java.security

Class DigestInputStream

java.lang.Object

java.io.InputStream

java.io.FilterInputStream

java.security.DigestInputStream

All Implemented Interfaces:

Closeable, AutoCloseable

public class DigestInputStream
extends FilterInputStream

DigestInputStream is a class that ties an InputStream with a MessageDigest. The Message Digest is used by the class to update it self as bytes are read from the InputStream. The updating to the digest depends on the on flag which is set to true by default to tell the class to update the data in the message digest.

Field Summary

Fields

Modifier and Type	Field and Description
protected MessageDigest	digest The message digest for the DigestInputStream

Fields inherited from class java.io.FilterInputStream

in

Constructor Summary

Constructors

Constructor and Description
DigestInputStream(InputStream stream, MessageDigest digest) Constructs a new DigestInputStream.

Method Summary

Methods

Modifier and Type	Method and Description
MessageDigest	getMessageDigest() Returns the MessageDigest associated with this DigestInputStream
void	on(boolean on) Sets the flag specifing if this DigestInputStream updates the digest in the write() methods.
int	read() Reads a byte from the input stream and updates the digest.
int	read(byte[] b, int off, int len) Reads bytes from the input stream and updates the digest.
void	setMessageDigest(MessageDigest digest) Sets the current MessageDigest to current parameter
String	toString() Converts the input stream and underlying message digest to a string.

Methods inherited from class java.io.FilterInputStream

available, close, mark, markSupported, read, reset, skip

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

digest

protected MessageDigest digest

The message digest for the DigestInputStream

Constructor Detail

DigestInputStream

public DigestInputStream(InputStream stream,
                 MessageDigest digest)

Constructs a new DigestInputStream. It associates a MessageDigest with the stream to compute the stream as data is written.

Parameters:

stream - An InputStream to associate this stream with

digest - A MessageDigest to hash the stream with

Method Detail

getMessageDigest

public MessageDigest getMessageDigest()

Returns the MessageDigest associated with this DigestInputStream

Returns:

The MessageDigest used to hash this stream

setMessageDigest

public void setMessageDigest(MessageDigest digest)

Sets the current MessageDigest to current parameter

Parameters:

digest - A MessageDigest to associate with this stream

read

public int read()
         throws IOException

Reads a byte from the input stream and updates the digest. This method reads the underlying input stream and if the on flag is true then updates the message digest.

Overrides:

read in class FilterInputStream

Returns:

Returns a byte from the input stream, -1 is returned to indicate that the end of stream was reached before this read call

Throws:

IOException - if an IO error occurs in the underlying input stream, this error is thrown

read

public int read(byte[] b,
       int off,
       int len)
         throws IOException

Reads bytes from the input stream and updates the digest. This method reads the underlying input stream and if the on flag is true then updates the message digest.

Overrides:

read in class FilterInputStream

Parameters:

b - a byte array to store the data from the input stream

off - an offset to start at in the array

len - length of data to read

Returns:

Returns count of bytes read, -1 is returned to indicate that the end of stream was reached before this read call

Throws:

IOException - if an IO error occurs in the underlying input stream, this error is thrown

on

public void on(boolean on)

Sets the flag specifing if this DigestInputStream updates the digest in the write() methods. The default is on;

Parameters:

on - True means it digests stream, false means it does not

toString

public String toString()

Converts the input stream and underlying message digest to a string.

Overrides:

toString in class Object

Returns:

A string representing the input stream and message digest.

See Also:

Object.getClass(), Object.hashCode(), Class.getName(), Integer.toHexString(int)