date.cpp

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//: C02:Date.cpp {O}
// From "Thinking in C++, Volume 2", by Bruce Eckel & Chuck Allison.
// (c) 1995-2004 MindView, Inc. All Rights Reserved.
// See source code use permissions stated in the file 'License.txt',
// distributed with the code package available at www.MindView.net.
#include "Date.h"
#include <iostream>
#include <sstream>
#include <cstdlib>
#include <string>
#include <algorithm> // For swap()
#include <ctime>
#include <cassert>
#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) throw(Date::DateError) {
  if(!(1 <= mon && mon <= 12))
    throw DateError("Bad month in Date ctor");
  if(!(1 <= dy && dy <= daysInMonth[isleap(year)][mon]))
    throw DateError("Bad day in Date ctor");
  year = yr;
  month = mon;
  day = dy;
}

Date::Date(const std::string& s) throw(Date::DateError) {
  // Assume YYYYMMDD format
  if(!(s.size() == 8))
    throw DateError("Bad string in Date ctor");
  for(int n = 8; --n >= 0;)
    if(!isdigit(s[n]))
      throw DateError("Bad string in Date ctor");
  string buf = s.substr(0, 4);
  year = atoi(buf.c_str());
  buf = s.substr(4, 2);
  month = atoi(buf.c_str());
  buf = s.substr(6, 2);
  day = atoi(buf.c_str());
  if(!(1 <= month && month <= 12))
    throw DateError("Bad month in Date ctor");
   if(!(1 <= day && day <=
     daysInMonth[isleap(year)][month]))
    throw DateError("Bad day in Date ctor");
}

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

Date::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 Date::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 Date::Duration(years, months, days);
}

ostream& operator<<(ostream& os, const Date& d) {
  char fillc = os.fill('0');
  os << setw(2) << d.getMonth() << '-'
     << setw(2) << d.getDay() << '-'
     << setw(4) << setfill(fillc) << d.getYear();
  return os;
}

istream& operator>>(istream& is, Date& d) {
  is >> d.month;
  char dash;
  is >> dash;
  if(dash != '-')
    is.setstate(ios::failbit);
  is >> d.day;
  is >> dash;
  if(dash != '-')
    is.setstate(ios::failbit);
  is >> d.year;
  return is;
} ///:~