001    /* CharsetProvider.java -- charset service provider interface
002       Copyright (C) 2002, 2006, 2007 Free Software Foundation
003    
004    This file is part of GNU Classpath.
005    
006    GNU Classpath is free software; you can redistribute it and/or modify
007    it under the terms of the GNU General Public License as published by
008    the Free Software Foundation; either version 2, or (at your option)
009    any later version.
010    
011    GNU Classpath is distributed in the hope that it will be useful, but
012    WITHOUT ANY WARRANTY; without even the implied warranty of
013    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
014    General Public License for more details.
015    
016    You should have received a copy of the GNU General Public License
017    along with GNU Classpath; see the file COPYING.  If not, write to the
018    Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
019    02110-1301 USA.
020    
021    Linking this library statically or dynamically with other modules is
022    making a combined work based on this library.  Thus, the terms and
023    conditions of the GNU General Public License cover the whole
024    combination.
025    
026    As a special exception, the copyright holders of this library give you
027    permission to link this library with independent modules to produce an
028    executable, regardless of the license terms of these independent
029    modules, and to copy and distribute the resulting executable under
030    terms of your choice, provided that you also meet, for each linked
031    independent module, the terms and conditions of the license of that
032    module.  An independent module is a module which is not derived from
033    or based on this library.  If you modify this library, you may extend
034    this exception to your version of the library, but you are not
035    obligated to do so.  If you do not wish to do so, delete this
036    exception statement from your version. */
037    
038    package java.nio.charset.spi;
039    
040    import java.nio.charset.Charset;
041    import java.util.Iterator;
042    
043    
044    /**
045     * This class allows an implementor to provide additional character sets. The
046     * subclass must have a nullary constructor, and be attached to charset
047     * implementation classes. These extensions are loaded via the context class
048     * loader. To provide the charset extension, all files named
049     * <code>META-INF/services/java.nio.charset.spi.CharsetProvider</code> are
050     * read from the classpath. Each one should be a UTF-8 encoded list of
051     * fully-qualified names of concrete subclasses of this class; whitespace is
052     * ignored, and '#' starts comments. Duplicates are ignored. The
053     * implementations must be accessible to the classloader that requests them.
054     *
055     * @author Eric Blake (ebb9@email.byu.edu)
056     * @see Charset
057     * @since 1.4
058     * @status updated to 1.4
059     */
060    public abstract class CharsetProvider
061    {
062      /**
063       * Initialize a new charset provider. This performs a security check on
064       * RuntimePermission("charsetProvider").
065       *
066       * @throws SecurityException if building a new set is not allowed
067       */
068      protected CharsetProvider()
069      {
070        // We only do the security check for custom providers, not for the
071        // built in ones.
072        SecurityManager s = System.getSecurityManager();
073        if (s != null &&
074            ! (this instanceof gnu.java.nio.charset.Provider))
075            // GCJ LOCAL - We have the iconv provider in standard.omit
076            // || this instanceof gnu.java.nio.charset.iconv.IconvProvider))
077          s.checkPermission(new RuntimePermission("charsetProvider"));
078      }
079    
080      /**
081       * Returns an iterator over the charsets defined by this provider.
082       *
083       * @return the iterator
084       * @see Charset#availableCharsets()
085       */
086      public abstract Iterator<Charset> charsets();
087    
088      /**
089       * Returns the named charset, by canonical name or alias.
090       *
091       * @param name the name of the character
092       *
093       * @return the charset, or null if not supported
094       */
095      public abstract Charset charsetForName(String name);
096    } // class CharsetProvider