MessageDigest
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.
Constructors
Constructor for subclasses to call.
Returns a clone if the implementation is cloneable.
protected abstract byte[]
Completes the hash computation by performing final operations such as padding.
protected int
Completes the hash computation by performing final operations such as padding.
protected int
Returns the digest length in bytes.
protected abstract void
Resets the digest for further use.
protected abstract void
Updates the digest using the specified byte.
protected abstract void
Updates the digest using the specified array of bytes, starting at the specified offset.
protected void
Update the digest using the specified ByteBuffer.
public MessageDigestSpi()
Constructor for subclasses to call.
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.
protected abstract void engineUpdate(byte input)
Updates the digest using the specified byte.
input - the byte to use for the update.
protected abstract void engineUpdate(byte[] input, int offset, int len)
Updates the digest using the specified array of bytes, starting at the specified offset.
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.
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.
input - the ByteBuffer
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.
throws
DigestExceptionCompletes 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.
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.
DigestException - if an error occurs.
protected abstract void engineReset()
Resets the digest for further use.
Returns a clone if the implementation is cloneable.
clone in class Object
CloneNotSupportedException - if this is called on an implementation that does not support Cloneable.
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