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    1   /*
    2    * Copyright (c) 1995, 2006, Oracle and/or its affiliates. All rights reserved.
    3    * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
    4    *
    5    * This code is free software; you can redistribute it and/or modify it
    6    * under the terms of the GNU General Public License version 2 only, as
    7    * published by the Free Software Foundation.  Oracle designates this
    8    * particular file as subject to the "Classpath" exception as provided
    9    * by Oracle in the LICENSE file that accompanied this code.
   10    *
   11    * This code is distributed in the hope that it will be useful, but WITHOUT
   12    * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
   13    * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
   14    * version 2 for more details (a copy is included in the LICENSE file that
   15    * accompanied this code).
   16    *
   17    * You should have received a copy of the GNU General Public License version
   18    * 2 along with this work; if not, write to the Free Software Foundation,
   19    * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
   20    *
   21    * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
   22    * or visit www.oracle.com if you need additional information or have any
   23    * questions.
   24    */
   25   
   26   package java.io;
   27   
   28   import java.io;
   29   
   30   /**
   31    * A piped output stream can be connected to a piped input stream
   32    * to create a communications pipe. The piped output stream is the
   33    * sending end of the pipe. Typically, data is written to a
   34    * <code>PipedOutputStream</code> object by one thread and data is
   35    * read from the connected <code>PipedInputStream</code> by some
   36    * other thread. Attempting to use both objects from a single thread
   37    * is not recommended as it may deadlock the thread.
   38    * The pipe is said to be <a name=BROKEN> <i>broken</i> </a> if a
   39    * thread that was reading data bytes from the connected piped input
   40    * stream is no longer alive.
   41    *
   42    * @author  James Gosling
   43    * @see     java.io.PipedInputStream
   44    * @since   JDK1.0
   45    */
   46   public
   47   class PipedOutputStream extends OutputStream {
   48   
   49           /* REMIND: identification of the read and write sides needs to be
   50              more sophisticated.  Either using thread groups (but what about
   51              pipes within a thread?) or using finalization (but it may be a
   52              long time until the next GC). */
   53       private PipedInputStream sink;
   54   
   55       /**
   56        * Creates a piped output stream connected to the specified piped
   57        * input stream. Data bytes written to this stream will then be
   58        * available as input from <code>snk</code>.
   59        *
   60        * @param      snk   The piped input stream to connect to.
   61        * @exception  IOException  if an I/O error occurs.
   62        */
   63       public PipedOutputStream(PipedInputStream snk)  throws IOException {
   64           connect(snk);
   65       }
   66   
   67       /**
   68        * Creates a piped output stream that is not yet connected to a
   69        * piped input stream. It must be connected to a piped input stream,
   70        * either by the receiver or the sender, before being used.
   71        *
   72        * @see     java.io.PipedInputStream#connect(java.io.PipedOutputStream)
   73        * @see     java.io.PipedOutputStream#connect(java.io.PipedInputStream)
   74        */
   75       public PipedOutputStream() {
   76       }
   77   
   78       /**
   79        * Connects this piped output stream to a receiver. If this object
   80        * is already connected to some other piped input stream, an
   81        * <code>IOException</code> is thrown.
   82        * <p>
   83        * If <code>snk</code> is an unconnected piped input stream and
   84        * <code>src</code> is an unconnected piped output stream, they may
   85        * be connected by either the call:
   86        * <blockquote><pre>
   87        * src.connect(snk)</pre></blockquote>
   88        * or the call:
   89        * <blockquote><pre>
   90        * snk.connect(src)</pre></blockquote>
   91        * The two calls have the same effect.
   92        *
   93        * @param      snk   the piped input stream to connect to.
   94        * @exception  IOException  if an I/O error occurs.
   95        */
   96       public synchronized void connect(PipedInputStream snk) throws IOException {
   97           if (snk == null) {
   98               throw new NullPointerException();
   99           } else if (sink != null || snk.connected) {
  100               throw new IOException("Already connected");
  101           }
  102           sink = snk;
  103           snk.in = -1;
  104           snk.out = 0;
  105           snk.connected = true;
  106       }
  107   
  108       /**
  109        * Writes the specified <code>byte</code> to the piped output stream.
  110        * <p>
  111        * Implements the <code>write</code> method of <code>OutputStream</code>.
  112        *
  113        * @param      b   the <code>byte</code> to be written.
  114        * @exception IOException if the pipe is <a href=#BROKEN> broken</a>,
  115        *          {@link #connect(java.io.PipedInputStream) unconnected},
  116        *          closed, or if an I/O error occurs.
  117        */
  118       public void write(int b)  throws IOException {
  119           if (sink == null) {
  120               throw new IOException("Pipe not connected");
  121           }
  122           sink.receive(b);
  123       }
  124   
  125       /**
  126        * Writes <code>len</code> bytes from the specified byte array
  127        * starting at offset <code>off</code> to this piped output stream.
  128        * This method blocks until all the bytes are written to the output
  129        * stream.
  130        *
  131        * @param      b     the data.
  132        * @param      off   the start offset in the data.
  133        * @param      len   the number of bytes to write.
  134        * @exception IOException if the pipe is <a href=#BROKEN> broken</a>,
  135        *          {@link #connect(java.io.PipedInputStream) unconnected},
  136        *          closed, or if an I/O error occurs.
  137        */
  138       public void write(byte b[], int off, int len) throws IOException {
  139           if (sink == null) {
  140               throw new IOException("Pipe not connected");
  141           } else if (b == null) {
  142               throw new NullPointerException();
  143           } else if ((off < 0) || (off > b.length) || (len < 0) ||
  144                      ((off + len) > b.length) || ((off + len) < 0)) {
  145               throw new IndexOutOfBoundsException();
  146           } else if (len == 0) {
  147               return;
  148           }
  149           sink.receive(b, off, len);
  150       }
  151   
  152       /**
  153        * Flushes this output stream and forces any buffered output bytes
  154        * to be written out.
  155        * This will notify any readers that bytes are waiting in the pipe.
  156        *
  157        * @exception IOException if an I/O error occurs.
  158        */
  159       public synchronized void flush() throws IOException {
  160           if (sink != null) {
  161               synchronized (sink) {
  162                   sink.notifyAll();
  163               }
  164           }
  165       }
  166   
  167       /**
  168        * Closes this piped output stream and releases any system resources
  169        * associated with this stream. This stream may no longer be used for
  170        * writing bytes.
  171        *
  172        * @exception  IOException  if an I/O error occurs.
  173        */
  174       public void close()  throws IOException {
  175           if (sink != null) {
  176               sink.receivedLast();
  177           }
  178       }
  179   }

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