DigestOutputStream

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 ouput 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.

Field Summary

protected MessageDigest digest The message digest associated with this stream.

Inherited Field Summary

Public Constructor Summary

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

Public Method Summary

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.

Inherited Method Summary

Fields

protected MessageDigest digest

The message digest associated with this stream.

Public Constructors

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.

Public Methods

public MessageDigest getMessageDigest ()

Returns the message digest associated with this stream.

Returns
  • the message digest associated with this stream.

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.

public void setMessageDigest (MessageDigest digest)

Associates the specified message digest with this stream.

Parameters
digest the message digest to be associated with this stream.

public String toString ()

Prints a string representation of this digest output stream and its associated message digest object.

Returns
  • a printable representation of this object.

public 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. 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.

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.

public 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. 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.

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