Class DigestInputStream
- 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 Type | Field | Description |
---|---|---|
protected MessageDigest | digest | The message digest associated with this stream. |
Fields declared in class java.io.FilterInputStream
in
Constructor Summary
Constructor | Description |
---|---|
DigestInputStream(InputStream stream,
MessageDigest digest) | Creates a digest input stream, using the specified input stream and message digest. |
Method Summary
Modifier and Type | Method | Description |
---|---|---|
MessageDigest | getMessageDigest() | Returns 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. |
String | 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, transferTo
Methods declared in class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
Field Detail
digest
protected MessageDigest digest
The message digest associated with this stream.
Constructor Detail
DigestInputStream
public DigestInputStream(InputStream stream, MessageDigest digest)
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 Detail
getMessageDigest
public MessageDigest getMessageDigest()
Returns the message digest associated with this stream.
- Returns:
- the message digest associated with this stream.
- See Also:
setMessageDigest(java.security.MessageDigest)
setMessageDigest
public void setMessageDigest(MessageDigest digest)
Associates the specified message digest with this stream.
- Parameters:
-
digest
- the message digest to be associated with this stream. - See Also:
getMessageDigest()
read
public int read() throws IOException
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 (see on
), this method will then call update
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
public int read(byte[] b, int off, int len) throws IOException
Reads into a byte array, and updates the message digest (if the digest function is on). That is, this method reads up to len
bytes from the input stream into the array b
, starting at offset off
. This method blocks until the data is actually read. If the digest function is on (see on
), this method will then call update
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 the read
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
public String toString()
Prints a string representation of this digest input stream and its associated message digest object.