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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}/../technotes/guides/security/StandardNames.html#Service">
* 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
*
* @since 9
*/
@Override
public String toString() {
return getClass().getSimpleName();
}
}