mirror of git://gcc.gnu.org/git/gcc.git
148 lines
4.6 KiB
Java
148 lines
4.6 KiB
Java
/* MessageDigestSpi.java --- The message digest service provider interface.
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Copyright (C) 1999 Free Software Foundation, Inc.
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This file is part of GNU Classpath.
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GNU Classpath is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.
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GNU Classpath is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with GNU Classpath; see the file COPYING. If not, write to the
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Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
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02111-1307 USA.
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As a special exception, if you link this library with other files to
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produce an executable, this library does not by itself cause the
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resulting executable to be covered by the GNU General Public License.
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This exception does not however invalidate any other reasons why the
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executable file might be covered by the GNU General Public License. */
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package java.security;
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/**
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This is the Service Provider Interface (SPI) for MessageDigest
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class in java.security. It provides the back end functionality
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for the MessageDigest class so that it can compute message
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hashes. The default hashes are SHA-1 and MD5. A message hash
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takes data of arbitrary length and produces a unique number
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representing it.
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Cryptography service providers who want to implement their
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own message digest hashes need only to subclass this class.
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The implementation of a Cloneable interface is left to up to
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the programmer of a subclass.
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@version 0.0
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@author Mark Benvenuto <ivymccough@worldnet.att.net>
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*/
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public abstract class MessageDigestSpi
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{
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/**
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Default constructor of the MessageDigestSpi class
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*/
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public MessageDigestSpi()
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{
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}
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/**
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Returns the length of the digest. It may be overridden by the
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provider to return the length of the digest. Default is to
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return 0. It is concrete for backwards compatibility with JDK1.1
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message digest classes.
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@return Length of Digest in Bytes
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@since 1.2
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*/
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protected int engineGetDigestLength()
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{
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return 0;
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}
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/**
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Updates the digest with the specified byte.
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@param input the byte to update digest with
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*/
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protected abstract void engineUpdate(byte input);
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/**
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Updates the digest with the specified bytes starting with the
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offset and proceeding for the specified length.
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@param input the byte array to update digest with
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@param offset the offset of the byte to start with
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@param len the number of the bytes to update with
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*/
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protected abstract void engineUpdate(byte[]input, int offset, int len);
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/**
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Computes the final digest of the stored bytes and returns
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them. It performs any necessary padding. The message digest
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should reset sensitive data after performing the digest.
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@return An array of bytes containing the digest
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*/
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protected abstract byte[] engineDigest();
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/**
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Computes the final digest of the stored bytes and returns
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them. It performs any necessary padding. The message digest
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should reset sensitive data after performing the digest. This
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method is left concrete for backwards compatibility with JDK1.1
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message digest classes.
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@param buf An array of bytes to store the digest
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@param offset An offset to start storing the digest at
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@param len The length of the buffer
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@return Returns the length of the buffer
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@since 1.2
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*/
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protected int engineDigest(byte[]buf, int offset, int len)
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throws DigestException
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{
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if (engineGetDigestLength() > len)
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throw new DigestException("Buffer is too small.");
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byte tmp[] = engineDigest();
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if (tmp.length > len)
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throw new DigestException("Buffer is too small");
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System.arraycopy(tmp, 0, buf, offset, tmp.length);
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return tmp.length;
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}
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/**
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Resets the digest engine. Reinitializes internal variables
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and clears sensitive data.
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*/
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protected abstract void engineReset();
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/**
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Returns a clone of this class.
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If cloning is not supported, then by default the class throws a
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CloneNotSupportedException. The MessageDigestSpi provider
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implementation has to overload this class in order to be
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cloneable.
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*/
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public Object clone() throws CloneNotSupportedException
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{
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if (this instanceof Cloneable)
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return super.clone();
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else
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throw new CloneNotSupportedException();
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}
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}
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