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Class javax.crypto.CipherInputStream

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

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 initialised before being used by a CipherInputStream.

For example, if the Cipher is initialised 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 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 overridden 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.

See Also:
InputStream, FilterInputStream, Cipher, CipherOutputStream

Variable Index

 o ident

Constructor Index

 o CipherInputStream(InputStream)
Constructs a CipherInputStream from an InputStream without specifying a Cipher.
 o CipherInputStream(InputStream, Cipher)
Constructs a CipherInputStream from an InputStream and a Cipher.

Method Index

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

Variables

 o ident
 public static final String ident

Constructors

 o CipherInputStream
 public CipherInputStream(InputStream in,
                          Cipher cipher)
Constructs a CipherInputStream from an InputStream and a Cipher.

Parameters:
in - The input stream.
cipher - The decrypting/encrypting object.
 o CipherInputStream
 protected CipherInputStream(InputStream in)
Constructs a CipherInputStream from an InputStream without specifying a Cipher. This has the effect of constructing a CipherInputStream using a NullCipher.

Parameters:
in - The input stream.

Methods

 o 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.

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

Parameters:
b - the buffer into which the data is 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.
Overrides:
read in class FilterInputStream
See Also:
read
 o 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.

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.
Overrides:
read in class FilterInputStream
See Also:
read
 o skip
 public long skip(long n) throws IOException
Skips n bytes of input 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.

Parameters:
n - the number of bytes to be skipped.
Returns:
the actual number of bytes skipped.
Throws: IOException
if an I/O error occurs.
Overrides:
skip in class FilterInputStream
 o 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.

Returns:
the number of bytes that can be read from this input stream without blocking.
Throws: IOException
if an I/O error occurs.
Overrides:
available in class FilterInputStream
 o 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.

Throws: IOException
- if an I/O error occurs.
Overrides:
close in class FilterInputStream
 o 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 FilterInputStream
See Also:
mark, reset

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