gcc/libjava/java/security/AlgorithmParameters.java

/* AlgorithmParameters.java --- Algorithm Parameters Implementation Class
   Copyright (C) 1999, 2003 Free Software Foundation, Inc.

This file is 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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any later version.

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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
General Public License for more details.

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02111-1307 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
executable, regardless of the license terms of these independent
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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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this exception to your version of the library, but you are not
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exception statement from your version. */

package java.security;

import java.security.spec.InvalidParameterSpecException;
import java.security.spec.AlgorithmParameterSpec;
import java.io.IOException;

/**
 * <p>This class is used as an opaque representation of cryptographic
 * parameters.</p>
 *
 * <p>An <code>AlgorithmParameters</code> object for managing the parameters
 * for a particular algorithm can be obtained by calling one of the
 * <code>getInstance()</code> factory methods (static methods that return
 * instances of a given class).</p>
 *
 * <p>There are two ways to request such an implementation: by specifying
 * either just an algorithm name, or both an algorithm name and a package
 * provider.</p>
 *
 * <ul>
 *    <li>If just an algorithm name is specified, the system will determine if
 *    there is an AlgorithmParameters implementation for the algorithm requested
 *    available in the environment, and if there is more than one, if there is
 *    a preferred one.</li>
 *    <li>If both an algorithm name and a package provider are specified, the
 *    system will determine if there is an implementation in the package
 *    requested, and throw an exception if there is not.</li>
 * </ul>
 *
 * <p>Once an <code>AlgorithmParameters</code> object is returned, it must be
 * initialized via a call to <code>init()</code>, using an appropriate
 * parameter specification or parameter encoding.</p>
 *
 * <p>A transparent parameter specification is obtained from an
 * <ocde>AlgorithmParameters</code> object via a call to
 * <code>getParameterSpec()</code>, and a byte encoding of the parameters is
 * obtained via a call to <code>getEncoded()</code>.</p>
 *
 * @author Mark Benvenuto
 * @since 1.2
 * @see AlgorithmParameterSpec
 * @see java.security.spec.DSAParameterSpec
 * @see KeyPairGenerator
 */
public class AlgorithmParameters
{
  /** Service name for algorithm parameters. */
  private static final String ALGORITHM_PARAMETERS = "AlgorithmParameters";

  private AlgorithmParametersSpi paramSpi;
  private Provider provider;
  private String algorithm;

  /**
   * Creates an <code>AlgorithmParameters</code> object.
   *
   * @param paramSpi the delegate.
   * @param provider the provider.
   * @param algorithm the algorithm.
   */
  protected AlgorithmParameters(AlgorithmParametersSpi paramSpi,
                                Provider provider, String algorithm)
  {
    this.paramSpi = paramSpi;
    this.provider = provider;
    this.algorithm = algorithm;
  }

  /**
   * Returns the name of the algorithm associated with this parameter object.
   *
   * @return the algorithm name.
   */
  public final String getAlgorithm()
  {
    return algorithm;
  }

  /**
   * <p>Generates a parameter object for the specified algorithm.</p>
   *
   * <p>If the default provider package provides an implementation of the
   * requested algorithm, an instance of <code>AlgorithmParameters</code>
   * containing that implementation is returned. If the algorithm is not
   * available in the default package, other packages are searched.</p>
   *
   * <p>The returned parameter object must be initialized via a call to
   * <code>init()</code>, using an appropriate parameter specification or
   * parameter encoding.</p>
   *
   * @param algorithm the name of the algorithm requested.
   * @return the new parameter object.
   * @throws NoSuchAlgorithmException if the algorithm is not available in the
   * environment.
   */
  public static AlgorithmParameters getInstance(String algorithm)
    throws NoSuchAlgorithmException
  {
    Provider[] p = Security.getProviders();
    for (int i = 0; i < p.length; i++)
      try
        {
          return getInstance(algorithm, p[i]);
        }
      catch (NoSuchAlgorithmException ignored) {}

    throw new NoSuchAlgorithmException(algorithm);
  }

  /**
   * <p>Generates a parameter object for the specified algorithm, as supplied
   * by the specified provider, if such an algorithm is available from the
   * provider.</p>
   *
   * <p>The returned parameter object must be initialized via a call to
   * <code>init()</code>, using an appropriate parameter specification or
   * parameter encoding.</p>
   *
   * @param algorithm the name of the algorithm requested.
   * @param provider the name of the provider.
   * @return the new parameter object.
   * @throws NoSuchAlgorithmException if the algorithm is not available in the
   * package supplied by the requested provider.
   * @throws NoSuchProviderException if the provider is not available in the
   * environment.
   * @throws IllegalArgumentException if the provider name is null or empty.
   * @see Provider
   */
  public static AlgorithmParameters getInstance(String algorithm, String provider)
    throws NoSuchAlgorithmException, NoSuchProviderException
  {
    if (provider == null || provider.length() == 0)
      throw new IllegalArgumentException("Illegal provider");
    
    Provider p = Security.getProvider(provider);
    if (p == null)
      throw new NoSuchProviderException();

    return getInstance(algorithm, p);
  }

  /**
   * Generates an <code>AlgorithmParameterGenerator</code> object for the
   * requested algorithm, as supplied from the specified provider, if such a
   * parameter generator is available from the provider. Note: the
   * <code>provider</code> doesn't have to be registered.
   *
   * @param algorithm the string name of the algorithm.
   * @param provider the provider.
   * @return the new <code>AlgorithmParameterGenerator</code> object.
   * @throws NoSuchAlgorithmException if the <code>algorithm</code> is not
   * available from the <code>provider</code>.
   * @throws IllegalArgumentException if the <code>provider</code> is
   * <code>null</code>.
   * @since 1.4
   */
  public static AlgorithmParameters getInstance(String algorithm,
                                                Provider provider)
    throws NoSuchAlgorithmException
  {
    if (provider == null)
      throw new IllegalArgumentException("Illegal provider");

    try
      {
	return new AlgorithmParameters((AlgorithmParametersSpi)
	  Engine.getInstance(ALGORITHM_PARAMETERS, algorithm, provider),
	  provider, algorithm);
      }
    catch (ClassCastException cce)
      {
	throw new NoSuchAlgorithmException(algorithm);
      }
  }

  /**
   * Returns the provider of this parameter object.
   *
   * @return the provider of this parameter object.
   */
  public final Provider getProvider()
  {
    return provider;
  }

  /**
   * Initializes this parameter object using the parameters specified in
   * <code>paramSpec</code>.
   *
   * @param paramSpec the parameter specification.
   * @throws InvalidParameterSpecException if the given parameter specification
   * is inappropriate for the initialization of this parameter object, or if
   * this parameter object has already been initialized.
   */
  public final void init(AlgorithmParameterSpec paramSpec)
    throws InvalidParameterSpecException
  {
    paramSpi.engineInit(paramSpec);
  }

  /**
   * Imports the specified parameters and decodes them according to the primary
   * decoding format for parameters. The primary decoding format for parameters
   * is ASN.1, if an ASN.1 specification for this type of parameters exists.
   *
   * @param params the encoded parameters.
   * @throws IOException on decoding errors, or if this parameter object has
   * already been initialized.
   */
  public final void init(byte[]params) throws IOException
  {
    paramSpi.engineInit(params);
  }

  /**
   * Imports the parameters from params and decodes them according to the
   * specified decoding scheme. If <code>format</code> is <code>null</code>,
   * the primary decoding format for parameters is used. The primary decoding
   * format is ASN.1, if an ASN.1 specification for these parameters exists.
   *
   * @param params the encoded parameters.
   * @param format the name of the decoding scheme.
   * @throws IOException on decoding errors, or if this parameter object has
   * already been initialized.
   */
  public final void init(byte[]params, String format) throws IOException
  {
    paramSpi.engineInit(params, format);
  }

  /**
   * Returns a (transparent) specification of this parameter object.
   * <code>paramSpec</code> identifies the specification class in which the
   * parameters should be returned. It could, for example, be
   * <code>DSAParameterSpec.class</code>, to indicate that the parameters should
   * be returned in an instance of the {@link java.security.spec.DSAParameterSpec}
   * class.
   *
   * @param paramSpec the specification class in which the parameters should be
   * returned.
   * @return the parameter specification.
   * @throws InvalidParameterSpecException if the requested parameter
   * specification is inappropriate for this parameter object, or if this
   * parameter object has not been initialized.
   */
  public final AlgorithmParameterSpec getParameterSpec(Class paramSpec)
    throws InvalidParameterSpecException
  {
    return paramSpi.engineGetParameterSpec(paramSpec);
  }

  /**
   * Returns the parameters in their primary encoding format. The primary
   * encoding format for parameters is ASN.1, if an ASN.1 specification for
   * this type of parameters exists.
   *
   * @return the parameters encoded using their primary encoding format.
   * @throws IOException on encoding errors, or if this parameter object has not
   * been initialized.
   */
  public final byte[] getEncoded() throws IOException
  {
    return paramSpi.engineGetEncoded();
  }

  /**
   * Returns the parameters encoded in the specified scheme. If format is
   * <code>null</code>, the primary encoding format for parameters is used. The
   * primary encoding format is ASN.1, if an ASN.1 specification for these
   * parameters exists.
   *
   * @param format the name of the encoding format.
   * @return the parameters encoded using the specified encoding scheme.
   * @throws IOException on encoding errors, or if this parameter object has
   * not been initialized.
   */
  public final byte[] getEncoded(String format) throws IOException
  {
    return paramSpi.engineGetEncoded(format);
  }

  /**
   * Returns a formatted string describing the parameters.
   *
   * @return a formatted string describing the parameters, or <code>null</code>
   * if this parameter object has not been initialized.
   */
  public final String toString()
  {
    return paramSpi.engineToString();
  }
}