nio/charset/Charset.java

/* Charset.java --
   Copyright (C) 2002, 2004, 2005, 2007  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., 51 Franklin Street, Fifth Floor, Boston, MA
02110-1301 USA.

Linking this library statically or dynamically with other modules is
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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
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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.classpath.ServiceFactory;
import gnu.classpath.SystemProperties;
import gnu.java.nio.charset.Provider;

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.URL;
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.charset.spi.CharsetProvider;
import java.util.Collections;
import java.util.Enumeration;
import java.util.HashSet;
import java.util.Iterator;
import java.util.LinkedHashSet;
import java.util.Locale;
import java.util.Set;
import java.util.SortedMap;
import java.util.TreeMap;

/**
 * @author Jesse Rosenstock
 * @since 1.4
 * @status updated to 1.5
 */
public abstract class Charset implements Comparable<Charset>
{
  private CharsetEncoder cachedEncoder;
  private CharsetDecoder cachedDecoder;

  /**
   * Extra Charset providers.
   */
  private static CharsetProvider[] providers;

  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]);
      }

    cachedEncoder = null;
    cachedDecoder = null;
    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);
      }
  }

  /**
   * Returns the system default charset.
   *
   * This may be set by the user or VM with the file.encoding
   * property.
   *
   * @since 1.5
   */
  public static Charset defaultCharset()
  {
    String encoding;

    try
      {
	encoding = SystemProperties.getProperty("file.encoding");
      }
    catch(SecurityException e)
      {
	// Use fallback.
	encoding = "ISO-8859-1";
      }
    catch(IllegalArgumentException e)
      {
	// Use fallback.
	encoding = "ISO-8859-1";
      }

    try
      {
	return forName(encoding);
      }
    catch(UnsupportedCharsetException e)
      {
	// Ignore.
      }
    catch(IllegalCharsetNameException e)
      {
	// Ignore.
      }
    catch(IllegalArgumentException e)
      {
	// Ignore.
      }

    throw new IllegalStateException("Can't get default charset!");
  }

  public static boolean isSupported (String charsetName)
  {
    return charsetForName (charsetName) != null;
  }

  /**
   * Returns the Charset instance for the charset of the given name.
   *
   * @param charsetName
   * @return the Charset instance for the indicated charset
   * @throws UnsupportedCharsetException if this VM does not support
   * the charset of the given name.
   * @throws IllegalCharsetNameException if the given charset name is
   * legal.
   * @throws IllegalArgumentException if <code>charsetName</code> is null.
   */
  public static Charset forName (String charsetName)
  {
    // Throws IllegalArgumentException as the JDK does.
    if(charsetName == null)
        throw new IllegalArgumentException("Charset name must not be null.");

    Charset cs = charsetForName (charsetName);
    if (cs == null)
      throw new UnsupportedCharsetException (charsetName);
    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);
    // Try the default provider first
    // (so we don't need to load external providers unless really necessary)
    // if it is an exotic charset try loading the external providers.
    Charset cs = provider().charsetForName(charsetName);
    if (cs == null)
      {
	CharsetProvider[] providers = providers2();
	for (int i = 0; i < providers.length; i++)
	  {
	    cs = providers[i].charsetForName(charsetName);
	    if (cs != null)
	      break;
	  }
      }
    return cs;
  }

  public static SortedMap<String, Charset> availableCharsets()
  {
    TreeMap<String, Charset> charsets
      = new TreeMap(String.CASE_INSENSITIVE_ORDER);
    for (Iterator<Charset> i = provider().charsets(); i.hasNext(); )
      {
	Charset cs = i.next();
	charsets.put(cs.name(), cs);
      }

    CharsetProvider[] providers = providers2();
    for (int j = 0; j < providers.length; j++)
      {
        for (Iterator<Charset> i = providers[j].charsets(); i.hasNext(); )
          {
            Charset cs = (Charset) i.next();
            charsets.put(cs.name(), cs);
          }
      }

    return Collections.unmodifiableSortedMap(charsets);
  }

  private static CharsetProvider provider()
  {
    try
      {
	String s = System.getProperty("charset.provider");
	if (s != null)
	  {
	    CharsetProvider p =
	      (CharsetProvider) ((Class.forName(s)).newInstance());
	    return p;
	  }
      }
    catch (Exception e)
      {
	// Ignore.
      }

    return Provider.provider();
  }

  /**
   * We need to support multiple providers, reading them from
   * java.nio.charset.spi.CharsetProvider in the resource directory
   * META-INF/services. This returns the "extra" charset providers.
   */
  private static CharsetProvider[] providers2()
  {
    if (providers == null)
      {
        try
          {
            Iterator i = ServiceFactory.lookupProviders(CharsetProvider.class);
            LinkedHashSet set = new LinkedHashSet();
            while (i.hasNext())
              set.add(i.next());

            providers = new CharsetProvider[set.size()];
            set.toArray(providers);
          }
        catch (Exception e)
          {
            throw new RuntimeException(e);
          }
      }
    return providers;
  }

  public final String name ()
  {
    return canonicalName;
  }

  public final Set<String> aliases ()
  {
    if (aliases == null)
      return Collections.<String>emptySet();

    // should we cache the aliasSet instead?
    int n = aliases.length;
    HashSet<String> aliasSet = new HashSet<String> (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;
  }

  // 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.
  public final synchronized ByteBuffer encode (CharBuffer cb)
  {
    try
      {
	if (cachedEncoder == null)
	  {
	    cachedEncoder = newEncoder ()
	      .onMalformedInput (CodingErrorAction.REPLACE)
	      .onUnmappableCharacter (CodingErrorAction.REPLACE);
	  } else
	  cachedEncoder.reset();
	return cachedEncoder.encode (cb);
      }
    catch (CharacterCodingException e)
      {
        throw new AssertionError (e);
      }
  }

  public final ByteBuffer encode (String str)
  {
    return encode (CharBuffer.wrap (str));
  }

  // 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.
  public final synchronized CharBuffer decode (ByteBuffer bb)
  {
    try
      {
	if (cachedDecoder == null)
	  {
	    cachedDecoder = newDecoder ()
	      .onMalformedInput (CodingErrorAction.REPLACE)
	      .onUnmappableCharacter (CodingErrorAction.REPLACE);
	  } else
	  cachedDecoder.reset();

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

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