libvieter/src/cron/expression.c

116 lines
3.8 KiB
C

#include "vieter_cron.h"
#include <time.h>
const uint8_t month_days[] = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
cron_expression *ce_init() { return malloc(sizeof(cron_expression)); }
void ce_free(cron_expression *ce) {
free(ce->months);
free(ce->days);
free(ce->hours);
free(ce->minutes);
free(ce);
}
void ce_next(cron_simple_time *out, cron_expression *ce,
cron_simple_time *ref) {
// For all of these values, the rule is the following: if their value is
// the length of their respective array in the CronExpression object, that
// means we've looped back around. This means that the "bigger" value has
// to be incremented by one. For example, if the minutes have looped
// around, that means that the hour has to be incremented as well.
uint8_t month_index = 0;
uint8_t day_index = 0;
uint8_t hour_index = 0;
uint8_t minute_index = 0;
// This chain is the same logic multiple times, namely that if a "bigger"
// value loops around, then the smaller value will always reset as well.
// For example, if we're going to a new day, the hour & minute will always
// be their smallest value again.
while (month_index < ce->month_count &&
ref->month > ce->months[month_index]) {
month_index++;
}
if (month_index < ce->month_count && ref->month == ce->months[month_index]) {
while (day_index < ce->day_count && ref->day > ce->days[day_index]) {
day_index++;
}
if (day_index < ce->day_count && ref->day == ce->days[day_index]) {
while (hour_index < ce->hour_count && ref->hour > ce->hours[hour_index]) {
hour_index++;
}
if (hour_index < ce->hour_count && ref->hour == ce->hours[hour_index]) {
// Minute is the only value where we explicitely make sure we
// can't match sref's value exactly. This is to ensure we only
// return values in the future.
while (minute_index < ce->minute_count &&
ref->minute >= ce->minutes[minute_index]) {
minute_index++;
}
}
}
}
// Here, we increment the "bigger" values by one if the smaller ones loop
// around. The order is important, as it allows a sort-of waterfall effect
// to occur which updates all values if required.
if (minute_index == ce->minute_count && hour_index < ce->hour_count) {
hour_index++;
}
if (hour_index == ce->hour_count && day_index < ce->day_count) {
day_index++;
}
if (day_index == ce->day_count && month_index < ce->month_count) {
month_index++;
}
out->minute = ce->minutes[minute_index % ce->minute_count];
out->hour = ce->hours[hour_index % ce->hour_count];
out->day = ce->days[day_index % ce->day_count];
// Sometimes, we end up with a day that does not exist within the selected
// month, e.g. day 30 in February. When this occurs, we reset day back to
// the smallest value & loop over to the next month that does have this
// day.
if (out->day > month_days[ce->months[month_index % ce->month_count] - 1]) {
out->day = ce->days[0];
month_index++;
while (out->day >
month_days[ce->months[month_index % ce->month_count] - 1]) {
month_index++;
}
}
out->month = ce->months[month_index % ce->month_count];
if (month_index >= ce->month_count) {
out->year = ref->year + 1;
} else {
out->year = ref->year;
}
}
void ce_next_from_now(cron_simple_time *out, cron_expression *ce) {
time_t t = time(NULL);
struct tm gm;
gmtime_r(&t, &gm);
cron_simple_time ref = {// tm_year contains years since 1900
.year = 1900 + gm.tm_year,
// tm_mon goes from 0 to 11
.month = gm.tm_mon + 1,
.day = gm.tm_mday,
.hour = gm.tm_hour,
.minute = gm.tm_min};
ce_next(out, ce, &ref);
}