| /* MessageDigestSpi.java --- The message digest service provider interface. |
| Copyright (C) 1999, 2005 Free Software Foundation, Inc. |
| |
| This file is 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, or (at your option) |
| any later version. |
| |
| GNU Classpath is distributed in the hope that it will be useful, but |
| 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. |
| |
| You should have received a copy of the GNU General Public License |
| along with GNU Classpath; see the file COPYING. If not, write to the |
| Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA |
| 02111-1307 USA. |
| |
| Linking this library statically or dynamically with other modules is |
| making a combined work based on this library. Thus, the terms and |
| conditions of the GNU General Public License cover the whole |
| combination. |
| |
| As a special exception, the copyright holders of this library give you |
| permission to link this library with independent modules to produce an |
| executable, regardless of the license terms of these independent |
| modules, and to copy and distribute the resulting executable under |
| terms of your choice, provided that you also meet, for each linked |
| independent module, the terms and conditions of the license of that |
| module. An independent module is a module which is not derived from |
| or based on this library. If you modify this library, you may extend |
| this exception to your version of the library, but you are not |
| obligated to do so. If you do not wish to do so, delete this |
| exception statement from your version. */ |
| |
| package java.security; |
| |
| /** |
| This is the Service Provider Interface (SPI) for MessageDigest |
| class in java.security. It provides the back end functionality |
| for the MessageDigest class so that it can compute message |
| hashes. The default hashes are SHA-1 and MD5. A message hash |
| takes data of arbitrary length and produces a unique number |
| representing it. |
| |
| Cryptography service providers who want to implement their |
| own message digest hashes need only to subclass this class. |
| |
| The implementation of a Cloneable interface is left to up to |
| the programmer of a subclass. |
| |
| @version 0.0 |
| |
| @author Mark Benvenuto (ivymccough@worldnet.att.net) |
| */ |
| public abstract class MessageDigestSpi |
| { |
| /** |
| Default constructor of the MessageDigestSpi class |
| */ |
| public MessageDigestSpi() |
| { |
| } |
| |
| /** |
| Returns the length of the digest. It may be overridden by the |
| provider to return the length of the digest. Default is to |
| return 0. It is concrete for backwards compatibility with JDK1.1 |
| message digest classes. |
| |
| @return Length of Digest in Bytes |
| |
| @since 1.2 |
| */ |
| protected int engineGetDigestLength() |
| { |
| return 0; |
| } |
| |
| /** |
| Updates the digest with the specified byte. |
| |
| @param input the byte to update digest with |
| */ |
| protected abstract void engineUpdate(byte input); |
| |
| |
| /** |
| Updates the digest with the specified bytes starting with the |
| offset and proceeding for the specified length. |
| |
| @param input the byte array to update digest with |
| @param offset the offset of the byte to start with |
| @param len the number of the bytes to update with |
| */ |
| protected abstract void engineUpdate(byte[]input, int offset, int len); |
| |
| /** |
| Computes the final digest of the stored bytes and returns |
| them. It performs any necessary padding. The message digest |
| should reset sensitive data after performing the digest. |
| |
| @return An array of bytes containing the digest |
| */ |
| protected abstract byte[] engineDigest(); |
| |
| /** |
| Computes the final digest of the stored bytes and returns |
| them. It performs any necessary padding. The message digest |
| should reset sensitive data after performing the digest. This |
| method is left concrete for backwards compatibility with JDK1.1 |
| message digest classes. |
| |
| @param buf An array of bytes to store the digest |
| @param offset An offset to start storing the digest at |
| @param len The length of the buffer |
| @return Returns the length of the buffer |
| |
| @since 1.2 |
| */ |
| protected int engineDigest(byte[]buf, int offset, int len) |
| throws DigestException |
| { |
| if (engineGetDigestLength() > len) |
| throw new DigestException("Buffer is too small."); |
| |
| byte[] tmp = engineDigest(); |
| if (tmp.length > len) |
| throw new DigestException("Buffer is too small"); |
| |
| System.arraycopy(tmp, 0, buf, offset, tmp.length); |
| return tmp.length; |
| } |
| |
| /** |
| Resets the digest engine. Reinitializes internal variables |
| and clears sensitive data. |
| */ |
| protected abstract void engineReset(); |
| |
| /** |
| Returns a clone of this class. |
| |
| If cloning is not supported, then by default the class throws a |
| CloneNotSupportedException. The MessageDigestSpi provider |
| implementation has to overload this class in order to be |
| cloneable. |
| */ |
| public Object clone() throws CloneNotSupportedException |
| { |
| return super.clone(); |
| } |
| } |