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/* DeflateTransformer.java --

   Copyright (C) 2003, 2006 Free Software Foundation, Inc.

This file is a 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 of the License, 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; if not, write to the Free Software

Foundation, Inc., 51 Franklin St, 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.javax.crypto.assembly;

import java.util.Map;

import java.util.zip.DataFormatException;

import java.util.zip.Deflater;

import java.util.zip.Inflater;

/**

 * A {@link Transformer} Adapter allowing inclusion of a DEFLATE compression

 * algorithm in an {@link Assembly} chain. The {@link Direction#FORWARD}

 * transformation is a compression (deflate) of input data, while the

 * {@link Direction#REVERSED} one is a decompression (inflate) that restores the

 * original data.

 * <p>

 * This {@link Transformer} uses a {@link Deflater} instance to carry on the

 * compression, and an {@link Inflater} to do the decompression.

 * <p>

 * When using such a {@link Transformer}, in an {@link Assembly}, there must

 * be at least one element behind this instance in the constructed chain;

 * otherwise, a {@link TransformerException} is thrown at initialisation time.

 */

class DeflateTransformer

    extends Transformer

{

  private Deflater compressor;

  private Inflater decompressor;

  private int outputBlockSize = 512; // default zlib buffer size

  private byte[] zlibBuffer;

  DeflateTransformer()

  {

    super();

  }

  void initDelegate(Map attributes) throws TransformerException

  {

    if (tail == null)

      {

        IllegalStateException cause = new IllegalStateException(

            "Compression transformer missing its tail!");

        throw new TransformerException("initDelegate()", cause);

      }

    outputBlockSize = tail.currentBlockSize();

    zlibBuffer = new byte[outputBlockSize];

    Direction flow = (Direction) attributes.get(DIRECTION);

    if (flow == Direction.FORWARD)

      compressor = new Deflater();

    else

      decompressor = new Inflater();

  }

  int delegateBlockSize()

  {

    return 1;

  }

  void resetDelegate()

  {

    compressor = null;

    decompressor = null;

    outputBlockSize = 1;

    zlibBuffer = null;

  }

  byte[] updateDelegate(byte[] in, int offset, int length)

      throws TransformerException

  {

    byte[] result;

    if (wired == Direction.FORWARD)

      {

        compressor.setInput(in, offset, length);

        while (! compressor.needsInput())

          compress();

      }

    else // decompression: inflate first and then update tail

      decompress(in, offset, length);

    result = inBuffer.toByteArray();

    inBuffer.reset();

    return result;

  }

  byte[] lastUpdateDelegate() throws TransformerException

  {

    // process multiples of blocksize as much as possible

    if (wired == Direction.FORWARD) // compressing

      {

        if (! compressor.finished())

          {

            compressor.finish();

            while (! compressor.finished())

              compress();

          }

      }

    else // decompressing

      {

        if (! decompressor.finished())

          {

            IllegalStateException cause = new IllegalStateException(

                "Compression transformer, after last update, must be finished "

                + "but isn't");

            throw new TransformerException("lastUpdateDelegate()", cause);

          }

      }

    byte[] result = inBuffer.toByteArray();

    inBuffer.reset();

    return result;

  }

  private void compress()

  {

    int len = compressor.deflate(zlibBuffer);

    if (len > 0)

      inBuffer.write(zlibBuffer, 0, len);

  }

  private void decompress(byte[] in, int offset, int length)

      throws TransformerException

  {

    decompressor.setInput(in, offset, length);

    int len = 1;

    while (len > 0)

      {

        try

          {

            len = decompressor.inflate(zlibBuffer);

          }

        catch (DataFormatException x)

          {

            throw new TransformerException("decompress()", x);

          }

        if (len > 0)

          inBuffer.write(zlibBuffer, 0, len);

      }

  }

}