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	/*
	* Copyright (c) 1997, 2017, Oracle and/or its affiliates. All rights reserved.
	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
	*
	* This code is free software; you can redistribute it and/or modify it
	* under the terms of the GNU General Public License version 2 only, as
	* published by the Free Software Foundation. Oracle designates this
	* particular file as subject to the "Classpath" exception as provided
	* by Oracle in the LICENSE file that accompanied this code.
	*
	* This code is distributed in the hope that it will be useful, but WITHOUT
	* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
	* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
	* version 2 for more details (a copy is included in the LICENSE file that
	* accompanied this code).
	*
	* You should have received a copy of the GNU General Public License version
	* 2 along with this work; if not, write to the Free Software Foundation,
	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
	*
	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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	package java.security;

	import java.security.spec.AlgorithmParameterSpec;
	import java.util.Objects;

	/**
	* The {@code AlgorithmParameterGenerator} class is used to generate a
	* set of
	* parameters to be used with a certain algorithm. Parameter generators
	* are constructed using the {@code getInstance} factory methods
	* (static methods that return instances of a given class).
	*
	* <P>The object that will generate the parameters can be initialized
	* in two different ways: in an algorithm-independent manner, or in an
	* algorithm-specific manner:
	*
	* <ul>
	* <li>The algorithm-independent approach uses the fact that all parameter
	* generators share the concept of a "size" and a
	* source of randomness. The measure of size is universally shared
	* by all algorithm parameters, though it is interpreted differently
	* for different algorithms. For example, in the case of parameters for
	* the <i>DSA</i> algorithm, "size" corresponds to the size
	* of the prime modulus (in bits).
	* When using this approach, algorithm-specific parameter generation
	* values - if any - default to some standard values, unless they can be
	* derived from the specified size.
	*
	* <li>The other approach initializes a parameter generator object
	* using algorithm-specific semantics, which are represented by a set of
	* algorithm-specific parameter generation values. To generate
	* Diffie-Hellman system parameters, for example, the parameter generation
	* values usually
	* consist of the size of the prime modulus and the size of the
	* random exponent, both specified in number of bits.
	* </ul>
	*
	* <P>In case the client does not explicitly initialize the
	* AlgorithmParameterGenerator (via a call to an {@code init} method),
	* each provider must supply (and document) a default initialization.
	* See the Keysize Restriction sections of the
	* {@extLink security_guide_jdk_providers JDK Providers}
	* document for information on the AlgorithmParameterGenerator defaults
	* used by JDK providers.
	* However, note that defaults may vary across different providers.
	* Additionally, the default value for a provider may change in a future
	* version. Therefore, it is recommended to explicitly initialize the
	* AlgorithmParameterGenerator instead of relying on provider-specific defaults.
	*
	* <p> Every implementation of the Java platform is required to support the
	* following standard {@code AlgorithmParameterGenerator} algorithms and
	* keysizes in parentheses:
	* <ul>
	* <li>{@code DiffieHellman} (1024, 2048)</li>
	* <li>{@code DSA} (1024, 2048)</li>
	* </ul>
	* These algorithms are described in the <a href=
	* "{@docRoot}/../specs/security/standard-names.html#algorithmparametergenerator-algorithms">
	* AlgorithmParameterGenerator section</a> of the
	* Java Security Standard Algorithm Names Specification.
	* Consult the release documentation for your implementation to see if any
	* other algorithms are supported.
	*
	* @author Jan Luehe
	*
	*
	* @see AlgorithmParameters
	* @see java.security.spec.AlgorithmParameterSpec
	*
	* @since 1.2
	*/

	public class AlgorithmParameterGenerator {

	// The provider
	private Provider provider;

	// The provider implementation (delegate)
	private AlgorithmParameterGeneratorSpi paramGenSpi;

	// The algorithm
	private String algorithm;

	/**
	* Creates an AlgorithmParameterGenerator object.
	*
	* @param paramGenSpi the delegate
	* @param provider the provider
	* @param algorithm the algorithm
	*/
	protected AlgorithmParameterGenerator
	(AlgorithmParameterGeneratorSpi paramGenSpi, Provider provider,
	String algorithm) {
	this.paramGenSpi = paramGenSpi;
	this.provider = provider;
	this.algorithm = algorithm;
	}

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

	/**
	* Returns an AlgorithmParameterGenerator object for generating
	* a set of parameters to be used with the specified algorithm.
	*
	* <p> This method traverses the list of registered security Providers,
	* starting with the most preferred Provider.
	* A new AlgorithmParameterGenerator object encapsulating the
	* AlgorithmParameterGeneratorSpi implementation from the first
	* Provider that supports the specified algorithm is returned.
	*
	* <p> Note that the list of registered providers may be retrieved via
	* the {@link Security#getProviders() Security.getProviders()} method.
	*
	* @implNote
	* The JDK Reference Implementation additionally uses the
	* {@code jdk.security.provider.preferred}
	* {@link Security#getProperty(String) Security} property to determine
	* the preferred provider order for the specified algorithm. This
	* may be different than the order of providers returned by
	* {@link Security#getProviders() Security.getProviders()}.
	*
	* @param algorithm the name of the algorithm this
	* parameter generator is associated with.
	* See the AlgorithmParameterGenerator section in the <a href=
	* "{@docRoot}/../specs/security/standard-names.html#algorithmparametergenerator-algorithms">
	* Java Security Standard Algorithm Names Specification</a>
	* for information about standard algorithm names.
	*
	* @return the new {@code AlgorithmParameterGenerator} object
	*
	* @throws NoSuchAlgorithmException if no {@code Provider} supports an
	* {@code AlgorithmParameterGeneratorSpi} implementation for the
	* specified algorithm
	*
	* @throws NullPointerException if {@code algorithm} is {@code null}
	*
	* @see Provider
	*/
	public static AlgorithmParameterGenerator getInstance(String algorithm)
	throws NoSuchAlgorithmException {
	Objects.requireNonNull(algorithm, "null algorithm name");
	try {
	Object[] objs = Security.getImpl(algorithm,
	"AlgorithmParameterGenerator",
	(String)null);
	return new AlgorithmParameterGenerator
	((AlgorithmParameterGeneratorSpi)objs[0],
	(Provider)objs[1],
	algorithm);
	} catch(NoSuchProviderException e) {
	throw new NoSuchAlgorithmException(algorithm + " not found");
	}
	}

	/**
	* Returns an AlgorithmParameterGenerator object for generating
	* a set of parameters to be used with the specified algorithm.
	*
	* <p> A new AlgorithmParameterGenerator object encapsulating the
	* AlgorithmParameterGeneratorSpi implementation from the specified provider
	* is returned. The specified provider must be registered
	* in the security provider list.
	*
	* <p> Note that the list of registered providers may be retrieved via
	* the {@link Security#getProviders() Security.getProviders()} method.
	*
	* @param algorithm the name of the algorithm this
	* parameter generator is associated with.
	* See the AlgorithmParameterGenerator section in the <a href=
	* "{@docRoot}/../specs/security/standard-names.html#algorithmparametergenerator-algorithms">
	* Java Security Standard Algorithm Names Specification</a>
	* for information about standard algorithm names.
	*
	* @param provider the string name of the Provider.
	*
	* @return the new {@code AlgorithmParameterGenerator} object
	*
	* @throws IllegalArgumentException if the provider name is {@code null}
	* or empty
	*
	* @throws NoSuchAlgorithmException if an
	* {@code AlgorithmParameterGeneratorSpi}
	* implementation for the specified algorithm is not
	* available from the specified provider
	*
	* @throws NoSuchProviderException if the specified provider is not
	* registered in the security provider list
	*
	* @throws NullPointerException if {@code algorithm} is {@code null}
	*
	* @see Provider
	*/
	public static AlgorithmParameterGenerator getInstance(String algorithm,
	String provider)
	throws NoSuchAlgorithmException, NoSuchProviderException
	{
	Objects.requireNonNull(algorithm, "null algorithm name");
	if (provider == null \|\| provider.length() == 0)
	throw new IllegalArgumentException("missing provider");
	Object[] objs = Security.getImpl(algorithm,
	"AlgorithmParameterGenerator",
	provider);
	return new AlgorithmParameterGenerator
	((AlgorithmParameterGeneratorSpi)objs[0], (Provider)objs[1],
	algorithm);
	}

	/**
	* Returns an AlgorithmParameterGenerator object for generating
	* a set of parameters to be used with the specified algorithm.
	*
	* <p> A new AlgorithmParameterGenerator object encapsulating the
	* AlgorithmParameterGeneratorSpi implementation from the specified Provider
	* object is returned. Note that the specified Provider object
	* does not have to be registered in the provider list.
	*
	* @param algorithm the string name of the algorithm this
	* parameter generator is associated with.
	* See the AlgorithmParameterGenerator section in the <a href=
	* "{@docRoot}/../specs/security/standard-names.html#algorithmparametergenerator-algorithms">
	* Java Security Standard Algorithm Names Specification</a>
	* for information about standard algorithm names.
	*
	* @param provider the {@code Provider} object.
	*
	* @return the new {@code AlgorithmParameterGenerator} object
	*
	* @throws IllegalArgumentException if the specified provider is
	* {@code null}
	*
	* @throws NoSuchAlgorithmException if an
	* {@code AlgorithmParameterGeneratorSpi}
	* implementation for the specified algorithm is not available
	* from the specified {@code Provider} object
	*
	* @throws NullPointerException if {@code algorithm} is {@code null}
	*
	* @see Provider
	*
	* @since 1.4
	*/
	public static AlgorithmParameterGenerator getInstance(String algorithm,
	Provider provider)
	throws NoSuchAlgorithmException
	{
	Objects.requireNonNull(algorithm, "null algorithm name");
	if (provider == null)
	throw new IllegalArgumentException("missing provider");
	Object[] objs = Security.getImpl(algorithm,
	"AlgorithmParameterGenerator",
	provider);
	return new AlgorithmParameterGenerator
	((AlgorithmParameterGeneratorSpi)objs[0], (Provider)objs[1],
	algorithm);
	}

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

	/**
	* Initializes this parameter generator for a certain size.
	* To create the parameters, the {@code SecureRandom}
	* implementation of the highest-priority installed provider is used as
	* the source of randomness.
	* (If none of the installed providers supply an implementation of
	* {@code SecureRandom}, a system-provided source of randomness is
	* used.)
	*
	* @param size the size (number of bits).
	*/
	public final void init(int size) {
	paramGenSpi.engineInit(size, new SecureRandom());
	}

	/**
	* Initializes this parameter generator for a certain size and source
	* of randomness.
	*
	* @param size the size (number of bits).
	* @param random the source of randomness.
	*/
	public final void init(int size, SecureRandom random) {
	paramGenSpi.engineInit(size, random);
	}

	/**
	* Initializes this parameter generator with a set of algorithm-specific
	* parameter generation values.
	* To generate the parameters, the {@code SecureRandom}
	* implementation of the highest-priority installed provider is used as
	* the source of randomness.
	* (If none of the installed providers supply an implementation of
	* {@code SecureRandom}, a system-provided source of randomness is
	* used.)
	*
	* @param genParamSpec the set of algorithm-specific parameter generation values.
	*
	* @exception InvalidAlgorithmParameterException if the given parameter
	* generation values are inappropriate for this parameter generator.
	*/
	public final void init(AlgorithmParameterSpec genParamSpec)
	throws InvalidAlgorithmParameterException {
	paramGenSpi.engineInit(genParamSpec, new SecureRandom());
	}

	/**
	* Initializes this parameter generator with a set of algorithm-specific
	* parameter generation values.
	*
	* @param genParamSpec the set of algorithm-specific parameter generation values.
	* @param random the source of randomness.
	*
	* @exception InvalidAlgorithmParameterException if the given parameter
	* generation values are inappropriate for this parameter generator.
	*/
	public final void init(AlgorithmParameterSpec genParamSpec,
	SecureRandom random)
	throws InvalidAlgorithmParameterException {
	paramGenSpi.engineInit(genParamSpec, random);
	}

	/**
	* Generates the parameters.
	*
	* @return the new AlgorithmParameters object.
	*/
	public final AlgorithmParameters generateParameters() {
	return paramGenSpi.engineGenerateParameters();
	}
	}

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