文字パイプフロー(スレッドフロー):PipedReader、PipedWriter
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 aPipedReader
so * that it is connected to the piped writer *src
. Data written tosrc
* 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 aPipedReader
so that it is connected * to the piped writersrc
and uses the specified * pipe size for the pipe's buffer. Data written tosrc
* 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 aPipedReader
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 aPipedWriter
* before being used. */ public PipedReader() { initPipe(DEFAULT_PIPE_SIZE); } /** * Creates aPipedReader
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 aPipedWriter
* 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 writersrc
. * If this object is already connected to some * other piped writer, anIOException
* is thrown. ** If
src
is an * unconnected piped writer andsnk
* 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 tolen
characters of data from this piped * stream into an array of characters. Less thanlen
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();
}
}
}