/*---------------------------------------------------------------------------*\
    Copyright            : (C) 2011 Symscape
    Website              : www.symscape.com
-------------------------------------------------------------------------------
License
    This file is part of OpenFOAM.

    OpenFOAM 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.

    OpenFOAM 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 OpenFOAM.  If not, see <http://www.gnu.org/licenses/>.

Class
    timer

Description
    Implements a timeout mechanism. Usage is as following:

    timer myTimer(5);     // 5 sec
    ..
    if (timedOut(myTimer))
    {
        // timed out
    }
    else
    {
        // do something possible blocking
    }

    Constructor set signal handler on sigalarm and alarm(). Destructor
    clears these.

    timedOut is macro because setjmp can't be in member function of timer.
    ?something to do with stack frames.

    WARNING: setjmp restores complete register state so including local vars
    held in regs. So if in blocking part something gets calced in a stack
    based variable make sure it is declared 'volatile'.

SourceFiles
    timer.C

\*---------------------------------------------------------------------------*/

#ifndef timer_H
#define timer_H

#include "className.H"

#include <signal.h>
#include <setjmp.h>

// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

// keep setjmp in same stack frame so no function calls
#define timedOut(x) \
    (((x).newTimeOut_ > 0) ? setjmp(Foam::timer::envAlarm) : false)

namespace Foam
{

/*---------------------------------------------------------------------------*\
                           Class timer Declaration
\*---------------------------------------------------------------------------*/

class timer
{
    // Private data

        //- old signal
        static __p_sig_fn_t oldAction_;

        //- old alarm() value
        static unsigned int oldTimeOut_;


    // Private Member Functions

        //- alarm handler
        static void signalHandler(int);


public:

    // Public data

        //- Declare name of the class and it's debug switch
        ClassName("timer");

        //- current time out value. Needed by macro timedOut
        unsigned int newTimeOut_;

        //- state for setjmp. Needed by macro timedOut
        static jmp_buf envAlarm;


    // Constructors

        //- Construct from components.
        //  newTimeOut=0 makes it do nothing.
        timer(const unsigned int newTimeOut);


    // Destructor

        ~timer();
};


// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

} // End namespace Foam

// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

#endif

// ************************************************************************* //
