MessageDigestSpi JDK 1.6)

Description

publicabstract abstract class MessageDigestSpi

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.

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: MessageDigest

Methods

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public Object clone () throws CloneNotSupportedException

Returns a clone if the implementation is cloneable.

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

protectedabstract byte engineDigest ()

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

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

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

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.
Returns: the length of the digest stored in the output buffer.
Parameters:
- buf - the output buffer in which to store the digest
- offset - offset to start from in the output buffer
- len - 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.
Throws:
- DigestException - if an error occurs.
Since: 1.2

protected int engineGetDigestLength ()

Returns the digest length in bytes.

protectedabstract void engineReset ()

Resets the digest for further use.

protectedabstract void engineUpdate (byte input)

Updates the digest using the specified byte.

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

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

Updates the digest using the specified array of bytes,
starting at the specified offset.
Parameters:
- input - the array of bytes to use for the update.
- offset - the offset to start from in the array of bytes.
- len - the number of bytes to use, starting at offset.

protected void engineUpdate (ByteBuffer input)

Update the digest using the specified ByteBuffer.

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 - the ByteBuffer
Since: 1.5