/* * Copyright (c) 1995, 2006, 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; /** * 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 <code>PipedInputStream</code> * object by one thread  and data is written * to the corresponding <code>PipedOutputStream</code> * 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 <a name=BROKEN> <i>broken</i> </a> if a * thread that was providing data bytes to the connected * piped output stream is no longer alive. * * @author  James Gosling * @see     java.io.PipedOutputStream * @since   JDK1.0 */public class PipedInputStream extends InputStream {    boolean closedByWriter = false;    volatile 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;     private static final int DEFAULT_PIPE_SIZE = 1024;     /**     * The default size of the pipe's circular input buffer.     * @since   JDK1.1     */    // This used to be a constant before the pipe size was allowed    // to change. This field will continue to be maintained    // for backward compatibility.    protected static final int PIPE_SIZE = DEFAULT_PIPE_SIZE;     /**     * The circular buffer into which incoming data is placed.     * @since   JDK1.1     */    protected byte buffer[];     /**     * 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. <code>in&lt;0</code> implies the buffer is empty,     * <code>in==out</code> implies the buffer is full     * @since   JDK1.1     */    protected int in = -1;     /**     * 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     */    protected int out = 0;     /**     * Creates a <code>PipedInputStream</code> so     * that it is connected to the piped output     * stream <code>src</code>. Data bytes 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 PipedInputStream(PipedOutputStream src) throws IOException {        this(src, DEFAULT_PIPE_SIZE);    }     /**     * Creates a <code>PipedInputStream</code> so that it is     * connected to the piped output stream     * <code>src</code> and uses the specified pipe size for     * the pipe's buffer.     * Data bytes 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</code>.     * @since      1.6     */    public PipedInputStream(PipedOutputStream src, int pipeSize)            throws IOException {         initPipe(pipeSize);         connect(src);    }     /**     * Creates a <code>PipedInputStream</code> so     * that it is not yet {@linkplain #connect(java.io.PipedOutputStream)     * connected}.     * It must be {@linkplain java.io.PipedOutputStream#connect(     * java.io.PipedInputStream) connected} to a     * <code>PipedOutputStream</code> before being used.     */    public PipedInputStream() {        initPipe(DEFAULT_PIPE_SIZE);    }     /**     * Creates a <code>PipedInputStream</code> so that it is not yet     * {@linkplain #connect(java.io.PipedOutputStream) connected} and     * uses the specified pipe size for the pipe's buffer.     * It must be {@linkplain java.io.PipedOutputStream#connect(     * java.io.PipedInputStream)     * connected} to a <code>PipedOutputStream</code> before being used.     *     * @param      pipeSize the size of the pipe's buffer.     * @exception  IllegalArgumentException if <code>pipeSize <= 0</code>.     * @since      1.6     */    public PipedInputStream(int pipeSize) {        initPipe(pipeSize);    }     private void initPipe(int pipeSize) {         if (pipeSize <= 0) {            throw new IllegalArgumentException("Pipe Size <= 0");         }         buffer = new byte[pipeSize];    }     /**     * Causes this piped input stream to be connected     * to the piped  output stream <code>src</code>.     * If this object is already connected to some     * other piped output  stream, an <code>IOException</code>     * is thrown.     * <p>     * If <code>src</code> is an     * unconnected piped output stream and <code>snk</code>     * is an unconnected piped input stream, they     * may be connected by either the call:     * <p>     * <pre><code>snk.connect(src)</code> </pre>     * <p>     * or the call:     * <p>     * <pre><code>src.connect(snk)</code> </pre>     * <p>     * The two     * calls have the same effect.     *     * @param      src   The piped output stream to connect to.     * @exception  IOException  if an I/O error occurs.     */    public void connect(PipedOutputStream src) throws IOException {        src.connect(this);    }     /**     * Receives a byte of data.  This method will block if no input is     * available.     * @param b the byte being received     * @exception IOException If the pipe is <a href=#BROKEN> <code>broken</code></a>,     *          {@link #connect(java.io.PipedOutputStream) unconnected},     *          closed, or if an I/O error occurs.     * @since     JDK1.1     */    protected synchronized void receive(int b) throws IOException {        checkStateForReceive();        writeSide = Thread.currentThread();        if (in == out)            awaitSpace();        if (in < 0) {            in = 0;            out = 0;        }        buffer[in++] = (byte)(b & 0xFF);        if (in >= buffer.length) {            in = 0;        }    }     /**     * Receives data into an array of bytes.  This method will     * block until some input is available.     * @param b the buffer into which the data is received     * @param off the start offset of the data     * @param len the maximum number of bytes received     * @exception IOException If the pipe is <a href=#BROKEN> broken</a>,     *           {@link #connect(java.io.PipedOutputStream) unconnected},     *           closed,or if an I/O error occurs.     */    synchronized void receive(byte b[], int off, int len)  throws IOException {        checkStateForReceive();        writeSide = Thread.currentThread();        int bytesToTransfer = len;        while (bytesToTransfer > 0) {            if (in == out)                awaitSpace();            int nextTransferAmount = 0;            if (out < in) {                nextTransferAmount = buffer.length - in;            } else if (in < out) {                if (in == -1) {                    in = out = 0;                    nextTransferAmount = buffer.length - in;                } else {                    nextTransferAmount = out - in;                }            }            if (nextTransferAmount > bytesToTransfer)                nextTransferAmount = bytesToTransfer;            assert(nextTransferAmount > 0);            System.arraycopy(b, off, buffer, in, nextTransferAmount);            bytesToTransfer -= nextTransferAmount;            off += nextTransferAmount;            in += nextTransferAmount;            if (in >= buffer.length) {                in = 0;            }        }    }     private void checkStateForReceive() 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");        }    }     private void awaitSpace() throws IOException {        while (in == out) {            checkStateForReceive();             /* full: kick any waiting readers */            notifyAll();            try {                wait(1000);            } catch (InterruptedException ex) {                throw new java.io.InterruptedIOException();            }        }    }     /**     * Notifies all waiting threads that the last byte of data has been     * received.     */    synchronized void receivedLast() {        closedByWriter = true;        notifyAll();    }     /**     * Reads the next byte of data from this piped input stream. The     * value byte is returned as an <code>int</code> in the range     * <code>0</code> to <code>255</code>.     * This method blocks until input data is available, the end of the     * stream is detected, or an exception is thrown.     *     * @return     the next byte of data, or <code>-1</code> if the end of the     *             stream is reached.     * @exception  IOException  if the pipe is     *           {@link #connect(java.io.PipedOutputStream) unconnected},     *           <a href=#BROKEN> <code>broken</code></a>, closed,     *           or if 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++] & 0xFF;        if (out >= buffer.length) {            out = 0;        }        if (in == out) {            /* now empty */            in = -1;        }         return ret;    }     /**     * Reads up to <code>len</code> bytes of data from this piped input     * stream into an array of bytes. Less than <code>len</code> bytes     * will be read if the end of the data stream is reached or if     * <code>len</code> exceeds the pipe's buffer size.     * If <code>len </code> 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.     *     * @param      b     the buffer into which the data is read.     * @param      off   the start offset in the destination array <code>b</code>     * @param      len   the maximum number of bytes read.     * @return     the total number of bytes read into the buffer, or     *             <code>-1</code> if there is no more data because the end of     *             the stream has been reached.     * @exception  NullPointerException If <code>b</code> is <code>null</code>.     * @exception  IndexOutOfBoundsException If <code>off</code> is negative,     * <code>len</code> is negative, or <code>len</code> is greater than     * <code>b.length - off</code>     * @exception  IOException if the pipe is <a href=#BROKEN> <code>broken</code></a>,     *           {@link #connect(java.io.PipedOutputStream) unconnected},     *           closed, or if an I/O error occurs.     */    public synchronized int read(byte b[], int off, int len)  throws IOException {        if (b == null) {            throw new NullPointerException();        } else if (off < 0 || len < 0 || len > b.length - off) {            throw new IndexOutOfBoundsException();        } else if (len == 0) {            return 0;        }         /* possibly wait on the first character */        int c = read();        if (c < 0) {            return -1;        }        b[off] = (byte) c;        int rlen = 1;        while ((in >= 0) && (len > 1)) {             int available;             if (in > out) {                available = Math.min((buffer.length - out), (in - out));            } else {                available = buffer.length - out;            }             // A byte is read beforehand outside the loop            if (available > (len - 1)) {                available = len - 1;            }            System.arraycopy(buffer, out, b, off + rlen, available);            out += available;            rlen += available;            len -= available;             if (out >= buffer.length) {                out = 0;            }            if (in == out) {                /* now empty */                in = -1;            }        }        return rlen;    }     /**     * Returns the number of bytes that can be read from this input     * stream without blocking.     *     * @return the number of bytes that can be read from this input stream     *         without blocking, or {@code 0} if this input stream has been     *         closed by invoking its {@link #close()} method, or if the pipe     *         is {@link #connect(java.io.PipedOutputStream) unconnected}, or     *          <a href=#BROKEN> <code>broken</code></a>.     *     * @exception  IOException  if an I/O error occurs.     * @since   JDK1.0.2     */    public synchronized int available() throws IOException {        if(in < 0)            return 0;        else if(in == out)            return buffer.length;        else if (in > out)            return in - out;        else            return in + buffer.length - out;    }     /**     * Closes this piped input stream and releases any system resources     * associated with the stream.     *     * @exception  IOException  if an I/O error occurs.     */    public void close()  throws IOException {        closedByReader = true;        synchronized (this) {            in = -1;        }    }}