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/* UTF_16Decoder.java --

   Copyright (C) 2002, 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.CoderResult;

/**

 * Decoder for UTF-16, UTF-15LE, and UTF-16BE.

 *

 * @author Jesse Rosenstock

 */

final class UTF_16Decoder extends CharsetDecoder

{

  // byte orders

  static final int BIG_ENDIAN = 0;

  static final int LITTLE_ENDIAN = 1;

  static final int UNKNOWN_ENDIAN = 2;

  static final int MAYBE_BIG_ENDIAN = 3;

  static final int MAYBE_LITTLE_ENDIAN = 4;

  private static final char BYTE_ORDER_MARK = 0xFEFF;

  private static final char REVERSED_BYTE_ORDER_MARK = 0xFFFE;

  private final int originalByteOrder;

  private int byteOrder;

  UTF_16Decoder (Charset cs, int byteOrder)

  {

    super (cs, 0.5f, 1.0f);

    this.originalByteOrder = byteOrder;

    this.byteOrder = byteOrder;

  }

  protected CoderResult decodeLoop (ByteBuffer in, CharBuffer out)

  {

    // TODO: Optimize this in the case in.hasArray() / out.hasArray()

    int inPos = in.position ();

    try

      {

        while (in.remaining () >= 2)

          {

            byte b1 = in.get ();

            byte b2 = in.get ();

            // handle byte order mark

            if (byteOrder == UNKNOWN_ENDIAN ||

                byteOrder == MAYBE_BIG_ENDIAN ||

                byteOrder == MAYBE_LITTLE_ENDIAN)

              {

                char c = (char) (((b1 & 0xFF) << 8) | (b2 & 0xFF));

                if (c == BYTE_ORDER_MARK)

                  {

                    if (byteOrder == MAYBE_LITTLE_ENDIAN)

                      {

                        return CoderResult.malformedForLength (2);

                      }

                    byteOrder = BIG_ENDIAN;

                    inPos += 2;

                    continue;

                  }

                else if (c == REVERSED_BYTE_ORDER_MARK)

                  {

                    if (byteOrder == MAYBE_BIG_ENDIAN)

                      {

                        return CoderResult.malformedForLength (2);

                      }

                    byteOrder = LITTLE_ENDIAN;

                    inPos += 2;

                    continue;

                  }

                else

                  {

                    // assume big or little endian, do not consume bytes,

                    // continue with normal processing

                    byteOrder = (byteOrder == MAYBE_LITTLE_ENDIAN ?

                                 LITTLE_ENDIAN : BIG_ENDIAN);

                  }

              }

            // FIXME: Change so you only do a single comparison here.

            char c = (byteOrder == BIG_ENDIAN

                      ? (char) (((b1 & 0xFF) << 8) | (b2 & 0xFF))

                      : (char) (((b2 & 0xFF) << 8) | (b1 & 0xFF)));

            if (0xD800 <= c && c <= 0xDFFF)

              {

                // c is a surrogate

                // make sure c is a high surrogate

                if (c > 0xDBFF)

                  return CoderResult.malformedForLength (2);

                if (in.remaining () < 2)

                  return CoderResult.UNDERFLOW;

                byte b3 = in.get ();

                byte b4 = in.get ();

                char d = (byteOrder == BIG_ENDIAN

                          ? (char) (((b3 & 0xFF) << 8) | (b4 & 0xFF))

                          : (char) (((b4 & 0xFF) << 8) | (b3 & 0xFF)));

                // make sure d is a low surrogate

                if (d < 0xDC00 || d > 0xDFFF)

                  return CoderResult.malformedForLength (2);

                out.put (c);

                out.put (d);

                inPos += 4;

              }

            else

              {

                if (!out.hasRemaining ())

                  return CoderResult.UNDERFLOW;

                out.put (c);

                inPos += 2;

              }

          }

        return CoderResult.UNDERFLOW;

      }

    finally

      {

        in.position (inPos);

      }

  }

  protected void implReset ()

  {

    byteOrder = originalByteOrder;

  }

}