CipherOutputStream

public class CipherOutputStream extends FilterOutputStream

A CipherOutputStream is composed of an OutputStream and a Cipher so that write() methods first process the data before writing them out to the underlying OutputStream. The cipher must be fully initialized before being used by a CipherOutputStream.

For example, if the cipher is initialized for encryption, the CipherOutputStream will attempt to encrypt data before writing out the encrypted data.

This class adheres strictly to the semantics, especially the failure semantics, of its ancestor classes java.io.OutputStream and java.io.FilterOutputStream. This class has exactly those methods specified in its ancestor classes, and overrides them all. Moreover, this class catches all exceptions that are not thrown by its ancestor classes.

It is crucial for a programmer using this class not to use methods that are not defined or overriden in this class (such as a new method or constructor that is later added to one of the super classes), because the design and implementation of those methods are unlikely to have considered security impact with regard to CipherOutputStream.

See Also

• OutputStream
• FilterOutputStream
• Cipher
• CipherInputStream

Inherited Field Summary

From class java.io.FilterOutputStream

protected OutputStream

out

The underlying output stream to be filtered.

Public Constructor Summary

CipherOutputStream(OutputStream os, Cipher c) Constructs a CipherOutputStream from an OutputStream and a Cipher.

Protected Constructor Summary

CipherOutputStream(OutputStream os) Constructs a CipherOutputStream from an OutputStream without specifying a Cipher.

Public Method Summary

void	close() Closes this output stream and releases any system resources associated with this stream.
void	flush() Flushes this output stream by forcing any buffered output bytes that have already been processed by the encapsulated cipher object to be written out.
void	write(byte[] b) Writes b.length bytes from the specified byte array to this output stream.
void	write(byte[] b, int off, int len) Writes len bytes from the specified byte array starting at offset off to this output stream.
void	write(int b) Writes the specified byte to this output stream.

Inherited Method Summary

From class java.io.FilterOutputStream

void	close() Closes this output stream and releases any system resources associated with the stream.
void	flush() Flushes this output stream and forces any buffered output bytes to be written out to the stream.
void	write(byte[] b) Writes b.length bytes to this output stream.
void	write(byte[] b, int off, int len) Writes len bytes from the specified byte array starting at offset off to this output stream.
void	write(int b) Writes the specified byte to this output stream.

From class java.io.OutputStream

void	close() Closes this output stream and releases any system resources associated with this stream.
void	flush() Flushes this output stream and forces any buffered output bytes to be written out.
void	write(byte[] b) Writes b.length bytes from the specified byte array to this output stream.
void	write(byte[] b, int off, int len) Writes len bytes from the specified byte array starting at offset off to this output stream.
abstract void	write(int b) Writes the specified byte to this output stream.

From class java.lang.Object

Object	clone() Creates and returns a copy of this Object.
boolean	equals(Object obj) Compares this instance with the specified object and indicates if they are equal.
void	finalize() Invoked when the garbage collector has detected that this instance is no longer reachable.
final Class<?>	getClass() Returns the unique instance of Class that represents this object's class.
int	hashCode() Returns an integer hash code for this object.
final void	notify() Causes a thread which is waiting on this object's monitor (by means of calling one of the wait() methods) to be woken up.
final void	notifyAll() Causes all threads which are waiting on this object's monitor (by means of calling one of the wait() methods) to be woken up.
String	toString() Returns a string containing a concise, human-readable description of this object.
final void	wait(long timeout, int nanos) Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object or until the specified timeout expires.
final void	wait(long timeout) Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object or until the specified timeout expires.
final void	wait() Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object.

From interface java.io.Closeable

abstract void

close() Closes this stream and releases any system resources associated with it.

From interface java.io.Flushable

abstract void

flush() Flushes this stream by writing any buffered output to the underlying stream.

From interface java.lang.AutoCloseable

abstract void

close() Closes this resource, relinquishing any underlying resources.

Public Constructors

public CipherOutputStream (OutputStream os, Cipher c)

Constructs a CipherOutputStream from an OutputStream and a Cipher.
Note: if the specified output stream or cipher is null, a NullPointerException may be thrown later when they are used.

Parameters

os	the OutputStream object
c	an initialized Cipher object

Protected Constructors

protected CipherOutputStream (OutputStream os)

Constructs a CipherOutputStream from an OutputStream without specifying a Cipher. This has the effect of constructing a CipherOutputStream using a NullCipher.
Note: if the specified output stream is null, a NullPointerException may be thrown later when it is used.

Parameters

os	the OutputStream object

Public Methods

public void close ()

Closes this output stream and releases any system resources associated with this stream.

This method invokes the doFinal method of the encapsulated cipher object, which causes any bytes buffered by the encapsulated cipher to be processed. The result is written out by calling the flush method of this output stream.

This method resets the encapsulated cipher object to its initial state and calls the close method of the underlying output stream.

Throws

IOException	if an I/O error occurs.

public void flush ()

Flushes this output stream by forcing any buffered output bytes that have already been processed by the encapsulated cipher object to be written out.

Any bytes buffered by the encapsulated cipher and waiting to be processed by it will not be written out. For example, if the encapsulated cipher is a block cipher, and the total number of bytes written using one of the write methods is less than the cipher's block size, no bytes will be written out.

Throws

IOException	if an I/O error occurs.

public void write (byte[] b)

Writes b.length bytes from the specified byte array to this output stream.

The write method of CipherOutputStream calls the write method of three arguments with the three arguments b, 0, and b.length.

Parameters

b	the data.

Throws

NullPointerException	if b is null.
IOException	if an I/O error occurs.

See Also

• write(byte[], int, int)

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

Writes len bytes from the specified byte array starting at offset off to this output stream.

Parameters

b	the data.
off	the start offset in the data.
len	the number of bytes to write.

Throws

IOException	if an I/O error occurs.

public void write (int b)

Writes the specified byte to this output stream.

Parameters

b	the byte.

Throws

IOException	if an I/O error occurs.