MessageDigestSpi.java

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package java.security;

import java.nio.ByteBuffer;

import sun.security.jca.JCAUtil;

/**
 * This class defines the <i>Service Provider Interface</i> (<b>SPI</b>)
 * for the {@code MessageDigest} class, which provides the functionality
 * of a message digest algorithm, such as MD5 or SHA. Message digests are
 * secure one-way hash functions that take arbitrary-sized data and output a
 * fixed-length hash value.
 *
 * <p> All the abstract methods in this class must be implemented by a
 * cryptographic service provider who wishes to supply the implementation
 * of a particular message digest algorithm.
 *
 * <p> Implementations are free to implement the Cloneable interface.
 *
 * @author Benjamin Renaud
 * @since 1.2
 *
 *
 * @see MessageDigest
 */

public abstract class MessageDigestSpi {

    // for re-use in engineUpdate(ByteBuffer input)
    private byte[] tempArray;

    /**
     * Returns the digest length in bytes.
     *
     * <p>This concrete method has been added to this previously-defined
     * abstract class. (For backwards compatibility, it cannot be abstract.)
     *
     * <p>The default behavior is to return 0.
     *
     * <p>This method may be overridden by a provider to return the digest
     * length.
     *
     * @return the digest length in bytes.
     *
     * @since 1.2