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/* ByteCharset.java -- Abstract class for generic 1-byte encodings.

   Copyright (C) 2005 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.

You should have received a copy of the GNU General Public License

along with GNU Classpath; see the file COPYING.  If not, write to the

Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA

02110-1301 USA.

Linking this library statically or dynamically with other modules is

making a combined work based on this library.  Thus, the terms and

conditions of the GNU General Public License cover the whole

combination.

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

modules, and to copy and distribute the resulting executable under

terms of your choice, provided that you also meet, for each linked

independent module, the terms and conditions of the license of that

module.  An independent module is a module which is not derived from

or based on this library.  If you modify this library, you may extend

this exception to your version of the library, but you are not

obligated to do so.  If you do not wish to do so, delete this

exception statement from your version. */

package gnu.java.nio.charset;

import java.nio.ByteBuffer;

import java.nio.CharBuffer;

import java.nio.charset.Charset;

import java.nio.charset.CharsetDecoder;

import java.nio.charset.CharsetEncoder;

import java.nio.charset.CoderResult;

/**

 * A generic encoding framework for single-byte encodings, utilizing a look-up

 * table.

 *

 * This replaces the gnu.java.io.EncoderEightBitLookup class, created by Aron

 * Renn.

 *

 * @author Sven de Marothy

 * @modified Ian Rogers

 */

abstract class ByteCharset extends Charset

{

  protected final char[] lookupTable;

  /**

   * Char to signify the character in the table is undefined

   */

  protected static final char NONE = (char) 0xFFFD;

  ByteCharset(String canonicalName, String[] aliases, char[] lookup)

  {

    super(canonicalName, aliases);

    lookupTable = lookup;

  }

  /**

   * Most western charsets include ASCII, but this should be overloaded for

   * others.

   */

  public boolean contains(Charset cs)

  {

    return cs instanceof US_ASCII || (cs.getClass() == getClass());

  }

  char[] getLookupTable()

  {

    return lookupTable;

  }

  public CharsetDecoder newDecoder()

  {

    return new Decoder(this);

  }

  public CharsetEncoder newEncoder()

  {

    return new Encoder(this);

  }

  private static final class Decoder extends CharsetDecoder

  {

    /** Lookup of byte to char mappings */

    private final char[] lookup;

    /** Helper to decode loops */

    private final ByteDecodeLoopHelper helper = new ByteDecodeLoopHelper()

    {

      protected boolean isMappable(byte b)

      {

        return lookup[(int) (b & 0xFF)] != NONE;

      }

      protected char mapToChar(byte b)

      {

        return lookup[(int) (b & 0xFF)];

      }

    };

    // Package-private to avoid a trampoline constructor.

    Decoder(ByteCharset cs)

    {

      super(cs, 1.0f, 1.0f);

      lookup = cs.getLookupTable();

    }

    protected CoderResult decodeLoop(ByteBuffer in, CharBuffer out)

    {

      return helper.decodeLoop(in, out);

    }

  }

  private static final class Encoder extends CharsetEncoder

  {

    /** Lookup of char to byte mappings */

    private final byte[] lookup;

    /** Helper to encode loops */

    private final ByteEncodeLoopHelper helper = new ByteEncodeLoopHelper()

    {

      protected boolean isMappable(char c)

      {

        return canEncode(c);

      }

      protected byte mapToByte(char c)

      {

        return lookup[c];

      }

    };

    // Package-private to avoid a trampoline constructor.

    Encoder(ByteCharset cs)

    {

      super(cs, 1.0f, 1.0f);

      char[] lookup_table = cs.getLookupTable();

      // Create the inverse look-up table.

      // determine required size of encoding_table:

      int max = 0;

      for (int i = 0; i < lookup_table.length; i++)

        {

          int c = (int) lookup_table[i];

          max = (c > max && c < NONE) ? c : max;

        }

      lookup = new byte[max + 1];

      for (int i = 0; i < lookup_table.length; i++)

        {

          int c = (int) lookup_table[i];

          if (c != 0 && c < NONE)

            {

              lookup[c] = (byte) i;

            }

        }

    }

    public boolean canEncode(char c)

    {

      byte b = (c < lookup.length) ? lookup[c] : 0;

      return b != 0 || c == 0;

    }

    public boolean canEncode(CharSequence cs)

    {

      for (int i = 0; i < cs.length(); ++i)

        {

          if (!canEncode(cs.charAt(i)))

            return false;

        }

      return true;

    }

    protected CoderResult encodeLoop(CharBuffer in, ByteBuffer out)

    {

      return helper.encodeLoop(in, out);

    }

  }

}