Implement some time.h functions

inc/time.h

@@ -1,15 +1,28 @@
 #pragma once
 
-#include <stdint.h>
+// 7.29.1 p.2: Macros
+
+#define __STDC_VERSION_TIME_H__ 202311L
 
 #if !defined(NULL)
     #define NULL ((void *)0)
 #endif
 
-#define TIME_UTC 1
-
 #define CLOCKS_PER_SEC  ((clock_t)1000000)
 
+#define TIME_UTC 1
+#define TIME_MONOTONIC 2
+#define TIME_ACTIVE 3
+#define TIME_THREAD_ACTIVE 4
+
+// 7.29.1 p.4: Types
+
+#if defined(_WIN32)
+    typedef unsigned long long size_t;
+#else
+    typedef unsigned long size_t;
+#endif
+
 typedef unsigned long long clock_t;
 typedef unsigned long long time_t;
 
@@ -36,28 +49,30 @@ typedef unsigned long long time_t;
     };
 #endif
 
-clock_t    clock       (void);
+// Basic timer functions
-time_t     time        (time_t *timer);
+clock_t clock(void);
-time_t     mktime      (struct tm *timeptr);
+time_t time(time_t *timer);
-double     difftime    (time_t time1, time_t time0);
+double difftime(time_t time1, time_t time0);
-int        timespec_get(struct timespec *ts, int base);
-char      *asctime     (const struct tm *timeptr);
-char      *ctime       (const time_t *timer);
-struct tm *gmtime      (const time_t *timer);
-struct tm *localtime   (const time_t *timer);
 
-size_t strftime(
+// Human-readable time functions
-    char *restrict s,
+time_t mktime(struct tm *timeptr);
-    size_t maxsize,
+struct tm *gmtime(const time_t *timer);
-    const char *restrict format,
+struct tm *localtime(const time_t *timer);
-    const struct tm *restrict timeptr
+
-);
+// Timespec functions
+int timespec_get(struct timespec *ts, int base);
+int timespec_getres(struct timespec *ts, int base);
+
+// Time formatting functions
+char *asctime(const struct tm *timeptr);
+char *ctime(const time_t *timer);
+size_t strftime(char *restrict str, size_t sz, const char *restrict fmt, const struct tm *restrict time);
 
 #ifdef __STDC_WANT_LIB_EXT1__
 
 errno_t asctime_s(char *s, rsize_t maxsize, const struct tm *timeptr);
-errno_t ctime_s  (char *s, rsize_t maxsize, const time_t *timer);
+errno_t ctime_s(char *s, rsize_t maxsize, const time_t *timer);
-struct tm *gmtime_s   (const time_t * restrict timer, struct tm * restrict result);
+struct tm *gmtime_s(const time_t * restrict timer, struct tm * restrict result);
 struct tm *localtime_s(const time_t * restrict timer, struct tm * restrict result);
 
 #endif

src/os_win/time.c

@@ -1,17 +1,18 @@
 
-#define TIME_TICKS_PER_SEC          1000
+#define NS_PER_SEC                  1000000000
-#define FILE_TICKS_PER_SEC          10000000
+#define NS_PER_MS                   1000000
-#define FILE_TICKS_UNTIL_UNIX_EPOCH 116444736000000000ULL
 
-#define NANOS_PER_SEC               1000000000
+#define TIME_TICKS_PER_SEC          1000000000ULL
-#define NANOS_PER_FILE_TICK         (NANOS_PER_SEC / FILE_TICKS_PER_SEC)
+#define NS_BEFORE_UNIX_EPOCH        11644473600000000000ULL
-#define NANOS_PER_TIME_TICK         (NANOS_PER_SEC / TIME_TICKS_PER_SEC)
 
+typedef struct tm tm_t;
 
 // Store the time since we started running the process
 static uint64_t timer_freq;
 static uint64_t timer_start;
 
+// Initialize timers
+
 static void _setup_timer(void) {
     LARGE_INTEGER freq, start;
     QueryPerformanceFrequency(&freq);
@@ -20,19 +21,63 @@ static void _setup_timer(void) {
     timer_freq  = freq.QuadPart;
 }
 
-static ULONGLONG win32_get_unix_nanos() {
+// Timestamp utilitity functions
-    FILETIME ft;
+
-    GetSystemTimeAsFileTime(&ft);
+static ULONGLONG _time_filetime_to_ns(FILETIME ft) {
     ULARGE_INTEGER ft64 = {
         .LowPart  = ft.dwLowDateTime,
         .HighPart = ft.dwHighDateTime,
     };
     ULONGLONG fticks = ft64.QuadPart;
-    ULONGLONG unix_fticks = fticks - FILE_TICKS_UNTIL_UNIX_EPOCH;
+    return fticks * 100;
-    ULONGLONG unix_nanos  = unix_fticks * NANOS_PER_FILE_TICK;
-    return unix_nanos;
 }
 
+static ULONGLONG _time_utc_ns() {
+    FILETIME ft;
+    GetSystemTimeAsFileTime(&ft);
+    ULONGLONG ns = _time_filetime_to_ns(ft);
+    ULONGLONG unix_ns = ns - NS_BEFORE_UNIX_EPOCH;
+    return unix_ns;
+}
+
+static ULONGLONG _time_mono_ns() {
+    ULONGLONG time_ms = GetTickCount64();
+    ULONGLONG time_ns = time_ms * NS_PER_MS;
+    return time_ns;
+}
+
+static ULONGLONG _time_process_ns() {
+    FILETIME _1;
+    FILETIME _2;
+    FILETIME ktime;
+    FILETIME utime;
+    HANDLE current_process = GetCurrentProcess();
+    if(GetProcessTimes(current_process, &_1, &_2, &ktime, &utime) == 0) {
+        abort();
+    }
+    ULONGLONG kernel_time = _time_filetime_to_ns(ktime);
+    ULONGLONG user_time = _time_filetime_to_ns(utime);
+    ULONGLONG cpu_time = kernel_time + user_time;
+    return cpu_time;
+}
+
+static ULONGLONG _time_thread_ns() {
+    FILETIME _1;
+    FILETIME _2;
+    FILETIME ktime;
+    FILETIME utime;
+    HANDLE current_thread = GetCurrentThread();
+    if(GetThreadTimes(current_thread, &_1, &_2, &ktime, &utime) == 0) {
+        abort();
+    }
+    ULONGLONG kernel_time = _time_filetime_to_ns(ktime);
+    ULONGLONG user_time = _time_filetime_to_ns(utime);
+    ULONGLONG cpu_time = kernel_time + user_time;
+    return cpu_time;
+}
+
+// Timer functions
+
 clock_t clock(void) {
     LARGE_INTEGER curr;
     if (!QueryPerformanceCounter(&curr)) {
@@ -42,14 +87,14 @@ clock_t clock(void) {
         return -1;
     }
     clock_t ticks = curr.QuadPart - timer_start;
-    // Basically millis / timer_freq * CLOCKS_PER_SEC but more precise
+    // Same as (ticks / timer_freq * CLOCKS_PER_SEC) but more precise
     return ticks / timer_freq * CLOCKS_PER_SEC
          + ticks % timer_freq * CLOCKS_PER_SEC / timer_freq;
 }
 
 time_t time(time_t *timer) {
-    ULONGLONG unix_nanos  = win32_get_unix_nanos();
+    ULONGLONG unix_nanos  = _time_mono_ns();
-    time_t    timer_ticks = unix_nanos / NANOS_PER_TIME_TICK;
+    time_t    timer_ticks = unix_nanos;
     if(timer != NULL) {
         *timer = timer_ticks;
     }
@@ -63,9 +108,290 @@ double difftime(time_t time1, time_t time0) {
 }
 
 int timespec_get(struct timespec *ts, int base) {
-    if (base != TIME_UTC) return 0;
+    ULONGLONG current_ns;
-    ULONGLONG unix_nanos = win32_get_unix_nanos();
+    switch(base) {
-    ts->tv_sec  = unix_nanos / NANOS_PER_SEC;
+        case TIME_UTC:           current_ns = _time_utc_ns(); break;
-    ts->tv_nsec = unix_nanos;
+        case TIME_MONOTONIC:     current_ns = _time_mono_ns(); break;
+        case TIME_ACTIVE:        current_ns = _time_process_ns(); break;
+        case TIME_THREAD_ACTIVE: current_ns = _time_thread_ns(); break;
+        default: return 0;
+    }
+    ts->tv_sec  = current_ns / NS_PER_SEC;
+    ts->tv_nsec = current_ns;
     return base;
 }
+
+int timespec_getres(struct timespec *ts, int base) {
+    switch(base) {
+        case TIME_UTC:           return NS_PER_SEC;
+        case TIME_MONOTONIC:     return NS_PER_SEC;
+        case TIME_ACTIVE:        return NS_PER_SEC;
+        case TIME_THREAD_ACTIVE: return NS_PER_SEC;
+        default: return 0;
+    }
+}
+
+// Human-readable time
+
+const int _days_in_month[12] = {
+    31,28, 31,30,31, 30,31,31, 30,31,30, 31
+};
+
+const int _month_days_since_year_start[12] = {
+    0,
+    31,
+    31+28,
+    31+28+31,
+    31+28+31+30,
+    31+28+31+30+31,
+    31+28+31+30+31+30,
+    31+28+31+30+31+30+31,
+    31+28+31+30+31+30+31+31,
+    31+28+31+30+31+30+31+31+30,
+    31+28+31+30+31+30+31+31+30+31,
+    31+28+31+30+31+30+31+31+30+31+30,
+};
+
+static bool _is_leap_year(int year) {
+    if(year % 400 == 0) {
+        return true;
+    }
+    if(year % 100 == 0) {
+        return false;
+    }
+    if(year % 4 == 0) {
+        return true;
+    }
+    return false;
+}
+
+static int _leap_years_before(int year) {
+    year--;
+    return (year / 4) - (year / 100) + (year / 400);
+}
+
+static int _leap_years_between(int start, int end) {
+    return _leap_years_before(end) - _leap_years_before(start + 1);
+}
+
+static int _whole_days_since_year_start(int year, int mon, int day) {
+    int days = _month_days_since_year_start[mon] + day;
+    if(mon > 1 || (mon == 1 && day > 27)) {
+        if(_is_leap_year(year)) {
+            days += 1;
+        }
+    }
+    return days;
+}
+
+static void _tm_adjust(tm_t *time) {
+    long long year = 1900 + time->tm_year;
+    long long mon = time->tm_mon;
+    long long day = time->tm_mday - 1;
+    long long hour = time->tm_hour;
+    long long min = time->tm_min;
+    long long sec = time->tm_sec;
+    // Adjust
+    if(sec < 0) {
+        min -= (-sec+59)/60;
+        sec = (sec%60 + 60) % 60;
+    }
+    else if(sec >= 60) {
+        min += sec / 60;
+        sec %= 60;
+    }
+    if(min < 0) {
+        hour -= (-min+59)/60;
+        min = (min%60 + 60) % 60;
+    }
+    else if(min >= 60) {
+        hour += min / 60;
+        min %= 60;
+    }
+    if(hour < 0) {
+        day -= (-hour+23)/24;
+        hour = (hour%24 + 24) % 24;
+    }
+    else if(hour >= 24) {
+        day += hour / 24;
+        hour %= 24;
+    }
+    if(mon < 0) {
+        year -= (-mon+11)/12;
+        mon = (mon%12+12)%12;
+    }
+    else if(mon >= 12) {
+        year += mon / 12;
+        mon %= 12;
+    }
+    if(day < 0) {
+        for(;;) {
+            int mon_prev = mon - 1;
+            int year_prev = year;
+            if(mon_prev == -1) {
+                mon_prev = 11;
+                year_prev -= 1;
+            }
+            int days_in_prev_month = _days_in_month[mon_prev];
+            if(mon_prev == 1 && _is_leap_year(year_prev)) {
+                days_in_prev_month += 1;
+            }
+            if(-day > days_in_prev_month) {
+                day += days_in_prev_month;
+                mon -= 1;
+                if(mon == -1) {
+                    mon = 11;
+                    year -= 1;
+                }
+            }
+            else {
+                break; // Can't subtract any whole months, exit the loop
+            }
+        }
+        if(day < 0) {
+            mon -= 1;
+            day = _days_in_month[mon] + day;
+            if(mon == -1) {
+                mon = 11;
+                year -= 1;
+            }
+        }
+    }
+    else {
+        for(;;) {
+            int days_in_month = _days_in_month[mon];
+            if(mon == 1 && _is_leap_year(year)) {
+                days_in_month += 1;
+            }
+            if(day < days_in_month) {
+                break;
+            }
+            day -= days_in_month;
+            mon += 1;
+        }
+    }
+    // Refill the struct with normalized time
+    time->tm_year = year - 1900;
+    time->tm_mon = mon;
+    time->tm_mday = day + 1;
+    time->tm_hour = hour;
+    time->tm_min = min;
+    time->tm_sec = sec;
+}
+
+time_t mktime(tm_t *time) {
+    // Get the human-readable time from the structure
+    _tm_adjust(time);
+    long long year = 1900 + time->tm_year;
+    long long mon = time->tm_mon;
+    long long day = time->tm_mday - 1;
+    long long hour = time->tm_hour;
+    long long min = time->tm_min;
+    long long sec = time->tm_sec;
+    if(year < 1970) {
+        return (time_t)(-1);
+    }
+    // Calculate unix timestamp
+    time_t timestamp;
+    timestamp = (year - 1970) * 365 + _leap_years_between(1970, year);
+    time_t days_since_year = _whole_days_since_year_start(year, mon, day);
+    timestamp = timestamp + days_since_year;
+    time_t days_since_epoch = timestamp;
+    timestamp = timestamp * 24 + hour;
+    timestamp = timestamp * 60 + min;
+    timestamp = timestamp * 60 + sec;
+    timestamp = timestamp * NS_PER_SEC;
+    // Refill the week day and year day
+    time->tm_wday = (days_since_epoch % 7 + 4) % 7; // 1970-01-01 is thursday (wday=4)
+    time->tm_yday = days_since_year;
+    time->tm_isdst = -1;
+    return timestamp;
+}
+
+// Breaking-down of the time
+
+tm_t *gmtime(const time_t *timer) {
+    tm_t *time = malloc(sizeof(tm_t));
+    time_t timestamp = *timer;
+    timestamp /= NS_PER_SEC;
+    time->tm_sec = timestamp % 60;
+    timestamp /= 60;
+    time->tm_min = timestamp % 60;
+    timestamp /= 60;
+    time->tm_hour = timestamp % 24;
+    timestamp /= 24;
+    int year = 1970;
+    int days = timestamp;
+    // Start subtracting 400,100,4-year-stretches
+    const int DAYS_IN_400_YEARS = 365 * 400 + 97;
+    const int DAYS_IN_100_YEARS = 365 * 100 + 24;
+    const int DAYS_IN_4_YEARS   = 365 * 4 + 1;
+    year += (days / DAYS_IN_400_YEARS) * 400;
+    days %= DAYS_IN_400_YEARS;
+    year += (days / DAYS_IN_100_YEARS) * 100;
+    days %= DAYS_IN_100_YEARS;
+    year += (days / DAYS_IN_4_YEARS) * 4;
+    days %= DAYS_IN_4_YEARS;
+    // Save
+    int days_since_epoch = days;
+    // Count remaining up-to 3 years in a loop
+    for(;;) {
+        int this_year_days = 365 + _is_leap_year(year);
+        if(days < this_year_days) {
+            break;
+        }
+        year += 1;
+        days -= this_year_days;
+    }
+    // Save
+    int days_since_year = days;
+    // Find the current month
+    int month = 0;
+    for(;;) {
+        int days_in_month = _days_in_month[month] + _is_leap_year(year);
+        if(days < days_in_month) {
+            break;
+        }
+        days -= days_in_month;
+        month += 1;
+    }
+    time->tm_year = year - 1900;
+    time->tm_mon = month;
+    time->tm_mday = days + 1;
+    time->tm_wday = (days_since_epoch % 7 + 4) % 7; // 1970-01-01 is thursday (wday=4)
+    time->tm_yday = days_since_year;
+    time->tm_isdst = -1;
+    return time;
+}
+
+static bool _offset_utc_time_to_local(tm_t *time) {
+    TIME_ZONE_INFORMATION tz;
+    if(GetTimeZoneInformation(&tz) == TIME_ZONE_ID_INVALID) {
+        return false;
+    }
+    int bias = tz.Bias;
+    time->tm_min -= bias;
+    _tm_adjust(time);
+    return true;
+}
+
+tm_t *localtime(const time_t *timer) {
+    tm_t *utc_time = gmtime(timer);
+    if(!_offset_utc_time_to_local(utc_time)) {
+        return NULL;
+    }
+    return utc_time;
+}
+
+// String formatting
+
+char *asctime(const tm_t *timeptr) {
+    return NULL;
+}
+char *ctime(const time_t *timer) {
+    return NULL;
+}
+
+size_t strftime(char *restrict s, size_t size, const char *restrict fmt, const tm_t *restrict time) {
+    return 0;
+}

test/test_time.c

@@ -1,10 +1,26 @@
-
-#include <time.h>
 #include <stdio.h>
+#include <time.h>
+static const char *const wday[] = {
+    "Sunday", "Monday", "Tuesday", "Wednesday",
+    "Thursday", "Friday", "Saturday", "-unknown-"
+};
 
 int main() {
-    time_t t1 = time(NULL);
+    // July 4, 2001: Wednesday
-    time_t t2 = time(NULL);
+    struct tm time_str;
-    double s = difftime(t2, t1);
+    time_str.tm_year = 2001 - 1900;
+    time_str.tm_mon = 7 - 1;
+    time_str.tm_mday = 4;
+    time_str.tm_hour = 0;
+    time_str.tm_min = 0;
+    time_str.tm_sec = 1;
+    time_str.tm_isdst = -1;
+    time_t timestamp;
+    if((timestamp = mktime(&time_str)) == (time_t)(-1)) {
+        time_str.tm_wday = 7;
+    }
+    char const *day_of_week = wday[time_str.tm_wday];
+    struct tm *gmt = gmtime(&timestamp);
+    struct tm *local = localtime(&timestamp);
     return 0;
 }