191 lines
6 KiB
C
191 lines
6 KiB
C
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/***
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*gmtime.c - breaks down a time value into GMT date/time info
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*
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* Copyright (c) 1985-2001, Microsoft Corporation. All rights reserved.
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*
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*Purpose:
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* defines gmtime() - breaks the clock value down into GMT time/date
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* information; return pointer to structure with the data.
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*
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*Revision History:
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* 01-??-84 RLB Module created
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* 05-??-84 DCW Split off from rest off ctime routines.
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* 02-18-87 JCR For MS C, gmtime now returns NULL for out of range
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* time/date. (This is for ANSI compatibility.)
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* 04-10-87 JCR Changed long declaration to time_t and added const
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* 05-21-87 SKS Declare "struct tm tb" as NEAR data
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* 11-10-87 SKS Removed IBMC20 switch
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* 12-11-87 JCR Added "_LOAD_DS" to declaration
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* 05-24-88 PHG Merge DLL and regular versions
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* 06-06-89 JCR 386 mthread support
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* 11-06-89 KRS Add (unsigned) to handle years 2040-2099 correctly
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* 03-20-90 GJF Replaced _LOAD_DS with _CALLTYPE1, added #include
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* <cruntime.h>, removed #include <register.h> and
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* fixed the copyright. Also, cleaned up the formatting
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* a bit.
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* 10-04-90 GJF New-style function declarator.
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* 07-17-91 GJF Multi-thread support for Win32 [_WIN32_].
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* 02-17-93 GJF Changed for new _getptd().
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* 03-24-93 GJF Propagated changes from 16-bit tree.
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* 04-06-93 SKS Replace _CRTAPI* with __cdecl
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* 09-06-94 CFW Replace MTHREAD with _MT.
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* 01-10-95 CFW Debug CRT allocs.
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* 02-07-98 GJF Changes for Win64: replaced long with time_t.
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*
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*******************************************************************************/
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#include <cruntime.h>
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#include <time.h>
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#include <ctime.h>
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#include <stddef.h>
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#include <internal.h>
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#include <mtdll.h>
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#ifdef _MT
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#include <malloc.h>
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#include <stddef.h>
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#endif
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#include <dbgint.h>
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static struct tm tb = { 0 }; /* time block */
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/***
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*struct tm *gmtime(timp) - convert *timp to a structure (UTC)
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*
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*Purpose:
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* Converts the calendar time value, in internal format (time_t), to
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* broken-down time (tm structure) with the corresponding UTC time.
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*
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*Entry:
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* const time_t *timp - pointer to time_t value to convert
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*
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*Exit:
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* returns pointer to filled-in tm structure.
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* returns NULL if *timp < 0L
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*
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*Exceptions:
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*
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*******************************************************************************/
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struct tm * __cdecl gmtime (
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const time_t *timp
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)
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{
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time_t caltim = *timp; /* calendar time to convert */
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int islpyr = 0; /* is-current-year-a-leap-year flag */
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REG1 int tmptim;
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REG3 int *mdays; /* pointer to days or lpdays */
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#ifdef _MT
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REG2 struct tm *ptb; /* will point to gmtime buffer */
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_ptiddata ptd = _getptd();
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#else
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REG2 struct tm *ptb = &tb;
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#endif
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if ( caltim < 0 )
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return(NULL);
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#ifdef _MT
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/* Use per thread buffer area (malloc space, if necessary) */
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if ( (ptd->_gmtimebuf != NULL) || ((ptd->_gmtimebuf =
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_malloc_crt(sizeof(struct tm))) != NULL) )
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ptb = ptd->_gmtimebuf;
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else
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ptb = &tb; /* malloc error: use static buffer */
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#endif
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/*
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* Determine years since 1970. First, identify the four-year interval
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* since this makes handling leap-years easy (note that 2000 IS a
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* leap year and 2100 is out-of-range).
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*/
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tmptim = (int)(caltim / _FOUR_YEAR_SEC);
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caltim -= ((time_t)tmptim * _FOUR_YEAR_SEC);
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/*
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* Determine which year of the interval
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*/
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tmptim = (tmptim * 4) + 70; /* 1970, 1974, 1978,...,etc. */
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if ( caltim >= _YEAR_SEC ) {
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tmptim++; /* 1971, 1975, 1979,...,etc. */
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caltim -= _YEAR_SEC;
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if ( caltim >= _YEAR_SEC ) {
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tmptim++; /* 1972, 1976, 1980,...,etc. */
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caltim -= _YEAR_SEC;
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/*
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* Note, it takes 366 days-worth of seconds to get past a leap
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* year.
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*/
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if ( caltim >= (_YEAR_SEC + _DAY_SEC) ) {
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tmptim++; /* 1973, 1977, 1981,...,etc. */
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caltim -= (_YEAR_SEC + _DAY_SEC);
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}
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else {
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/*
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* In a leap year after all, set the flag.
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*/
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islpyr++;
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}
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}
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}
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/*
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* tmptim now holds the value for tm_year. caltim now holds the
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* number of elapsed seconds since the beginning of that year.
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*/
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ptb->tm_year = tmptim;
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/*
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* Determine days since January 1 (0 - 365). This is the tm_yday value.
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* Leave caltim with number of elapsed seconds in that day.
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*/
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ptb->tm_yday = (int)(caltim / _DAY_SEC);
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caltim -= (time_t)(ptb->tm_yday) * _DAY_SEC;
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/*
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* Determine months since January (0 - 11) and day of month (1 - 31)
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*/
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if ( islpyr )
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mdays = _lpdays;
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else
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mdays = _days;
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for ( tmptim = 1 ; mdays[tmptim] < ptb->tm_yday ; tmptim++ ) ;
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ptb->tm_mon = --tmptim;
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ptb->tm_mday = ptb->tm_yday - mdays[tmptim];
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/*
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* Determine days since Sunday (0 - 6)
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*/
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ptb->tm_wday = ((int)(*timp / _DAY_SEC) + _BASE_DOW) % 7;
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/*
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* Determine hours since midnight (0 - 23), minutes after the hour
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* (0 - 59), and seconds after the minute (0 - 59).
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*/
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ptb->tm_hour = (int)(caltim / 3600);
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caltim -= (time_t)ptb->tm_hour * 3600L;
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ptb->tm_min = (int)(caltim / 60);
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ptb->tm_sec = (int)(caltim - (ptb->tm_min) * 60);
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ptb->tm_isdst = 0;
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return( (struct tm *)ptb );
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}
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