Class DigestOutputStream

java.lang.Object
- java.io.OutputStream
- - java.io.FilterOutputStream
  - - java.security.DigestOutputStream

All Implemented Interfaces:: Closeable, Flushable, AutoCloseable

public class DigestOutputStream
extends FilterOutputStream

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 output stream's write methods.

It is possible to turn this stream on or off (see on). When it is on, a call to one of the write 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.

Since:: 1.2
See Also:: MessageDigest, DigestInputStream

Field Summary

Fields
Modifier and Type	Field	Description
`protected MessageDigest`	`digest`	The message digest associated with this stream.

Fields declared in class java.io.FilterOutputStream

out

Constructor Summary

Constructors
Constructor	Description
`DigestOutputStream(OutputStream stream, MessageDigest digest)`	Creates a digest output stream, using the specified output stream and message digest.

Method Summary

All Methods Instance Methods Concrete Methods
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.
`void`	`setMessageDigest(MessageDigest digest)`	Associates the specified message digest with this stream.
`String`	`toString()`	Prints a string representation of this digest output stream and its associated message digest object.
`void`	`write(byte[] b, int off, int len)`	Updates the message digest (if the digest function is on) using the specified subarray, and in any case writes the subarray to the output stream.
`void`	`write(int b)`	Updates the message digest (if the digest function is on) using the specified byte, and in any case writes the byte to the output stream.

Methods declared in class java.io.FilterOutputStream

close, flush, write

Methods declared in class java.io.OutputStream

nullOutputStream

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

DigestOutputStream

public DigestOutputStream(OutputStream stream,
                          MessageDigest digest)

Creates a digest output stream, using the specified output stream and message digest.

Parameters:: stream - the output 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()

write

public void write(int b)
           throws IOException

Updates the message digest (if the digest function is on) using the specified byte, and in any case writes the byte to the output stream. That is, if the digest function is on (see on), this method calls update on the message digest associated with this stream, passing it the byte b. This method then writes the byte to the output stream, blocking until the byte is actually written.

Overrides:: write in class FilterOutputStream
Parameters:: b - the byte to be used for updating and writing to the output stream.
Throws:: IOException - if an I/O error occurs.
See Also:: MessageDigest.update(byte)

write

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

Updates the message digest (if the digest function is on) using the specified subarray, and in any case writes the subarray to the output stream. That is, if the digest function is on (see on), this method calls update on the message digest associated with this stream, passing it the subarray specifications. This method then writes the subarray bytes to the output stream, blocking until the bytes are actually written.

Overrides:: write in class FilterOutputStream
Parameters:: b - the array containing the subarray to be used for updating and writing to the output stream.; off - the offset into b of the first byte to be updated and written.; len - the number of bytes of data to be updated and written from b, starting at offset off.
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 write 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 output stream and its associated message digest object.

Overrides:: toString in class Object
Returns:: a string representation of the object.