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/***
*localtim.c - Convert time_t value to time structure** Copyright (c) 1985-2001, Microsoft Corporation. All rights reserved.**Purpose:* Converts time stored as a time_t value to a structure of type* struct tm expressed as local time.**Revision History:* 01-??-84 RLB Module created* 05-??-84 DCW split off from the rest of the ctime routines* 02-18-87 JCR made localtime work when gmtime returns null* 03-31-87 JCR fixed bug pertaining to uninitialized _isindst(tb)* 04-10-87 JCR changed long declaration to time_t and added const* 11-10-87 SKS Removed IBMC20 switch* 11-18-87 SKS Change tzset() to __tzset()* 12-11-87 JCR Added "_LOAD_DS" to declaration* 11-06-89 KRS Added (unsigned) to handle years 2040-2099 correctly.* 03-20-90 GJF Replaced _LOAD_DS with _CALLTYPE1, added #include* <cruntime.h>, removed #include <register.h> and* fixed the copyright. Also, cleaned up the formatting* a bit.* 10-04-90 GJF New-style function declarator. Also, rewrote expr.* to avoid using cast as lvalue.* 01-21-91 GJF ANSI naming.* 08-10-92 PBS Posix support (TZ stuff).* 03-24-93 GJF Ported C8-16 version and adapted for exotic Daylight* Savings Time conversions which are legal under POSIX.* 04-06-93 SKS Replace _CRTAPI* with __cdecl* 07-15-93 GJF Replaced _tzset() call with __tzset() call.* 09-20-93 GJF Merged NT SDK and Cuda version (amount to picking up* fixes to Posix build).* 11-04-93 GJF Picked up a fix for the Posix build.* 02-13-95 GJF Call _tzset for Mac builds (temp change?). Also,* picked up bug fix from Mac version (setting of* tm_yday field in underflow case).* 08-31-95 GJF Use _dstbias as the Daylight Saving Time bias and* all for the beginning or end of the Epoch to be in a* DST.* 02-07-98 GJF Changes for Win64: replaced long type with time_t, * added some int casts where required, also use __int64* max value for bounds checking.* 09-25-98 GJF Set tm_isdst, when appropriate, at beginning/end of the* Epoch* 05-17-99 PML Remove all Macintosh support.* 11-03-99 RDL Win64 POSIX warning fix.********************************************************************************/
#include <cruntime.h>
#include <limits.h>
#include <time.h>
#include <stddef.h>
#include <ctime.h>
#include <internal.h>
/***
*struct tm *localtime(ptime) - convert time_t value to tm structure**Purpose:* Convert a value in internal (time_t) format to a tm struct* containing the corresponding local time.** NOTES:* (1) gmtime must be called before _isindst to ensure that the tb time* structure is initialized.* (2) gmtime and localtime use a single statically allocated buffer.* Each call to one of these routines destroys the contents of the* previous call.* (3) It is assumed that time_t is a 32-bit long integer representing* the number of seconds since 00:00:00, 01-01-70 (UTC) (i.e., the* Posix/Unix Epoch. Only non-negative values are supported.* (4) It is assumed that the maximum adjustment for local time is* less than three days (include Daylight Savings Time adjustment).* This only a concern in Posix where the specification of the TZ* environment restricts the combined offset for time zone and* Daylight Savings Time to 2 * (24:59:59), just under 50 hours.**Entry:* time_t *ptime - pointer to a long time value**Exit:* If *ptime is non-negative, returns a pointer to the tm structure.* Otherwise, returns NULL.**Exceptions:* See items (3) and (4) in the NOTES above. If these assumptions are* violated, behavior is undefined.********************************************************************************/
struct tm * __cdecl localtime ( const time_t *ptime ){ REG1 struct tm *ptm; time_t ltime;
/*
* Check for illegal time_t value */ if ( *ptime < 0 ) return( NULL );
#ifdef _POSIX_
tzset();#else
__tzset();#endif
#ifdef _WIN64
if ( (*ptime > 3 * _DAY_SEC) && (*ptime < _I64_MAX - 3 * _DAY_SEC) ) {#else
if ( (*ptime > 3 * _DAY_SEC) && (*ptime < LONG_MAX - 3 * _DAY_SEC) ) {#endif
/*
* The date does not fall within the first three, or last * three, representable days of the Epoch. Therefore, there * is no possibility of overflowing or underflowing the * time_t representation as we compensate for timezone and * Daylight Savings Time. */
ltime = *ptime - _timezone; ptm = gmtime( <ime );
/*
* Check and adjust for Daylight Saving Time. */ if ( _daylight && _isindst( ptm ) ) {#ifdef _POSIX_
ltime -= _dstoffset - _timezone;#else
ltime -= _dstbias;#endif
ptm = gmtime( <ime ); ptm->tm_isdst = 1; } } else { ptm = gmtime( ptime );
/*
* The date falls with the first three, or last three days * of the Epoch. It is possible the time_t representation * would overflow or underflow while compensating for * timezone and Daylight Savings Time. Therefore, make the * timezone and Daylight Savings Time adjustments directly * in the tm structure. The beginning of the Epoch is * 00:00:00, 01-01-70 (UTC) and the last representable second * in the Epoch is 03:14:07, 01-19-2038 (UTC). This will be * used in the calculations below. * * First, adjust for the timezone. */#ifdef _POSIX_
ltime = (time_t)ptm->tm_sec - _timezone;#else
if ( _daylight && _isindst(ptm) ) { ltime = (time_t)ptm->tm_sec - (_timezone + _dstbias); ptm->tm_isdst = 1; } else ltime = (time_t)ptm->tm_sec - _timezone;#endif
ptm->tm_sec = (int)(ltime % 60); if ( ptm->tm_sec < 0 ) { ptm->tm_sec += 60; ltime -= 60; }
ltime = (time_t)ptm->tm_min + ltime/60; ptm->tm_min = (int)(ltime % 60); if ( ptm->tm_min < 0 ) { ptm->tm_min += 60; ltime -= 60; }
ltime = (time_t)ptm->tm_hour + ltime/60; ptm->tm_hour = (int)(ltime % 24); if ( ptm->tm_hour < 0 ) { ptm->tm_hour += 24; ltime -=24; }
ltime /= 24;
if ( ltime > 0 ) { /*
* There is no possibility of overflowing the tm_mday * and tm_yday fields since the date can be no later * than January 19. */ ptm->tm_wday = (ptm->tm_wday + (int)ltime) % 7; ptm->tm_mday += (int)ltime; ptm->tm_yday += (int)ltime; } else if ( ltime < 0 ) { /*
* It is possible to underflow the tm_mday and tm_yday * fields. If this happens, then adjusted date must * lie in December 1969. */ ptm->tm_wday = (ptm->tm_wday + 7 + (int)ltime) % 7; if ( (ptm->tm_mday += (int)ltime) <= 0 ) { ptm->tm_mday += 31; ptm->tm_yday = 364; ptm->tm_mon = 11; ptm->tm_year--; } else { ptm->tm_yday += (int)ltime; } }
#ifdef _POSIX_
/*
* In Posix, it is possible either the first or last three * days of the Epoch might lie with Daylight Savings Time in * certain time zones. */ if ( _isindst(ptm) ) {
ltime = (long)ptm->tm_sec + _dstoffset; ptm->tm_sec = (int)(ltime % 60); if ( ptm->tm_sec < 0 ) { ptm->tm_sec += 60; ltime -= 60; }
ltime = (long)ptm->tm_min + ltime/60; ptm->tm_min = (int)(ltime % 60); if ( ptm->tm_min < 0 ) { ptm->tm_min += 60; ltime -= 60; }
ltime = (long)ptm->tm_hour + ltime/60; ptm->tm_hour = (int)(ltime % 24); if ( ptm->tm_hour < 0 ) { ptm->tm_hour += 24; ltime -=24; }
ltime /= 24;
if ( ltime > 0L ) { /*
* There is no possibility of overflowing the * tm_mday and tm_yday fields since the date * can be no later than January 19. */ ptm->tm_wday = (int)((ptm->tm_wday + ltime) % 7); ptm->tm_mday += (int)ltime; ptm->tm_yday += (int)ltime; } else if ( ltime < 0L ) { /*
* It is possible to underflow the tm_mday * and tm_yday fields. If this happens, then * adjusted date must lie in December 1969. */ ptm->tm_wday = (int)((ptm->tm_wday + 7 + ltime) % 7); if ( (ptm->tm_mday += (int)ltime) <= 0 ) { ptm->tm_mday += 31; ptm->tm_yday = 364; ptm->tm_mon = 11; ptm->tm_year--; } else { ptm->tm_yday += (int)ltime; } } }
#endif
}
return(ptm);}
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