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	/*
	* Copyright (c) 1998, 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
	* or visit www.oracle.com if you need additional information or have any
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	*/

	package java.security;

	/**
	* This class defines the <i>Service Provider Interface</i> (<b>SPI</b>)
	* for the {@link SecureRandom} class.
	* <p>
	* All the abstract methods in this class must be implemented by each
	* service provider who wishes to supply the implementation
	* of a cryptographically strong pseudo-random number generator.
	*
	* @implSpec
	* If the {@link #SecureRandomSpi(SecureRandomParameters)}
	* constructor is overridden in an implementation, it will always be called
	* whenever a {@code SecureRandom} is instantiated. Precisely, if an object is
	* instantiated with one of {@code SecureRandom}'s {@code getInstance} methods
	* <em>without</em> a {@link SecureRandomParameters} parameter,
	* the constructor will be called with a {@code null} argument and the
	* implementation is responsible for creating its own
	* {@code SecureRandomParameters} parameter for use when
	* {@link #engineGetParameters()} is called. If an object
	* is instantiated with one of {@code SecureRandom}'s {@code getInstance}
	* methods <em>with</em> a {@code SecureRandomParameters} argument,
	* the constructor will be called with that argument. The
	* {@link #engineGetParameters()} method must not return {@code null}.
	* <p>
	* Otherwise, if the {@code SecureRandomSpi(SecureRandomParameters)}
	* constructor is not overridden in an implementation, the
	* {@link #SecureRandomSpi()} constructor must be overridden and it will be
	* called if an object is instantiated with one of {@code SecureRandom}'s
	* {@code getInstance} methods <em>without</em> a
	* {@code SecureRandomParameters} argument. Calling one of
	* {@code SecureRandom}'s {@code getInstance} methods <em>with</em>
	* a {@code SecureRandomParameters} argument will never
	* return an instance of this implementation. The
	* {@link #engineGetParameters()} method must return {@code null}.
	* <p>
	* See {@link SecureRandom} for additional details on thread safety. By
	* default, a {@code SecureRandomSpi} implementation is considered to be
	* not safe for use by multiple concurrent threads and {@code SecureRandom}
	* will synchronize access to each of the applicable engine methods
	* (see {@link SecureRandom} for the list of methods). However, if a
	* {@code SecureRandomSpi} implementation is thread-safe, the <a href=
	* "{@docRoot}/../specs/security/standard-names.html#service-attributes">
	* service provider attribute</a> "ThreadSafe" should be set to "true" during
	* its registration, as follows:
	* <blockquote><pre>
	* put("SecureRandom.AlgName ThreadSafe", "true");</pre>
	* </blockquote>
	* or
	* <blockquote><pre>
	* putService(new Service(this, "SecureRandom", "AlgName", className,
	* null, Map.of("ThreadSafe", "true")));</pre>
	* </blockquote>
	* {@code SecureRandom} will call the applicable engine methods
	* without any synchronization.
	*
	* @since 1.2
	*/

	public abstract class SecureRandomSpi implements java.io.Serializable {

	private static final long serialVersionUID = -2991854161009191830L;

	/**
	* Constructor without a parameter.
	*/
	public SecureRandomSpi() {
	// ignored
	}

	/**
	* Constructor with a parameter.
	*
	* @param params the {@link SecureRandomParameters} object.
	* This argument can be {@code null}.
	* @throws IllegalArgumentException if {@code params} is
	* unrecognizable or unsupported by this {@code SecureRandom}
	*
	* @since 9
	*/
	protected SecureRandomSpi(SecureRandomParameters params) {
	// ignored
	}

	/**
	* Reseeds this random object with the given seed. The seed supplements,
	* rather than replaces, the existing seed. Thus, repeated calls
	* are guaranteed never to reduce randomness.
	*
	* @param seed the seed.
	*/
	protected abstract void engineSetSeed(byte[] seed);

	/**
	* Generates a user-specified number of random bytes.
	* <p>
	* Some random number generators can only generate a limited amount
	* of random bytes per invocation. If the size of {@code bytes}
	* is greater than this limit, the implementation should invoke
	* its generation process multiple times to completely fill the
	* buffer before returning from this method.
	*
	* @param bytes the array to be filled in with random bytes.
	*/
	protected abstract void engineNextBytes(byte[] bytes);

	/**
	* Generates a user-specified number of random bytes with
	* additional parameters.
	* <p>
	* Some random number generators can only generate a limited amount
	* of random bytes per invocation. If the size of {@code bytes}
	* is greater than this limit, the implementation should invoke
	* its generation process multiple times to completely fill the
	* buffer before returning from this method.
	*
	* @implSpec The default implementation throws
	* an {@link UnsupportedOperationException}.
	*
	* @param bytes the array to be filled in with random bytes
	* @param params additional parameters
	* @throws UnsupportedOperationException if the implementation
	* has not overridden this method
	* @throws IllegalArgumentException if {@code params} is {@code null},
	* illegal or unsupported by this {@code SecureRandom}
	*
	* @since 9
	*/
	protected void engineNextBytes(
	byte[] bytes, SecureRandomParameters params) {
	throw new UnsupportedOperationException();
	}

	/**
	* Returns the given number of seed bytes. This call may be used to
	* seed other random number generators.
	*
	* @param numBytes the number of seed bytes to generate.
	*
	* @return the seed bytes.
	*/
	protected abstract byte[] engineGenerateSeed(int numBytes);

	/**
	* Reseeds this random object with entropy input read from its
	* entropy source with additional parameters.
	* <p>
	* If this method is called by {@link SecureRandom#reseed()},
	* {@code params} will be {@code null}.
	* <p>
	* Do not override this method if the implementation does not
	* support reseeding.
	*
	* @implSpec The default implementation throws
	* an {@link UnsupportedOperationException}.
	*
	* @param params extra parameters, can be {@code null}.
	* @throws UnsupportedOperationException if the implementation
	* has not overridden this method
	* @throws IllegalArgumentException if {@code params} is
	* illegal or unsupported by this {@code SecureRandom}
	*
	* @since 9
	*/
	protected void engineReseed(SecureRandomParameters params) {
	throw new UnsupportedOperationException();
	}

	/**
	* Returns the effective {@link SecureRandomParameters} for this
	* {@code SecureRandom} instance.
	*
	* @implSpec The default implementation returns {@code null}.
	*
	* @return the effective {@link SecureRandomParameters} parameters,
	* or {@code null} if no parameters were used.
	*
	* @since 9
	*/
	protected SecureRandomParameters engineGetParameters() {
	return null;
	}

	/**
	* Returns a Human-readable string representation of this
	* {@code SecureRandom}.
	*
	* @return the string representation
	*/
	@Override
	public String toString() {
	return getClass().getSimpleName();
	}
	}

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