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/*************************************************************************
** SignalHandler.cpp **
** **
** This file is part of dvisvgm -- a fast DVI to SVG converter **
** Copyright (C) 2005-2022 Martin Gieseking <martin.gieseking@uos.de> **
** **
** This program is free software; you can redistribute it and/or **
** modify it under the terms of the GNU General Public License as **
** published by the Free Software Foundation; either version 3 of **
** the License, or (at your option) any later version. **
** **
** This program 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 for more details. **
** **
** You should have received a copy of the GNU General Public License **
** along with this program; if not, see <http://www.gnu.org/licenses/>. **
*************************************************************************/
#include <config.h>
#include <cerrno>
#include <csignal>
#include <cstdlib>
#include "SignalHandler.hpp"
#include "utility.hpp"
using namespace std;
volatile bool SignalHandler::_break = false;
/** Helper class that encapsulates the system-specific parts of
* registering and handling CTRL-C (SIGINT) events. */
class SignalHandler::Impl {
using HandlerFunc = void (*)(int);
public:
Impl ();
bool setSigintHandler (HandlerFunc handler);
bool restoreSigintHandler ();
private:
#ifdef HAVE_SIGACTION
struct sigaction _currentSigaction;
struct sigaction _origSigaction;
#else
HandlerFunc _origHandlerFunc;
#endif
};
SignalHandler::SignalHandler ()
: _impl(util::make_unique<SignalHandler::Impl>())
{
}
SignalHandler::~SignalHandler () {
stop();
}
/** Returns the singleton handler object. */
SignalHandler& SignalHandler::instance() {
static SignalHandler handler;
return handler;
}
/** Starts listening to CTRL-C signals.
* @return true if handler was activated. */
bool SignalHandler::start () {
if (!_active) {
_break = false;
if (_impl->setSigintHandler(callback))
_active = true;
}
return _active;
}
/** Stops listening for CTRL-C signals. */
void SignalHandler::stop () {
if (_active) {
_impl->restoreSigintHandler();
_active = false;
}
}
/** Checks for incoming signals and throws an exception if CTRL-C was caught.
* @throw SignalException */
void SignalHandler::check () {
if (_break)
throw SignalException();
}
void SignalHandler::trigger (bool notify) {
_break = true;
if (notify)
check();
}
/** This function is called on CTRL-C signals. */
void SignalHandler::callback (int) {
_break = true;
}
// Prefer sigaction() to signal() due to its more reliable interface and behavior.
// Use signal() as fallback on systems that don't provide sigaction().
#ifdef HAVE_SIGACTION
SignalHandler::Impl::Impl () {
_origSigaction.sa_handler = nullptr;
}
bool SignalHandler::Impl::setSigintHandler (HandlerFunc handler) {
sigemptyset(&_currentSigaction.sa_mask);
_currentSigaction.sa_handler = handler;
_currentSigaction.sa_flags = SA_SIGINFO;
return (sigaction(SIGINT, &_currentSigaction, &_origSigaction) == 0);
}
bool SignalHandler::Impl::restoreSigintHandler () {
if (_origSigaction.sa_handler == nullptr)
return false;
return (sigaction(SIGINT, &_origSigaction, nullptr) == 0);
}
#else // !HAVE_SIGACTION
SignalHandler::Impl::Impl () : _origHandlerFunc(SIG_ERR) {
}
bool SignalHandler::Impl::setSigintHandler (HandlerFunc handler) {
_origHandlerFunc = signal(SIGINT, handler);
return _origHandlerFunc != SIG_ERR;
}
bool SignalHandler::Impl::restoreSigintHandler () {
if (_origHandlerFunc == SIG_ERR)
return false;
return (signal(SIGINT, _origHandlerFunc) != SIG_ERR);
}
#endif
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