gcc/libjava/classpath/gnu/java/security/jce/prng/SecureRandomAdapter.java

/* SecureRandomAdapter.java -- 
   Copyright (C) 2001, 2002, 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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package gnu.java.security.jce.prng;

import gnu.java.security.prng.LimitReachedException;
import gnu.java.security.prng.MDGenerator;

import java.security.SecureRandomSpi;
import java.util.Collections;

/**
 * The implementation of a generic {@link java.security.SecureRandom} adapter
 * class to wrap GNU PRNG instances based on Message Digest algorithms.
 * <p>
 * This class defines the <i>Service Provider Interface</i> (<b>SPI</b>) for
 * the {@link java.security.SecureRandom} class, which provides the
 * functionality of a cryptographically strong pseudo-random number generator.
 * <p>
 * All the abstract methods in the {@link SecureRandomSpi} class are implemented
 * by this class and all its sub-classes.
 */
abstract class SecureRandomAdapter
    extends SecureRandomSpi
{
  /** Our underlying prng instance. */
  private MDGenerator adaptee = new MDGenerator();

  /** The name of the message digest algorithm used by the adaptee. */
  private String mdName;

  /**
   * Trivial protected constructor.
   * 
   * @param mdName the canonical name of the underlying hash algorithm.
   */
  protected SecureRandomAdapter(String mdName)
  {
    super();

    this.mdName = mdName;
    adaptee.init(Collections.singletonMap(MDGenerator.MD_NAME, mdName));
  }

  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 (! adaptee.isInitialised())
      this.engineSetSeed(new byte[0]);
    try
      {
        adaptee.nextBytes(bytes, 0, bytes.length);
      }
    catch (LimitReachedException ignored)
      {
      }
  }

  public void engineSetSeed(byte[] seed)
  {
    adaptee.addRandomBytes(seed);
  }
}