libdap
Updated for version 3.17.0
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00001 00002 // -*- mode: c++; c-basic-offset:4 -*- 00003 00004 // This file is part of libdap, A C++ implementation of the OPeNDAP Data 00005 // Access Protocol. 00006 00007 // Copyright (c) 2002,2003 OPeNDAP, Inc. 00008 // Author: James Gallagher <jgallagher@opendap.org> 00009 // 00010 // This library is free software; you can redistribute it and/or 00011 // modify it under the terms of the GNU Lesser General Public 00012 // License as published by the Free Software Foundation; either 00013 // version 2.1 of the License, or (at your option) any later version. 00014 // 00015 // This library is distributed in the hope that it will be useful, 00016 // but WITHOUT ANY WARRANTY; without even the implied warranty of 00017 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 00018 // Lesser General Public License for more details. 00019 // 00020 // You should have received a copy of the GNU Lesser General Public 00021 // License along with this library; if not, write to the Free Software 00022 // Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA 00023 // 00024 // You can contact OPeNDAP, Inc. at PO Box 112, Saunderstown, RI. 02874-0112. 00025 00026 // (c) COPYRIGHT URI/MIT 1994-2002 00027 // Please read the full copyright statement in the file COPYRIGHT_URI. 00028 // 00029 // Authors: 00030 // jhrg,jimg James Gallagher <jgallagher@gso.uri.edu> 00031 00032 #include "config.h" 00033 00034 #include <cstdlib> 00035 00036 #include <signal.h> 00037 #include <pthread.h> 00038 00039 #ifdef HAVE_UNISTD_H 00040 #include <unistd.h> //for _exit 00041 #endif 00042 00043 #include "SignalHandler.h" 00044 #include "util.h" 00045 00046 namespace libdap { 00047 00048 EventHandler *SignalHandler::d_signal_handlers[NSIG]; 00049 Sigfunc *SignalHandler::d_old_handlers[NSIG]; 00050 SignalHandler *SignalHandler::d_instance = 0; 00051 00052 // instance_control is used to ensure that in a MT environment d_instance is 00053 // correctly initialized. 00054 static pthread_once_t instance_control = PTHREAD_ONCE_INIT; 00055 00057 void 00058 SignalHandler::initialize_instance() 00059 { 00060 // MT-Safe if called via pthread_once or similar 00061 SignalHandler::d_instance = new SignalHandler; 00062 atexit(SignalHandler::delete_instance); 00063 } 00064 00066 void 00067 SignalHandler::delete_instance() 00068 { 00069 if (SignalHandler::d_instance) { 00070 for (int i = 0; i < NSIG; ++i) { 00071 // Fortify warns about a leak because the EventHandler objects 00072 // are not deleted, but that's OK - this is a singleton and 00073 // so the 'leak' is really just a constant amount of memory that 00074 // gets used. 00075 d_signal_handlers[i] = 0; 00076 d_old_handlers[i] = 0; 00077 } 00078 00079 delete SignalHandler::d_instance; 00080 SignalHandler::d_instance = 0; 00081 } 00082 } 00083 00090 void 00091 SignalHandler::dispatcher(int signum) 00092 { 00093 // Perform a sanity check... 00094 if (SignalHandler::d_signal_handlers[signum] != 0) 00095 // Dispatch the handler's hook method. 00096 SignalHandler::d_signal_handlers[signum]->handle_signal(signum); 00097 00098 Sigfunc *old_handler = SignalHandler::d_old_handlers[signum]; 00099 if (old_handler == SIG_IGN || old_handler == SIG_ERR) 00100 return; 00101 else if (old_handler == SIG_DFL) { 00102 switch (signum) { 00103 #if 0 00104 #ifndef WIN32 00105 case SIGHUP: 00106 case SIGKILL: 00107 case SIGUSR1: 00108 case SIGUSR2: 00109 case SIGPIPE: 00110 case SIGALRM: 00111 #endif 00112 case SIGINT: 00113 case SIGTERM: _exit(EXIT_FAILURE); 00114 00115 // register_handler() should never allow any fiddling with 00116 // signals other than those listed above. 00117 default: abort(); 00118 #endif 00119 // Calling _exit() or abort() is not a good thing for a library to be 00120 // doing. This results in a warning from rpmlint 00121 default: 00122 throw Error(internal_error, "Signal handler operation on an unsupported signal."); 00123 } 00124 } 00125 else 00126 old_handler(signum); 00127 } 00128 00130 SignalHandler* 00131 SignalHandler::instance() 00132 { 00133 pthread_once(&instance_control, initialize_instance); 00134 00135 return d_instance; 00136 } 00137 00150 EventHandler * 00151 SignalHandler::register_handler(int signum, EventHandler *eh, bool override) 00152 { 00153 // Check first for improper use. 00154 switch (signum) { 00155 #ifndef WIN32 00156 case SIGHUP: 00157 case SIGKILL: 00158 case SIGUSR1: 00159 case SIGUSR2: 00160 case SIGPIPE: 00161 case SIGALRM: 00162 #endif 00163 case SIGINT: 00164 case SIGTERM: break; 00165 00166 default: throw InternalErr(__FILE__, __LINE__, 00167 string("Call to register_handler with unsupported signal (") 00168 + long_to_string(signum) + string(").")); 00169 } 00170 00171 // Save the old EventHandler 00172 EventHandler *old_eh = SignalHandler::d_signal_handlers[signum]; 00173 00174 SignalHandler::d_signal_handlers[signum] = eh; 00175 00176 // Register the dispatcher to handle this signal. See Stevens, Advanced 00177 // Programming in the UNIX Environment, p.298. 00178 #ifndef WIN32 00179 struct sigaction sa; 00180 sa.sa_handler = dispatcher; 00181 sigemptyset(&sa.sa_mask); 00182 sa.sa_flags = 0; 00183 00184 // Try to suppress restarting system calls if we're handling an alarm. 00185 // This lets alarms block I/O calls that would normally restart. 07/18/03 00186 // jhrg 00187 if (signum == SIGALRM) { 00188 #ifdef SA_INTERUPT 00189 sa.sa_flags |= SA_INTERUPT; 00190 #endif 00191 } 00192 else { 00193 #ifdef SA_RESTART 00194 sa.sa_flags |= SA_RESTART; 00195 #endif 00196 } 00197 00198 struct sigaction osa; // extract the old handler/action 00199 00200 if (sigaction(signum, &sa, &osa) < 0) 00201 throw InternalErr(__FILE__, __LINE__, "Could not register a signal handler."); 00202 00203 // Take care of the case where this interface is used to register a 00204 // handler more than once. We want to make sure that the dispatcher is 00205 // not installed as the 'old handler' because that results in an infinite 00206 // loop. 02/10/04 jhrg 00207 if (override) 00208 SignalHandler::d_old_handlers[signum] = SIG_IGN; 00209 else if (osa.sa_handler != dispatcher) 00210 SignalHandler::d_old_handlers[signum] = osa.sa_handler; 00211 #endif 00212 00213 return old_eh; 00214 } 00215 00219 EventHandler * 00220 SignalHandler::remove_handler(int signum) 00221 { 00222 EventHandler *old_eh = SignalHandler::d_signal_handlers[signum]; 00223 00224 SignalHandler::d_signal_handlers[signum] = 0; 00225 00226 return old_eh; 00227 } 00228 00229 } // namespace libdap