/*
 * Copyright (c) 1996, 2013, 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;


/**
 * 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&lt;0</code> implies the buffer is empty,
 * <code>in==out</code> 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</code> so
 * that it is connected to the piped writer
 * <code>src</code>. Data written to <code>src</code>
 * 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 <code>PipedReader</code> so that it is connected
 * to the piped writer <code>src</code> and uses the specified
 * pipe size for the pipe's buffer. Data written to <code>src</code>
 * 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 <code>PipedReader</code> 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</code>
 * before being used.
 */
 public PipedReader() {
 initPipe(DEFAULT_PIPE_SIZE);
 }

 /**
 * Creates a <code>PipedReader</code> 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</code>
 * 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 <code>src</code>.
 * If this object is already connected to some
 * other piped writer, an <code>IOException</code>
 * is thrown.
 * <p>
 * If <code>src</code> is an
 * unconnected piped writer and <code>snk</code>
 * is an unconnected piped reader, they
 * may be connected by either the call:
 *
 * <pre><code>snk.connect(src)</code> </pre>
 * <p>
 * or the call:
 *
 * <pre><code>src.connect(snk)</code> </pre>
 * <p>
 * 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 <code>-1</code> 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</code> if the end of the
 * stream is reached.
 * @exception IOException if the pipe is
 * <a href=PipedInputStream.html#BROKEN> <code>broken</code></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;
 }

 /**
 * Reads up to <code>len</code> characters of data from this piped
 * stream into an array of characters. Less than <code>len</code> characters
 * will be read if the end of the data stream is reached or if
 * <code>len</code> 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
 * <code>-1</code> if there is no more data because the end of
 * the stream has been reached.
 * @exception IOException if the pipe is
 * <a href=PipedInputStream.html#BROKEN> <code>broken</code></a>,
 * {@link #connect(java.io.PipedWriter) unconnected}, closed,
 * or an I/O error occurs.
 * @exception IndexOutOfBoundsException {@inheritDoc}
 */
 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
 * <a href=PipedInputStream.html#BROKEN> <code>broken</code></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.
 *
 * @exception IOException if an I/O error occurs.
 */
 public void close() throws IOException {
 in = -1;
 closedByReader = true;
 }
}