java.lang.Object
java.io.InputStream
java.io.FilterInputStream
java.security.DigestInputStream
- All Implemented Interfaces:
Closeable
,AutoCloseable
public class DigestInputStream extends FilterInputStream
A transparent stream that updates the associated message digest using
the bits going through the stream.
To complete the message digest computation, call one of the
digest
methods on the associated message
digest after your calls to one of this digest input stream's
read
methods.
It is possible to turn this stream on or off (see
on
). When it is on, a call to one of the
read
methods
results in an update on the message digest. But when it is off,
the message digest is not updated. The default is for the stream
to be on.
Note that digest objects can compute only one digest (see
MessageDigest
),
so that in order to compute intermediate digests, a caller should
retain a handle onto the digest object, and clone it for each
digest to be computed, leaving the original digest untouched.
- Since:
- 1.2
- See Also:
MessageDigest
,DigestOutputStream
-
Field Summary
Modifier and TypeFieldDescriptionprotected MessageDigest
The message digest associated with this stream.Fields declared in class java.io.FilterInputStream
in
-
Constructor Summary
ConstructorDescriptionDigestInputStream(InputStream stream, MessageDigest digest)
Creates a digest input stream, using the specified input stream and message digest. -
Method Summary
Modifier and TypeMethodDescriptionReturns the message digest associated with this stream.void
on(boolean on)
Turns the digest function on or off.int
read()
Reads a byte, and updates the message digest (if the digest function is on).int
read(byte[] b, int off, int len)
Reads into a byte array, and updates the message digest (if the digest function is on).void
setMessageDigest(MessageDigest digest)
Associates the specified message digest with this stream.toString()
Prints a string representation of this digest input stream and its associated message digest object.Methods declared in class java.io.FilterInputStream
available, close, mark, markSupported, read, reset, skip
Methods declared in class java.io.InputStream
nullInputStream, readAllBytes, readNBytes, readNBytes, skipNBytes, transferTo
-
Field Details
-
digest
The message digest associated with this stream.
-
-
Constructor Details
-
DigestInputStream
Creates a digest input stream, using the specified input stream and message digest.- Parameters:
stream
- the input stream.digest
- the message digest to associate with this stream.
-
-
Method Details
-
getMessageDigest
Returns the message digest associated with this stream.- Returns:
- the message digest associated with this stream.
- See Also:
setMessageDigest(java.security.MessageDigest)
-
setMessageDigest
Associates the specified message digest with this stream.- Parameters:
digest
- the message digest to be associated with this stream.- See Also:
getMessageDigest()
-
read
Reads a byte, and updates the message digest (if the digest function is on). That is, this method reads a byte from the input stream, blocking until the byte is actually read. If the digest function is on (seeon
), this method will then callupdate
on the message digest associated with this stream, passing it the byte read.- Overrides:
read
in classFilterInputStream
- Returns:
- the byte read.
- Throws:
IOException
- if an I/O error occurs.- See Also:
MessageDigest.update(byte)
-
read
Reads into a byte array, and updates the message digest (if the digest function is on). That is, this method reads up tolen
bytes from the input stream into the arrayb
, starting at offsetoff
. This method blocks until the data is actually read. If the digest function is on (seeon
), this method will then callupdate
on the message digest associated with this stream, passing it the data.- Overrides:
read
in classFilterInputStream
- Parameters:
b
- the array into which the data is read.off
- the starting offset intob
of where the data should be placed.len
- the maximum number of bytes to be read from the input stream into b, starting at offsetoff
.- Returns:
- the actual number of bytes read. This is less than
len
if the end of the stream is reached prior to readinglen
bytes. -1 is returned if no bytes were read because the end of the stream had already been reached when the call was made. - Throws:
IOException
- if an I/O error occurs.- See Also:
MessageDigest.update(byte[], int, int)
-
on
public void on(boolean on)Turns the digest function on or off. The default is on. When it is on, a call to one of theread
methods results in an update on the message digest. But when it is off, the message digest is not updated.- Parameters:
on
- true to turn the digest function on, false to turn it off.
-
toString
Prints a string representation of this digest input stream and its associated message digest object.
-