libc/include/time.h - android_bionic - Gitiles

 /*
  * Copyright (C) 2008 The Android Open Source Project
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *  * Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  *  * Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in
  *    the documentation and/or other materials provided with the
  *    distribution.
  *
  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
  * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
  * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  */

 #pragma once

 /**
  * @file time.h
  * @brief Clock and timer functionality.
  */

 #include <sys/cdefs.h>
 #include <sys/time.h>
 #include <xlocale.h>

 __BEGIN_DECLS

 /* If we just use void* in the typedef, the compiler exposes that in error messages. */
 struct __timezone_t;

 /**
  * The `timezone_t` type that represents a timezone.
  *
  * To use this with std::unique_ptr you'll want something like
  * `std::unique_ptr<std::remove_pointer_t<timezone_t>, decltype(&tzfree)> tz{tzalloc("Asia/Seoul"), tzfree};`
  * to remove the pointer.
  */
 typedef struct __timezone_t* timezone_t;

 /** Divisor to compute seconds from the result of a call to clock(). */
 #define CLOCKS_PER_SEC 1000000

 /**
  * The name of the current timezone's non-daylight savings (`tzname[0]`) and
  * daylight savings (`tzname[1]`) variants. See tzset().
  */
 extern char* _Nonnull tzname[];

 /** Whether the current timezone ever uses daylight savings time. See tzset(). */
 extern int daylight;

 /** The difference in seconds between UTC and the current timezone. See tzset(). */
 extern long int timezone;

 struct sigevent;

 /**
  * A "broken-down" time, useful for parsing/formatting times for human consumption.
  */
 struct tm {
   /** Seconds, 0-60. (60 is a leap second.) */
   int tm_sec;
   /** Minutes, 0-59. */
   int tm_min;
   /** Hours, 0-23. */
   int tm_hour;
   /** Day of month, 1-31. */
   int tm_mday;
   /** Month of year, 0-11. (Not 1-12!) */
   int tm_mon;
   /** Years since 1900. (So 2023 is 123, not 2023!) */
   int tm_year;
   /** Day of week, 0-6. (Sunday is 0, Saturday is 6.) */
   int tm_wday;
   /** Day of year, 0-365. */
   int tm_yday;
   /** Daylight savings flag, positive for DST in effect, 0 for DST not in effect, and -1 for unknown. */
   int tm_isdst;
   /** Offset from UTC (GMT) in seconds for this time. */
   long int tm_gmtoff;
   /** Name of the timezone for this time. */
   const char* _Nullable tm_zone;
 };

 /** Alternative name for `tm_zone` in `struct tm`. */
 #define TM_ZONE tm_zone

 /**
  * [time(2)](https://man7.org/linux/man-pages/man2/time.2.html) returns
  * the number of seconds since the Unix epoch (1970-01-01 00:00:00 +0000).
  *
  * Returns the time in seconds on success, and returns -1 and sets `errno` on failure.
  */
 time_t time(time_t* _Nullable __t);

 /**
  * [nanosleep(2)](https://man7.org/linux/man-pages/man2/nanosleep.2.html) sleeps
  * for at least the given time (or until a signal arrives).
  *
  * Returns 0 on success, and returns -1 and sets `errno` on failure. If the sleep
  * was interrupted by a signal, `errno` will be `EINTR` and `remainder` will be
  * the amount of time remaining.
  */
 int nanosleep(const struct timespec* _Nonnull __duration, struct timespec* _Nullable __remainder);

 /**
  * [asctime(3)](https://man7.org/linux/man-pages/man3/asctime.3p.html) formats
  * the time `tm` as a string.
  *
  * Returns a pointer to a string on success, and returns NULL on failure.
  *
  * That string will be overwritten by later calls to this function.
  *
  * New code should prefer strftime().
  */
 char* _Nullable asctime(const struct tm* _Nonnull __tm);

 /**
  * [asctime_r(3)](https://man7.org/linux/man-pages/man3/asctime_r.3p.html) formats
  * the time `tm` as a string in the given buffer `buf`.
  *
  * Returns a pointer to a string on success, and returns NULL on failure.
  *
  * New code should prefer strftime().
  */
 char* _Nullable asctime_r(const struct tm* _Nonnull __tm, char* _Nonnull __buf);

 /**
  * [difftime(3)](https://man7.org/linux/man-pages/man3/difftime.3.html) returns
  * the difference between two times.
  *
  * Returns the difference in seconds.
  */
 double difftime(time_t __lhs, time_t __rhs);

 /**
  * [mktime(3)](https://man7.org/linux/man-pages/man3/mktime.3p.html) converts
  * broken-down time `tm` into the number of seconds since the Unix epoch.
  *
  * See tzset() for details of how the timezone is set, and mktime_rz()
  * for an alternative.
  *
  * Returns the time in seconds on success, and returns -1 and sets `errno` on failure.
  */
 time_t mktime(struct tm* _Nonnull __tm);

 /**
  * mktime_z(3) converts broken-down time `tm` into the number of seconds
  * since the Unix epoch, assuming the given timezone.
  *
  * Returns the time in seconds on success, and returns -1 and sets `errno` on failure.
  *
  * Available since API level 35.
  */
 time_t mktime_z(timezone_t _Nonnull __tz, struct tm* _Nonnull __tm) __INTRODUCED_IN(35);

 /**
  * [localtime(3)](https://man7.org/linux/man-pages/man3/localtime.3p.html) converts
  * the number of seconds since the Unix epoch in `t` to a broken-down time, taking
  * the device's timezone into account.
  *
  * That broken-down time will be overwritten by later calls to this function.
  *
  * Returns a pointer to a broken-down time on success, and returns null and sets `errno` on failure.
  */
 struct tm* _Nullable localtime(const time_t* _Nonnull __t);

 /**
  * [localtime_r(3)](https://man7.org/linux/man-pages/man3/localtime_r.3p.html) converts
  * the number of seconds since the Unix epoch in `t` to a broken-down time.
  * That broken-down time will be written to the given struct `tm`.
  *
  * See tzset() for details of how the timezone is set, and localtime_rz()
  * for an alternative.
  *
  * Returns a pointer to a broken-down time on success, and returns null and sets `errno` on failure.
  */
 struct tm* _Nullable localtime_r(const time_t* _Nonnull __t, struct tm* _Nonnull __tm);

 /**
  * localtime_rz(3) converts the number of seconds since the Unix epoch in
  * `t` to a broken-down time, assuming the given timezone. That broken-down
  * time will be written to the given struct `tm`.
  *
  * Returns a pointer to a broken-down time on success, and returns null and sets `errno` on failure.
  *
  * Available since API level 35.
  */
 struct tm* _Nullable localtime_rz(timezone_t _Nonnull __tz, const time_t* _Nonnull __t, struct tm* _Nonnull __tm) __INTRODUCED_IN(35);

 /**
  * Inverse of localtime().
  */
 time_t timelocal(struct tm* _Nonnull __tm);

 /**
  * [gmtime(3)](https://man7.org/linux/man-pages/man3/gmtime.3p.html) converts
  * the number of seconds since the Unix epoch in `t` to a broken-down time, using
  * UTC (historically also known as GMT).
  *
  * That broken-down time will be overwritten by later calls to this function.
  *
  * Returns a pointer to a broken-down time on success, and returns null and sets `errno` on failure.
  */
 struct tm* _Nullable gmtime(const time_t* _Nonnull __t);

 /**
  * [gmtime_r(3)](https://man7.org/linux/man-pages/man3/gmtime_r.3p.html) converts
  * the number of seconds since the Unix epoch in `t` to a broken-down time, using
  * UTC (historically also known as GMT).
  *
  * That broken-down time will be written to the provided struct `tm`.
  *
  * Returns a pointer to a broken-down time on success, and returns null and sets `errno` on failure.
  */
 struct tm* _Nullable gmtime_r(const time_t* _Nonnull __t, struct tm* _Nonnull __tm);

 /**
  * Inverse of gmtime().
  */
 time_t timegm(struct tm* _Nonnull __tm);

 /**
  * [strptime(3)](https://man7.org/linux/man-pages/man3/strptime.3.html) parses
  * a string `s` assuming format `fmt` into broken-down time `tm`.
  *
  * Returns a pointer to the first character _not_ parsed, or null if no characters were parsed.
  */
 char* _Nullable strptime(const char* _Nonnull __s, const char* _Nonnull __fmt, struct tm* _Nonnull __tm) __strftimelike(2);

 /**
  * Equivalent to strptime() on Android where only C/POSIX locales are available.
  */
 char* _Nullable strptime_l(const char* _Nonnull __s, const char* _Nonnull __fmt, struct tm* _Nonnull __tm, locale_t _Nonnull __l) __strftimelike(2) __INTRODUCED_IN(28);

 /**
  * [strftime(3)](https://man7.org/linux/man-pages/man3/strftime.3.html) formats
  * a broken-down time `tm` into the buffer `buf` using format `fmt`.
  *
  * Returns a pointer to the first character _not_ parsed, or null if no characters were parsed.
  */
 size_t strftime(char* _Nonnull __buf, size_t __n, const char* _Nonnull __fmt, const struct tm* _Nullable __tm) __strftimelike(3);

 /**
  * Equivalent to strftime() on Android where only C/POSIX locales are available.
  */
 size_t strftime_l(char* _Nonnull __buf, size_t __n, const char* _Nonnull __fmt, const struct tm* _Nullable __tm, locale_t _Nonnull __l) __strftimelike(3);

 /**
  * [ctime(3)](https://man7.org/linux/man-pages/man3/ctime.3p.html) formats
  * the time `tm` as a string.
  *
  * Returns a pointer to a string on success, and returns NULL on failure.
  *
  * That string will be overwritten by later calls to this function.
  *
  * New code should prefer strftime().
  */
 char* _Nullable ctime(const time_t* _Nonnull __t);

 /**
  * [ctime_r(3)](https://man7.org/linux/man-pages/man3/ctime.3p.html) formats
  * the time `tm` as a string in the given buffer `buf`.
  *
  * Returns a pointer to a string on success, and returns NULL on failure.
  *
  * New code should prefer strftime().
  */
 char* _Nullable ctime_r(const time_t* _Nonnull __t, char* _Nonnull __buf);

 /**
  * [tzset(3)](https://man7.org/linux/man-pages/man3/tzset.3.html) tells
  * libc that the timezone has changed.
  *
  * tzset() on Android looks at both the system property
  * `persist.sys.timezone` and the environment variable `TZ`. The former is
  * the device's current timezone as shown in Settings, while the latter is
  * usually unset but can be used to override the global setting. This is a
  * bad idea outside of unit tests or single-threaded programs because it's
  * inherently thread-unsafe. See tzalloc(), localtime_rz(), mktime_z(),
  * and tzfree() for an alternative.
  */
 void tzset(void);

 /**
  * tzalloc(3) allocates a timezone corresponding to the given Olson ID.
  *
  * A null `id` returns the system timezone (as seen in Settings) from
  * the system property `persist.sys.timezone`, ignoring `$TZ`. Although
  * tzset() honors `$TZ`, callers of tzalloc() can use `$TZ` themselves if
  * that's the (thread-unsafe) behavior they want, but by ignoring `$TZ`
  * tzalloc() is thread safe (though obviously the system timezone can
  * change, especially if your mobile device is actually mobile!).
  *
  * To use this with std::unique_ptr you'll want something like
  * `std::unique_ptr<std::remove_pointer_t<timezone_t>, decltype(&tzfree)> tz{tzalloc("Asia/Seoul"), tzfree};`
  * to remove the pointer.
  *
  * Returns a timezone object on success, and returns NULL and sets `errno` on failure.
  *
  * Available since API level 35.
  */
 timezone_t _Nullable tzalloc(const char* _Nullable __id) __INTRODUCED_IN(35);

 /**
  * tzfree(3) frees a timezone object returned by tzalloc().
  *
  * To use this with std::unique_ptr you'll want something like
  * `std::unique_ptr<std::remove_pointer_t<timezone_t>, decltype(&tzfree)> tz{tzalloc("Asia/Seoul"), tzfree};`
  * to remove the pointer.
  *
  * Available since API level 35.
  */
 void tzfree(timezone_t _Nullable __tz) __INTRODUCED_IN(35);

 /**
  * [clock(3)](https://man7.org/linux/man-pages/man3/clock.3.html)
  * returns an approximation of CPU time used, equivalent to
  * `clock_gettime(CLOCK_PROCESS_CPUTIME_ID)` but with more confusing
  * units. Use `CLOCKS_PER_SEC` to convert the result to seconds.
  *
  * Returns the time in seconds on success, and returns -1 and sets `errno` on failure.
  *
  * New code should prefer `clock_gettime(CLOCK_PROCESS_CPUTIME_ID)`.
  */
 clock_t clock(void);

 /**
  * [clock_getcpuclockid(3)](https://man7.org/linux/man-pages/man3/clock_getcpuclockid.3.html)
  * gets the clock ID of the cpu-time clock for the given `pid`.
  *
  * Returns 0 on success, and returns -1 and returns an error number on failure.
  */
 int clock_getcpuclockid(pid_t __pid, clockid_t* _Nonnull __clock) __INTRODUCED_IN(23);

 /**
  * [clock_getres(2)](https://man7.org/linux/man-pages/man2/clock_getres.2.html)
  * gets the resolution of the given clock.
  *
  * Returns 0 on success, and returns -1 and returns an error number on failure.
  */
 int clock_getres(clockid_t __clock, struct timespec* _Nullable __resolution);

 /**
  * [clock_gettime(2)](https://man7.org/linux/man-pages/man2/clock_gettime.2.html)
  * gets the time according to the given clock.
  *
  * Returns 0 on success, and returns -1 and returns an error number on failure.
  */
 int clock_gettime(clockid_t __clock, struct timespec* _Nonnull __ts);

 /**
  * [clock_nanosleep(2)](https://man7.org/linux/man-pages/man2/clock_nanosleep.2.html)
  * sleeps for the given time (or until the given time if the TIMER_ABSTIME flag
  * is used), as measured by the given clock.
  *
  * Returns 0 on success, and returns -1 and returns an error number on failure.
  * If the sleep was interrupted by a signal, the return value will be `EINTR`
  * and `remainder` will be the amount of time remaining.
  */
 int clock_nanosleep(clockid_t __clock, int __flags, const struct timespec* _Nonnull __time, struct timespec* _Nullable __remainder);

 /**
  * [clock_settime(2)](https://man7.org/linux/man-pages/man2/clock_settime.2.html)
  * sets the time for the given clock.
  *
  * Returns 0 on success, and returns -1 and returns an error number on failure.
  */
 int clock_settime(clockid_t __clock, const struct timespec* _Nonnull __ts);

 /**
  * [timer_create(2)](https://man7.org/linux/man-pages/man2/timer_create.2.html)
  * creates a POSIX timer.
  *
  * Returns 0 on success, and returns -1 and sets `errno` on failure.
  */
 int timer_create(clockid_t __clock, struct sigevent* _Nullable __event, timer_t _Nonnull * _Nonnull __timer_ptr);

 /**
  * [timer_delete(2)](https://man7.org/linux/man-pages/man2/timer_delete.2.html)
  * destroys a POSIX timer.
  *
  * Returns 0 on success, and returns -1 and sets `errno` on failure.
  */
 int timer_delete(timer_t _Nonnull __timer);

 /**
  * [timer_settime(2)](https://man7.org/linux/man-pages/man2/timer_settime.2.html)
  * starts or stops a POSIX timer.
  *
  * Returns 0 on success, and returns -1 and sets `errno` on failure.
  */
 int timer_settime(timer_t _Nonnull __timer, int __flags, const struct itimerspec* _Nonnull __new_value, struct itimerspec* _Nullable __old_value);

 /**
  * [timer_gettime(2)](https://man7.org/linux/man-pages/man2/timer_gettime.2.html)
  * gets the time until the given timer next fires.
  *
  * Returns 0 on success, and returns -1 and sets `errno` on failure.
  */
 int timer_gettime(timer_t _Nonnull _timer, struct itimerspec* _Nonnull __ts);

 /**
  * [timer_getoverrun(2)](https://man7.org/linux/man-pages/man2/timer_getoverrun.2.html)
  * gets the overrun count (the number of times the timer should have fired, but
  * didn't) for the last time the timer fired.
  *
  * Returns the overrun count on success, and returns -1 and sets `errno` on failure.
  */
 int timer_getoverrun(timer_t _Nonnull __timer);

 /**
  * The timebase for timespec_get() and timespec_getres() corresponding to CLOCK_REALTIME.
  *
  * Available since API level 29.
  */
 #define TIME_UTC (CLOCK_REALTIME+1)

 /**
  * The timebase for timespec_get() and timespec_getres() corresponding to CLOCK_MONOTONIC.
  *
  * Available since API level 35.
  */
 #define TIME_MONOTONIC (CLOCK_MONOTONIC+1)

 /**
  * The timebase for timespec_get() and timespec_getres() corresponding to CLOCK_PROCESS_CPUTIME_ID.
  *
  * Available since API level 35.
  */
 #define TIME_ACTIVE (CLOCK_PROCESS_CPUTIME_ID+1)

 /**
  * The timebase for timespec_get() and timespec_getres() corresponding to CLOCK_THREAD_CPUTIME_ID.
  *
  * Available since API level 35.
  */
 #define TIME_THREAD_ACTIVE (CLOCK_THREAD_CPUTIME_ID+1)

 /**
  * timespec_get(3) is equivalent to clock_gettime() for the clock corresponding to the given base.
  *
  * Returns the base on success and returns 0 on failure.
  *
  * Available since API level 29 for TIME_UTC; other bases arrived later.
  * Code for Android should prefer clock_gettime().
  */
 int timespec_get(struct timespec* _Nonnull __ts, int __base) __INTRODUCED_IN(29);

 /**
  * timespec_getres(3) is equivalent to clock_getres() for the clock corresponding to the given base.
  *
  * Returns the base on success and returns 0 on failure.
  *
  * Available since API level 35.
  * Code for Android should prefer clock_gettime().
  */
 int timespec_getres(struct timespec* _Nonnull __ts, int __base) __INTRODUCED_IN(35);

 __END_DECLS
	/*
	* Copyright (C) 2008 The Android Open Source Project
	* All rights reserved.
	*
	* Redistribution and use in source and binary forms, with or without
	* modification, are permitted provided that the following conditions
	* are met:
	* * Redistributions of source code must retain the above copyright
	* notice, this list of conditions and the following disclaimer.
	* * Redistributions in binary form must reproduce the above copyright
	* notice, this list of conditions and the following disclaimer in
	* the documentation and/or other materials provided with the
	* distribution.
	*
	* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
	* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
	* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
	* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
	* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
	* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
	* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
	* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
	* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
	* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
	* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
	* SUCH DAMAGE.
	*/

	#pragma once

	/**
	* @file time.h
	* @brief Clock and timer functionality.
	*/

	#include <sys/cdefs.h>
	#include <sys/time.h>
	#include <xlocale.h>

	__BEGIN_DECLS

	/* If we just use void* in the typedef, the compiler exposes that in error messages. */
	struct __timezone_t;

	/**
	* The `timezone_t` type that represents a timezone.
	*
	* To use this with std::unique_ptr you'll want something like
	* `std::unique_ptr<std::remove_pointer_t<timezone_t>, decltype(&tzfree)> tz{tzalloc("Asia/Seoul"), tzfree};`
	* to remove the pointer.
	*/
	typedef struct __timezone_t* timezone_t;

	/** Divisor to compute seconds from the result of a call to clock(). */
	#define CLOCKS_PER_SEC 1000000

	/**
	* The name of the current timezone's non-daylight savings (`tzname[0]`) and
	* daylight savings (`tzname[1]`) variants. See tzset().
	*/
	extern char* _Nonnull tzname[];

	/** Whether the current timezone ever uses daylight savings time. See tzset(). */
	extern int daylight;

	/** The difference in seconds between UTC and the current timezone. See tzset(). */
	extern long int timezone;

	struct sigevent;

	/**
	* A "broken-down" time, useful for parsing/formatting times for human consumption.
	*/
	struct tm {
	/** Seconds, 0-60. (60 is a leap second.) */
	int tm_sec;
	/** Minutes, 0-59. */
	int tm_min;
	/** Hours, 0-23. */
	int tm_hour;
	/** Day of month, 1-31. */
	int tm_mday;
	/** Month of year, 0-11. (Not 1-12!) */
	int tm_mon;
	/** Years since 1900. (So 2023 is 123, not 2023!) */
	int tm_year;
	/** Day of week, 0-6. (Sunday is 0, Saturday is 6.) */
	int tm_wday;
	/** Day of year, 0-365. */
	int tm_yday;
	/** Daylight savings flag, positive for DST in effect, 0 for DST not in effect, and -1 for unknown. */
	int tm_isdst;
	/** Offset from UTC (GMT) in seconds for this time. */
	long int tm_gmtoff;
	/** Name of the timezone for this time. */
	const char* _Nullable tm_zone;
	};

	/** Alternative name for `tm_zone` in `struct tm`. */
	#define TM_ZONE tm_zone

	/**
	* [time(2)](https://man7.org/linux/man-pages/man2/time.2.html) returns
	* the number of seconds since the Unix epoch (1970-01-01 00:00:00 +0000).
	*
	* Returns the time in seconds on success, and returns -1 and sets `errno` on failure.
	*/
	time_t time(time_t* _Nullable __t);

	/**
	* [nanosleep(2)](https://man7.org/linux/man-pages/man2/nanosleep.2.html) sleeps
	* for at least the given time (or until a signal arrives).
	*
	* Returns 0 on success, and returns -1 and sets `errno` on failure. If the sleep
	* was interrupted by a signal, `errno` will be `EINTR` and `remainder` will be
	* the amount of time remaining.
	*/
	int nanosleep(const struct timespec* _Nonnull __duration, struct timespec* _Nullable __remainder);

	/**
	* [asctime(3)](https://man7.org/linux/man-pages/man3/asctime.3p.html) formats
	* the time `tm` as a string.
	*
	* Returns a pointer to a string on success, and returns NULL on failure.
	*
	* That string will be overwritten by later calls to this function.
	*
	* New code should prefer strftime().
	*/
	char* _Nullable asctime(const struct tm* _Nonnull __tm);

	/**
	* [asctime_r(3)](https://man7.org/linux/man-pages/man3/asctime_r.3p.html) formats
	* the time `tm` as a string in the given buffer `buf`.
	*
	* Returns a pointer to a string on success, and returns NULL on failure.
	*
	* New code should prefer strftime().
	*/
	char* _Nullable asctime_r(const struct tm* _Nonnull __tm, char* _Nonnull __buf);

	/**
	* [difftime(3)](https://man7.org/linux/man-pages/man3/difftime.3.html) returns
	* the difference between two times.
	*
	* Returns the difference in seconds.
	*/
	double difftime(time_t __lhs, time_t __rhs);

	/**
	* [mktime(3)](https://man7.org/linux/man-pages/man3/mktime.3p.html) converts
	* broken-down time `tm` into the number of seconds since the Unix epoch.
	*
	* See tzset() for details of how the timezone is set, and mktime_rz()
	* for an alternative.
	*
	* Returns the time in seconds on success, and returns -1 and sets `errno` on failure.
	*/
	time_t mktime(struct tm* _Nonnull __tm);

	/**
	* mktime_z(3) converts broken-down time `tm` into the number of seconds
	* since the Unix epoch, assuming the given timezone.
	*
	* Returns the time in seconds on success, and returns -1 and sets `errno` on failure.
	*
	* Available since API level 35.
	*/
	time_t mktime_z(timezone_t _Nonnull __tz, struct tm* _Nonnull __tm) __INTRODUCED_IN(35);

	/**
	* [localtime(3)](https://man7.org/linux/man-pages/man3/localtime.3p.html) converts
	* the number of seconds since the Unix epoch in `t` to a broken-down time, taking
	* the device's timezone into account.
	*
	* That broken-down time will be overwritten by later calls to this function.
	*
	* Returns a pointer to a broken-down time on success, and returns null and sets `errno` on failure.
	*/
	struct tm* _Nullable localtime(const time_t* _Nonnull __t);

	/**
	* [localtime_r(3)](https://man7.org/linux/man-pages/man3/localtime_r.3p.html) converts
	* the number of seconds since the Unix epoch in `t` to a broken-down time.
	* That broken-down time will be written to the given struct `tm`.
	*
	* See tzset() for details of how the timezone is set, and localtime_rz()
	* for an alternative.
	*
	* Returns a pointer to a broken-down time on success, and returns null and sets `errno` on failure.
	*/
	struct tm* _Nullable localtime_r(const time_t* _Nonnull __t, struct tm* _Nonnull __tm);

	/**
	* localtime_rz(3) converts the number of seconds since the Unix epoch in
	* `t` to a broken-down time, assuming the given timezone. That broken-down
	* time will be written to the given struct `tm`.
	*
	* Returns a pointer to a broken-down time on success, and returns null and sets `errno` on failure.
	*
	* Available since API level 35.
	*/
	struct tm* _Nullable localtime_rz(timezone_t _Nonnull __tz, const time_t* _Nonnull __t, struct tm* _Nonnull __tm) __INTRODUCED_IN(35);

	/**
	* Inverse of localtime().
	*/
	time_t timelocal(struct tm* _Nonnull __tm);

	/**
	* [gmtime(3)](https://man7.org/linux/man-pages/man3/gmtime.3p.html) converts
	* the number of seconds since the Unix epoch in `t` to a broken-down time, using
	* UTC (historically also known as GMT).
	*
	* That broken-down time will be overwritten by later calls to this function.
	*
	* Returns a pointer to a broken-down time on success, and returns null and sets `errno` on failure.
	*/
	struct tm* _Nullable gmtime(const time_t* _Nonnull __t);

	/**
	* [gmtime_r(3)](https://man7.org/linux/man-pages/man3/gmtime_r.3p.html) converts
	* the number of seconds since the Unix epoch in `t` to a broken-down time, using
	* UTC (historically also known as GMT).
	*
	* That broken-down time will be written to the provided struct `tm`.
	*
	* Returns a pointer to a broken-down time on success, and returns null and sets `errno` on failure.
	*/
	struct tm* _Nullable gmtime_r(const time_t* _Nonnull __t, struct tm* _Nonnull __tm);

	/**
	* Inverse of gmtime().
	*/
	time_t timegm(struct tm* _Nonnull __tm);

	/**
	* [strptime(3)](https://man7.org/linux/man-pages/man3/strptime.3.html) parses
	* a string `s` assuming format `fmt` into broken-down time `tm`.
	*
	* Returns a pointer to the first character _not_ parsed, or null if no characters were parsed.
	*/
	char* _Nullable strptime(const char* _Nonnull __s, const char* _Nonnull __fmt, struct tm* _Nonnull __tm) __strftimelike(2);

	/**
	* Equivalent to strptime() on Android where only C/POSIX locales are available.
	*/
	char* _Nullable strptime_l(const char* _Nonnull __s, const char* _Nonnull __fmt, struct tm* _Nonnull __tm, locale_t _Nonnull __l) __strftimelike(2) __INTRODUCED_IN(28);

	/**
	* [strftime(3)](https://man7.org/linux/man-pages/man3/strftime.3.html) formats
	* a broken-down time `tm` into the buffer `buf` using format `fmt`.
	*
	* Returns a pointer to the first character _not_ parsed, or null if no characters were parsed.
	*/
	size_t strftime(char* _Nonnull __buf, size_t __n, const char* _Nonnull __fmt, const struct tm* _Nullable __tm) __strftimelike(3);

	/**
	* Equivalent to strftime() on Android where only C/POSIX locales are available.
	*/
	size_t strftime_l(char* _Nonnull __buf, size_t __n, const char* _Nonnull __fmt, const struct tm* _Nullable __tm, locale_t _Nonnull __l) __strftimelike(3);

	/**
	* [ctime(3)](https://man7.org/linux/man-pages/man3/ctime.3p.html) formats
	* the time `tm` as a string.
	*
	* Returns a pointer to a string on success, and returns NULL on failure.
	*
	* That string will be overwritten by later calls to this function.
	*
	* New code should prefer strftime().
	*/
	char* _Nullable ctime(const time_t* _Nonnull __t);

	/**
	* [ctime_r(3)](https://man7.org/linux/man-pages/man3/ctime.3p.html) formats
	* the time `tm` as a string in the given buffer `buf`.
	*
	* Returns a pointer to a string on success, and returns NULL on failure.
	*
	* New code should prefer strftime().
	*/
	char* _Nullable ctime_r(const time_t* _Nonnull __t, char* _Nonnull __buf);

	/**
	* [tzset(3)](https://man7.org/linux/man-pages/man3/tzset.3.html) tells
	* libc that the timezone has changed.
	*
	* tzset() on Android looks at both the system property
	* `persist.sys.timezone` and the environment variable `TZ`. The former is
	* the device's current timezone as shown in Settings, while the latter is
	* usually unset but can be used to override the global setting. This is a
	* bad idea outside of unit tests or single-threaded programs because it's
	* inherently thread-unsafe. See tzalloc(), localtime_rz(), mktime_z(),
	* and tzfree() for an alternative.
	*/
	void tzset(void);

	/**
	* tzalloc(3) allocates a timezone corresponding to the given Olson ID.
	*
	* A null `id` returns the system timezone (as seen in Settings) from
	* the system property `persist.sys.timezone`, ignoring `$TZ`. Although
	* tzset() honors `$TZ`, callers of tzalloc() can use `$TZ` themselves if
	* that's the (thread-unsafe) behavior they want, but by ignoring `$TZ`
	* tzalloc() is thread safe (though obviously the system timezone can
	* change, especially if your mobile device is actually mobile!).
	*
	* To use this with std::unique_ptr you'll want something like
	* `std::unique_ptr<std::remove_pointer_t<timezone_t>, decltype(&tzfree)> tz{tzalloc("Asia/Seoul"), tzfree};`
	* to remove the pointer.
	*
	* Returns a timezone object on success, and returns NULL and sets `errno` on failure.
	*
	* Available since API level 35.
	*/
	timezone_t _Nullable tzalloc(const char* _Nullable __id) __INTRODUCED_IN(35);

	/**
	* tzfree(3) frees a timezone object returned by tzalloc().
	*
	* To use this with std::unique_ptr you'll want something like
	* `std::unique_ptr<std::remove_pointer_t<timezone_t>, decltype(&tzfree)> tz{tzalloc("Asia/Seoul"), tzfree};`
	* to remove the pointer.
	*
	* Available since API level 35.
	*/
	void tzfree(timezone_t _Nullable __tz) __INTRODUCED_IN(35);

	/**
	* [clock(3)](https://man7.org/linux/man-pages/man3/clock.3.html)
	* returns an approximation of CPU time used, equivalent to
	* `clock_gettime(CLOCK_PROCESS_CPUTIME_ID)` but with more confusing
	* units. Use `CLOCKS_PER_SEC` to convert the result to seconds.
	*
	* Returns the time in seconds on success, and returns -1 and sets `errno` on failure.
	*
	* New code should prefer `clock_gettime(CLOCK_PROCESS_CPUTIME_ID)`.
	*/
	clock_t clock(void);

	/**
	* [clock_getcpuclockid(3)](https://man7.org/linux/man-pages/man3/clock_getcpuclockid.3.html)
	* gets the clock ID of the cpu-time clock for the given `pid`.
	*
	* Returns 0 on success, and returns -1 and returns an error number on failure.
	*/
	int clock_getcpuclockid(pid_t __pid, clockid_t* _Nonnull __clock) __INTRODUCED_IN(23);

	/**
	* [clock_getres(2)](https://man7.org/linux/man-pages/man2/clock_getres.2.html)
	* gets the resolution of the given clock.
	*
	* Returns 0 on success, and returns -1 and returns an error number on failure.
	*/
	int clock_getres(clockid_t __clock, struct timespec* _Nullable __resolution);

	/**
	* [clock_gettime(2)](https://man7.org/linux/man-pages/man2/clock_gettime.2.html)
	* gets the time according to the given clock.
	*
	* Returns 0 on success, and returns -1 and returns an error number on failure.
	*/
	int clock_gettime(clockid_t __clock, struct timespec* _Nonnull __ts);

	/**
	* [clock_nanosleep(2)](https://man7.org/linux/man-pages/man2/clock_nanosleep.2.html)
	* sleeps for the given time (or until the given time if the TIMER_ABSTIME flag
	* is used), as measured by the given clock.
	*
	* Returns 0 on success, and returns -1 and returns an error number on failure.
	* If the sleep was interrupted by a signal, the return value will be `EINTR`
	* and `remainder` will be the amount of time remaining.
	*/
	int clock_nanosleep(clockid_t __clock, int __flags, const struct timespec* _Nonnull __time, struct timespec* _Nullable __remainder);

	/**
	* [clock_settime(2)](https://man7.org/linux/man-pages/man2/clock_settime.2.html)
	* sets the time for the given clock.
	*
	* Returns 0 on success, and returns -1 and returns an error number on failure.
	*/
	int clock_settime(clockid_t __clock, const struct timespec* _Nonnull __ts);

	/**
	* [timer_create(2)](https://man7.org/linux/man-pages/man2/timer_create.2.html)
	* creates a POSIX timer.
	*
	* Returns 0 on success, and returns -1 and sets `errno` on failure.
	*/
	int timer_create(clockid_t __clock, struct sigevent* _Nullable __event, timer_t _Nonnull * _Nonnull __timer_ptr);

	/**
	* [timer_delete(2)](https://man7.org/linux/man-pages/man2/timer_delete.2.html)
	* destroys a POSIX timer.
	*
	* Returns 0 on success, and returns -1 and sets `errno` on failure.
	*/
	int timer_delete(timer_t _Nonnull __timer);

	/**
	* [timer_settime(2)](https://man7.org/linux/man-pages/man2/timer_settime.2.html)
	* starts or stops a POSIX timer.
	*
	* Returns 0 on success, and returns -1 and sets `errno` on failure.
	*/
	int timer_settime(timer_t _Nonnull __timer, int __flags, const struct itimerspec* _Nonnull __new_value, struct itimerspec* _Nullable __old_value);

	/**
	* [timer_gettime(2)](https://man7.org/linux/man-pages/man2/timer_gettime.2.html)
	* gets the time until the given timer next fires.
	*
	* Returns 0 on success, and returns -1 and sets `errno` on failure.
	*/
	int timer_gettime(timer_t _Nonnull _timer, struct itimerspec* _Nonnull __ts);

	/**
	* [timer_getoverrun(2)](https://man7.org/linux/man-pages/man2/timer_getoverrun.2.html)
	* gets the overrun count (the number of times the timer should have fired, but
	* didn't) for the last time the timer fired.
	*
	* Returns the overrun count on success, and returns -1 and sets `errno` on failure.
	*/
	int timer_getoverrun(timer_t _Nonnull __timer);

	/**
	* The timebase for timespec_get() and timespec_getres() corresponding to CLOCK_REALTIME.
	*
	* Available since API level 29.
	*/
	#define TIME_UTC (CLOCK_REALTIME+1)

	/**
	* The timebase for timespec_get() and timespec_getres() corresponding to CLOCK_MONOTONIC.
	*
	* Available since API level 35.
	*/
	#define TIME_MONOTONIC (CLOCK_MONOTONIC+1)

	/**
	* The timebase for timespec_get() and timespec_getres() corresponding to CLOCK_PROCESS_CPUTIME_ID.
	*
	* Available since API level 35.
	*/
	#define TIME_ACTIVE (CLOCK_PROCESS_CPUTIME_ID+1)

	/**
	* The timebase for timespec_get() and timespec_getres() corresponding to CLOCK_THREAD_CPUTIME_ID.
	*
	* Available since API level 35.
	*/
	#define TIME_THREAD_ACTIVE (CLOCK_THREAD_CPUTIME_ID+1)

	/**
	* timespec_get(3) is equivalent to clock_gettime() for the clock corresponding to the given base.
	*
	* Returns the base on success and returns 0 on failure.
	*
	* Available since API level 29 for TIME_UTC; other bases arrived later.
	* Code for Android should prefer clock_gettime().
	*/
	int timespec_get(struct timespec* _Nonnull __ts, int __base) __INTRODUCED_IN(29);

	/**
	* timespec_getres(3) is equivalent to clock_getres() for the clock corresponding to the given base.
	*
	* Returns the base on success and returns 0 on failure.
	*
	* Available since API level 35.
	* Code for Android should prefer clock_gettime().
	*/
	int timespec_getres(struct timespec* _Nonnull __ts, int __base) __INTRODUCED_IN(35);

	__END_DECLS