java.security

Class MessageDigestSpi

java.lang.Object

java.security.MessageDigestSpi

Direct Known Subclasses:

MessageDigest, OpenSSLMessageDigestJDK

public abstract class MessageDigestSpi
extends Object

MessageDigestSpi is the Service Provider Interface (SPI) definition for MessageDigest. Examples of digest algorithms are MD5 and SHA. A digest is a secure one way hash function for a stream of bytes. It acts like a fingerprint for a stream of bytes.

See Also:

MessageDigest

Constructor Summary

Constructors

Constructor and Description
MessageDigestSpi()

Method Summary

Modifier and Type	Method and Description
Object	clone() Creates and returns a copy of this Object.
protected abstract byte[]	engineDigest() Computes and returns the final hash value for this MessageDigestSpi.
protected int	engineDigest(byte[] buf, int offset, int len) Computes and stores the final hash value for this MessageDigestSpi.
protected int	engineGetDigestLength() Returns the engine digest length in bytes.
protected abstract void	engineReset() Puts this MessageDigestSpi back in an initial state, such that it is ready to compute a one way hash value.
protected abstract void	engineUpdate(byte input) Updates this MessageDigestSpi using the given byte.
protected abstract void	engineUpdate(byte[] input, int offset, int len) Updates this MessageDigestSpi using the given byte[].
protected void	engineUpdate(ByteBuffer input) Updates this MessageDigestSpi using the given input.

Methods inherited from class java.lang.Object

equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

MessageDigestSpi

public MessageDigestSpi()

Method Detail

engineGetDigestLength

protected int engineGetDigestLength()

Returns the engine digest length in bytes. If the implementation does not implement this function 0 is returned.

Returns:

the digest length in bytes, or 0.

engineUpdate

protected abstract void engineUpdate(byte input)

Updates this MessageDigestSpi using the given byte.

Parameters:

input - the byte to update this MessageDigestSpi with.

See Also:

engineReset()

engineUpdate

protected abstract void engineUpdate(byte[] input,
                                     int offset,
                                     int len)

Updates this MessageDigestSpi using the given byte[].

Parameters:

input - the byte array.

offset - the index of the first byte in input to update from.

len - the number of bytes in input to update from.

Throws:

IllegalArgumentException - if offset or len are not valid in respect to input.

engineUpdate

protected void engineUpdate(ByteBuffer input)

Updates this MessageDigestSpi using the given input.

Parameters:

input - the ByteBuffer.

engineDigest

protected abstract byte[] engineDigest()

Computes and returns the final hash value for this MessageDigestSpi. After the digest is computed the receiver is reset.

Returns:

the computed one way hash value.

See Also:

engineReset()

engineDigest

protected int engineDigest(byte[] buf,
                           int offset,
                           int len)
                    throws DigestException

Computes and stores the final hash value for this MessageDigestSpi. After the digest is computed the receiver is reset.

Parameters:

buf - the buffer to store the result in.

offset - the index of the first byte in buf to store in.

len - the number of bytes allocated for the digest.

Returns:

the number of bytes written to buf.

Throws:

DigestException - if an error occures.

IllegalArgumentException - if offset or len are not valid in respect to buf.

See Also:

engineReset()

engineReset

protected abstract void engineReset()

Puts this MessageDigestSpi back in an initial state, such that it is ready to compute a one way hash value.

clone

public Object clone()
             throws CloneNotSupportedException

Description copied from class: Object

Creates and returns a copy of this Object. The default implementation returns a so-called "shallow" copy: It creates a new instance of the same class and then copies the field values (including object references) from this instance to the new instance. A "deep" copy, in contrast, would also recursively clone nested objects. A subclass that needs to implement this kind of cloning should call super.clone() to create the new instance and then create deep copies of the nested, mutable objects.

Overrides:

clone in class Object

Returns:

a copy of this object.

Throws:

CloneNotSupportedException - if this object's class does not implement the Cloneable interface.