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Class java.security.MessageDigestSpi

java.lang.Object
    |
    +----java.security.MessageDigestSpi

public abstract class MessageDigestSpi

extends Object

All the abstract methods in this class must be implemented by s 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

MessageDigestSpi()

clone()

Returns a clone if the implementation is cloneable.

engineDigest()

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

engineDigest(byte[], int, int)

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

engineGetDigestLength()

Returns the digest length in bytes.

engineReset()

Resets the digest for further use.

engineUpdate(byte)

Updates the digest using the specified byte.

engineUpdate(byte[], int, int)

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

public MessageDigestSpi()

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:

the digest length in bytes.

protected abstract void engineUpdate(byte input)

Updates the digest using the specified byte.

Parameters:

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. This should be a no-op if the digest has been finalized.

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 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:

the array of bytes for the resulting hash value.

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 - 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.

Returns:

the length of the digest stored in the output buffer.

Throws: DigestException

if an error occurs.

protected abstract void engineReset()

Resets the digest for further use.

public Object clone() throws CloneNotSupportedException

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.

Overrides:

clone in class Object

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