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| 1 | /* | ||
| 2 | * Copyright (c) 1998, 2007, 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 sun.misc; | ||
| 27 | import java.util.Hashtable; | ||
| 28 | |||
| 29 | /** | ||
| 30 | * This class provides ANSI/ISO C signal support. A Java program can register | ||
| 31 | * signal handlers for the current process. There are two restrictions: | ||
| 32 | * <ul> | ||
| 33 | * <li> | ||
| 34 | * Java code cannot register a handler for signals that are already used | ||
| 35 | * by the Java VM implementation. The <code>Signal.handle</code> | ||
| 36 | * function raises an <code>IllegalArgumentException</code> if such an attempt | ||
| 37 | * is made. | ||
| 38 | * <li> | ||
| 39 | * When <code>Signal.handle</code> is called, the VM internally registers a | ||
| 40 | * special C signal handler. There is no way to force the Java signal handler | ||
| 41 | * to run synchronously before the C signal handler returns. Instead, when the | ||
| 42 | * VM receives a signal, the special C signal handler creates a new thread | ||
| 43 | * (at priority <code>Thread.MAX_PRIORITY</code>) to | ||
| 44 | * run the registered Java signal handler. The C signal handler immediately | ||
| 45 | * returns. Note that because the Java signal handler runs in a newly created | ||
| 46 | * thread, it may not actually be executed until some time after the C signal | ||
| 47 | * handler returns. | ||
| 48 | * </ul> | ||
| 49 | * <p> | ||
| 50 | * Signal objects are created based on their names. For example: | ||
| 51 | * <blockquote><pre> | ||
| 52 | * new Signal("INT"); | ||
| 53 | * </blockquote></pre> | ||
| 54 | * constructs a signal object corresponding to <code>SIGINT</code>, which is | ||
| 55 | * typically produced when the user presses <code>Ctrl-C</code> at the command line. | ||
| 56 | * The <code>Signal</code> constructor throws <code>IllegalArgumentException</code> | ||
| 57 | * when it is passed an unknown signal. | ||
| 58 | * <p> | ||
| 59 | * This is an example of how Java code handles <code>SIGINT</code>: | ||
| 60 | * <blockquote><pre> | ||
| 61 | * SignalHandler handler = new SignalHandler () { | ||
| 62 | * public void handle(Signal sig) { | ||
| 63 | * ... // handle SIGINT | ||
| 64 | * } | ||
| 65 | * }; | ||
| 66 | * Signal.handle(new Signal("INT"), handler); | ||
| 67 | * </blockquote></pre> | ||
| 68 | * | ||
| 69 | * @author Sheng Liang | ||
| 70 | * @author Bill Shannon | ||
| 71 | * @see sun.misc.SignalHandler | ||
| 72 | * @since 1.2 | ||
| 73 | */ | ||
| 74 | public final class Signal { | ||
| 75 | private static Hashtable handlers = new Hashtable(4); | ||
| 76 | private static Hashtable signals = new Hashtable(4); | ||
| 77 | |||
| 78 | private int number; | ||
| 79 | private String name; | ||
| 80 | |||
| 81 | /* Returns the signal number */ | ||
| 82 | public int getNumber() { | ||
| 83 | return number; | ||
| 84 | } | ||
| 85 | |||
| 86 | /** | ||
| 87 | * Returns the signal name. | ||
| 88 | * | ||
| 89 | * @return the name of the signal. | ||
| 90 | * @see sun.misc.Signal#Signal(String name) | ||
| 91 | */ | ||
| 92 | public String getName() { | ||
| 93 | return name; | ||
| 94 | } | ||
| 95 | |||
| 96 | /** | ||
| 97 | * Compares the equality of two <code>Signal</code> objects. | ||
| 98 | * | ||
| 99 | * @param other the object to compare with. | ||
| 100 | * @return whether two <code>Signal</code> objects are equal. | ||
| 101 | */ | ||
| 102 | public boolean equals(Object other) { | ||
| 103 | if (this == other) { | ||
| 104 | return true; | ||
| 105 | } | ||
| 106 | if (other == null || !(other instanceof Signal)) { | ||
| 107 | return false; | ||
| 108 | } | ||
| 109 | Signal other1 = (Signal)other; | ||
| 110 | return name.equals(other1.name) && (number == other1.number); | ||
| 111 | } | ||
| 112 | |||
| 113 | /** | ||
| 114 | * Returns a hashcode for this Signal. | ||
| 115 | * | ||
| 116 | * @return a hash code value for this object. | ||
| 117 | */ | ||
| 118 | public int hashCode() { | ||
| 119 | return number; | ||
| 120 | } | ||
| 121 | |||
| 122 | /** | ||
| 123 | * Returns a string representation of this signal. For example, "SIGINT" | ||
| 124 | * for an object constructed using <code>new Signal ("INT")</code>. | ||
| 125 | * | ||
| 126 | * @return a string representation of the signal | ||
| 127 | */ | ||
| 128 | public String toString() { | ||
| 129 | return "SIG" + name; | ||
| 130 | } | ||
| 131 | |||
| 132 | /** | ||
| 133 | * Constructs a signal from its name. | ||
| 134 | * | ||
| 135 | * @param name the name of the signal. | ||
| 136 | * @exception IllegalArgumentException unknown signal | ||
| 137 | * @see sun.misc.Signal#getName() | ||
| 138 | */ | ||
| 139 | public Signal(String name) { | ||
| 140 | number = findSignal(name); | ||
| 141 | this.name = name; | ||
| 142 | if (number < 0) { | ||
| 143 | throw new IllegalArgumentException("Unknown signal: " + name); | ||
| 144 | } | ||
| 145 | } | ||
| 146 | |||
| 147 | /** | ||
| 148 | * Registers a signal handler. | ||
| 149 | * | ||
| 150 | * @param sig a signal | ||
| 151 | * @param handler the handler to be registered with the given signal. | ||
| 152 | * @result the old handler | ||
| 153 | * @exception IllegalArgumentException the signal is in use by the VM | ||
| 154 | * @see sun.misc.Signal#raise(Signal sig) | ||
| 155 | * @see sun.misc.SignalHandler | ||
| 156 | * @see sun.misc.SignalHandler#SIG_DFL | ||
| 157 | * @see sun.misc.SignalHandler#SIG_IGN | ||
| 158 | */ | ||
| 159 | public static synchronized SignalHandler handle(Signal sig, | ||
| 160 | SignalHandler handler) | ||
| 161 | throws IllegalArgumentException { | ||
| 162 | long newH = (handler instanceof NativeSignalHandler) ? | ||
| 163 | ((NativeSignalHandler)handler).getHandler() : 2; | ||
| 164 | long oldH = handle0(sig.number, newH); | ||
| 165 | if (oldH == -1) { | ||
| 166 | throw new IllegalArgumentException | ||
| 167 | ("Signal already used by VM or OS: " + sig); | ||
| 168 | } | ||
| 169 | signals.put(new Integer(sig.number), sig); | ||
| 170 | synchronized (handlers) { | ||
| 171 | SignalHandler oldHandler = (SignalHandler)handlers.get(sig); | ||
| 172 | handlers.remove(sig); | ||
| 173 | if (newH == 2) { | ||
| 174 | handlers.put(sig, handler); | ||
| 175 | } | ||
| 176 | if (oldH == 0) { | ||
| 177 | return SignalHandler.SIG_DFL; | ||
| 178 | } else if (oldH == 1) { | ||
| 179 | return SignalHandler.SIG_IGN; | ||
| 180 | } else if (oldH == 2) { | ||
| 181 | return oldHandler; | ||
| 182 | } else { | ||
| 183 | return new NativeSignalHandler(oldH); | ||
| 184 | } | ||
| 185 | } | ||
| 186 | } | ||
| 187 | |||
| 188 | /** | ||
| 189 | * Raises a signal in the current process. | ||
| 190 | * | ||
| 191 | * @param sig a signal | ||
| 192 | * @see sun.misc.Signal#handle(Signal sig, SignalHandler handler) | ||
| 193 | */ | ||
| 194 | public static void raise(Signal sig) throws IllegalArgumentException { | ||
| 195 | if (handlers.get(sig) == null) { | ||
| 196 | throw new IllegalArgumentException("Unhandled signal: " + sig); | ||
| 197 | } | ||
| 198 | raise0(sig.number); | ||
| 199 | } | ||
| 200 | |||
| 201 | /* Called by the VM to execute Java signal handlers. */ | ||
| 202 | private static void dispatch(final int number) { | ||
| 203 | final Signal sig = (Signal)signals.get(new Integer(number)); | ||
| 204 | final SignalHandler handler = (SignalHandler)handlers.get(sig); | ||
| 205 | |||
| 206 | Runnable runnable = new Runnable () { | ||
| 207 | public void run() { | ||
| 208 | // Don't bother to reset the priority. Signal handler will | ||
| 209 | // run at maximum priority inherited from the VM signal | ||
| 210 | // dispatch thread. | ||
| 211 | // Thread.currentThread().setPriority(Thread.NORM_PRIORITY); | ||
| 212 | handler.handle(sig); | ||
| 213 | } | ||
| 214 | }; | ||
| 215 | if (handler != null) { | ||
| 216 | new Thread(runnable, sig + " handler").start(); | ||
| 217 | } | ||
| 218 | } | ||
| 219 | |||
| 220 | /* Find the signal number, given a name. Returns -1 for unknown signals. */ | ||
| 221 | private static native int findSignal(String sigName); | ||
| 222 | /* Registers a native signal handler, and returns the old handler. | ||
| 223 | * Handler values: | ||
| 224 | * 0 default handler | ||
| 225 | * 1 ignore the signal | ||
| 226 | * 2 call back to Signal.dispatch | ||
| 227 | * other arbitrary native signal handlers | ||
| 228 | */ | ||
| 229 | private static native long handle0(int sig, long nativeH); | ||
| 230 | /* Raise a given signal number */ | ||
| 231 | private static native void raise0(int sig); | ||
| 232 | } | ||