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:
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
| |
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.
|
Developers
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. |
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. |
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. |
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 |
void engineUpdate (byte input)
Updates the digest using the specified byte.
| Parameters | |
|---|---|
input |
byte:
the byte to use for the update.
|
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.
|