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	/*
	* Copyright (c) 1996, 2021, Oracle and/or its affiliates. All rights reserved.
	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
	*
	* This code is free software; you can redistribute it and/or modify it
	* under the terms of the GNU General Public License version 2 only, as
	* published by the Free Software Foundation. Oracle designates this
	* particular file as subject to the "Classpath" exception as provided
	* by Oracle in the LICENSE file that accompanied this code.
	*
	* This code is distributed in the hope that it will be useful, but WITHOUT
	* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
	* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
	* version 2 for more details (a copy is included in the LICENSE file that
	* accompanied this code).
	*
	* You should have received a copy of the GNU General Public License version
	* 2 along with this work; if not, write to the Free Software Foundation,
	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
	*
	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
	* or visit www.oracle.com if you need additional information or have any
	* questions.
	*/

	package java.io;

	import java.util.Objects;

	/**
	* Piped character-input streams.
	*
	* @author Mark Reinhold
	* @since 1.1
	*/

	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. {@code in < 0} implies the buffer is empty,
	* {@code 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 {@code PipedReader} so
	* that it is connected to the piped writer
	* {@code src}. Data written to {@code src}
	* will then be available as input from this stream.
	*
	* @param src the stream to connect to.
	* @throws IOException if an I/O error occurs.
	*/
	public PipedReader(PipedWriter src) throws IOException {
	this(src, DEFAULT_PIPE_SIZE);
	}

	/**
	* Creates a {@code PipedReader} so that it is connected
	* to the piped writer {@code src} and uses the specified
	* pipe size for the pipe's buffer. Data written to {@code 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.
	* @throws IOException if an I/O error occurs.
	* @throws IllegalArgumentException if {@code pipeSize <= 0}.
	* @since 1.6
	*/
	public PipedReader(PipedWriter src, int pipeSize) throws IOException {
	initPipe(pipeSize);
	connect(src);
	}


	/**
	* Creates a {@code 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 {@code PipedWriter}
	* before being used.
	*/
	public PipedReader() {
	initPipe(DEFAULT_PIPE_SIZE);
	}

	/**
	* Creates a {@code 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 {@code PipedWriter}
	* before being used.
	*
	* @param pipeSize the size of the pipe's buffer.
	* @throws 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 {@code src}.
	* If this object is already connected to some
	* other piped writer, an {@code IOException}
	* is thrown.
	* <p>
	* If {@code src} is an
	* unconnected piped writer and {@code snk}
	* is an unconnected piped reader, they
	* may be connected by either the call:
	*
	* <pre>{@code snk.connect(src)} </pre>
	* <p>
	* or the call:
	*
	* <pre>{@code src.connect(snk)} </pre>
	* <p>
	* The two calls have the same effect.
	*
	* @param src The piped writer to connect to.
	* @throws 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 {@code -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 {@code -1} if the end of the
	* stream is reached.
	* @throws IOException if the pipe is
	* <a href=PipedInputStream.html#BROKEN> {@code broken}</a>,
	* {@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;
	}

	/**
	* {@inheritDoc}
	*
	* <p> Fewer than {@code len} characters will be read if
	* {@code len} exceeds the pipe's buffer size.
	*
	* @param cbuf {@inheritDoc}
	* @param off {@inheritDoc}
	* @param len {@inheritDoc}
	*
	* @return {@inheritDoc}
	*
	* @throws IndexOutOfBoundsException {@inheritDoc}
	* @throws IOException if the pipe is
	* <a href=PipedInputStream.html#BROKEN> {@code broken}</a>,
	* {@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");
	}

	Objects.checkFromIndexSize(off, len, cbuf.length);
	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.
	*
	* @throws IOException if the pipe is
	* <a href=PipedInputStream.html#BROKEN> {@code broken}</a>,
	* {@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.
	*
	* @throws IOException if an I/O error occurs.
	*/
	public void close() throws IOException {
	in = -1;
	closedByReader = true;
	}
	}

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