gnu.java.security.hash

Class BaseHash

Implemented Interfaces:
Cloneable, IMessageDigest
Known Direct Subclasses:
Haval, MD2, MD4, MD5, RipeMD128, RipeMD160, Sha160, Sha256, Sha384, Sha512, Tiger, Whirlpool

public abstract class BaseHash
extends Object
implements IMessageDigest

A base abstract class to facilitate hash implementations.

Field Summary

protected int
blockSize
The hash (inner) block size in bytes.
protected byte[]
buffer
Temporary input buffer.
protected long
count
Number of bytes processed so far.
protected int
hashSize
The hash (output) size in bytes.
protected String
name
The canonical name prefix of the hash.

Constructor Summary

BaseHash(String name, int hashSize, int blockSize)
Trivial constructor for use by concrete subclasses.

Method Summary

int
blockSize()
abstract Object
clone()
This method may be called to create a new copy of the Object.
byte[]
digest()
protected abstract byte[]
getResult()
Constructs the result from the contents of the current context.
int
hashSize()
String
name()
protected abstract byte[]
padBuffer()
Returns the byte array to use as padding before completing a hash operation.
void
reset()
protected abstract void
resetContext()
Resets the instance for future re-use.
abstract boolean
selfTest()
protected abstract void
transform(byte[] in, int offset)
The block digest transformation per se.
void
update(byte b)
void
update(byte[] b)
void
update(byte[] b, int offset, int len)

Methods inherited from class java.lang.Object

clone, equals, extends Object> getClass, finalize, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details

blockSize

protected int blockSize
The hash (inner) block size in bytes.

buffer

protected byte[] buffer
Temporary input buffer.

count

protected long count
Number of bytes processed so far.

hashSize

protected int hashSize
The hash (output) size in bytes.

name

protected String name
The canonical name prefix of the hash.

Constructor Details

BaseHash

protected BaseHash(String name,
                   int hashSize,
                   int blockSize)
Trivial constructor for use by concrete subclasses.
Parameters:
name - the canonical name prefix of this instance.
hashSize - the block size of the output in bytes.
blockSize - the block size of the internal transform.

Method Details

blockSize

public int blockSize()
Specified by:
blockSize in interface IMessageDigest

clone

public abstract Object clone()
This method may be called to create a new copy of the Object. The typical behavior is as follows:
  • o == o.clone() is false
  • o.getClass() == o.clone().getClass() is true
  • o.equals(o) is true

However, these are not strict requirements, and may be violated if necessary. Of the three requirements, the last is the most commonly violated, particularly if the subclass does not override Object.equals(Object).

If the Object you call clone() on does not implement Cloneable (which is a placeholder interface), then a CloneNotSupportedException is thrown. Notice that Object does not implement Cloneable; this method exists as a convenience for subclasses that do.

Object's implementation of clone allocates space for the new Object using the correct class, without calling any constructors, and then fills in all of the new field values with the old field values. Thus, it is a shallow copy. However, subclasses are permitted to make a deep copy.

All array types implement Cloneable, and override this method as follows (it should never fail):

 public Object clone()
 {
   try
     {
       super.clone();
     }
   catch (CloneNotSupportedException e)
     {
       throw new InternalError(e.getMessage());
     }
 }
 
Specified by:
clone in interface IMessageDigest
Overrides:
clone in interface Object
Returns:
a copy of the Object
See Also:
Cloneable

digest

public byte[] digest()
Specified by:
digest in interface IMessageDigest

getResult

protected abstract byte[] getResult()
Constructs the result from the contents of the current context.
Returns:
the output of the completed hash operation.

hashSize

public int hashSize()
Specified by:
hashSize in interface IMessageDigest

name

public String name()
Specified by:
name in interface IMessageDigest

padBuffer

protected abstract byte[] padBuffer()
Returns the byte array to use as padding before completing a hash operation.
Returns:
the bytes to pad the remaining bytes in the buffer before completing a hash operation.

reset

public void reset()
Specified by:
reset in interface IMessageDigest

resetContext

protected abstract void resetContext()
Resets the instance for future re-use.

selfTest

public abstract boolean selfTest()
Specified by:
selfTest in interface IMessageDigest

transform

protected abstract void transform(byte[] in,
                                  int offset)
The block digest transformation per se.
Parameters:
in - the blockSize long block, as an array of bytes to digest.
offset - the index where the data to digest is located within the input buffer.

update

public void update(byte b)
Specified by:
update in interface IMessageDigest

update

public void update(byte[] b)
Specified by:
update in interface IMessageDigest

update

public void update(byte[] b,
                   int offset,
                   int len)
Specified by:
update in interface IMessageDigest

BaseHash.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. 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; if not, write to the Free Software 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 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.