Top Description Fields Constructors Methods
java.security

public abstract Class MessageDigestSpi

extends Object
Class Inheritance
Known Direct Subclasses
sun.security.provider.DigestBase, java.security.MessageDigest
Imports
java.nio.ByteBuffer, sun.security.jca.JCAUtil
This class defines the Service Provider Interface (SPI) for the MessageDigest class, which provides the functionality of a message digest algorithm, such as MD5 or SHA. Message digests are secure one-way hash functions that take arbitrary-sized data and output a fixed-length hash value.

All the abstract methods in this class must be implemented by a cryptographic service provider who wishes to supply the implementation of a particular message digest algorithm.

Implementations are free to implement the Cloneable interface.

Author
Benjamin Renaud
Since
1.2
See Also
MessageDigest

Field Summary

Modifier and TypeField and Description
private byte[]
tempArray

Constructor Summary

AccessConstructor and Description
public
MessageDigestSpi()

Constructor for subclasses to call.

Method Summary

Modifier and TypeMethod and Description
public Object

Returns:

a clone if the implementation is cloneable.
clone()

Overrides java.lang.Object.clone.

Returns a clone if the implementation is cloneable.

protected abstract byte[]

Returns:

the array of bytes for the resulting hash value.
engineDigest()

Completes the hash computation by performing final operations such as padding.

protected int

Returns:

the length of the digest stored in the output buffer.
engineDigest(byte[]
the output buffer in which to store the digest
buf, int
offset to start from in the output buffer
offset, int
number of bytes within buf allotted for the digest. Both this default implementation and the SUN provider do not return partial digests. The presence of this parameter is solely for consistency in our API's. If the value of this parameter is less than the actual digest length, the method will throw a DigestException. This parameter is ignored if its value is greater than or equal to the actual digest length.
len)

Completes the hash computation by performing final operations such as padding.

protected int

Returns:

the digest length in bytes.
engineGetDigestLength()

Returns the digest length in bytes.

protected abstract void
engineReset()

Resets the digest for further use.

protected abstract void
engineUpdate(byte
the byte to use for the update.
input)

Updates the digest using the specified byte.

protected abstract void
engineUpdate(byte[]
the array of bytes to use for the update.
input, int
the offset to start from in the array of bytes.
offset, int
the number of bytes to use, starting at offset.
len)

Updates the digest using the specified array of bytes, starting at the specified offset.

protected void
engineUpdate(ByteBuffer
the ByteBuffer
input)

Update the digest using the specified ByteBuffer.

Inherited from java.lang.Object:
equalsfinalizegetClasshashCodenotifynotifyAlltoStringwaitwaitwait

Field Detail

tempArrayback to summary
private byte[] tempArray

Constructor Detail

MessageDigestSpiback to summary
public MessageDigestSpi()

Constructor for subclasses to call.

Method Detail

cloneback to summary
public Object clone() throws CloneNotSupportedException

Overrides java.lang.Object.clone.

Returns a clone if the implementation is cloneable.

Returns:Object

a clone if the implementation is cloneable.

Exceptions
CloneNotSupportedException:
if this is called on an implementation that does not support Cloneable.
engineDigestback to summary
protected abstract byte[] engineDigest()

Completes the hash computation by performing final operations such as padding. Once engineDigest has been called, the engine should be reset (see engineReset). Resetting is the responsibility of the engine implementor.

Returns:byte[]

the array of bytes for the resulting hash value.

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

Completes the hash computation by performing final operations such as padding. Once engineDigest has been called, the engine should be reset (see engineReset). Resetting is the responsibility of the engine implementor. This method should be abstract, but we leave it concrete for binary compatibility. Knowledgeable providers should override this method.

Parameters
buf:byte[]

the output buffer in which to store the digest

offset:int

offset to start from in the output buffer

len:int

number of bytes within buf allotted for the digest. Both this default implementation and the SUN provider do not return partial digests. The presence of this parameter is solely for consistency in our API's. If the value of this parameter is less than the actual digest length, the method will throw a DigestException. This parameter is ignored if its value is greater than or equal to the actual digest length.

Returns:int

the length of the digest stored in the output buffer.

Exceptions
DigestException:
if an error occurs.
Since
1.2
engineGetDigestLengthback to summary
protected int engineGetDigestLength()

Returns the digest length in bytes.

This concrete method has been added to this previously-defined abstract class. (For backwards compatibility, it cannot be abstract.)

The default behavior is to return 0.

This method may be overridden by a provider to return the digest length.

Returns:int

the digest length in bytes.

Since
1.2
engineResetback to summary
protected abstract void engineReset()

Resets the digest for further use.

engineUpdateback to summary
protected abstract void engineUpdate(byte input)

Updates the digest using the specified byte.

Parameters
input:byte

the byte to use for the update.

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

Updates the digest using the specified array of bytes, starting at the specified offset.

Parameters
input:byte[]

the array of bytes to use for the update.

offset:int

the offset to start from in the array of bytes.

len:int

the number of bytes to use, starting at offset.

engineUpdateback to summary
protected void engineUpdate(ByteBuffer input)

Update the digest using the specified ByteBuffer. The digest is updated using the input.remaining() bytes starting at input.position(). Upon return, the buffer's position will be equal to its limit; its limit will not have changed.

Parameters
input:ByteBuffer

the ByteBuffer

Since
1.5