/*

 * Copyright (c) 1995, 2019, 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}

 * object by one thread  and data is written

 * to the corresponding {@code PipedOutputStream}

 * 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 id="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   1.0

 */

public class PipedInputStream extends InputStream {

    boolean closedByWriter;

    volatile boolean closedByReader;

    boolean connected;

        /* 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   1.1

     */

    // 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   1.1

     */

    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} implies the buffer is full

     * @since   1.1

     */

    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   1.1

     */

    protected int out = 0;

    /**

     * Creates a {@code PipedInputStream} so

     * that it is connected to the piped output

     * stream {@code src}. Data bytes 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 PipedInputStream(PipedOutputStream src) throws IOException {

        this(src, DEFAULT_PIPE_SIZE);

    }

    /**

     * Creates a {@code PipedInputStream} so that it is

     * connected to the piped output stream

     * {@code src} and uses the specified pipe size for

     * the pipe's buffer.

     * Data bytes 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 PipedInputStream(PipedOutputStream src, int pipeSize)

            throws IOException {

         initPipe(pipeSize);

         connect(src);

    }

    /**

     * Creates a {@code PipedInputStream} 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} before being used.

     */

    public PipedInputStream() {

        initPipe(DEFAULT_PIPE_SIZE);

    }

    /**

     * Creates a {@code PipedInputStream} 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} before being used.

     *

     * @param      pipeSize the size of the pipe's buffer.

     * @throws     IllegalArgumentException if {@code pipeSize <= 0}.

     * @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}.

     * If this object is already connected to some

     * other piped output  stream, an {@code IOException}

     * is thrown.

     * <p>

     * If {@code src} is an

     * unconnected piped output stream and {@code snk}

     * is an unconnected piped input stream, 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 output stream to connect to.

     * @throws     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

     * @throws  IOException If the pipe is <a href="#BROKEN"> {@code broken}</a>,

     *          {@link #connect(java.io.PipedOutputStream) unconnected},

     *          closed, or if an I/O error occurs.

     * @since   1.1

     */

    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

     * @throws   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} in the range

     * {@code 0} to {@code 255}.

     * 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} if the end of the

     *           stream is reached.

     * @throws   IOException  if the pipe is

     *           {@link #connect(java.io.PipedOutputStream) unconnected},

     *           <a href="#BROKEN"> {@code broken}</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} bytes of data from this piped input

     * stream into an array of bytes. Less than {@code len} bytes

     * will be read if the end of the data stream is reached or if

     * {@code len} exceeds the pipe's buffer size.

     * If {@code len } 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}

     * @param      len   the maximum number of bytes read.

     * @return     the total number of bytes read into the buffer, or

     *             {@code -1} if there is no more data because the end of

     *             the stream has been reached.

     * @throws     NullPointerException If {@code b} is {@code null}.

     * @throws     IndexOutOfBoundsException If {@code off} is negative,

     *             {@code len} is negative, or {@code len} is greater than

     *             {@code b.length - off}

     * @throws     IOException if the pipe is <a href="#BROKEN"> {@code broken}</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}</a>.

     *

     * @throws IOException  if an I/O error occurs.

     * @since  1.0.2

     */

    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.

     *

     * @throws     IOException  if an I/O error occurs.

     */

    public void close()  throws IOException {

        closedByReader = true;

        synchronized (this) {

            in = -1;

        }

    }

}