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Diffstat (limited to 'src/date.h')
-rw-r--r-- | src/date.h | 61 |
1 files changed, 61 insertions, 0 deletions
diff --git a/src/date.h b/src/date.h new file mode 100644 index 000000000..488a9dc3a --- /dev/null +++ b/src/date.h @@ -0,0 +1,61 @@ +/* $Id$ */ + +#ifndef DATE_H +#define DATE_H + +#include "openttd.h" + +/** + * 1 day is 74 ticks; _date_fract used to be uint16 and incremented by 885. On + * an overflow the new day begun and 65535 / 885 = 74. + * 1 tick is approximately 30 ms. + * 1 day is thus about 2 seconds (74 * 30 = 2220) on a machine that can run OpenTTD normally + */ +#define DAY_TICKS 74 + +/* + * ORIGINAL_BASE_YEAR, ORIGINAL_MAX_YEAR and DAYS_TILL_ORIGINAL_BASE_YEAR are + * primarily used for loading newgrf and savegame data and returning some + * newgrf (callback) functions that were in the original (TTD) inherited + * format, where '_date == 0' meant that it was 1920-01-01. + */ + +/** The minimum starting year/base year of the original TTD */ +#define ORIGINAL_BASE_YEAR 1920 +/** The maximum year of the original TTD */ +#define ORIGINAL_MAX_YEAR 2090 + +/** + * The offset in days from the '_date == 0' till + * 'ConvertYMDToDate(ORIGINAL_BASE_YEAR, 0, 1)' + */ +#define DAYS_TILL_ORIGINAL_BASE_YEAR (365 * ORIGINAL_BASE_YEAR + ORIGINAL_BASE_YEAR / 4 - ORIGINAL_BASE_YEAR / 100 + ORIGINAL_BASE_YEAR / 400) + +/* The absolute minimum & maximum years in OTTD */ +#define MIN_YEAR 0 +/* MAX_YEAR, nicely rounded value of the number of years that can + * be encoded in a single 32 bits date, about 2^31 / 366 years. */ +#define MAX_YEAR 5000000 + +/* Year and Date are defined elsewhere */ +typedef uint8 Month; +typedef uint8 Day; +typedef uint16 DateFract; + +typedef struct YearMonthDay { + Year year; + Month month; + Day day; +} YearMonthDay; + +extern Year _cur_year; +extern Month _cur_month; +extern Date _date; +extern DateFract _date_fract; + + +void SetDate(Date date); +void ConvertDateToYMD(Date date, YearMonthDay *ymd); +Date ConvertYMDToDate(Year year, Month month, Day day); + +#endif /* DATE_H */ |