java.lang.Object
java.security.MessageDigestSpi
- Direct Known Subclasses:
MessageDigest
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.
- Since:
- 1.2
- See Also:
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Constructor Summary
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Method Summary
Modifier and TypeMethodDescriptionclone()
Returns a clone if the implementation is cloneable.protected abstract byte[]
Completes the hash computation by performing final operations such as padding.protected int
engineDigest
(byte[] buf, int offset, int len) Completes the hash computation by performing final operations such as padding.protected int
Returns the digest length in bytes.protected abstract void
Resets the digest for further use.protected abstract void
engineUpdate
(byte input) Updates the digest using the specified byte.protected abstract void
engineUpdate
(byte[] input, int offset, int len) Updates the digest using the specified array of bytes, starting at the specified offset.protected void
engineUpdate
(ByteBuffer input) Update the digest using the specified ByteBuffer.
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Constructor Details
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MessageDigestSpi
public MessageDigestSpi()Constructor for subclasses to call.
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Method Details
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engineGetDigestLength
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.
- Since:
- 1.2
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engineUpdate
protected abstract void engineUpdate(byte input) Updates the digest using the specified byte.- Parameters:
input
- the byte to use for the update.
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engineUpdate
protected abstract void engineUpdate(byte[] input, int offset, int len) Updates the digest using the specified array of bytes, starting at the specified offset.- 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 atoffset
.
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engineUpdate
Update the digest using the specified ByteBuffer. The digest is updated using theinput.remaining()
bytes starting atinput.position()
. Upon return, the buffer's position will be equal to its limit; its limit will not have changed.- Parameters:
input
- the ByteBuffer- Since:
- 1.5
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engineDigest
protected abstract byte[] engineDigest()Completes the hash computation by performing final operations such as padding. OnceengineDigest
has been called, the engine should be reset (seeengineReset
). Resetting is the responsibility of the engine implementor.- Returns:
- the array of bytes for the resulting hash value.
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engineDigest
Completes the hash computation by performing final operations such as padding. OnceengineDigest
has been called, the engine should be reset (seeengineReset
). 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 digestoffset
- offset to start from in the output bufferlen
- number of bytes withinbuf
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 aDigestException
. 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.- Since:
- 1.2
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engineReset
protected abstract void engineReset()Resets the digest for further use. -
clone
Returns a clone if the implementation is cloneable.- Overrides:
clone
in classObject
- Returns:
- a clone if the implementation is cloneable.
- Throws:
CloneNotSupportedException
- if this is called on an implementation that does not supportCloneable
.- See Also:
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