mirror of https://github.com/lianthony/NT4.0
You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
252 lines
6.8 KiB
252 lines
6.8 KiB
/***
|
|
*localtim.c - Convert time_t value to time structure
|
|
*
|
|
* Copyright (c) 1985-1993, 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.
|
|
* 07-15-93 GJF Replaced _tzset() call with __tzset() call.
|
|
*
|
|
*******************************************************************************/
|
|
|
|
#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 * _CRTAPI1 localtime (
|
|
const time_t *ptime
|
|
)
|
|
{
|
|
REG1 struct tm *ptm;
|
|
long ltime;
|
|
|
|
/*
|
|
* Check for illegal time_t value
|
|
*/
|
|
if ( (long)*ptime < 0L )
|
|
return( NULL );
|
|
|
|
#ifdef _POSIX_
|
|
tzset();
|
|
#else
|
|
__tzset();
|
|
#endif
|
|
|
|
if ( (*ptime > 3 * _DAY_SEC) && (*ptime < LONG_MAX - 3 * _DAY_SEC) ) {
|
|
/*
|
|
* 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 = (long)*ptime - _timezone;
|
|
ptm = gmtime( <ime );
|
|
|
|
/*
|
|
* Check and adjust for Daylight Saving Time.
|
|
*/
|
|
if ( _daylight && _isindst( ptm ) ) {
|
|
#ifdef _POSIX_
|
|
ltime -= _dstoffset - _timezone;
|
|
#else
|
|
ltime += 3600L;
|
|
#endif
|
|
ptm = gmtime( (time_t *)<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 theEpoch is 03:14:07, 01-19-2038 (UTC). This will be
|
|
* used in the calculations below.
|
|
*
|
|
* First, adjust for the timezone.
|
|
*/
|
|
ltime = (long)ptm->tm_sec - _timezone;
|
|
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 = (ptm->tm_wday + ltime) % 7;
|
|
ptm->tm_mday += ltime;
|
|
ptm->tm_yday += 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 = (ptm->tm_wday + 7 + ltime) % 7;
|
|
if ( (ptm->tm_mday += ltime) <= 0 ) {
|
|
ptm->tm_mday += 31;
|
|
ptm->tm_yday = 365;
|
|
ptm->tm_mon = 11;
|
|
ptm->tm_year--;
|
|
}
|
|
else {
|
|
ptm->tm_yday += 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 = (ptm->tm_wday + ltime) % 7;
|
|
ptm->tm_mday += ltime;
|
|
ptm->tm_yday += 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 = (ptm->tm_wday + 7 + ltime) % 7;
|
|
if ( (ptm->tm_mday += ltime) <= 0 ) {
|
|
ptm->tm_mday += 31;
|
|
ptm->tm_yday = 365;
|
|
ptm->tm_mon = 12;
|
|
ptm->tm_year--;
|
|
}
|
|
else {
|
|
ptm->tm_yday += ltime;
|
|
}
|
|
}
|
|
}
|
|
|
|
#endif
|
|
|
|
}
|
|
|
|
|
|
return(ptm);
|
|
}
|