/* IMessageDigest.java -- 
Copyright (C) 2001, 2002, 2006 Free Software Foundation, Inc.

This file is a part of GNU Classpath.

GNU Classpath is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or (at
your option) any later version.

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WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
General Public License for more details.

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Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301
USA

Linking this library statically or dynamically with other modules is
making a combined work based on this library.  Thus, the terms and
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permission to link this library with independent modules to produce an
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package com.classpath.hash;

/**
 * The basic visible methods of any hash algorithm.
 * <p>
 * A hash (or message digest) algorithm produces its output by iterating a basic
 * compression function on blocks of data.
 */
public interface MessageDigest
{
	/**
	 * Returns the output length in bytes of this message digest algorithm.
	 *
	 * @return the output length in bytes of this message digest algorithm.
	 */
	public int hashSize();

	/**
	 * Returns the algorithm's (inner) block size in bytes.
	 *
	 * @return the algorithm's inner block size in bytes.
	 */
	public int blockSize();

	/**
	 * Continues a message digest operation using the input byte.
	 *
	 * @param b the input byte to digest.
	 */
	public void update(byte b);

	/**
	 * Continues a message digest operation, by filling the buffer, processing
	 * data in the algorithm's HASH_SIZE-bit block(s), updating the context and
	 * count, and buffering the remaining bytes in buffer for the next operation.
	 *
	 * @param in the input block.
	 */
	public void update(byte[] in);

	/**
	 * Continues a message digest operation, by filling the buffer, processing
	 * data in the algorithm's HASH_SIZE-bit block(s), updating the context and
	 * count, and buffering the remaining bytes in buffer for the next operation.
	 *
	 * @param in the input block.
	 * @param offset start of meaningful bytes in input block.
	 * @param length number of bytes, in input block, to consider.
	 */
	public void update(byte[] in, int offset, int length);

	/**
	 * Completes the message digest by performing final operations such as padding
	 * and resetting the instance.
	 *
	 * @return the array of bytes representing the hash value.
	 */
	public byte[] digest();

	/**
	 * Resets the current context of this instance clearing any eventually cached
	 * intermediary values.
	 */
	public void reset();

	/**
	 * A basic test. Ensures that the digest of a pre-determined message is equal
	 * to a known pre-computed value.
	 *
	 * @return <code>true</code> if the implementation passes a basic self-test.
	 *         Returns <code>false</code> otherwise.
	 */
	public boolean selfTest();
}
