SignalHandler.h

// -*- mode: c++; c-basic-offset:4 -*-

// This file is part of libdap, A C++ implementation of the OPeNDAP Data
// Access Protocol.

// Copyright (c) 2002,2003 OPeNDAP, Inc.
// Author: James Gallagher <jgallagher@opendap.org>
//
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 2.1 of the License, or (at your option) any later version.
//
// This library 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
// Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
//
// You can contact OPeNDAP, Inc. at PO Box 112, Saunderstown, RI. 02874-0112.

#ifndef signal_handler_h
#define signal_handler_h

#include <signal.h>

#include "EventHandler.h"
#include "InternalErr.h"

namespace libdap
{

typedef void Sigfunc(int); // Plauger, 1992

class SignalHandler
{
private:
    // Ensure we're a Singleton.
    SignalHandler() {}
    SignalHandler(const SignalHandler &) {}

    // Singleton pointer.
    static SignalHandler *d_instance;

    // Table of pointers to instances of EventHandlers. Since EventHandler is
    // abstract, the pointers will actually reference instances that are
    // children of EventHandler. NSIG is defined in signal.h but this may be
    // a portability issue.
    static EventHandler *d_signal_handlers[NSIG];

    // This array holds the old signal handlers. Once the handler in
    // d_signal_handler[signum] is run, look here to see what the original
    // action was. This is important since libdap++ is often embedded in code
    // that already has a non-default signal handler for things like SIGINT.
    static Sigfunc *d_old_handlers[NSIG];

    // Entry point adapter installed into sigaction(). This must be a static
    // method (or a regular C-function) to conform to sigaction's interface.
    // this is the part of SignalHandler that uses the Adapter pattern.
    static void dispatcher(int signum);

    // Delete the global instance. Call this with atexit().
    static void delete_instance();

    // Call this using pthread_once() to ensure there's only one instance
    // when running in a MT world.
    static void initialize_instance();

    friend class SignalHandlerTest;
    friend class HTTPCacheTest;

public:
    static SignalHandler *instance();

    virtual ~SignalHandler() {}

    EventHandler *register_handler(int signum, EventHandler *eh,
                                   bool override = false);

    EventHandler *remove_handler(int signum);
};

} // namespace libdap

#endif // signal_handler_h