文字パイプフロー(スレッドフロー):PipedReader、PipedWriter


文字パイプフロー(スレッドフロー)--PipedReader、PipedWriter.パイプラインフロー(スレッドフロー)のアップグレード版!,主な用途もオンラインスレッド間通信ですが、これは文字を伝送するのに使えます.具体的には、PipedInputStream、PipedOutputStreamというパイプラインフロー(スレッドフロー)を参照してください.ここでは、文字パイプストリームのソースコードを説明しません.
PipedReader:
/*
 * Copyright (c) 1996, 2013, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */

package java.io;


/**
 * Piped character-input streams.
 *
 * @author      Mark Reinhold
 * @since       JDK1.1
 */

public class PipedReader extends Reader {
    boolean closedByWriter = false;
    boolean closedByReader = false;
    boolean connected = false;

    /* REMIND: identification of the read and write sides needs to be
       more sophisticated.  Either using thread groups (but what about
       pipes within a thread?) or using finalization (but it may be a
       long time until the next GC). */
    Thread readSide;
    Thread writeSide;

   /**
    * The size of the pipe's circular input buffer.
    */
    private static final int DEFAULT_PIPE_SIZE = 1024;

    /**
     * The circular buffer into which incoming data is placed.
     */
    char buffer[];

    /**
     * The index of the position in the circular buffer at which the
     * next character of data will be stored when received from the connected
     * piped writer. in<0 implies the buffer is empty,
     * in==out implies the buffer is full
     */
    int in = -1;

    /**
     * The index of the position in the circular buffer at which the next
     * character of data will be read by this piped reader.
     */
    int out = 0;

    /**
     * Creates a PipedReader so
     * that it is connected to the piped writer
     * src. Data written to src
     * will then be available as input from this stream.
     *
     * @param      src   the stream to connect to.
     * @exception  IOException  if an I/O error occurs.
     */
    public PipedReader(PipedWriter src) throws IOException {
        this(src, DEFAULT_PIPE_SIZE);
    }

    /**
     * Creates a PipedReader so that it is connected
     * to the piped writer src and uses the specified
     * pipe size for the pipe's buffer. Data written to src
     * will then be  available as input from this stream.

     * @param      src       the stream to connect to.
     * @param      pipeSize  the size of the pipe's buffer.
     * @exception  IOException  if an I/O error occurs.
     * @exception  IllegalArgumentException if {@code pipeSize <= 0}.
     * @since      1.6
     */
    public PipedReader(PipedWriter src, int pipeSize) throws IOException {
        initPipe(pipeSize);
        connect(src);
    }


    /**
     * Creates a PipedReader so
     * that it is not yet {@linkplain #connect(java.io.PipedWriter)
     * connected}. It must be {@linkplain java.io.PipedWriter#connect(
     * java.io.PipedReader) connected} to a PipedWriter
     * before being used.
     */
    public PipedReader() {
        initPipe(DEFAULT_PIPE_SIZE);
    }

    /**
     * Creates a PipedReader so that it is not yet
     * {@link #connect(java.io.PipedWriter) connected} and uses
     * the specified pipe size for the pipe's buffer.
     * It must be  {@linkplain java.io.PipedWriter#connect(
     * java.io.PipedReader) connected} to a PipedWriter
     * before being used.
     *
     * @param   pipeSize the size of the pipe's buffer.
     * @exception  IllegalArgumentException if {@code pipeSize <= 0}.
     * @since      1.6
     */
    public PipedReader(int pipeSize) {
        initPipe(pipeSize);
    }

    private void initPipe(int pipeSize) {
        if (pipeSize <= 0) {
            throw new IllegalArgumentException("Pipe size <= 0");
        }
        buffer = new char[pipeSize];
    }

    /**
     * Causes this piped reader to be connected
     * to the piped  writer src.
     * If this object is already connected to some
     * other piped writer, an IOException
     * is thrown.
     * 

* If src is an * unconnected piped writer and snk * is an unconnected piped reader, they * may be connected by either the call: * *

snk.connect(src) 
*
* or the call:
*
*
src.connect(snk) 
*

* The two calls have the same effect. * * @param src The piped writer to connect to. * @exception IOException if an I/O error occurs. */ public void connect(PipedWriter src) throws IOException { src.connect(this); } /** * Receives a char of data. This method will block if no input is * available. */ synchronized void receive(int c) throws IOException { if (!connected) { throw new IOException("Pipe not connected"); } else if (closedByWriter || closedByReader) { throw new IOException("Pipe closed"); } else if (readSide != null && !readSide.isAlive()) { throw new IOException("Read end dead"); } writeSide = Thread.currentThread(); while (in == out) { if ((readSide != null) && !readSide.isAlive()) { throw new IOException("Pipe broken"); } /* full: kick any waiting readers */ notifyAll(); try { wait(1000); } catch (InterruptedException ex) { throw new java.io.InterruptedIOException(); } } if (in < 0) { in = 0; out = 0; } buffer[in++] = (char) c; if (in >= buffer.length) { in = 0; } } /** * Receives data into an array of characters. This method will * block until some input is available. */ synchronized void receive(char c[], int off, int len) throws IOException { while (--len >= 0) { receive(c[off++]); } } /** * Notifies all waiting threads that the last character of data has been * received. */ synchronized void receivedLast() { closedByWriter = true; notifyAll(); } /** * Reads the next character of data from this piped stream. * If no character 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. * * @return the next character of data, or -1 if the end of the * stream is reached. * @exception IOException if the pipe is * broken, * {@link #connect(java.io.PipedWriter) unconnected}, closed, * or an I/O error occurs. */ public synchronized int read() throws IOException { if (!connected) { throw new IOException("Pipe not connected"); } else if (closedByReader) { throw new IOException("Pipe closed"); } else if (writeSide != null && !writeSide.isAlive() && !closedByWriter && (in < 0)) { throw new IOException("Write end dead"); } readSide = Thread.currentThread(); int trials = 2; while (in < 0) { if (closedByWriter) { /* closed by writer, return EOF */ return -1; } if ((writeSide != null) && (!writeSide.isAlive()) && (--trials < 0)) { throw new IOException("Pipe broken"); } /* might be a writer waiting */ notifyAll(); try { wait(1000); } catch (InterruptedException ex) { throw new java.io.InterruptedIOException(); } } int ret = buffer[out++]; if (out >= buffer.length) { out = 0; } if (in == out) { /* now empty */ in = -1; } return ret; } /** * Reads up to len characters of data from this piped * stream into an array of characters. Less than len characters * will be read if the end of the data stream is reached or if * len exceeds the pipe's buffer size. This method * blocks until at least one character of input is available. * * @param cbuf the buffer into which the data is read. * @param off the start offset of the data. * @param len the maximum number of characters read. * @return the total number of characters read into the buffer, or * -1 if there is no more data because the end of * the stream has been reached. * @exception IOException if the pipe is * broken, * {@link #connect(java.io.PipedWriter) unconnected}, closed, * or an I/O error occurs. */ public synchronized int read(char cbuf[], int off, int len) throws IOException { if (!connected) { throw new IOException("Pipe not connected"); } else if (closedByReader) { throw new IOException("Pipe closed"); } else if (writeSide != null && !writeSide.isAlive() && !closedByWriter && (in < 0)) { throw new IOException("Write end dead"); } if ((off < 0) || (off > cbuf.length) || (len < 0) || ((off + len) > cbuf.length) || ((off + len) < 0)) { throw new IndexOutOfBoundsException(); } else if (len == 0) { return 0; } /* possibly wait on the first character */ int c = read(); if (c < 0) { return -1; } cbuf[off] = (char)c; int rlen = 1; while ((in >= 0) && (--len > 0)) { cbuf[off + rlen] = buffer[out++]; rlen++; if (out >= buffer.length) { out = 0; } if (in == out) { /* now empty */ in = -1; } } return rlen; } /** * Tell whether this stream is ready to be read. A piped character * stream is ready if the circular buffer is not empty. * * @exception IOException if the pipe is * broken, * {@link #connect(java.io.PipedWriter) unconnected}, or closed. */ public synchronized boolean ready() throws IOException { if (!connected) { throw new IOException("Pipe not connected"); } else if (closedByReader) { throw new IOException("Pipe closed"); } else if (writeSide != null && !writeSide.isAlive() && !closedByWriter && (in < 0)) { throw new IOException("Write end dead"); } if (in < 0) { return false; } else { return true; } } /** * Closes this piped stream and releases any system resources * associated with the stream. * * @exception IOException if an I/O error occurs. */ public void close() throws IOException { in = -1; closedByReader = true; } }

PipedWriter:

/*
 * Copyright (c) 1996, 2006, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */

package java.io;


/**
 * Piped character-output streams.
 *
 * @author      Mark Reinhold
 * @since       JDK1.1
 */

public class PipedWriter extends Writer {

    /* REMIND: identification of the read and write sides needs to be
       more sophisticated.  Either using thread groups (but what about
       pipes within a thread?) or using finalization (but it may be a
       long time until the next GC). */
    private PipedReader sink;

    /* This flag records the open status of this particular writer. It
     * is independent of the status flags defined in PipedReader. It is
     * used to do a sanity check on connect.
     */
    private boolean closed = false;

    /**
     * Creates a piped writer connected to the specified piped
     * reader. Data characters written to this stream will then be
     * available as input from snk.
     *
     * @param      snk   The piped reader to connect to.
     * @exception  IOException  if an I/O error occurs.
     */
    public PipedWriter(PipedReader snk)  throws IOException {
        connect(snk);
    }

    /**
     * Creates a piped writer that is not yet connected to a
     * piped reader. It must be connected to a piped reader,
     * either by the receiver or the sender, before being used.
     *
     * @see     java.io.PipedReader#connect(java.io.PipedWriter)
     * @see     java.io.PipedWriter#connect(java.io.PipedReader)
     */
    public PipedWriter() {
    }

    /**
     * Connects this piped writer to a receiver. If this object
     * is already connected to some other piped reader, an
     * IOException is thrown.
     * 

* If snk is an unconnected piped reader and * src is an unconnected piped writer, they may * be connected by either the call: *


     * src.connect(snk)
* or the call:
*

     * snk.connect(src)
* The two calls have the same effect.
*
* @param snk the piped reader to connect to.
* @exception IOException if an I/O error occurs.
*/
public synchronized void connect(PipedReader snk) throws IOException {
if (snk == null) {
throw new NullPointerException();
} else if (sink != null || snk.connected) {
throw new IOException("Already connected");
} else if (snk.closedByReader || closed) {
throw new IOException("Pipe closed");
}
sink = snk;
snk.in = -1;
snk.out = 0;
snk.connected = true;
}
/**
* Writes the specified char to the piped output stream.
* If a thread was reading data characters from the connected piped input
* stream, but the thread is no longer alive, then an
* IOException is thrown.
*
* Implements the write method of Writer .
*
* @param c the char to be written.
* @exception IOException if the pipe is
* broken ,
* {@link #connect(java.io.PipedReader) unconnected}, closed
* or an I/O error occurs.
*/
public void write(int c) throws IOException {
if (sink == null) {
throw new IOException("Pipe not connected");
}
sink.receive(c);
}
/**
* Writes len characters from the specified character array
* starting at offset off to this piped output stream.
* This method blocks until all the characters are written to the output
* stream.
* If a thread was reading data characters from the connected piped input
* stream, but the thread is no longer alive, then an
* IOException is thrown.
*
* @param cbuf the data.
* @param off the start offset in the data.
* @param len the number of characters to write.
* @exception IOException if the pipe is
* broken ,
* {@link #connect(java.io.PipedReader) unconnected}, closed
* or an I/O error occurs.
*/
public void write(char cbuf[], int off, int len) throws IOException {
if (sink == null) {
throw new IOException("Pipe not connected");
} else if ((off | len | (off + len) | (cbuf.length - (off + len))) < 0) {
throw new IndexOutOfBoundsException();
}
sink.receive(cbuf, off, len);
}
/**
* Flushes this output stream and forces any buffered output characters
* to be written out.
* This will notify any readers that characters are waiting in the pipe.
*
* @exception IOException if the pipe is closed, or an I/O error occurs.
*/
public synchronized void flush() throws IOException {
if (sink != null) {
if (sink.closedByReader || closed) {
throw new IOException("Pipe closed");
}
synchronized (sink) {
sink.notifyAll();
}
}
}
/**
* Closes this piped output stream and releases any system resources
* associated with this stream. This stream may no longer be used for
* writing characters.
*
* @exception IOException if an I/O error occurs.
*/
public void close() throws IOException {
closed = true;
if (sink != null) {
sink.receivedLast();
}
}
}