider ().charsets (); i.hasNext (); )
      {
        Charset cs = (Charset) i.next ();
        charsets.put (cs.name (), cs);
      }

    return Collections.unmodifiableSortedMap (charsets);
  }

  // XXX: we need to support multiple providers, reading them from
  // java.nio.charset.spi.CharsetProvider in the resource directory
  // META-INF/services
  private static CharsetProvider provider ()
  {
    return Provider.provider ();
  }

  public final String name ()
  {
    return canonicalName;
  }

  public final Set aliases ()
  {
    if (aliases == null)
      return Collections.EMPTY_SET;

    // should we cache the aliasSet instead?
    int n = aliases.length;
    HashSet aliasSet = new HashSet (n);
    for (int i = 0; i < n; ++i)
        aliasSet.add (aliases[i]);
    return Collections.unmodifiableSet (aliasSet);
  }

  public String displayName ()
  {
    return canonicalName;
  }

  public String displayName (Locale locale)
  {
    return canonicalName;
  }

  public final boolean isRegistered ()
  {
    return (!canonicalName.startsWith ("x-")
            && !canonicalName.startsWith ("X-"));
  }

  public abstract boolean contains (Charset cs);

  public abstract CharsetDecoder newDecoder ();

  public abstract CharsetEncoder newEncoder ();

  public boolean canEncode ()
  {
    return true;
  }

  public final ByteBuffer encode (CharBuffer cb)
  {
    try
      {
        // NB: This implementation serializes different threads calling
        // Charset.encode(), a potential performance problem.  It might
        // be better to remove the cache, or use ThreadLocal to cache on
        // a per-thread basis.
        synchronized (Charset.class)
          {
            if (cachedEncoder == null)
              {
                cachedEncoder = newEncoder ()
                  .onMalformedInput (CodingErrorAction.REPLACE)
                  .onUnmappableCharacter (CodingErrorAction.REPLACE);
              }

            return cachedEncoder.encode (cb);
          }
      }
    catch (CharacterCodingException e)
      {
        throw new AssertionError (e);
      }
  }
  
  public final ByteBuffer encode (String str)
  {
    return encode (CharBuffer.wrap (str));
  }

  public final CharBuffer decode (ByteBuffer bb)
  {
    try
      {
        // NB: This implementation serializes different threads calling
        // Charset.decode(), a potential performance problem.  It might
        // be better to remove the cache, or use ThreadLocal to cache on
        // a per-thread basis.
        synchronized (Charset.class)
          {
            if (cachedDecoder == null)
              {
                cachedDecoder = newDecoder ()
                  .onMalformedInput (CodingErrorAction.REPLACE)
                  .onUnmappableCharacter (CodingErrorAction.REPLACE);
              }

            return cachedDecoder.decode (bb);
          }
      }
    catch (CharacterCodingException e)
      {
        throw new AssertionError (e);
      }
  }

  public final int compareTo (Object ob)
  {
    return canonicalName.compareToIgnoreCase (((Charset) ob).canonicalName);
  }

  public final int hashCode ()
  {
    return canonicalName.hashCode ();
  }

  public final boolean equals (Object ob)
  {
    if (ob instanceof Charset)
      return canonicalName.equalsIgnoreCase (((Charset) ob).canonicalName);
    else
      return false;
  }

  public final String toString ()
  {
    return canonicalName;
  }
}