tzhelp.h

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//
// C++ Interface: TZ Data Helper functions
//
// Description: some calculator inlines
//
//
// Author: Konrad Rosenbaum <konrad@silmor.de>, (C) 2010
//
// Copyright: See README/COPYING files that come with this distribution
//
//

#ifndef TIMEZONE_INLINE_HELPERS_H
#define TIMEZONE_INLINE_HELPERS_H

#include <QtGlobal>
#include <QByteArray>

namespace TimeZoneLib {

static const qint64 SecondsPerDay=86400;

inline qint64 decodeInt(const QByteArray&a,int s=4)
{
        if(a.size()<s)return 0;
        qint64 r=0;
        if(((signed char)a[0])<0)r=-1;
        for(int i=0;i<s;i++){
                r<<=8;
                r|=(unsigned char)a[i];
        }
        return r;
}

inline qint64 decodeInt64(const QByteArray&a){return decodeInt(a,8);}

inline bool isLeapYear(int year)
{
        if((year%400)==0)return true;//every 400th is leapy
        if((year%100)==0)return false;//every 100th is not
        if((year%4)==0)return true;//every fourth is leapy
        return false;//all others are not leapy
}

inline qint64 daysSinceEpoch(int year,int month=1,int day=1)
{
        qint64 ret=0;
        //calculate jan 1st
        if(year>=1970){
                for(int y=1970;y<year;y++)
                        if(isLeapYear(y))ret+=366;
                        else ret+=365;
        }else{
                for(int y=1969;y>=year;y--)
                        if(isLeapYear(y))ret-=366;
                        else ret-=365;
        }
        //calculate 1st of month
        // for each month: add the days of the previous one, and the previous, ...
        switch(month){
                case 12:ret+=30;//nov
                case 11:ret+=31;//oct
                case 10:ret+=30;//sep
                case 9:ret+=31;//aug
                case 8:ret+=31;//jul
                case 7:ret+=30;//jun
                case 6:ret+=31;//may
                case 5:ret+=30;//apr
                case 4:ret+=31;//mar
                case 3:ret+=28;if(isLeapYear(year))ret++;//feb
                case 2:ret+=31;//jan
                default:break;
        }
        //add day
        ret+=day-1;
        
        return ret;
}

inline int pmod(qint64 num,int mod)
{
        num%=mod;
        while(num<0)num+=mod;
        return num;
}

inline qint64 fdiv(qint64 num,qint64 div)
{
        if(div<0){
                div*=-1;num*=-1;
        }
        if(num>0)return num/div;
        qint64 m=num%div;
        num/=div;if(m)num--;
        return num;
}

inline int weekDayOf(int year,int month=1,int day=1)
{
        return pmod(daysSinceEpoch(year,month,day)+4,7);
}

inline int weekDaySinceEpoch(qint64 daySinceEpoch)
{
        return pmod(daySinceEpoch+4,7);
}

inline qint64 firstWeekDayOf(int year,int month,int wday)
{
        wday=pmod(wday,7);
        qint64 day=daysSinceEpoch(year,month);
        do{
                if(weekDaySinceEpoch(day)==wday)return day;
                day++;
        }while(true);
}

inline qint64 lastWeekDayOf(int year,int month,int wday)
{
        wday=pmod(wday,7);
        if(month>=12){
                month=1;
                year++;
        }else month++;
        qint64 day=daysSinceEpoch(year,month);day--;
        do{
                if(weekDaySinceEpoch(day)==wday)return day;
                day--;
        }while(true);
}

inline void stamp2Time(qint64 stamp,quint8&h,quint8&m,quint8&s)
{
        stamp=pmod(stamp,SecondsPerDay);
        s=stamp%60;
        m=(stamp/60)%60;
        h=stamp/3600;
}

inline void offset2Date(qint64 off,qint16&y,quint8&m,quint8&d)
{
        //try to find the year
        y=1970;
        if(off>0){
                while(off>366){
                        off-=365;
                        if(isLeapYear(y))off--;
                        y++;
                }
        }else{
                while(off<0){
                        off+=365;
                        y--;
                        if(isLeapYear(y))off++;
                }
        }
        //find month
        if(off<31){m=1;d=off+1;return;}else off-=31;
        if(off<28){m=2;d=off+1;return;}else off-=28;
        if(isLeapYear(y)){
                if(off)off--;
                else{m=2;d=29;return;}
        }
        if(off<31){m=3;d=off+1;return;}else off-=31;
        if(off<30){m=4;d=off+1;return;}else off-=30;
        if(off<31){m=5;d=off+1;return;}else off-=31;
        if(off<30){m=6;d=off+1;return;}else off-=30;
        if(off<31){m=7;d=off+1;return;}else off-=31;
        if(off<31){m=8;d=off+1;return;}else off-=31;
        if(off<30){m=9;d=off+1;return;}else off-=30;
        if(off<31){m=10;d=off+1;return;}else off-=31;
        if(off<30){m=11;d=off+1;return;}else off-=30;
        if(off<31){m=12;d=off+1;return;}else off-=31;
        //something left over, move to next year
        y++;m=1;d=off+1;
}

inline void stamp2Date(qint64 off,qint16&y,quint8&m,quint8&d)
{
        qint64 de=fdiv(off,SecondsPerDay);
        offset2Date(de,y,m,d);
}

inline qint64 dateTime2stamp(qint64 days,quint8 h,quint8 m,quint8 s)
{
        qint64 r=days*SecondsPerDay;
        r+=h*3600 + m*60 + s;
        return r;
}

inline qint64 dateTime2stamp(int y,quint8 mon,quint8 day,quint8 hr,quint8 min,quint8 s)
{
        return dateTime2stamp(daysSinceEpoch(y,mon,day),hr,min,s);
}

//end of namespace
}

#endif