问题描述
我有一些使用Oracle函数add_months的代码将日期增加X个月。
I have some code that uses the Oracle function add_months to increment a Date by X number of months.
我现在需要重新实现相同的逻辑C / C ++函数。因为我不想/需要进去,我不能简单地向oracle发出查询来获取新的日期。
I now need to re-implement the same logic in a C / C++ function. For reasons I don't want/need to go into I can't simply issue a query to oracle to get the new date.
有没有人知道一个简单和可靠的方式将X个月的时间添加到time_t?
计算类型的一些示例如下所示。
Does anyone know of a simple and reliable way of adding X number of months to a time_t?Some examples of the types of calculations are shown below.
30/01/2009 + 1个月= 28/02/2009
31/01/2009 + 1个月= 28/02/2009
27/02/2009 + 1个月= 27/03/2009
28/02/2009 + 1月= 31/03/2009
31/01/2009 + 50个月= 31/03/2013
30/01/2009 + 1 month = 28/02/2009
31/01/2009 + 1 month = 28/02/2009
27/02/2009 + 1 month = 27/03/2009
28/02/2009 + 1 month = 31/03/2009
31/01/2009 + 50 months = 31/03/2013
推荐答案
方法 AddMonths_OracleStyle 可以满足您的需要。
Method AddMonths_OracleStyle does what you need.
也许您可能希望将IsLeapYear和GetDaysInMonth替换为某些库管理器方法。
Perhaps you would want to replace IsLeapYear and GetDaysInMonth to some librarian methods.
#include <ctime>
#include <assert.h>
bool IsLeapYear(int year)
{
if (year % 4 != 0) return false;
if (year % 400 == 0) return true;
if (year % 100 == 0) return false;
return true;
}
int daysInMonths[] = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
int GetDaysInMonth(int year, int month)
{
assert(month >= 0);
assert(month < 12);
int days = daysInMonths[month];
if (month == 1 && IsLeapYear(year)) // February of a leap year
days += 1;
return days;
}
tm AddMonths_OracleStyle(const tm &d, int months)
{
bool isLastDayInMonth = d.tm_mday == GetDaysInMonth(d.tm_year, d.tm_mon);
int year = d.tm_year + months / 12;
int month = d.tm_mon + months % 12;
if (month > 11)
{
year += 1;
month -= 12;
}
int day;
if (isLastDayInMonth)
day = GetDaysInMonth(year, month); // Last day of month maps to last day of result month
else
day = std::min(d.tm_mday, GetDaysInMonth(year, month));
tm result = tm();
result.tm_year = year;
result.tm_mon = month;
result.tm_mday = day;
result.tm_hour = d.tm_hour;
result.tm_min = d.tm_min;
result.tm_sec = d.tm_sec;
return result;
}
time_t AddMonths_OracleStyle(const time_t &date, int months)
{
tm d = tm();
localtime_s(&d, &date);
tm result = AddMonths_OracleStyle(d, months);
return mktime(&result);
}
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