org.brewchain.core.crypto.hash

接口 Digest

所有已知实现类:

DigestEngine, Keccak256, Keccak512

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.

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方法概要

限定符和类型	方法和说明
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.

方法详细资料

update

void update(byte in)

Insert one more input data byte.

参数:

in - the input byte

update

void update(byte[] inbuf)

Insert some more bytes.

参数:

inbuf - the data bytes

update

void update(byte[] inbuf,
            int off,
            int len)

Insert some more bytes.

参数:

inbuf - the data buffer

off - the data offset in inbuf

len - the data length (in bytes)

digest

byte[] digest()

Finalize the current hash computation and return the hash value in a newly-allocated array. The object is resetted.

返回:

the hash output

digest

byte[] digest(byte[] inbuf)

Input some bytes, then finalize the current hash computation and return the hash value in a newly-allocated array. The object is resetted.

参数:

inbuf - the input data

返回:

the hash output

digest

int digest(byte[] outbuf,
           int off,
           int len)

Finalize the current hash computation and store the hash value in the provided output buffer. The 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.

参数:

outbuf - the output buffer

off - the output offset within outbuf

len - the requested hash output length (in bytes)

返回:

the number of bytes actually written in outbuf

getDigestLength

int getDigestLength()

Get the natural hash function output length (in bytes).

返回:

the digest output length (in bytes)

reset

void reset()

Reset the object: this makes it suitable for a new hash computation. The current computation, if any, is discarded.

copy

Digest copy()

Clone the current state. The returned object evolves independantly of this object.

返回:

the clone

getBlockLength

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.

返回:

the internal block length (in bytes), or -n

toString

java.lang.String toString()

Get the display name for this function (e.g. "SHA-1" for SHA-1).

覆盖:

toString 在类中 java.lang.Object

另请参阅:

Object