J. Duke | 319a3b9 | 2007-12-01 00:00:00 +0000 | [diff] [blame^] | 1 | /* |
| 2 | * Copyright 1995-2006 Sun Microsystems, Inc. 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. Sun designates this |
| 8 | * particular file as subject to the "Classpath" exception as provided |
| 9 | * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, |
| 22 | * CA 95054 USA or visit www.sun.com if you need additional information or |
| 23 | * have any 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 | } |