public bool GetNext(DateTime start, DateTime end, out DateTime next)
{
// Initialize the next output
//
next = DateTime.MinValue;
// Don't want to select the actual start date.
//
DateTime baseSearch = start.AddMinutes(1.0);
int baseMinute = baseSearch.Minute;
int baseHour = baseSearch.Hour;
int baseDay = baseSearch.Day;
int baseMonth = baseSearch.Month;
int baseYear = baseSearch.Year;
// Get the next minute value
//
int minute = _minutes.Next(baseMinute);
if (minute == CronEntryBase.RolledOver)
{
// We need to roll forward to the next hour.
//
minute = _minutes.First;
baseHour++;
// Don't need to worry about baseHour>23 case because
// that will roll off our list in the next step.
}
// Get the next hour value
//
int hour = _hours.Next(baseHour);
if (hour == CronEntryBase.RolledOver)
{
// Roll forward to the next day.
//
minute = _minutes.First;
hour = _hours.First;
baseDay++;
// Don't need to worry about baseDay>31 case because
// that will roll off our list in the next step.
}
else if (hour > baseHour)
{
// Original hour must not have been in the list.
// Reset the minutes.
//
minute = _minutes.First;
}
// Get the next day value.
//
int day = _days.Next(baseDay);
if (day == CronEntryBase.RolledOver)
{
// Roll forward to the next month
//
minute = _minutes.First;
hour = _hours.First;
day = _days.First;
baseMonth++;
// Need to worry about rolling over to the next year here
// because we need to know the number of days in a month
// and that is year dependent (leap year).
//
if (baseMonth > 12)
{
// Roll over to next year.
//
baseMonth = 1;
baseYear++;
}
}
else if (day > baseDay)
{
// Original day no in the value list...reset.
//
minute = _minutes.First;
hour = _hours.First;
}
while (day > DateTime.DaysInMonth(baseYear, baseMonth))
{
// Have a value for the day that is not a valid day
// in the current month. Move to the next month.
//
minute = _minutes.First;
hour = _hours.First;
day = _days.First;
baseMonth++;
// This original month could not be December because
// it can handle the maximum value of days (31). So
// we do not have to worry about baseMonth == 13 case.
}
// Get the next month value.
//
int month = _months.Next(baseMonth);
if (month == CronEntryBase.RolledOver)
{
// Roll forward to the next year.
//
minute = _minutes.First;
hour = _hours.First;
day = _days.First;
month = _months.First;
baseYear++;
}
else if (month > baseMonth)
{
// Original month not in the value list...reset.
//
minute = _minutes.First;
hour = _hours.First;
day = _days.First;
}
while (day > DateTime.DaysInMonth(baseYear, month))
{
// Have a value for the day that is not a valid day
// in the current month. Move to the next month.
//
minute = _minutes.First;
hour = _hours.First;
day = _days.First;
month = _months.Next(month + 1);
if (month == CronEntryBase.RolledOver)
{
// Roll forward to the next year.
//
minute = _minutes.First;
hour = _hours.First;
day = _days.First;
month = _months.First;
baseYear++;
}
}
// Is the date / time we found beyond the end search contraint?
//
DateTime suggested = new DateTime(baseYear, month, day, hour, minute, 0, 0);
if (suggested >= end)
{
return(false);
}
// Does the date / time we found satisfy the day of the week contraint?
//
if (_daysOfWeek.Values.Contains((int)suggested.DayOfWeek))
{
// We have a good date.
//
next = suggested;
return(true);
}
// We need to recursively look for a date in the future. Because this
// search resulted in a day that does not satisfy the day of week
// contraint, start the search on the next day.
//
return(GetNext(new DateTime(baseYear, month, day, 23, 59, 0, 0), out next));
}
