public abstract class

MessageDigestSpi

extends Object
java.lang.Object
   ↳ java.security.MessageDigestSpi
Known Direct Subclasses

Class Overview

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

Summary

Public Constructors
MessageDigestSpi()
Public Methods
Object clone()
Creates and returns a copy of this Object.
Protected Methods
abstract byte[] engineDigest()
Computes and returns the final hash value for this MessageDigestSpi.
int engineDigest(byte[] buf, int offset, int len)
Computes and stores the final hash value for this MessageDigestSpi.
int engineGetDigestLength()
Returns the engine digest length in bytes.
abstract void engineReset()
Puts this MessageDigestSpi back in an initial state, such that it is ready to compute a one way hash value.
abstract void engineUpdate(byte input)
Updates this MessageDigestSpi using the given byte.
void engineUpdate(ByteBuffer input)
Updates this MessageDigestSpi using the given input.
abstract void engineUpdate(byte[] input, int offset, int len)
Updates this MessageDigestSpi using the given byte[].
[Expand]
Inherited Methods
From class java.lang.Object

Public Constructors

public MessageDigestSpi ()

Since: API Level 1

Public Methods

public Object clone ()

Since: API Level 1

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.

Returns
  • a copy of this object.
Throws
CloneNotSupportedException

Protected Methods

protected abstract byte[] engineDigest ()

Since: API Level 1

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

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

Since: API Level 1

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

protected int engineGetDigestLength ()

Since: API Level 1

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.

protected abstract void engineReset ()

Since: API Level 1

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)

Since: API Level 1

Updates this MessageDigestSpi using the given byte.

Parameters
input the byte to update this MessageDigestSpi with.
See Also

protected void engineUpdate (ByteBuffer input)

Since: API Level 1

Updates this MessageDigestSpi using the given input.

Parameters
input the ByteBuffer.

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

Since: API Level 1

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.