gcc/libjava/classpath/gnu/javax/crypto/assembly/DeflateTransformer.java

/* 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
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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
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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;

/**
 * <p>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>
 *
 * <p>This {@link Transformer} uses a {@link Deflater} instance to carry on the
 * compression, and an {@link Inflater} to do the decompression.</p>
 *
 * <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.</p>
 *
 * @version Revision: $
 */
class DeflateTransformer extends Transformer
{

  // Constants and variables
  // -------------------------------------------------------------------------

  private Deflater compressor;

  private Inflater decompressor;

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

  private byte[] zlibBuffer;

  // Constructor(s)
  // -------------------------------------------------------------------------

  DeflateTransformer()
  {
    super();

  }

  // Class methods
  // -------------------------------------------------------------------------

  // Instance methods
  // -------------------------------------------------------------------------

  void initDelegate(Map attributes) throws TransformerException
  {
    if (tail == null)
      {
        throw new TransformerException(
                                       "initDelegate()",
                                       new IllegalStateException(
                                                                 "Compression transformer missing its tail!"));
      }
    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 outputBlockSize;
    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(byte[] in, int offset, int length)
  //   throws TransformerException {
  //      // process multiples of blocksize as much as possible
  //      byte[] result = this.updateDelegate(in, offset, length);
  //      inBuffer.write(result, 0, result.length);
  //      if (wired == Direction.FORWARD) { // compressing
  //         if (!compressor.finished()) {
  //            compressor.finish();
  //            while (!compressor.finished()) {
  //               compress();
  //            }
  //         }
  //      } else { // decompressing
  //         if (!decompressor.finished()) {
  //            throw new TransformerException("lastUpdateDelegate()",
  //                  new IllegalStateException("Compression transformer, after last "
  //                  +"update, must be finished but isn't"));
  //         }
  //      }
  //
  //      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())
          {
            throw new TransformerException(
                                           "lastUpdateDelegate()",
                                           new IllegalStateException(
                                                                     "Compression transformer, after last "
                                                                         + "update, must be finished but isn't"));
          }
      }
    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);
          }
      }
  }
}