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Class javax.crypto.CipherInputStream

java.lang.Object
  |
  +--java.io.InputStream
        |
        +--java.io.FilterInputStream
              |
              +--javax.crypto.CipherInputStream

public class CipherInputStream
extends java.io.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(long) method skips only data that have been processed by the 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:
JCE1.2
See Also:
java.io.InputStream, java.io.FilterInputStream, Cipher, CipherOutputStream

Fields inherited from class java.io.FilterInputStream
in
 
Constructor Summary
CipherInputStream(java.io.InputStream is, Cipher c)
          Constructs a CipherInputStream from an InputStream and a Cipher.
CipherInputStream(java.io.InputStream is)
          Constructs a CipherInputStream from an InputStream without specifying 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 over and discards n bytes of data from this input stream.
 
Methods inherited from class java.io.FilterInputStream
available, close, mark, markSupported, read, read, read, reset, skip
 
Methods inherited from class java.io.InputStream
available, close, mark, markSupported, read, read, read, reset, skip
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notifyAll, notify, toString, wait, wait, wait
 

Constructor Detail

CipherInputStream

public CipherInputStream(java.io.InputStream is,
                         Cipher c)
Constructs a CipherInputStream from an InputStream and a Cipher.

CipherInputStream

protected CipherInputStream(java.io.InputStream is)
Constructs a CipherInputStream from an InputStream without specifying a Cipher. This has the effect of constructing a CipherInputStream using a NullCipher.
Method Detail

read

public int read()
        throws java.io.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.

Returns:
the next byte of data, or -1 if the end of the stream is reached.
Throws:
java.io.IOException - if an I/O error occurs.
Overrides:
read in class java.io.FilterInputStream

read

public int read(byte[] b)
        throws java.io.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.

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:
java.io.IOException - if an I/O error occurs.
Overrides:
read in class java.io.FilterInputStream
See Also:
read(byte[], int, int)

read

public int read(byte[] b,
                int off,
                int len)
        throws java.io.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.
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:
java.io.IOException - if an I/O error occurs.
Overrides:
read in class java.io.FilterInputStream
See Also:
read()

skip

public long skip(long n)
         throws java.io.IOException
Skips over and discards n bytes of data from this input stream. The skip method may, for a variety of reasons, end up skipping over some smaller number of bytes, possibly 0. The actual number of bytes skipped is returned.
Parameters:
n - the number of bytes to be skipped.
Returns:
the actual number of bytes skipped.
Throws:
java.io.IOException - if an I/O error occurs.
Overrides:
skip in class java.io.FilterInputStream

available

public int available()
             throws java.io.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.
Returns:
the number of bytes that can be read from this input stream without blocking.
Throws:
java.io.IOException - if an I/O error occurs.
Overrides:
available in class java.io.FilterInputStream

close

public void close()
          throws java.io.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.

Throws:
java.io.IOException - if an I/O error occurs.
Overrides:
close in class java.io.FilterInputStream

markSupported

public boolean markSupported()
Tests if this input stream supports the mark and reset methods, which it does not.
Returns:
false, since this class does not support the mark and reset methods.
Overrides:
markSupported in class java.io.FilterInputStream
See Also:
mark(int), reset()

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