javax.crypto

## Class CipherInputStream

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

- All Implemented Interfaces:
    Closeable, AutoCloseable

      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

    Constructors
    Modifier | Constructor and Description
    --- | ---
    `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

    Methods
    Modifier and Type | Method and Description
    --- | ---
    `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 in the destination array `buf`
        `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

    - #### 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`
      Specified by:
        `close` in interface `AutoCloseable`
      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()`

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