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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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 * accompanied this code).
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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(SecureRandomInstantiateParameters)}
 * 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 SecureRandomInstantiateParameters} parameter,
 * the constructor will be called with a {@code null} argument and the
 * implementation is responsible for creating its own
 * {@code SecureRandomInstantiateParameters} 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 SecureRandomInstantiateParameters} argument,
 * the constructor will be called with that argument. The
 * {@link #engineGetParameters()} method must not return {@code null}.
 * <p>
 * Otherwise, if the {@code SecureRandomSpi(SecureRandomInstantiateParameters)}
 * 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 SecureRandomInstantiateParameters} argument. Calling one of
 * {@code SecureRandom}'s {@code getInstance} methods <em>with</em>
 * a {@code SecureRandomInstantiateParameters} argument will never
 * return an instance of this implementation. The
 * {@link #engineGetParameters()} method must return {@code null}.
 *
 * @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 SecureRandomInstantiateParameters} object.
     *               This argument can be {@code null}.
     * @throws IllegalArgumentException if {@code params} is
     *         unrecognizable or unsupported by this {@code SecureRandom}
     *
     * @since 9
     */
    protected SecureRandomSpi(SecureRandomInstantiateParameters 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.
     *
     * @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.
     *
     * @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},
     *         unrecognizable or unsupported by this {@code SecureRandom}
     *
     * @since 9
     */
    protected void engineNextBytes(
            byte[] bytes, SecureRandomNextBytesParameters params) {
        throw new UnsupportedOperationException("not supported");
    }

    /**
     * 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}.
     *
     * @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
     *         unrecognizable or unsupported by this {@code SecureRandom}
     *
     * @since 9
     */
    protected void engineReseed(SecureRandomReseedParameters params) {
        throw new UnsupportedOperationException("not supported");
    }

    /**
     * Returns the effective {@link SecureRandomInstantiateParameters}
     * that is actually used to instantiate this {@code SecureRandom}.
     *
     * @implSpec The default implementation returns {@code null}.
     *
     * @return the parameters used in instantiation, or {@code null} if no
     * parameters were used.
     *
     * @since 9
     */
    protected SecureRandomInstantiateParameters engineGetParameters() {
        return null;
    }

    @Override
    public String toString() {
        return getClass().getSimpleName();
    }
}