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Add time and realtime clock functions

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Adds functions to query the system's realtime clock, convert time intervals to/from a calendar date and time in either UTC or the local time, and perform time related calculations.

An SDL_Time type (a time interval represented in nanoseconds), and SDL_DateTime struct (broken down calendar date and time) were added to facilitate this functionality.

Querying the system time results in a value expressed in nanoseconds since the Unix epoch (Jan 1, 1970) in UTC +0000. Conversions to and from the various platform epochs and units are performed when required.

Any direct handling of timezones and DST were intentionally avoided. The offset from UTC is provided when converting from UTC to a local time by calculating the difference between the original UTC and the resulting local time, but no other timezone or DST information is used.

The preferred date formatting and 12/24 hour time for the system locale can be retrieved via global preferences.

Helper functions for obtaining the day of week or day or year for calendar date, and getting the number of days in a month in a given year are provided for convenience. These are simple, but useful for performing various time related calculations.

An automated test for time conversion is included, as is a simple standalone test to display the current system date and time onscreen along with a calendar, the rendering of which demonstrates the use of the utility functions (press up/down to increment or decrement the current month, and keys 1-5 to change the date and time formats).
This commit is contained in:
Frank Praznik 2024-02-29 13:06:26 -05:00 • committed by Sam Lantinga
parent b6c9a72740
commit a6fbf0488c
41 changed files with 1862 additions and 78 deletions
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193
src/time/unix/SDL_systime.c Normal file
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/*
Simple DirectMedia Layer
Copyright (C) 1997-2024 Sam Lantinga <slouken@libsdl.org>
This software is provided 'as-is', without any express or implied
warranty. In no event will the authors be held liable for any damages
arising from the use of this software.
Permission is granted to anyone to use this software for any purpose,
including commercial applications, and to alter it and redistribute it
freely, subject to the following restrictions:
1. The origin of this software must not be misrepresented; you must not
claim that you wrote the original software. If you use this software
in a product, an acknowledgment in the product documentation would be
appreciated but is not required.
2. Altered source versions must be plainly marked as such, and must not be
misrepresented as being the original software.
3. This notice may not be removed or altered from any source distribution.
*/
#include "SDL_internal.h"
#ifdef SDL_TIME_UNIX
#include "../SDL_time_c.h"
#include <errno.h>
#include <langinfo.h>
#include <sys/time.h>
#include <time.h>
#if !defined(HAVE_CLOCK_GETTIME) && defined(SDL_PLATFORM_APPLE)
#include <mach/clock.h>
#include <mach/mach.h>
#include <mach/mach_time.h>
#endif
void SDL_GetSystemTimeLocalePreferences(SDL_DATE_FORMAT *df, SDL_TIME_FORMAT *tf)
{
/* This *should* be well-supported aside from very old legacy systems, but apparently
* Android didn't add this until SDK version 26, so a check is needed...
*/
#ifdef HAVE_NL_LANGINFO
const char *s = nl_langinfo(D_FMT);
/* Figure out the preferred system date format from the first format character. */
if (s) {
while (*s) {
switch (*s++) {
case 'Y':
case 'y':
case 'F':
case 'C':
*df = SDL_DATE_FORMAT_YYYYMMDD;
goto found_date;
case 'd':
case 'e':
*df = SDL_DATE_FORMAT_DDMMYYYY;
goto found_date;
case 'b':
case 'D':
case 'h':
case 'm':
*df = SDL_DATE_FORMAT_MMDDYYYY;
goto found_date;
default:
break;
}
}
}
found_date:
s = nl_langinfo(T_FMT);
/* Figure out the preferred system date format. */
if (s) {
while (*s) {
switch (*s++) {
case 'H':
case 'k':
case 'T':
*tf = SDL_TIME_FORMAT_24HR;
return;
case 'I':
case 'l':
case 'r':
*tf = SDL_TIME_FORMAT_12HR;
return;
default:
break;
}
}
}
#endif
}
int SDL_GetCurrentTime(SDL_Time *ticks)
{
if (!ticks) {
return SDL_InvalidParamError("ticks");
}
#ifdef HAVE_CLOCK_GETTIME
struct timespec tp;
if (clock_gettime(CLOCK_REALTIME, &tp) == 0) {
tp.tv_sec = SDL_min(tp.tv_sec, SDL_NS_TO_SECONDS(SDL_MAX_TIME) - 1);
*ticks = SDL_SECONDS_TO_NS(tp.tv_sec) + tp.tv_nsec;
return 0;
}
SDL_SetError("Failed to retrieve system time (%i)", errno);
#elif defined(SDL_PLATFORM_APPLE)
clock_serv_t cclock;
int ret = host_get_clock_service(mach_host_self(), CALENDAR_CLOCK, &cclock);
if (ret == 0) {
mach_timespec_t mts;
SDL_zero(mts);
ret = clock_get_time(cclock, &mts);
if (ret == 0) {
/* mach_timespec_t tv_sec is 32-bit, so no overflow possible */
*ticks = SDL_SECONDS_TO_NS(mts.tv_sec) + mts.tv_nsec;
}
mach_port_deallocate(mach_task_self(), cclock);
if (!ret) {
return 0;
}
}
SDL_SetError("Failed to retrieve system time (%i)", ret);
#else
struct timeval tv;
SDL_zero(tv);
if (gettimeofday(&tv, NULL) == 0) {
tv.tv_sec = SDL_min(tv.tv_sec, SDL_NS_TO_SECONDS(SDL_MAX_TIME) - 1);
*ticks = SDL_SECONDS_TO_NS(tv.tv_sec) + SDL_US_TO_NS(tv.tv_usec);
return 0;
}
SDL_SetError("Failed to retrieve system time (%i)", errno);
#endif
return -1;
}
int SDL_TimeToDateTime(SDL_Time ticks, SDL_DateTime *dt, SDL_bool localTime)
{
#if defined (HAVE_GMTIME_R) || defined(HAVE_LOCALTIME_R)
struct tm tm_storage;
#endif
struct tm *tm = NULL;
if (!dt) {
return SDL_InvalidParamError("dt");
}
const time_t tval = (time_t)SDL_NS_TO_SECONDS(ticks);
if (localTime) {
#ifdef HAVE_LOCALTIME_R
tm = localtime_r(&tval, &tm_storage);
#else
tm = localtime(&tval);
#endif
} else {
#ifdef HAVE_GMTIME_R
tm = gmtime_r(&tval, &tm_storage);
#else
tm = gmtime(&tval);
#endif
}
if (tm) {
dt->year = tm->tm_year + 1900;
dt->month = tm->tm_mon + 1;
dt->day = tm->tm_mday;
dt->hour = tm->tm_hour;
dt->minute = tm->tm_min;
dt->second = tm->tm_sec;
dt->nanosecond = ticks % SDL_NS_PER_SECOND;
dt->day_of_week = tm->tm_wday;
dt->utc_offset = tm->tm_gmtoff;
return 0;
}
return SDL_SetError("SDL_DateTime conversion failed (%i)", errno);
}
#endif /* SDL_TIME_UNIX */