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public interface Digest
This interface documents the API for a hash function. This
interface somewhat mimics the standard java.security.MessageDigest
class. We do not extend that class in
order to provide compatibility with reduced Java implementations such
as J2ME. Implementing a java.security.Provider
compatible
with Sun's JCA ought to be easy.
A Digest
object maintains a running state for a hash
function computation. Data is inserted with update()
calls;
the result is obtained from a digest()
method (where some
final data can be inserted as well). When a digest output has been
produced, the objet is automatically resetted, and can be used
immediately for another digest operation. The state of a computation
can be cloned with the copy()
method; this can be used to get
a partial hash result without interrupting the complete
computation.
Digest
objects are stateful and hence not thread-safe;
however, distinct Digest
objects can be accessed concurrently
without any problem.
==========================(LICENSE BEGIN)============================ Copyright (c) 2007-2010 Projet RNRT SAPHIR Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions: The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software. THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. ===========================(LICENSE END)=============================
Method Summary | |
---|---|
Digest |
copy()
Clone the current state. |
byte[] |
digest()
Finalize the current hash computation and return the hash value in a newly-allocated array. |
byte[] |
digest(byte[] inbuf)
Input some bytes, then finalize the current hash computation and return the hash value in a newly-allocated array. |
int |
digest(byte[] outbuf,
int off,
int len)
Finalize the current hash computation and store the hash value in the provided output buffer. |
int |
getBlockLength()
Return the "block length" for the hash function. |
int |
getDigestLength()
Get the natural hash function output length (in bytes). |
void |
reset()
Reset the object: this makes it suitable for a new hash computation. |
java.lang.String |
toString()
Get the display name for this function (e.g. |
void |
update(byte in)
Insert one more input data byte. |
void |
update(byte[] inbuf)
Insert some more bytes. |
void |
update(byte[] inbuf,
int off,
int len)
Insert some more bytes. |
Method Detail |
---|
void update(byte in)
in
- the input bytevoid update(byte[] inbuf)
inbuf
- the data bytesvoid update(byte[] inbuf, int off, int len)
inbuf
- the data bufferoff
- the data offset in inbuf
len
- the data length (in bytes)byte[] digest()
byte[] digest(byte[] inbuf)
inbuf
- the input data
int digest(byte[] outbuf, int off, int len)
len
parameter
contains the maximum number of bytes that should be written;
no more bytes than the natural hash function output length will
be produced. If len
is smaller than the natural
hash output length, the hash output is truncated to its first
len
bytes. The object is resetted.
outbuf
- the output bufferoff
- the output offset within outbuf
len
- the requested hash output length (in bytes)
outbuf
int getDigestLength()
void reset()
Digest copy()
int getBlockLength()
Return the "block length" for the hash function. This
value is naturally defined for iterated hash functions
(Merkle-Damgard). It is used in HMAC (that's what the
HMAC specification
names the "B
" parameter).
If the function is "block-less" then this function may
return -n
where n
is an integer such that the
block length for HMAC ("B
") will be inferred from the
key length, by selecting the smallest multiple of n
which is no smaller than the key length. For instance, for
the Fugue-xxx hash functions, this function returns -4: the
virtual block length B is the HMAC key length, rounded up to
the next multiple of 4.
-n
java.lang.String toString()
Get the display name for this function (e.g. "SHA-1"
for SHA-1).
toString
in class java.lang.Object
Object
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