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package javax.crypto;
import java.io.OutputStream;
import java.io.IOException;
import java.io.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.
* <p>
* For example, if the cipher is initialized for encryption, the
* CipherOutputStream will attempt to encrypt data before writing out the
* encrypted data.
* <p>
* 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.
* <p>
* 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.
*
* @since JCE1.2
* @see OutputStream
* @see FilterOutputStream
* @see Cipher
* @see CipherInputStream
*/
public class CipherOutputStream
extends FilterOutputStream
{
private Cipher c;
private byte[] oneByte = new byte[1];
/**
* Constructs a CipherOutputStream from an OutputStream and a
* Cipher.
*/
public CipherOutputStream(
OutputStream os,
Cipher c)
{
super(os);
this.c = c;
}
/**
* Constructs a CipherOutputStream from an OutputStream without
* specifying a Cipher. This has the effect of constructing a
* CipherOutputStream using a NullCipher.
*/
protected CipherOutputStream(
OutputStream os)
{
this(os, new NullCipher());
}
/**
* Writes the specified byte to this output stream.
*
* @param b the <code>byte</code>.
* @exception IOException if an I/O error occurs.
* @since JCE1.2
*/
public void write(
int b)
throws IOException
{
oneByte[0] = (byte)b;
byte[] bytes = c.update(oneByte, 0, 1);
if (bytes != null)
{
out.write(bytes, 0, bytes.length);
}
}
/**
* Writes <code>b.length</code> bytes from the specified byte array
* to this output stream.
* <p>
* The <code>write</code> method of
* <code>CipherOutputStream</code> calls the <code>write</code>
* method of three arguments with the three arguments
* <code>b</code>, <code>0</code>, and <code>b.length</code>.
*
* @param b the data.
* @exception IOException if an I/O error occurs.
* @since JCE1.2
* @see #write(byte[], int, int)
*/
public void write(
byte[] b)
throws IOException
{
write(b, 0, b.length);
}
/**
* Writes <code>len</code> bytes from the specified byte array
* starting at offset <code>off</code> to this output stream.
*
* @param b the data.
* @param off the start offset in the data.
* @param len the number of bytes to write.
* @exception IOException if an I/O error occurs.
* @since JCE1.2
*/
public void write(
byte[] b,
int off,
int len)
throws IOException
{
byte[] bytes = c.update(b, off, len);
if (bytes != null)
{
out.write(bytes, 0, bytes.length);
}
}
/**
* Flushes this output stream by forcing any buffered output bytes
* that have already been processed by the encapsulated cipher object
* to be written out.
*
* <p>
* 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 <code>write</code> methods is less than
* the cipher's block size, no bytes will be written out.
*
* @exception IOException if an I/O error occurs.
* @since JCE1.2
*/
public void flush()
throws IOException
{
super.flush();
}
/**
* Closes this output stream and releases any system resources
* associated with this stream.
* <p>
* This method invokes the <code>doFinal</code> 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
* <code>flush</code> method of this output stream.
* <p>
* This method resets the encapsulated cipher object to its initial state
* and calls the <code>close</code> method of the underlying output
* stream.
*
* @exception IOException if an I/O error occurs.
* @since JCE1.2
*/
public void close()
throws IOException
{
try
{
byte[] bytes = c.doFinal();
if (bytes != null)
{
out.write(bytes, 0, bytes.length);
}
}
catch (Exception e)
{
throw new IOException("Error closing stream: " + e.toString());
}
flush();
super.close();
}
}
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