Steve Karg
fd3be47d86
* Added daylight savings time calculation module with unit testing. * Added datetime daylight savings time and clock API * Added basic datetime_local() clock using mstimer as basis and time-sync option. Integrated clock with ports/stm32f4xx example.
230 lines
7.6 KiB
C
230 lines
7.6 KiB
C
/**
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* @file
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* @brief computes whether day is during daylight savings time
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* @note Public domain algorithms from ACM
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* @author Steve Karg <skarg@users.sourceforge.net>
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* @date 1997
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* @copyright SPDX-License-Identifier: CC-PDDC
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*/
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#include <stdint.h>
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#include <stdbool.h>
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#include "days.h"
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#include "dst.h"
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/**
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* This function returns the number of seconds after midnight
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*
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* @param hours - hours after midnight (0..23)
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* @param minutes - minutes after hour (0..59)
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* @param seconds - holds seconds after minute (0..59)
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*
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* @return true if date-time falls in DST. false if not.
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*/
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static uint32_t
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time_to_seconds(uint32_t hours, uint32_t minutes, uint32_t seconds)
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{
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return (((hours) * 60 * 60) + ((minutes) * 60) + (seconds));
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}
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/**
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* This function returns the day of the month for starting the Nth week
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*
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* @param year - Year of our Lord A.D. (1900..9999)
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* @param month - months of the year (1=Jan,...,12=Dec)
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* @param ordinal - Ordinal Day of the Month
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* 1=1st, 2=2nd, 3=3rd, 4=4th, or 5=LAST
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* @return day of the month (1..31)
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*/
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static uint8_t
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ordinal_week_month_day(uint16_t year, uint8_t month, uint8_t ordinal)
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{
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uint8_t day = 0;
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if (ordinal == 5) {
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/* last week of the month */
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day = days_per_month(year, month) - 6;
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} else {
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if (ordinal) {
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ordinal--;
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day = 1 + (ordinal * 7);
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}
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}
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return day;
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}
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/**
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* This function returns true if the date-time is during DST
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*
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* @param year - Year of our Lord A.D. (2000,2001,..2099)
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* @param month - months of the year (1=Jan,...,12=Dec)
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* @param day - day of the month (1..31)
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* @param hour - hours after midnight (0..23)
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* @param minute - minutes after hour (0..59)
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* @param second - holds seconds after minute (0..59)
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*
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* @return true if date-time falls in DST. false if not.
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*/
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bool dst_active(
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struct daylight_savings_data *data,
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uint16_t year,
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uint8_t month,
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uint8_t day,
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uint8_t hour,
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uint8_t minute,
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uint8_t second)
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{
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bool active = false;
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uint8_t i = 0;
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uint32_t time_now = 0;
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uint32_t time_dst = 0;
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uint8_t day_of_week = 0;
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uint8_t days = 0;
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uint32_t days_begin = 0;
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uint32_t days_now = 0;
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uint32_t days_end = 0;
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if (data->Ordinal) {
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if ((month >= data->Begin_Month) && (month <= data->End_Month)) {
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if (month == data->Begin_Month) {
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days = days_per_month(year, month);
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i = ordinal_week_month_day(year, month, data->Begin_Week);
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for (; i <= days; i++) {
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day_of_week = days_of_week(
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data->Epoch_Day,
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days_since_epoch(data->Epoch_Year, year, month, i));
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if (day_of_week == data->Begin_Day) {
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if (day == i) {
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time_now = time_to_seconds(hour, minute, second);
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/* begins at 2 AM Standard Time */
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time_dst = time_to_seconds(2, 0, 0);
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if (time_now >= time_dst) {
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active = true;
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}
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} else if (day > i) {
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active = true;
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}
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break;
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}
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}
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} else if (month == data->End_Month) {
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days = days_per_month(year, month);
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i = ordinal_week_month_day(year, month, data->End_Week);
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for (; i <= days; i++) {
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day_of_week = days_of_week(
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data->Epoch_Day,
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days_since_epoch(data->Epoch_Year, year, month, i));
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if (day_of_week == data->End_Day) {
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if (day == i) {
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time_now = time_to_seconds(hour, minute, second);
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/* ends at 2 AM Daylight time,
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which is 1 AM Standard Time */
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time_dst = time_to_seconds(1, 0, 0);
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if (time_now < time_dst) {
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active = true;
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}
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} else if (day < i) {
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active = true;
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}
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break;
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}
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}
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} else {
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/* months between the beginning and end months */
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active = true;
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}
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}
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} else {
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days_now = days_since_epoch(data->Epoch_Year, year, month, day);
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days_begin = days_since_epoch(
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data->Epoch_Year, year, data->Begin_Month, data->Begin_Day);
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days_end = days_since_epoch(
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data->Epoch_Year, year, data->End_Month, data->End_Day);
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if ((days_now >= days_begin) && (days_now <= days_end)) {
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if (days_now == days_begin) {
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time_now = time_to_seconds(hour, minute, second);
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/* begins at 2 AM Standard Time */
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time_dst = time_to_seconds(2, 0, 0);
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if (time_now >= time_dst) {
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active = true;
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}
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} else if (days_now == days_end) {
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time_now = time_to_seconds(hour, minute, second);
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/* ends at 2 AM Daylight time,
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which is 1 AM Standard Time */
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time_dst = time_to_seconds(1, 0, 0);
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if (time_now < time_dst) {
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active = true;
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}
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} else {
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active = true;
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}
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}
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}
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return active;
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}
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/**
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* @brief This function sets the daylight savings time parameters
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* @param data - daylight savings time data
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* @param ordinal - true when ordinal day of month used, false if specific dates
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* @param begin_month - month DST begins 1=Jan,...,12=Dec
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* @param begin_day - day of the month DST begins
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* 1..31 for specific day, or day of week 1..7 for ordinal day
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* @param begin_which_day - which ordinal day of the month is used
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* 1=1st, 2=2nd, 3=3rd, 4=4th, or 5=LAST
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* @param end_month - month DST ends 1=Jan,...,12=Dec
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* @param end_day - day of the month DST ends
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* 1..31 for specific day, or day of week 1..7 for ordinal day
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* @param end_which_day - which ordinal day of the month is used
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* 1=1st, 2=2nd, 3=3rd, 4=4th, or 5=LAST
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* @param epoch_day - day of the week for the BACnet Epoch (1=Monday..7=Sunday)
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* @param epoch_year - year of the BACnet Epoch (1900..9999)
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*/
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void dst_init(
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struct daylight_savings_data *data,
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bool ordinal,
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uint8_t begin_month,
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uint8_t begin_day,
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uint8_t begin_which_day,
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uint8_t end_month,
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uint8_t end_day,
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uint8_t end_which_day,
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uint8_t epoch_day,
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uint16_t epoch_year)
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{
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if (data) {
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data->Ordinal = ordinal;
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data->Begin_Month = begin_month;
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data->Begin_Day = begin_day;
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data->Begin_Week = begin_which_day;
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data->End_Month = end_month;
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data->End_Day = end_day;
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data->End_Week = end_which_day;
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data->Epoch_Day = epoch_day;
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data->Epoch_Year = epoch_year;
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}
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}
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/**
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* Initializes the daylight savings time parameters to their defaults.
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*/
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void dst_init_defaults(struct daylight_savings_data *data)
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{
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if (data) {
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/* Starts: Second=2 Sunday=7 in March=3 */
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/* Ends: First=1 Sunday=7 in November=11 */
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data->Ordinal = true;
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data->Begin_Month = 3;
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data->Begin_Day = 7;
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data->Begin_Week = 2;
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data->End_Month = 11;
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data->End_Day = 7;
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data->End_Week = 1;
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/* BACnet Epoch */
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data->Epoch_Day = 1 /* Monday=1 */;
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data->Epoch_Year = 1900;
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}
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}
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