001/* CharsetProvider.java -- charset service provider interface
002   Copyright (C) 2002, 2006, 2007 Free Software Foundation
003
004This file is part of GNU Classpath.
005
006GNU Classpath is free software; you can redistribute it and/or modify
007it under the terms of the GNU General Public License as published by
008the Free Software Foundation; either version 2, or (at your option)
009any later version.
010
011GNU Classpath is distributed in the hope that it will be useful, but
012WITHOUT ANY WARRANTY; without even the implied warranty of
013MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
014General Public License for more details.
015
016You should have received a copy of the GNU General Public License
017along with GNU Classpath; see the file COPYING.  If not, write to the
018Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
01902110-1301 USA.
020
021Linking this library statically or dynamically with other modules is
022making a combined work based on this library.  Thus, the terms and
023conditions of the GNU General Public License cover the whole
024combination.
025
026As a special exception, the copyright holders of this library give you
027permission to link this library with independent modules to produce an
028executable, regardless of the license terms of these independent
029modules, and to copy and distribute the resulting executable under
030terms of your choice, provided that you also meet, for each linked
031independent module, the terms and conditions of the license of that
032module.  An independent module is a module which is not derived from
033or based on this library.  If you modify this library, you may extend
034this exception to your version of the library, but you are not
035obligated to do so.  If you do not wish to do so, delete this
036exception statement from your version. */
037
038package java.nio.charset.spi;
039
040import java.nio.charset.Charset;
041import 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 */
060public 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