javax.crypto
Class CipherInputStream

java.lang.Object
  java.io.InputStream
      java.io.FilterInputStream
          javax.crypto.CipherInputStream

All Implemented Interfaces:

Closeable

public class CipherInputStream
extends FilterInputStream

A CipherInputStream is composed of an InputStream and a Cipher so that read() methods return data that are read in from the underlying InputStream but have been additionally processed by the Cipher. The Cipher must be fully initialized before being used by a CipherInputStream.

For example, if the Cipher is initialized for decryption, the CipherInputStream will attempt to read in data and decrypt them, before returning the decrypted data.

This class adheres strictly to the semantics, especially the failure semantics, of its ancestor classes java.io.FilterInputStream and java.io.InputStream. 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. In particular, the skip method skips, and the available method counts only data that have been processed by the encapsulated Cipher.

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 CipherInputStream.

Since:

1.4

See Also:

InputStream, FilterInputStream, Cipher, CipherOutputStream

Field Summary

Fields inherited from class java.io.FilterInputStream

in

Constructor Summary

protected	CipherInputStream(InputStream is) Constructs a CipherInputStream from an InputStream without specifying a Cipher.
	CipherInputStream(InputStream is, Cipher c) Constructs a CipherInputStream from an InputStream and a Cipher.

Method Summary

int	available() Returns the number of bytes that can be read from this input stream without blocking.
void	close() Closes this input stream and releases any system resources associated with the stream.
boolean	markSupported() Tests if this input stream supports the mark and reset methods, which it does not.
int	read() Reads the next byte of data from this input stream.
int	read(byte[] b) Reads up to b.length bytes of data from this input stream into an array of bytes.
int	read(byte[] b, int off, int len) Reads up to len bytes of data from this input stream into an array of bytes.
long	skip(long n) Skips n bytes of input from the bytes that can be read from this input stream without blocking.

Methods inherited from class java.io.FilterInputStream

mark, reset

Methods inherited from class java.lang.Object

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

Constructor Detail

CipherInputStream

public CipherInputStream(InputStream is,
                         Cipher c)

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

Parameters:

is - the to-be-processed input stream

c - an initialized Cipher object

CipherInputStream

protected CipherInputStream(InputStream is)

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

Parameters:

is - the to-be-processed input stream

Method Detail

read

public int read()
         throws IOException

Reads the next byte of data from this input stream. The value byte is returned as an int in the range 0 to 255. If no byte is available because the end of the stream has been reached, the value -1 is returned. This method blocks until input data is available, the end of the stream is detected, or an exception is thrown.

Overrides:

read in class FilterInputStream

Returns:

the next byte of data, or -1 if the end of the stream is reached.

Throws:

IOException - if an I/O error occurs.

Since:

JCE1.2

See Also:

FilterInputStream.in

read

public int read(byte[] b)
         throws IOException

Reads up to b.length bytes of data from this input stream into an array of bytes.

The read method of InputStream calls the read method of three arguments with the arguments b, 0, and b.length.

Overrides:

read in class FilterInputStream

Parameters:

b - the buffer into which the data is read.

Returns:

the total number of bytes read into the buffer, or -1 is there is no more data because the end of the stream has been reached.

Throws:

IOException - if an I/O error occurs.

Since:

JCE1.2

See Also:

InputStream.read(byte[], int, int)

read

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

Reads up to len bytes of data from this input stream into an array of bytes. This method blocks until some input is available. If the first argument is null, up to len bytes are read and discarded.

Overrides:

read in class FilterInputStream

Parameters:

b - the buffer into which the data is read.

off - the start offset of the data.

len - the maximum number of bytes read.

Returns:

the total number of bytes read into the buffer, or -1 if there is no more data because the end of the stream has been reached.

Throws:

IOException - if an I/O error occurs.

Since:

JCE1.2

See Also:

InputStream.read()

skip

public long skip(long n)
          throws IOException

Skips n bytes of input from the bytes that can be read from this input stream without blocking.

Fewer bytes than requested might be skipped. The actual number of bytes skipped is equal to n or the result of a call to available, whichever is smaller. If n is less than zero, no bytes are skipped.

The actual number of bytes skipped is returned.

Overrides:

skip in class FilterInputStream

Parameters:

n - the number of bytes to be skipped.

Returns:

the actual number of bytes skipped.

Throws:

IOException - if an I/O error occurs.

Since:

JCE1.2

available

public int available()
              throws IOException

Returns the number of bytes that can be read from this input stream without blocking. The available method of InputStream returns 0. This method should be overridden by subclasses.

Overrides:

available in class FilterInputStream

Returns:

the number of bytes that can be read from this input stream without blocking.

Throws:

IOException - if an I/O error occurs.

Since:

JCE1.2

See Also:

FilterInputStream.in

close

public void close()
           throws IOException

Closes this input stream and releases any system resources associated with the stream.

The close method of CipherInputStream calls the close method of its underlying input stream.

Specified by:

close in interface Closeable

Overrides:

close in class FilterInputStream

Throws:

IOException - if an I/O error occurs.

Since:

JCE1.2

See Also:

FilterInputStream.in

markSupported

public boolean markSupported()

Tests if this input stream supports the mark and reset methods, which it does not.

Overrides:

markSupported in class FilterInputStream

Returns:

false, since this class does not support the mark and reset methods.

Since:

JCE1.2

See Also:

InputStream.mark(int), InputStream.reset()