Date.cpp

/***************************************************************************
 *   Copyright (C) 2003 by eddiedu                                         *
 *   eddiedu@scale.com.br                                                  *
 *                                                                         *
 *   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 2 of the License, or     *
 *   (at your option) any later version.                                   *
 ***************************************************************************/
#include "Date.h"
#include <string>
#include <algorithm> // for swap()
#include <ctime>
#include <cassert>
#include <sstream>
#include <iomanip>
using namespace std;

namespace {
const int daysInMonth[][13] = {
    {0,31,28,31,30,31,30,31,31,30,31,30,31},
    {0,31,29,31,30,31,30,31,31,30,31,30,31}};
inline bool isleap(int y) {
return ((y%4 == 0) && (y%100 != 0)) || (y%400 == 0);
  }
}

Date::Date() {
// Get current date
  time_t tval = time(0);
struct tm *now = localtime(&tval);
  year = now->tm_year + 1900;
  month = now->tm_mon + 1;
  day = now->tm_mday;
}

Date::Date(int yr, int mon, int dy) {
  assert(1 <= mon && mon <= 12);
  assert(1 <= dy && 
    dy <= daysInMonth[isleap(year)][mon]);
  year = yr;
  month = mon;
  day = dy;
}

Date::Date(const std::string& s) {
// Assume YYYYMMDD format
  istringstream is(s);
  is >> setw(4) >> year;
  is >> setw(2) >> month;
  is >> setw(2) >> day;
}

int Date::getYear() const {
return year;
}

int Date::getMonth() const {
return month;
}

int Date::getDay() const {
return day;
}

string Date::toString() const {
  ostringstream os;
  os << setw(4) << year
   << setw(2) << month
   << setw(2) << day;
return os.str();
}

int Date::compare(const Date& d2) const {
int result = year - d2.year;
if (result == 0) {
    result = month - d2.month;
if (result == 0)
      result = day - d2.day;
  }
return result;   
}

int Date::daysInPrevMonth(int year, int month) {
if (month == 1) {
    --year;
    month = 12;
  }
else
    --month;
return daysInMonth[isleap(year)][month];
}

bool operator<(const Date& d1, const Date& d2) {
return d1.compare(d2) < 0;
}
bool operator<=(const Date& d1, const Date& d2) {
return d1.compare(d2) <= 0;
}
bool operator>(const Date& d1, const Date& d2) {
return d1.compare(d2) >= 0;
}
bool operator>=(const Date& d1, const Date& d2) {
return d1.compare(d2) >= 0;
}
bool operator==(const Date& d1, const Date& d2) {
return d1.compare(d2) == 0;
}
bool operator!=(const Date& d1, const Date& d2) {
return d1.compare(d2) != 0;
}

Duration 
duration(const Date& date1, const Date& date2) {
int y1 = date1.year;
int y2 = date2.year;
int m1 = date1.month;
int m2 = date2.month;
int d1 = date1.day;
int d2 = date2.day;

// Compute the compare
int order = date1.compare(date2);
if (order == 0)
return Duration(0,0,0);
else if (order > 0) {
// Make date1 precede date2 locally
using std::swap;
    swap(y1, y2);
    swap(m1, m2);
    swap(d1, d2);
  }

int years = y2 - y1;
int months = m2 - m1;
int days = d2 - d1;
  assert(years > 0 ||
     (years == 0 && months > 0) ||
     (years == 0 && months == 0 && days > 0) );

// Do the obvious corrections (must adjust days
// before months!) - This is a loop in case the
// previous month is February, and days < -28.
int lastMonth = m2;
int lastYear = y2;
while (days < 0) {
// Borrow from month
    assert(months > 0);
    days += Date::daysInPrevMonth(
      lastYear, lastMonth--);
    --months;
  }

if (months < 0) {
// Borrow from year
    assert(years > 0);
    months += 12;
    --years;
  }
return Duration(years, months, days);
}