331 lines
10 KiB
C
331 lines
10 KiB
C
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/***
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*mktime.c - Convert struct tm value to time_t value.
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*
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* Copyright (c) 1987-2001, Microsoft Corporation. All rights reserved.
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*
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*Purpose:
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* Defines mktime() and _mkgmtime(), routines to converts a time value
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* in a tm structure (possibly incomplete) into a time_t value, then
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* update (all) the structure fields with "normalized" values.
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*
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*Revision History:
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* 01-14-87 JCR Module created
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* 12-11-87 JCR Added "_LOAD_DS" to declaration
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* 06-15-89 PHG Now allows negative values and does DST by ANSI rules
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* 11-06-89 KRS Added (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> and fixed the copyright. Also, cleaned
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* up the formatting a bit.
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* 10-04-90 GJF New-style function declarator. Also, rewrote expr.
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* to avoid using casts as lvalues.
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* 10-26-90 GJF Added ulscount to avoid overflows. Ugly, temporary
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* hack (whole function needs to be revised for ANSI
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* conformance).
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* 01-22-91 GJF ANSI naming.
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* 03-24-93 GJF Propagated changes from 16-bit tree. Modified to
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* expose _mkgmtime() routine.
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* 04-06-93 SKS Replace _CRTAPI* with __cdecl
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* 07-15-93 GJF Replaced _tzset() call with __tzset() call.
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* 09-13-93 GJF Merged NT SDK and Cuda versions (amounted to picking
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* up MattBr's changes to the Posix build made last
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* April).
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* 02-10-95 GJF Conditionally call _tzset instead of __tzset for Mac
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* builds (probably temporary change).
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* 05-09-95 GJF Properly handle initial tm_mon values from -11 to -1.
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* 08-31-95 GJF Use _dstbias for Daylight Saving Time bias instead of
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* -3600L.
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* 05-17-99 PML Remove all Macintosh support.
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* 08-30-99 PML long -> time_t in a few casts.
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*
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*******************************************************************************/
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#include <cruntime.h>
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#include <stddef.h>
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#include <ctime.h>
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#include <time.h>
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#include <internal.h>
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/*
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* ChkAdd evaluates to TRUE if dest = src1 + src2 has overflowed
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*/
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#define ChkAdd(dest, src1, src2) ( ((src1 >= 0L) && (src2 >= 0L) \
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&& (dest < 0L)) || ((src1 < 0L) && (src2 < 0L) && (dest >= 0L)) )
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/*
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* ChkMul evaluates to TRUE if dest = src1 * src2 has overflowed
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*/
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#define ChkMul(dest, src1, src2) ( src1 ? (dest/src1 != src2) : 0 )
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/*
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* Core function for both mktime() and _mkgmtime()
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*/
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static time_t __cdecl _make_time_t( struct tm *, int);
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/***
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*time_t mktime(tb) - Normalize user time block structure
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*
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*Purpose:
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* Mktime converts a time structure, passed in as an argument, into a
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* calendar time value in internal format (time_t). It also completes
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* and updates the fields the of the passed in structure with 'normalized'
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* values. There are three practical uses for this routine:
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*
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* (1) Convert broken-down time to internal time format (time_t).
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* (2) To have mktime fill in the tm_wday, tm_yday, or tm_isdst fields.
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* (3) To pass in a time structure with 'out of range' values for some
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* fields and have mktime "normalize" them (e.g., pass in 1/35/87 and
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* get back 2/4/87).
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*Entry:
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* struct tm *tb - pointer to a tm time structure to convert and
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* normalize
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*
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*Exit:
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* If successful, mktime returns the specified calender time encoded as
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* a time_t value. Otherwise, (time_t)(-1) is returned to indicate an
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* error.
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*
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*Exceptions:
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* None.
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*
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*******************************************************************************/
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time_t __cdecl mktime (
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struct tm *tb
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)
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{
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return( _make_time_t(tb, 1) );
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}
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/***
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*time_t _mkgmtime(tb) - Convert broken down UTC time to time_t
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*
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*Purpose:
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* Convert a tm structure, passed in as an argument, containing a UTC
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* time value to internal format (time_t). It also completes and updates
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* the fields the of the passed in structure with 'normalized' values.
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*Entry:
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* struct tm *tb - pointer to a tm time structure to convert and
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* normalize
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*
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*Exit:
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* If successful, _mkgmtime returns the calender time encoded as time_t
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* Otherwise, (time_t)(-1) is returned to indicate an error.
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*
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*Exceptions:
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* None.
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*
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*******************************************************************************/
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time_t __cdecl _mkgmtime (
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struct tm *tb
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)
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{
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return( _make_time_t(tb, 0) );
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}
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/***
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*static time_t make_time_t(tb, ultflag) -
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*
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*Purpose:
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* Converts a struct tm value to a time_t value, then updates the struct
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* tm value. Either local time or UTC is supported, based on ultflag.
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* This is the routine that actually does the work for both mktime() and
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* _mkgmtime().
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*
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*Entry:
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* struct tm *tb - pointer to a tm time structure to convert and
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* normalize
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* int ultflag - use local time flag. the tb structure is assumed
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* to represent a local date/time if ultflag > 0.
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* otherwise, UTC is assumed.
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*
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*Exit:
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* If successful, mktime returns the specified calender time encoded as
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* a time_t value. Otherwise, (time_t)(-1) is returned to indicate an
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* error.
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*
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*Exceptions:
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* None.
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*
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*******************************************************************************/
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static time_t __cdecl _make_time_t (
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struct tm *tb,
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int ultflag
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)
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{
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time_t tmptm1, tmptm2, tmptm3;
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struct tm *tbtemp;
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/*
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* First, make sure tm_year is reasonably close to being in range.
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*/
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if ( ((tmptm1 = tb->tm_year) < _BASE_YEAR - 1) || (tmptm1 > _MAX_YEAR
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+ 1) )
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goto err_mktime;
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/*
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* Adjust month value so it is in the range 0 - 11. This is because
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* we don't know how many days are in months 12, 13, 14, etc.
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*/
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if ( (tb->tm_mon < 0) || (tb->tm_mon > 11) ) {
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/*
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* no danger of overflow because the range check above.
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*/
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tmptm1 += (tb->tm_mon / 12);
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if ( (tb->tm_mon %= 12) < 0 ) {
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tb->tm_mon += 12;
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tmptm1--;
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}
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/*
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* Make sure year count is still in range.
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*/
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if ( (tmptm1 < _BASE_YEAR - 1) || (tmptm1 > _MAX_YEAR + 1) )
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goto err_mktime;
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}
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/***** HERE: tmptm1 holds number of elapsed years *****/
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/*
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* Calculate days elapsed minus one, in the given year, to the given
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* month. Check for leap year and adjust if necessary.
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*/
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tmptm2 = _days[tb->tm_mon];
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if ( !(tmptm1 & 3) && (tb->tm_mon > 1) )
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tmptm2++;
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/*
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* Calculate elapsed days since base date (midnight, 1/1/70, UTC)
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*
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*
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* 365 days for each elapsed year since 1970, plus one more day for
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* each elapsed leap year. no danger of overflow because of the range
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* check (above) on tmptm1.
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*/
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tmptm3 = (tmptm1 - _BASE_YEAR) * 365L + ((tmptm1 - 1L) >> 2)
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- _LEAP_YEAR_ADJUST;
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/*
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* elapsed days to current month (still no possible overflow)
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*/
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tmptm3 += tmptm2;
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/*
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* elapsed days to current date. overflow is now possible.
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*/
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tmptm1 = tmptm3 + (tmptm2 = (time_t)(tb->tm_mday));
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if ( ChkAdd(tmptm1, tmptm3, tmptm2) )
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goto err_mktime;
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/***** HERE: tmptm1 holds number of elapsed days *****/
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/*
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* Calculate elapsed hours since base date
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*/
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tmptm2 = tmptm1 * 24L;
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if ( ChkMul(tmptm2, tmptm1, 24L) )
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goto err_mktime;
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tmptm1 = tmptm2 + (tmptm3 = (time_t)tb->tm_hour);
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if ( ChkAdd(tmptm1, tmptm2, tmptm3) )
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goto err_mktime;
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/***** HERE: tmptm1 holds number of elapsed hours *****/
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/*
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* Calculate elapsed minutes since base date
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*/
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tmptm2 = tmptm1 * 60L;
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if ( ChkMul(tmptm2, tmptm1, 60L) )
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goto err_mktime;
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tmptm1 = tmptm2 + (tmptm3 = (time_t)tb->tm_min);
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if ( ChkAdd(tmptm1, tmptm2, tmptm3) )
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goto err_mktime;
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/***** HERE: tmptm1 holds number of elapsed minutes *****/
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/*
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* Calculate elapsed seconds since base date
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*/
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tmptm2 = tmptm1 * 60L;
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if ( ChkMul(tmptm2, tmptm1, 60L) )
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goto err_mktime;
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tmptm1 = tmptm2 + (tmptm3 = (time_t)tb->tm_sec);
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if ( ChkAdd(tmptm1, tmptm2, tmptm3) )
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goto err_mktime;
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/***** HERE: tmptm1 holds number of elapsed seconds *****/
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if ( ultflag ) {
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/*
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* Adjust for timezone. No need to check for overflow since
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* localtime() will check its arg value
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*/
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#ifdef _POSIX_
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tzset();
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#else
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__tzset();
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#endif
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tmptm1 += _timezone;
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/*
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* Convert this second count back into a time block structure.
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* If localtime returns NULL, return an error.
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*/
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if ( (tbtemp = localtime(&tmptm1)) == NULL )
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goto err_mktime;
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/*
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* Now must compensate for DST. The ANSI rules are to use the
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* passed-in tm_isdst flag if it is non-negative. Otherwise,
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* compute if DST applies. Recall that tbtemp has the time without
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* DST compensation, but has set tm_isdst correctly.
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*/
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if ( (tb->tm_isdst > 0) || ((tb->tm_isdst < 0) &&
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(tbtemp->tm_isdst > 0)) ) {
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#ifdef _POSIX_
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tmptm1 -= _timezone;
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tmptm1 += _dstoffset;
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#else
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tmptm1 += _dstbias;
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#endif
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tbtemp = localtime(&tmptm1); /* reconvert, can't get NULL */
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}
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}
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else {
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if ( (tbtemp = gmtime(&tmptm1)) == NULL )
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goto err_mktime;
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}
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/***** HERE: tmptm1 holds number of elapsed seconds, adjusted *****/
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/***** for local time if requested *****/
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*tb = *tbtemp;
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return (time_t)tmptm1;
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err_mktime:
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/*
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* All errors come to here
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*/
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return (time_t)(-1);
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}
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