java.io

## Class PipedInputStream

- java.lang.Object
- - java.io.InputStream
  - - java.io.PipedInputStream

- All Implemented Interfaces:
    Closeable

      public class PipedInputStream
      extends InputStream

  A piped input stream should be connected to a piped output stream; the piped input stream then provides whatever data bytes are written to the piped output stream. Typically, data is read from a `PipedInputStream` object by one thread and data is written to the corresponding `PipedOutputStream` by some other thread. Attempting to use both objects from a single thread is not recommended, as it may deadlock the thread. The piped input stream contains a buffer, decoupling read operations from write operations, within limits. A pipe is said to be broken if a thread that was providing data bytes to the connected piped output stream is no longer alive.
  Since:
    JDK1.0
  See Also:
    `PipedOutputStream`

- - ### Field Summary

    Fields
    Modifier and Type | Field and Description
    --- | ---
    `protected byte[]` | `buffer` The circular buffer into which incoming data is placed.
    `protected int` | `in` The index of the position in the circular buffer at which the next byte of data will be stored when received from the connected piped output stream.
    `protected int` | `out` The index of the position in the circular buffer at which the next byte of data will be read by this piped input stream.
    `protected static int` | `PIPE_SIZE` The default size of the pipe's circular input buffer.

  - ### Constructor Summary

    Constructors
    Constructor and Description
    `PipedInputStream()` Creates a `PipedInputStream` so that it is not yet connected.
    `PipedInputStream(int pipeSize)` Creates a `PipedInputStream` so that it is not yet connected and uses the specified pipe size for the pipe's buffer.
    `PipedInputStream(PipedOutputStream src)` Creates a `PipedInputStream` so that it is connected to the piped output stream `src`.
    `PipedInputStream(PipedOutputStream src, int pipeSize)` Creates a `PipedInputStream` so that it is connected to the piped output stream `src` and uses the specified pipe size for the pipe's buffer.

  - ### 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 piped input stream and releases any system resources associated with the stream.
    `void` | `connect(PipedOutputStream src)` Causes this piped input stream to be connected to the piped output stream `src`.
    `int` | `read()` Reads the next byte of data from this piped input stream.
    `int` | `read(byte[] b, int off, int len)` Reads up to `len` bytes of data from this piped input stream into an array of bytes.
    `protected void` | `receive(int b)` Receives a byte of data.

    - ### Methods inherited from class java.io.InputStream

      `mark, markSupported, read, reset, skip`

    - ### Methods inherited from class java.lang.Object

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

- - ### Field Detail

    - #### PIPE_SIZE

          protected static final int PIPE_SIZE

      The default size of the pipe's circular input buffer.
      Since:
        JDK1.1
      See Also:
        Constant Field Values

    - #### buffer

          protected byte[] buffer

      The circular buffer into which incoming data is placed.
      Since:
        JDK1.1

    - #### in

          protected int in

      The index of the position in the circular buffer at which the next byte of data will be stored when received from the connected piped output stream. `in<0` implies the buffer is empty, `in==out` implies the buffer is full
      Since:
        JDK1.1

    - #### out

          protected int out

      The index of the position in the circular buffer at which the next byte of data will be read by this piped input stream.
      Since:
        JDK1.1

  - ### Constructor Detail

    - #### PipedInputStream

          public PipedInputStream(PipedOutputStream src)
                           throws IOException

      Creates a `PipedInputStream` so that it is connected to the piped output stream `src`. Data bytes written to `src` will then be available as input from this stream.
      Parameters:
        `src` - the stream to connect to.
      Throws:
        `IOException` - if an I/O error occurs.

    - #### PipedInputStream

          public PipedInputStream(PipedOutputStream src,
                          int pipeSize)
                           throws IOException

      Creates a `PipedInputStream` so that it is connected to the piped output stream `src` and uses the specified pipe size for the pipe's buffer. Data bytes written to `src` will then be available as input from this stream.
      Parameters:
        `src` - the stream to connect to.
        `pipeSize` - the size of the pipe's buffer.
      Throws:
        `IOException` - if an I/O error occurs.
        `IllegalArgumentException` - if `pipeSize <= 0`.
      Since:
        1.6

    - #### PipedInputStream

          public PipedInputStream()

      Creates a `PipedInputStream` so that it is not yet connected. It must be connected to a `PipedOutputStream` before being used.

    - #### PipedInputStream

          public PipedInputStream(int pipeSize)

      Creates a `PipedInputStream` so that it is not yet connected and uses the specified pipe size for the pipe's buffer. It must be connected to a `PipedOutputStream` before being used.
      Parameters:
        `pipeSize` - the size of the pipe's buffer.
      Throws:
        `IllegalArgumentException` - if `pipeSize <= 0`.
      Since:
        1.6

  - ### Method Detail

    - #### connect

          public void connect(PipedOutputStream src)
                       throws IOException

      Causes this piped input stream to be connected to the piped output stream `src`. If this object is already connected to some other piped output stream, an `IOException` is thrown.

      If `src` is an unconnected piped output stream and `snk` is an unconnected piped input stream, they may be connected by either the call:

          snk.connect(src)

      or the call:

          src.connect(snk)

      The two calls have the same effect.

      Parameters:
        `src` - The piped output stream to connect to.
      Throws:
        `IOException` - if an I/O error occurs.

    - #### receive

          protected void receive(int b)
                          throws IOException

      Receives a byte of data. This method will block if no input is available.
      Parameters:
        `b` - the byte being received
      Throws:
        `IOException` - If the pipe is `broken`, `unconnected`, closed, or if an I/O error occurs.
      Since:
        JDK1.1

    - #### read

          public int read()
                   throws IOException

      Reads the next byte of data from this piped input stream. The value byte is returned as an `int` in the range `0` to `255`. This method blocks until input data is available, the end of the stream is detected, or an exception is thrown.
      Specified by:
        `read` in class `InputStream`
      Returns:
        the next byte of data, or `-1` if the end of the stream is reached.
      Throws:
        `IOException` - if the pipe is `unconnected`, `broken`, closed, or if an I/O error occurs.

    - #### read

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

      Reads up to `len` bytes of data from this piped input stream into an array of bytes. Less than `len` bytes will be read if the end of the data stream is reached or if `len` exceeds the pipe's buffer size. If `len` is zero, then no bytes are read and 0 is returned; otherwise, the method blocks until at least 1 byte of input is available, end of the stream has been detected, or an exception is thrown.
      Overrides:
        `read` in class `InputStream`
      Parameters:
        `b` - the buffer into which the data is read.
        `off` - the start offset in the destination array `b`
        `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:
        `NullPointerException` - If `b` is `null`.
        `IndexOutOfBoundsException` - If `off` is negative, `len` is negative, or `len` is greater than `b.length - off`
        `IOException` - if the pipe is `broken`, `unconnected`, closed, or if an I/O error occurs.
      See Also:
        `InputStream.read()`

    - #### available

          public int available()
                        throws IOException

      Returns the number of bytes that can be read from this input stream without blocking.
      Overrides:
        `available` in class `InputStream`
      Returns:
        the number of bytes that can be read from this input stream without blocking, or `0` if this input stream has been closed by invoking its `close()` method, or if the pipe is `unconnected`, or `broken`.
      Throws:
        `IOException` - if an I/O error occurs.
      Since:
        JDK1.0.2

    - #### close

          public void close()
                     throws IOException

      Closes this piped input stream and releases any system resources associated with the stream.
      Specified by:
        `close` in interface `Closeable`
      Overrides:
        `close` in class `InputStream`
      Throws:
        `IOException` - if an I/O error occurs.

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