/* ARCFourRandomSpi.java -- 
   Copyright (C) 2002, 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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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
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
making a combined work based on this library.  Thus, the terms and
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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
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package gnu.javax.crypto.jce.prng;

import gnu.java.security.Registry;
import gnu.javax.crypto.prng.ARCFour;
import gnu.java.security.prng.IRandom;
import gnu.java.security.prng.LimitReachedException;
import gnu.javax.crypto.prng.PRNGFactory;

import java.security.SecureRandomSpi;
import java.util.HashMap;

/**
 * Implementation of the <i>Service Provider Interface</i> (<b>SPI</b>) for
 * the ARCFOUR keystream generator.
 */
public class ARCFourRandomSpi
    extends SecureRandomSpi
{
  /** Our underlying prng instance. */
  private IRandom adaptee;
  /** Have we been initialized? */
  private boolean virgin;

  /**
   * Default 0-arguments constructor.
   */
  public ARCFourRandomSpi()
  {
    super();
    adaptee = PRNGFactory.getInstance(Registry.ARCFOUR_PRNG);
    virgin = true;
  }

  public byte[] engineGenerateSeed(int numBytes)
  {
    if (numBytes < 1)
      return new byte[0];
    byte[] result = new byte[numBytes];
    this.engineNextBytes(result);
    return result;
  }

  public void engineNextBytes(byte[] bytes)
  {
    if (virgin)
      this.engineSetSeed(new byte[0]);
    try
      {
        adaptee.nextBytes(bytes, 0, bytes.length);
      }
    catch (LimitReachedException ignored)
      {
      }
  }

  public void engineSetSeed(byte[] seed)
  {
    HashMap attributes = new HashMap();
    attributes.put(ARCFour.ARCFOUR_KEY_MATERIAL, seed);
    adaptee.init(attributes);
    virgin = false;
  }
}