AlarmHandler.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 alarm_handler_h
#define alarm_handler_h

#include <cstdio>

#include <string>

#include "EventHandler.h"

namespace libdap {

/** Handle the time out alarm. When an OPeNDAP server runs until the time out
    alarm is triggered, this class provides the concrete implementation of
    EventHandler::handle_signal().

    @see EventHandler
    @see SignalHandler
    @author James Gallagher <jgallagher@opendap.org> */
class AlarmHandler : public EventHandler {
private:
    FILE *d_file; // Sink for the Error object.
    string d_version;

public:
    // Ensure that d_stream gets initialized...
    AlarmHandler() : d_file(0) {}

    explicit AlarmHandler(FILE *s)
        : d_file(s) //, d_stream( cout )
    {}

    /** Store information to be used by the handler.
        @param out Write to this stream.
        @deprecated The stream param is ignored. Use the default constructor instead. */
    explicit AlarmHandler(ostream &) : d_file(0) {}

    virtual ~AlarmHandler() {
        if (d_file)
            fclose(d_file);
    }

    /** Handle an alarm signal. When one of our servers gets an alarm, that
    means it has hit its time out. We need to dump two CRLF pairs down
    the stream and then send an Error object explaining that a timeout
    has been reached.

    Because this is a signal handler, it should call only reentrant
    system services, functions, et cetera. This handler never returns
    to the code that was running when the alarm signal was raised.

    @param signum We know it is SIGALRM; here as a check
    @return Never returns; calls exit after sending the Error object. */
    virtual void handle_signal(int signum) {
        if (signum != SIGALRM)
            throw Error("SIGALRM handler caught another signal!");

        throw Error("Timeout");
    }
};

} // namespace libdap

#endif