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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.CoderResult;

/**

 * Helper class to deal with decoding loops that read a byte at a time

 *

 * @author Ian Rogers

 */

public abstract class ByteDecodeLoopHelper

{

  /**

   * @return can the given byte be encoded

   */

  protected abstract boolean isMappable(byte b);

  /**

   * Map the given byte to a char, the given byte is guaranteed to be mappable

   */

  protected abstract char mapToChar(byte b);

  /**

   * Encodes one or more characters into one or more bytes, mapping each

   * character to only one byte

   *

   * @param in character buffer to read from

   * @param out byte buffer to write to

   * @return the result state of the encoder

   */

  CoderResult decodeLoop(ByteBuffer in, CharBuffer out)

  {

    if (in.hasArray() && out.hasArray())

      {

        return arrayDecodeLoop(in, out);

      } else

      {

        return normalDecodeLoop(in, out);

      }

  }

  /**

   * Encode loop using get and put operations

   */

  private CoderResult normalDecodeLoop(ByteBuffer in, CharBuffer out)

  {

    int outRemaining = out.remaining();

    int inRemaining = in.remaining();

    while (inRemaining > 0 && outRemaining > 0)

      {

        byte b = in.get();

        inRemaining--;

        if (!isMappable(b))

          {

            in.position(in.position() - 1);

            return CoderResult.unmappableForLength(1);

          }

        char c = mapToChar(b);

        out.put(c);

        outRemaining--;

      }

    if (inRemaining > 0)

      {

        return CoderResult.OVERFLOW;

      } else

      {

        return CoderResult.UNDERFLOW;

      }

  }

  /**

   * Encode loop using array read and write operations

   */

  private CoderResult arrayDecodeLoop(ByteBuffer in, CharBuffer out)

  {

    byte[] inArray = in.array();

    char[] outArray = out.array();

    int inPos = in.arrayOffset() + in.position();

    int outPos = out.arrayOffset() + out.position();

    int inRemaining = in.remaining();

    int outRemaining = out.remaining();

    CoderResult result;

        bailOut:

    if (inRemaining <= outRemaining)

      {

        for (int i = 0; i < inRemaining; i++)

          {

            byte b = inArray[inPos];

            inPos++;

            if (!isMappable(b))

              {

                inPos--;

                result = CoderResult.unmappableForLength(1);

                                break bailOut;

              }

            char c = mapToChar(b);

            outArray[outPos] = c;

            outPos++;

          }

        result = CoderResult.UNDERFLOW;

      }

    else

      {

        for (int i = 0; i < outRemaining; i++)

          {

            byte b = inArray[inPos];

            inPos++;

            if (!isMappable(b))

              {

                inPos--;

                result = CoderResult.unmappableForLength(1);

                                break bailOut;

              }

            char c = mapToChar(b);

            outArray[outPos] = c;

            outPos++;

          }

        result = CoderResult.OVERFLOW;

      }

    in.position(inPos - in.arrayOffset());

    out.position(outPos - out.arrayOffset());

    return result;

  }

}