public abstract class DigestEngine extends java.security.MessageDigest implements Digest
This class is a template which can be used to implement hash functions. It takes care of some of the API, and also provides an internal data buffer whose length is equal to the hash function internal block length.
Classes which use this template MUST provide a working Digest.getBlockLength() method even before initialization (alternatively,
they may define a custom getInternalBlockLength() which does
not call Digest.getBlockLength(). The MessageDigest.getDigestLength() should
also be operational from the beginning, but it is acceptable that it
returns 0 while the doInit() method has not been called
yet.
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| 构造器和说明 |
|---|
DigestEngine(java.lang.String alg)
Instantiate the engine.
|
| 限定符和类型 | 方法和说明 |
|---|---|
protected Digest |
copyState(DigestEngine dest)
This function copies the internal buffering state to some
other instance of a class extending
DigestEngine. |
byte[] |
digest()
Finalize the current hash computation and return the hash value
in a newly-allocated array.
|
byte[] |
digest(byte[] input)
Input some bytes, then finalize the current hash computation
and return the hash value in a newly-allocated array.
|
int |
digest(byte[] buf,
int offset,
int len)
Finalize the current hash computation and store the hash value
in the provided output buffer.
|
protected abstract void |
doInit()
This function is called at object creation time; the
implementation should use it to perform initialization tasks.
|
protected abstract void |
doPadding(byte[] buf,
int off)
Perform the final padding and store the result in the
provided buffer.
|
protected abstract void |
engineReset()
Reset the hash algorithm state.
|
protected int |
flush()
Flush internal buffers, so that less than a block of data
may at most be upheld.
|
protected byte[] |
getBlockBuffer()
Get a reference to an internal buffer with the same size
than a block.
|
protected long |
getBlockCount()
Get the "block count": this is the number of times the
processBlock(byte[]) method has been invoked for the
current hash operation. |
protected int |
getInternalBlockLength()
Get the internal block length.
|
protected abstract void |
processBlock(byte[] data)
Process one block of data.
|
void |
reset()
Reset the object: this makes it suitable for a new hash
computation.
|
void |
update(byte input)
Insert one more input data byte.
|
void |
update(byte[] input)
Insert some more bytes.
|
void |
update(byte[] input,
int offset,
int len)
Insert some more bytes.
|
clone, getAlgorithm, getDigestLength, getInstance, getInstance, getInstance, getProvider, isEqual, toString, updateengineDigest, engineDigest, engineGetDigestLength, engineUpdate, engineUpdate, engineUpdateequals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, waitcopy, getBlockLength, getDigestLength, toStringprotected abstract void engineReset()
engineReset 在类中 java.security.MessageDigestSpiprotected abstract void processBlock(byte[] data)
data - the data blockprotected abstract void doPadding(byte[] buf,
int off)
flush()
and then update(byte) with the appropriate padding
data in order to get the full input data.buf - the output bufferoff - the output offsetprotected abstract void doInit()
MessageDigestSpi.engineGetDigestLength()public byte[] digest()
Digestpublic byte[] digest(byte[] input)
Digestpublic int digest(byte[] buf,
int offset,
int len)
Digestlen 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.public void reset()
Digestpublic void update(byte input)
Digestpublic void update(byte[] input)
Digestpublic void update(byte[] input,
int offset,
int len)
Digestprotected int getInternalBlockLength()
processBlock(byte[]). The default implementation of this
method calls Digest.getBlockLength() and returns the same
value. Overriding this method is useful when the advertised
block length (which is used, for instance, by HMAC) is
suboptimal with regards to internal buffering needs.protected final int flush()
protected final byte[] getBlockBuffer()
flush(): if
flush() return the value n, then the
first n bytes of the array returned by this method
are the n bytes of input data which are still
unprocessed. The values of the remaining bytes are
undefined and may be altered at will.protected long getBlockCount()
processBlock(byte[]) method has been invoked for the
current hash operation. That counter is incremented
after the call to processBlock(byte[]).protected Digest copyState(DigestEngine dest)
DigestEngine.
It returns a reference to the copy. This method is intended
to be called by the implementation of the Digest.copy()
method.dest - the copydest