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

/* Assembly.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
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USA

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permission to link this library with independent modules to produce an
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exception statement from your version.  */


package gnu.javax.crypto.assembly;

import java.util.Map;

/**
 * <p>An <code>Assembly</code> is a construction consisting of a chain of
 * {@link Transformer} elements; each wired in pre- or post- transformation
 * mode. This chain is terminated by one <code>LoopbackTransformer</code>
 * element.</p>
 *
 * <p>Once constructed, and correctly initialised, the bulk of the methods
 * available on the <code>Assembly</code> are delegated to the <i>head</i>
 * of the {@link Transformer} chain of the <code>Assembly</code>.</p>
 *
 * @see Transformer
 */
public class Assembly
{

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

  public static final String DIRECTION = "gnu.crypto.assembly.assembly.direction";

  /** Flag that tells if the instance is initialised or not; and if yes how. */
  private Direction wired;

  /** The first Transformer in the chain. */
  private Transformer head;

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

  /**
   * Trivial constructor that sets the <i>chain</i> to a
   * <code>LoopbackTransformer</code>.
   */
  public Assembly()
  {
    super();

    wired = null;
    head = new LoopbackTransformer();
  }

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

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

  /**
   * Adds the designated {@link Transformer} and signals that it should operate
   * in pre-processing mode; i.e. it should apply its internal transformation
   * algorithm on the input data stream, <b>before</b> it passes that stream to
   * the next element in the <i>chain</i>.
   *
   * @param t the {@link Transformer} to add at the head of the current chain.
   * @throws IllegalArgumentException if the designated {@link Transformer}
   * has a non-null tail; i.e. it is already an element of a chain.
   */
  public void addPreTransformer(Transformer t)
  {
    wireTransformer(t, Operation.PRE_PROCESSING);
  }

  /**
   * Adds the designated {@link Transformer} and signals that it should operate
   * in post-processing mode; i.e. it should apply its internal transformation
   * algorithm on the input data stream, <b>after</b> it passes that stream to
   * the next element in the <i>chain</i>.
   *
   * @param t the {@link Transformer} to add at the head of the current chain.
   * @throws IllegalArgumentException if the designated {@link Transformer}
   * has a non-null tail; i.e. it is already an element of a chain.
   */
  public void addPostTransformer(Transformer t)
  {
    wireTransformer(t, Operation.POST_PROCESSING);
  }

  /**
   * Initialises the <code>Assembly</code> for operation with specific
   * characteristics.
   *
   * @param attributes a set of name-value pairs that describes the desired
   * future behaviour of this instance.
   * @throws IllegalStateException if the instance is already initialised.
   */
  public void init(Map attributes) throws TransformerException
  {
    if (wired != null)
      {
        throw new IllegalStateException();
      }
    Direction flow = (Direction) attributes.get(DIRECTION);
    if (flow == null)
      {
        flow = Direction.FORWARD;
      }
    attributes.put(Transformer.DIRECTION, flow);
    head.init(attributes);
    wired = flow;
  }

  /**
   * Resets the <code>Assembly</code> for re-initialisation and use with other
   * characteristics. This method always succeeds.
   */
  public void reset()
  {
    head.reset();
    wired = null;
  }

  /**
   * Convenience method that calls the method with same name and three
   * arguments, using a byte array of length <code>1</code> whose contents are
   * the designated byte.
   *
   * @param b the byte to process.
   * @return the result of transformation.
   * @throws IllegalStateException if the instance is not initialised.
   * @throws TransformerException if a transformation-related exception occurs
   * during the operation.
   * @see #update(byte[], int, int)
   */
  public byte[] update(byte b) throws TransformerException
  {
    return update(new byte[] { b }, 0, 1);
  }

  /**
   * Convenience method that calls the method with same name and three
   * arguments. All bytes in <code>in</code>, starting from index position
   * <code>0</code> are considered.
   *
   * @param in the input data bytes.
   * @return the result of transformation.
   * @throws IllegalStateException if the instance is not initialised.
   * @throws TransformerException if a transformation-related exception occurs
   * during the operation.
   * @see #update(byte[], int, int)
   */
  public byte[] update(byte[] in) throws TransformerException
  {
    return update(in, 0, in.length);
  }

  /**
   * Processes a designated number of bytes from a given byte array.
   *
   * @param in the input data bytes.
   * @param offset index of <code>in</code> from which to start considering
   * data.
   * @param length the count of bytes to process.
   * @return the result of transformation.
   * @throws IllegalStateException if the instance is not initialised.
   * @throws TransformerException if a transformation-related exception occurs
   * during the operation.
   */
  public byte[] update(byte[] in, int offset, int length)
      throws TransformerException
  {
    if (wired == null)
      {
        throw new IllegalStateException();
      }
    return head.update(in, offset, length);
  }

  /**
   * Convenience method that calls the method with same name and three
   * arguments using a 0-long byte array.
   *
   * @return the result of transformation.
   * @throws IllegalStateException if the instance is not initialised.
   * @throws TransformerException if a transformation-related exception occurs
   * during the operation.
   * @see #lastUpdate(byte[], int, int)
   */
  public byte[] lastUpdate() throws TransformerException
  {
    return lastUpdate(new byte[0], 0, 0);
  }

  /**
   * Convenience method that calls the method with same name and three
   * arguments, using a byte array of length <code>1</code> whose contents are
   * the designated byte.
   *
   * @param b the byte to process.
   * @return the result of transformation.
   * @throws IllegalStateException if the instance is not initialised.
   * @throws TransformerException if a transformation-related exception occurs
   * during the operation.
   * @see #lastUpdate(byte[], int, int)
   */
  public byte[] lastUpdate(byte b) throws TransformerException
  {
    return lastUpdate(new byte[] { b }, 0, 1);
  }

  /**
   * Convenience method that calls the method with same name and three
   * arguments. All bytes in <code>in</code>, starting from index position
   * <code>0</code> are considered.
   *
   * @param in the input data bytes.
   * @return the result of transformation.
   * @throws IllegalStateException if the instance is not initialised.
   * @throws TransformerException if a transformation-related exception occurs
   * during the operation.
   * @see #lastUpdate(byte[], int, int)
   */
  public byte[] lastUpdate(byte[] in) throws TransformerException
  {
    return lastUpdate(in, 0, in.length);
  }

  /**
   * Processes a designated number of bytes from a given byte array and
   * signals, at the same time, that this is the last <i>push</i> operation for
   * this <code>Assembly</code>.
   *
   * @param in the input data bytes.
   * @param offset index of <code>in</code> from which to start considering
   * data.
   * @param length the count of bytes to process.
   * @return the result of transformation.
   * @throws IllegalStateException if the instance is not initialised.
   * @throws TransformerException if a transformation-related exception
   * occurs during the operation.
   */
  public byte[] lastUpdate(byte[] in, int offset, int length)
      throws TransformerException
  {
    if (wired == null)
      {
        throw new IllegalStateException();
      }
    byte[] result = head.lastUpdate(in, offset, length);
    reset();
    return result;
  }

  // helper methods ----------------------------------------------------------

  private void wireTransformer(Transformer t, Operation mode)
  {
    if (t.tail != null)
      {
        throw new IllegalArgumentException();
      }
    t.setMode(mode);
    t.tail = head;
    head = t;
  }
}