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package java.security;

import java.io.*;

import java.security.spec.AlgorithmParameterSpec;

import java.security.spec.InvalidParameterSpecException;

import java.util.Objects;

/**

 * This class is used as an opaque representation of cryptographic parameters.

 *

 * <p>An {@code AlgorithmParameters} object for managing the parameters

 * for a particular algorithm can be obtained by

 * calling one of the {@code getInstance} factory methods

 * (static methods that return instances of a given class).

 *

 * <p>Once an {@code AlgorithmParameters} object is obtained, it must be

 * initialized via a call to {@code init}, using an appropriate parameter

 * specification or parameter encoding.

 *

 * <p>A transparent parameter specification is obtained from an

 * {@code AlgorithmParameters} object via a call to

 * {@code getParameterSpec}, and a byte encoding of the parameters is

 * obtained via a call to {@code getEncoded}.

 *

 * <p> Every implementation of the Java platform is required to support the

 * following standard {@code AlgorithmParameters} algorithms:

 * <ul>

 * <li>{@code AES}</li>

 * <li>{@code DESede}</li>

 * <li>{@code DiffieHellman}</li>

 * <li>{@code DSA}</li>

 * </ul>

 * These algorithms are described in the <a href=

 * "{@docRoot}/../specs/security/standard-names.html#algorithmparameters-algorithms">

 * AlgorithmParameters 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 java.security.spec.AlgorithmParameterSpec

 * @see java.security.spec.DSAParameterSpec

 * @see KeyPairGenerator

 *

 * @since 1.2

 */

public class AlgorithmParameters {

    // The provider

    private Provider provider;

    // The provider implementation (delegate)

    private AlgorithmParametersSpi paramSpi;

    // The algorithm

    private String algorithm;

    // Has this object been initialized?

    private boolean initialized = false;

    /**

     * Creates an AlgorithmParameters 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 this.algorithm;

    }

    /**

     * Returns a parameter object for the specified algorithm.

     *

     * <p> This method traverses the list of registered security Providers,

     * starting with the most preferred Provider.

     * A new AlgorithmParameters object encapsulating the

     * AlgorithmParametersSpi 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.

     *

     * <p> The returned parameter object must be initialized via a call to

     * {@code init}, using an appropriate parameter specification or

     * parameter encoding.

     *

     * @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 requested.

     * See the AlgorithmParameters section in the <a href=

     * "{@docRoot}/../specs/security/standard-names.html#algorithmparameters-algorithms">

     * Java Security Standard Algorithm Names Specification</a>

     * for information about standard algorithm names.

     *

     * @return the new parameter object

     *

     * @throws NoSuchAlgorithmException if no {@code Provider} supports an

     *         {@code AlgorithmParametersSpi} implementation for the

     *         specified algorithm

     *

     * @throws NullPointerException if {@code algorithm} is {@code null}

     *

     * @see Provider

     */

    public static AlgorithmParameters getInstance(String algorithm)

    throws NoSuchAlgorithmException {

        Objects.requireNonNull(algorithm, "null algorithm name");

        try {

            Object[] objs = Security.getImpl(algorithm, "AlgorithmParameters",

                                             (String)null);

            return new AlgorithmParameters((AlgorithmParametersSpi)objs[0],

                                           (Provider)objs[1],

                                           algorithm);

        } catch(NoSuchProviderException e) {

            throw new NoSuchAlgorithmException(algorithm + " not found");

        }

    }

    /**

     * Returns a parameter object for the specified algorithm.

     *

     * <p> A new AlgorithmParameters object encapsulating the

     * AlgorithmParametersSpi 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.

     *

     * <p>The returned parameter object must be initialized via a call to

     * {@code init}, using an appropriate parameter specification or

     * parameter encoding.

     *

     * @param algorithm the name of the algorithm requested.

     * See the AlgorithmParameters section in the <a href=

     * "{@docRoot}/../specs/security/standard-names.html#algorithmparameters-algorithms">

     * Java Security Standard Algorithm Names Specification</a>

     * for information about standard algorithm names.

     *

     * @param provider the name of the provider.

     *

     * @return the new parameter object

     *

     * @throws IllegalArgumentException if the provider name is {@code null}

     *         or empty

     *

     * @throws NoSuchAlgorithmException if an {@code AlgorithmParametersSpi}

     *         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 AlgorithmParameters getInstance(String algorithm,

                                                  String provider)

        throws NoSuchAlgorithmException, NoSuchProviderException

    {

        Objects.requireNonNull(algorithm, "null algorithm name");

        if (provider == null || provider.isEmpty())

            throw new IllegalArgumentException("missing provider");

        Object[] objs = Security.getImpl(algorithm, "AlgorithmParameters",

                                         provider);

        return new AlgorithmParameters((AlgorithmParametersSpi)objs[0],

                                       (Provider)objs[1],

                                       algorithm);

    }

    /**

     * Returns a parameter object for the specified algorithm.

     *

     * <p> A new AlgorithmParameters object encapsulating the

     * AlgorithmParametersSpi implementation from the specified Provider

     * object is returned.  Note that the specified Provider object

     * does not have to be registered in the provider list.

     *

     * <p>The returned parameter object must be initialized via a call to

     * {@code init}, using an appropriate parameter specification or

     * parameter encoding.

     *

     * @param algorithm the name of the algorithm requested.

     * See the AlgorithmParameters section in the <a href=

     * "{@docRoot}/../specs/security/standard-names.html#algorithmparameters-algorithms">

     * Java Security Standard Algorithm Names Specification</a>

     * for information about standard algorithm names.

     *

     * @param provider the name of the provider.

     *

     * @return the new parameter object

     *

     * @throws IllegalArgumentException if the 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 AlgorithmParameters 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, "AlgorithmParameters",

                                         provider);

        return new AlgorithmParameters((AlgorithmParametersSpi)objs[0],

                                       (Provider)objs[1],

                                       algorithm);

    }

    /**

     * Returns the provider of this parameter object.

     *

     * @return the provider of this parameter object

     */

    public final Provider getProvider() {

        return this.provider;

    }

    /**

     * Initializes this parameter object using the parameters

     * specified in {@code paramSpec}.

     *

     * @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

    {

        if (this.initialized)

            throw new InvalidParameterSpecException("already initialized");

        paramSpi.engineInit(paramSpec);

        this.initialized = true;

    }

    /**

     * 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 {

        if (this.initialized)

            throw new IOException("already initialized");

        paramSpi.engineInit(params);

        this.initialized = true;

    }

    /**

     * Imports the parameters from {@code params} and decodes them

     * according to the specified decoding scheme.

     * If {@code format} is null, 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 {

        if (this.initialized)

            throw new IOException("already initialized");

        paramSpi.engineInit(params, format);

        this.initialized = true;

    }

    /**

     * Returns a (transparent) specification of this parameter object.

     * {@code paramSpec} identifies the specification class in which

     * the parameters should be returned. It could, for example, be

     * {@code DSAParameterSpec.class}, to indicate that the

     * parameters should be returned in an instance of the

     * {@code DSAParameterSpec} class.

     *

     * @param <T> the type of the parameter specification to be returrned

     * @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 <T extends AlgorithmParameterSpec>

        T getParameterSpec(Class<T> paramSpec)

        throws InvalidParameterSpecException

    {

        if (this.initialized == false) {

            throw new InvalidParameterSpecException("not initialized");

        }

        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

    {

        if (this.initialized == false) {

            throw new IOException("not initialized");

        }

        return paramSpi.engineGetEncoded();

    }

    /**

     * Returns the parameters encoded in the specified scheme.

     * If {@code format} is null, 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

    {

        if (this.initialized == false) {

            throw new IOException("not initialized");

        }

        return paramSpi.engineGetEncoded(format);

    }

    /**

     * Returns a formatted string describing the parameters.

     *

     * @return a formatted string describing the parameters, or null if this

     * parameter object has not been initialized.

     */

    public final String toString() {

        if (this.initialized == false) {

            return null;

        }

        return paramSpi.engineToString();

    }

}