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

/* PaddingTransformer.java -- 
   Copyright (C) 2003, 2006 Free Software Foundation, Inc.

This file is a part of GNU Classpath.

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it under the terms of the GNU General Public License as published by
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General Public License for more details.

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Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301
USA

Linking this library statically or dynamically with other modules is
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permission to link this library with independent modules to produce an
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package gnu.javax.crypto.assembly;

import gnu.javax.crypto.pad.IPad;
import gnu.javax.crypto.pad.WrongPaddingException;

import java.util.Map;

/**
 * <p>An Adapter to use any {@link IPad} as a {@link Transformer} in an
 * {@link Assembly}.</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>
 */
class PaddingTransformer extends Transformer
{

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

  private IPad delegate;

  private int outputBlockSize = 1;

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

  PaddingTransformer(IPad padding)
  {
    super();

    this.delegate = padding;
  }

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

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

  void initDelegate(Map attributes) throws TransformerException
  {
    if (tail == null)
      {
        throw new TransformerException(
                                       "initDelegate()",
                                       new IllegalStateException(
                                                                 "Padding transformer missing its tail!"));
      }
    outputBlockSize = tail.currentBlockSize();
    delegate.init(outputBlockSize);
  }

  int delegateBlockSize()
  {
    return outputBlockSize;
  }

  void resetDelegate()
  {
    delegate.reset();
    outputBlockSize = 1;
  }

  byte[] updateDelegate(byte[] in, int offset, int length)
      throws TransformerException
  {
    inBuffer.write(in, offset, length);
    byte[] tmp = inBuffer.toByteArray();
    inBuffer.reset();
    byte[] result;
    if (wired == Direction.FORWARD)
      { // padding
        // buffers remaining bytes from (inBuffer + in) that are less than 1 block
        if (tmp.length < outputBlockSize)
          {
            inBuffer.write(tmp, 0, tmp.length);
            result = new byte[0];
          }
        else
          {
            int newlen = outputBlockSize * (tmp.length / outputBlockSize);
            inBuffer.write(tmp, newlen, tmp.length - newlen);
            result = new byte[newlen];
            System.arraycopy(tmp, 0, result, 0, newlen);
          }
      }
    else
      { // unpadding
        // always keep in own buffer a max of 1 block to cater for lastUpdate
        if (tmp.length < outputBlockSize)
          {
            inBuffer.write(tmp, 0, tmp.length);
            result = new byte[0];
          }
        else
          {
            result = new byte[tmp.length - outputBlockSize];
            System.arraycopy(tmp, 0, result, 0, result.length);
            inBuffer.write(tmp, result.length, outputBlockSize);
          }
      }
    return result;
  }

  byte[] lastUpdateDelegate() throws TransformerException
  {
    byte[] result;
    // process multiples of blocksize as much as possible
    // catenate result from processing inBuffer with last-update( tail )
    if (wired == Direction.FORWARD)
      { // padding
        result = inBuffer.toByteArray();
        byte[] padding = delegate.pad(result, 0, result.length);
        inBuffer.write(padding, 0, padding.length);
      }
    else
      { // unpadding
        byte[] tmp = inBuffer.toByteArray();
        inBuffer.reset();
        int realLength;
        try
          {
            realLength = tmp.length; // should be outputBlockSize
            realLength -= delegate.unpad(tmp, 0, tmp.length);
          }
        catch (WrongPaddingException x)
          {
            throw new TransformerException("lastUpdateDelegate()", x);
          }
        inBuffer.write(tmp, 0, realLength);
      }
    result = inBuffer.toByteArray();
    inBuffer.reset();
    return result;
  }
}