forked from vieter-v/libvieter
chore: added cron code
commit
f50bc4a3c4
GPG Key ID:
B75D4F293C7052DB
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@ -0,0 +1,118 @@
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#include "expression.h"
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#include <time.h>
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const uint8_t month_days[] = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
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cron_expression *ce_init() { return malloc(sizeof(cron_expression)); }
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void ce_free(cron_expression *ce) {
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free(ce->months);
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free(ce->days);
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free(ce->hours);
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free(ce->minutes);
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free(ce);
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}
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void ce_next(cron_simple_time *out, cron_expression *ce,
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cron_simple_time *ref) {
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// For all of these values, the rule is the following: if their value is
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// the length of their respective array in the CronExpression object, that
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// means we've looped back around. This means that the "bigger" value has
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// to be incremented by one. For example, if the minutes have looped
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// around, that means that the hour has to be incremented as well.
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uint8_t month_index = 0;
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uint8_t day_index = 0;
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uint8_t hour_index = 0;
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uint8_t minute_index = 0;
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// This chain is the same logic multiple times, namely that if a "bigger"
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// value loops around, then the smaller value will always reset as well.
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// For example, if we're going to a new day, the hour & minute will always
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// be their smallest value again.
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while (month_index < ce->month_count &&
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ref->month > ce->months[month_index]) {
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month_index++;
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}
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if (month_index < ce->month_count &&
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ref->month == ce->months[month_index]) {
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while (day_index < ce->day_count && ref->day > ce->days[day_index]) {
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day_index++;
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}
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if (day_index < ce->day_count && ref->day == ce->days[day_index]) {
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while (hour_index < ce->hour_count &&
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ref->hour > ce->hours[hour_index]) {
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hour_index++;
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}
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if (hour_index < ce->hour_count &&
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ref->hour == ce->hours[hour_index]) {
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// Minute is the only value where we explicitely make sure we
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// can't match sref's value exactly. This is to ensure we only
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// return values in the future.
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while (minute_index < ce->minute_count &&
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ref->minute >= ce->minutes[minute_index]) {
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minute_index++;
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}
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}
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}
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}
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// Here, we increment the "bigger" values by one if the smaller ones loop
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// around. The order is important, as it allows a sort-of waterfall effect
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// to occur which updates all values if required.
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if (minute_index == ce->minute_count && hour_index < ce->hour_count) {
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hour_index++;
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}
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if (hour_index == ce->hour_count && day_index < ce->day_count) {
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day_index++;
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}
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if (day_index == ce->day_count && month_index < ce->month_count) {
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month_index++;
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}
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out->minute = ce->minutes[minute_index % ce->minute_count];
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out->hour = ce->hours[hour_index % ce->hour_count];
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out->day = ce->days[day_index % ce->day_count];
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// Sometimes, we end up with a day that does not exist within the selected
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// month, e.g. day 30 in February. When this occurs, we reset day back to
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// the smallest value & loop over to the next month that does have this
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// day.
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if (out->day > month_days[ce->months[month_index % ce->month_count] - 1]) {
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out->day = ce->days[0];
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month_index++;
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while (out->day >
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month_days[ce->months[month_index % ce->month_count] - 1]) {
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month_index++;
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}
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}
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out->month = ce->months[month_index % ce->month_count];
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if (month_index >= ce->month_count) {
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out->year = ref->year + 1;
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} else {
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out->year = ref->year;
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}
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}
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void ce_next_from_now(cron_simple_time *out, cron_expression *ce) {
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time_t t = time(NULL);
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struct tm gm;
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gmtime_r(&t, &gm);
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cron_simple_time ref = {// tm_year contains years since 1900
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.year = 1900 + gm.tm_year,
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// tm_mon goes from 0 to 11
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.month = gm.tm_mon + 1,
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.day = gm.tm_mday,
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.hour = gm.tm_hour,
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.minute = gm.tm_min};
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ce_next(out, ce, &ref);
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}
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@ -0,0 +1,50 @@
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#ifndef VIETER_CRON
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#define VIETER_CRON
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#include <stdbool.h>
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#include <stdint.h>
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#include <stdlib.h>
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#include <string.h>
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#include <time.h>
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typedef enum cron_parse_error {
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cron_parse_ok = 0,
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cron_parse_invalid_expression = 1,
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cron_parse_invalid_number = 2,
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cron_parse_out_of_range = 3,
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cron_parse_too_many_parts = 4,
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cron_parse_not_enough_parts = 5
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} cron_parse_error;
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typedef struct cron_expression {
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uint8_t *minutes;
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uint8_t *hours;
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uint8_t *days;
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uint8_t *months;
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uint8_t minute_count;
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uint8_t hour_count;
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uint8_t day_count;
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uint8_t month_count;
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} cron_expression;
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typedef struct cron_simple_time {
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int year;
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int month;
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int day;
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int hour;
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int minute;
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} cron_simple_time;
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cron_expression *ce_init();
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void cron_ce_free(cron_expression *ce);
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void cron_ce_next(cron_simple_time *out, cron_expression *ce,
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cron_simple_time *ref);
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void cron_ce_next_from_now(cron_simple_time *out, cron_expression *ce);
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enum cron_parse_error cron_ce_parse_expression(cron_expression *out,
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const char *expression);
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#endif
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@ -0,0 +1,335 @@
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#include "expression.h"
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// This prefix is needed to properly compile
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const uint8_t parse_month_days[] = {31, 28, 31, 30, 31, 30,
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31, 31, 30, 31, 30, 31};
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// Allowed value ranges for the minute, hour, day and month field
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const uint8_t min[4] = {0, 0, 1, 1};
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const uint8_t max[4] = {59, 23, 31, 12};
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const uint8_t min_parts = 2;
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const uint8_t max_parts = 4;
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// Convert a string into a uint8_t value by parsing it using atoi and checking
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// whether it's contained within the given range
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#define SAFE_ATOI(v, s, min, max) \
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int _##v = atoi(s); \
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if ((_##v) == 0 && strcmp((s), "0") != 0) { \
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return cron_parse_invalid_number; \
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} \
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if (((_##v) < (min)) || ((_##v) > (max))) { \
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return cron_parse_out_of_range; \
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} \
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v = (uint8_t)(_##v);
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#define MAX(x, y) (((x) > (y)) ? (x) : (y))
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/**
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* Given a range expression, produce a bit field defining what numbers in the
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* min-max range the expression represents. Bit 0 (starting from the
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* right) corresponds to min, the bit max - min to max. All trailing bits
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* after this should be ignored. The given bitfield is modified in-place, so
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* multiple calls of this function can be performed on the same value to create
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* the effect of ORing their values.
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*
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* A range expression has one of the following forms:
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*
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* - *
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* - a
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* - a-b
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* - a/c
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* - a-b/c
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*/
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cron_parse_error ce_parse_range(uint64_t *out, char *s, uint8_t min,
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uint8_t max) {
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size_t slash_index = 0, dash_index = 0;
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size_t s_index = 0;
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char cur_char;
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bool is_valid_character;
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while ((cur_char = s[s_index]) != '\0') {
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is_valid_character = cur_char == '/' || cur_char == '-' ||
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cur_char == '*' ||
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(cur_char >= '0' && cur_char <= '9');
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if (!is_valid_character) {
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return cron_parse_invalid_expression;
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}
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if (cur_char == '/') {
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if (s_index == 0 || slash_index != 0) {
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return cron_parse_invalid_expression;
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}
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slash_index = s_index;
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s[s_index] = '\0';
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} else if (cur_char == '-') {
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// At most one dash is allowed, and it must be before the slash
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if (s_index == 0 || dash_index != 0 || slash_index != 0) {
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return cron_parse_invalid_expression;
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}
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dash_index = s_index;
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s[s_index] = '\0';
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}
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s_index++;
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}
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uint8_t start;
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uint8_t end = max;
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uint8_t interval = 0;
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if (s[0] == '*') {
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if (s[1] != '\0' || dash_index != 0) {
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return cron_parse_invalid_expression;
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}
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start = min;
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interval = 1;
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} else {
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SAFE_ATOI(start, s, min, max);
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if (dash_index > 0) {
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SAFE_ATOI(end, &s[dash_index + 1], min, max);
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interval = 1;
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}
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}
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if (slash_index > 0) {
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SAFE_ATOI(interval, &s[slash_index + 1], 1, max - min);
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}
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if (interval == 0) {
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*out |= ((uint64_t)1) << (start - min);
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} else {
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while (start <= end) {
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*out |= ((uint64_t)1) << (start - min);
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start += interval;
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}
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}
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return cron_parse_ok;
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}
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/*
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* Given an expression part, produce a bitfield defining what numbers in the
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* min-max range the part represents. A part consists of one or more range
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* expressions, separated by commas.
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*/
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cron_parse_error ce_parse_part(uint64_t *out, char *s, uint8_t min,
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uint8_t max) {
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*out = 0;
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char *next;
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cron_parse_error res;
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while ((next = strchr(s, ',')) != NULL) {
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next[0] = '\0';
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res = ce_parse_range(out, s, min, max);
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if (res != cron_parse_ok) {
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return res;
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}
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s = next + 1;
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}
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// Make sure to parse the final range as well
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return ce_parse_range(out, s, min, max);
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}
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/*
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* Return how many bits are set in the bitfield, better known as popcount. I
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* added my own implementation (taken from my algorithms course) as I don't want
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* to be dependent on GCC-specific extensions.
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*/
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uint8_t uint64_t_popcount(uint64_t n) {
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uint8_t set_bits = 0;
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while (n != 0) {
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// This sets the least significant bit to zero (very cool)
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n &= n - 1;
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set_bits++;
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}
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return set_bits;
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}
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/*
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* Convert a bitfield into an array containing the numbers in the min-max range
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* it represents.
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*/
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uint8_t bf_to_nums(uint8_t **out, uint64_t bf, uint8_t min, uint8_t max) {
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// Each bit field only has `max - min + 1` meaningful bits. All other bits
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// should be ignored, and can be any value. By shifting the bit field back
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// and forth, we set these excessive bits to zero, ensuring popcount returns
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// the correct value.
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uint8_t excess_bits = 64 - (max - min + 1);
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bf = (bf << excess_bits) >> excess_bits;
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uint8_t size = uint64_t_popcount(bf);
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uint8_t *buf = malloc(size * sizeof(uint8_t));
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uint8_t bit_index = 0, buf_index = 0;
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while (buf_index < size && bit_index <= max - min) {
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if (((uint64_t)1 << bit_index) & bf) {
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// Resize buffer if needed
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buf[buf_index] = min + bit_index;
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buf_index++;
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}
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bit_index++;
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}
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*out = buf;
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return size;
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}
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/*
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* Parse a cron expression string into a cron_expression struct.
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*/
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cron_parse_error ce_parse_expression(cron_expression *out,
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const char *expression) {
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// The parsing functions modify the input string in-place
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char *s = strdup(expression);
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char *orig_s = s;
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cron_parse_error res = cron_parse_ok;
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// First we divide the input string into its parts, divided by spaces.
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// Each part is delimited by a NULL byte.
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uint8_t part_count = 0;
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char *parts[max_parts];
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char *next_space;
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// Skip leading spaces
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size_t offset = 0;
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while (s[offset] == ' ') {
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offset++;
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}
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s += offset;
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while (part_count < max_parts && ((next_space = strchr(s, ' ')) != NULL)) {
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next_space[0] = '\0';
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parts[part_count] = s;
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part_count++;
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// Skip multiple spaces
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offset = 1;
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while (next_space[offset] == ' ') {
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offset++;
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}
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s = next_space + offset;
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}
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// Each iteration of the loop skips all trailing spaces. This means that, if
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// s[0] isn't '\0', there's still another part before the end of the string.
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if (s[0] != '\0') {
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if (part_count == max_parts) {
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res = cron_parse_too_many_parts;
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goto end;
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}
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parts[part_count] = s;
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part_count++;
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}
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if (part_count < min_parts) {
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res = cron_parse_not_enough_parts;
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goto end;
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}
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// We now parse the parts in reverse. This is because the month part
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// determines the maximum value of the day part.
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uint64_t bit_field = 0;
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// Months
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if (part_count >= 4) {
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res = ce_parse_part(&bit_field, parts[3], min[3], max[3]);
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if (res != cron_parse_ok) {
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goto end;
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}
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out->month_count = bf_to_nums(&out->months, bit_field, min[3], max[3]);
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}
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// If months aren't provided, they're replaced with a *
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else {
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out->month_count = bf_to_nums(&out->months, ~0, min[3], max[3]);
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}
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// Determine what the largest allowed day value is, given the months
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uint8_t max_day_value = 0;
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for (uint8_t i = 0; i < out->month_count; i++) {
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max_day_value =
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MAX(max_day_value, parse_month_days[out->months[i] - 1]);
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}
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// Days
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if (part_count >= 3) {
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bit_field = 0;
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res = ce_parse_part(&bit_field, parts[2], min[2], max_day_value);
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if (res != cron_parse_ok) {
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free(out->months);
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goto end;
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}
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out->day_count =
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bf_to_nums(&out->days, bit_field, min[2], max_day_value);
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}
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// If days aren't provided, they're replaced with a *
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else {
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out->day_count = bf_to_nums(&out->days, ~0, min[2], max_day_value);
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}
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// Hours
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bit_field = 0;
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res = ce_parse_part(&bit_field, parts[1], min[1], max[1]);
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if (res != cron_parse_ok) {
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free(out->months);
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free(out->days);
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goto end;
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}
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out->hour_count = bf_to_nums(&out->hours, bit_field, min[1], max[1]);
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// Minutes
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bit_field = 0;
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res = ce_parse_part(&bit_field, parts[0], min[0], max[0]);
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if (res != cron_parse_ok) {
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free(out->months);
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free(out->days);
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free(out->hours);
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goto end;
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}
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|
||||
out->minute_count = bf_to_nums(&out->minutes, bit_field, min[0], max[0]);
|
||||
|
||||
end:
|
||||
// s is cloned
|
||||
free(orig_s);
|
||||
|
||||
return res;
|
||||
}
|
||||
Loading…
Reference in New Issue