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package fr.cryptohash; // $Id: Digest.java 232 2010-06-17 14:19:24Z tp $ // w w w.j a v a2s .co m /** * <p>This interface documents the API for a hash function. This * interface somewhat mimics the standard {@code * java.security.MessageDigest} class. We do not extend that class in * order to provide compatibility with reduced Java implementations such * as J2ME. Implementing a {@code java.security.Provider} compatible * with Sun's JCA ought to be easy.</p> * * <p>A {@code Digest} object maintains a running state for a hash * function computation. Data is inserted with {@code update()} calls; * the result is obtained from a {@code digest()} method (where some * final data can be inserted as well). When a digest output has been * produced, the objet is automatically resetted, and can be used * immediately for another digest operation. The state of a computation * can be cloned with the {@link #copy} method; this can be used to get * a partial hash result without interrupting the complete * computation.</p> * * <p>{@code Digest} objects are stateful and hence not thread-safe; * however, distinct {@code Digest} objects can be accessed concurrently * without any problem.</p> * * <pre> * ==========================(LICENSE BEGIN)============================ * * Copyright (c) 2007-2010 Projet RNRT SAPHIR * * Permission is hereby granted, free of charge, to any person obtaining * a copy of this software and associated documentation files (the * "Software"), to deal in the Software without restriction, including * without limitation the rights to use, copy, modify, merge, publish, * distribute, sublicense, and/or sell copies of the Software, and to * permit persons to whom the Software is furnished to do so, subject to * the following conditions: * * The above copyright notice and this permission notice shall be * included in all copies or substantial portions of the Software. * * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. * * ===========================(LICENSE END)============================= * </pre> * * @version $Revision: 232 $ * @author Thomas Pornin <thomas.pornin@cryptolog.com> */ public interface Digest { /** * Insert one more input data byte. * * @param in the input byte */ public void update(byte in); /** * Insert some more bytes. * * @param inbuf the data bytes */ public void update(byte[] inbuf); /** * Insert some more bytes. * * @param inbuf the data buffer * @param off the data offset in {@code inbuf} * @param len the data length (in bytes) */ public void update(byte[] inbuf, int off, int len); /** * Finalize the current hash computation and return the hash value * in a newly-allocated array. The object is resetted. * * @return the hash output */ public byte[] digest(); /** * Input some bytes, then finalize the current hash computation * and return the hash value in a newly-allocated array. The object * is resetted. * * @param inbuf the input data * @return the hash output */ public byte[] digest(byte[] inbuf); /** * Finalize the current hash computation and store the hash value * in the provided output buffer. The {@code len} parameter * contains the maximum number of bytes that should be written; * no more bytes than the natural hash function output length will * be produced. If {@code len} is smaller than the natural * hash output length, the hash output is truncated to its first * {@code len} bytes. The object is resetted. * * @param outbuf the output buffer * @param off the output offset within {@code outbuf} * @param len the requested hash output length (in bytes) * @return the number of bytes actually written in {@code outbuf} */ public int digest(byte[] outbuf, int off, int len); /** * Get the natural hash function output length (in bytes). * * @return the digest output length (in bytes) */ public int getDigestLength(); /** * Reset the object: this makes it suitable for a new hash * computation. The current computation, if any, is discarded. */ public void reset(); /** * Clone the current state. The returned object evolves independantly * of this object. * * @return the clone */ public Digest copy(); /** * <p>Return the "block length" for the hash function. This * value is naturally defined for iterated hash functions * (Merkle-Damgard). It is used in HMAC (that's what the * <a href="http://tools.ietf.org/html/rfc2104">HMAC specification</a> * names the "{@code B}" parameter).</p> * * <p>If the function is "block-less" then this function may * return {@code -n} where {@code n} is an integer such that the * block length for HMAC ("{@code B}") will be inferred from the * key length, by selecting the smallest multiple of {@code n} * which is no smaller than the key length. For instance, for * the Fugue-xxx hash functions, this function returns -4: the * virtual block length B is the HMAC key length, rounded up to * the next multiple of 4.</p> * * @return the internal block length (in bytes), or {@code -n} */ public int getBlockLength(); /** * <p>Get the display name for this function (e.g. {@code "SHA-1"} * for SHA-1).</p> * * @see Object */ public String toString(); }