gdatetime.cpp

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//
// Copyright (C) 2001-2013 Graeme Walker <graeme_walker@users.sourceforge.net>
// 
// 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/>.
// ===
//
// gdatetime.cpp
//

#include "gdef.h"
#include "gdatetime.h"
#include "gstr.h"
#include "gassert.h"
#include <sstream>

namespace
{
        const std::time_t minute = 60U ;
        const std::time_t hour = 60U * minute ;
        const std::time_t day = 24U * hour ;
}

G::DateTime::EpochTime G::DateTime::now()
{
        return std::time(NULL) ;
}

G::DateTime::EpochTime G::DateTime::epochTime( const BrokenDownTime & bdt_in )
{
        // get a rough starting point
        BrokenDownTime bdt( bdt_in ) ;
        EpochTime start = std::mktime( &bdt ) ; // localtime

        // iterate over all timezones -- brute force for now
        const std::time_t delta = minute * 30U ;
        for( EpochTime t = (start-day-delta) ; t <= (start+day+delta) ; t += delta )
        {
                if( equivalent( t , bdt_in ) )
                        return t ;
        }
        throw Error() ;
}

G::DateTime::BrokenDownTime G::DateTime::utc( EpochTime epoch_time )
{
        static BrokenDownTime zero ;
        BrokenDownTime result = zero ;
        G::DateTime::gmtime_r( &epoch_time , &result ) ;
        return result ;
}

G::DateTime::BrokenDownTime G::DateTime::local( EpochTime epoch_time )
{
        static BrokenDownTime zero ;
        BrokenDownTime bdt_local = zero ;
        G::DateTime::localtime_r( &epoch_time , &bdt_local ) ;
        return bdt_local ;
}

G::DateTime::Offset G::DateTime::offset( EpochTime utc )
{
        BrokenDownTime bdt_local = local(utc) ;

        EpochTime local = epochTime(bdt_local) ;
        bool ahead = local >= utc ; // ie. east-of
        EpochTime n = ahead ? (local-utc) : (utc-local) ;
        return Offset( ahead , static_cast<unsigned int>(n) ) ;
}

std::string G::DateTime::offsetString( Offset offset )
{
        unsigned int hh = offset.second / 3600U ;
        unsigned int mm = (offset.second / 60U) % 60 ;

        std::ostringstream ss ;
        char sign = (offset.first || (hh==0&&mm==0)) ? '+' : '-' ;
        ss << sign << (hh/10U) << (hh%10U) << (mm/10) << (mm%10) ;
        return ss.str() ;
}

bool G::DateTime::equivalent( EpochTime t , const BrokenDownTime & bdt_in )
{
        BrokenDownTime bdt_test = utc(t) ;
        return same( bdt_test , bdt_in ) ;
}

bool G::DateTime::same( const BrokenDownTime & bdt1 , const BrokenDownTime & bdt2 )
{
        return 
                bdt1.tm_mday == bdt2.tm_mday &&
                bdt1.tm_hour == bdt2.tm_hour &&
                bdt1.tm_min == bdt2.tm_min ;
}