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MessageDigestSpi

public abstract class MessageDigestSpi
extends Object

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


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.

See also:

Summary

Public constructors

MessageDigestSpi()

Public methods

Object clone()

Returns a clone if the implementation is cloneable.

Protected methods

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

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

abstract byte[] engineDigest()

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

int engineGetDigestLength()

Returns the digest length in bytes.

abstract void engineReset()

Resets the digest for further use.

void engineUpdate(ByteBuffer input)

Update the digest using the specified ByteBuffer.

abstract void engineUpdate(byte input)

Updates the digest using the specified byte.

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

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

Inherited methods

From class java.lang.Object

Public constructors

MessageDigestSpi

Added in API level 1
MessageDigestSpi ()

Public methods

clone

Added in API level 1
Object clone ()

Returns a clone if the implementation is cloneable.

Returns
Object a clone if the implementation is cloneable.
Throws
CloneNotSupportedException if this is called on an implementation that does not support Cloneable.

Protected methods

engineDigest

Added in API level 1
int engineDigest (byte[] buf, 
                int offset, 
                int len)

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.
Throws
DigestException if an error occurs.

engineDigest

Added in API level 1
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.

engineGetDigestLength

Added in API level 1
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.

engineReset

Added in API level 1
void engineReset ()

Resets the digest for further use.

engineUpdate

Added in API level 1
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

engineUpdate

Added in API level 1
void engineUpdate (byte input)

Updates the digest using the specified byte.

Parameters
input byte: the byte to use for the update.

engineUpdate

Added in API level 1
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.
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