/***
*mktime.c - Convert struct tm value to time_t value.
*
* Copyright (c) 1987-1993, Microsoft Corporation. All rights reserved.
*
*Purpose:
* Defines mktime() and _mkgmtime(), routines to converts a time value
* in a tm structure (possibly incomplete) into a time_t value, then
* update (all) the structure fields with "normalized" values.
*
*Revision History:
* 01-14-87 JCR Module created
* 12-11-87 JCR Added "_LOAD_DS" to declaration
* 06-15-89 PHG Now allows negative values and does DST by ANSI rules
* 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> 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 casts as lvalues.
* 10-26-90 GJF Added ulscount to avoid overflows. Ugly, temporary
* hack (whole function needs to be revised for ANSI
* conformance).
* 01-22-91 GJF ANSI naming.
* 03-24-93 GJF Propagated changes from 16-bit tree. Modified to
* expose _mkgmtime() routine.
* 07-15-93 GJF Replaced _tzset() call with __tzset() call.
*
*******************************************************************************/
#include <cruntime.h>
#include <stddef.h>
#include <ctime.h>
#include <time.h>
#include <internal.h>
/*
* ChkAdd evaluates to TRUE if dest = src1 + src2 has overflowed
*/
#define ChkAdd(dest, src1, src2) ( ((src1 >= 0L) && (src2 >= 0L) \
&& (dest < 0L)) || ((src1 < 0L) && (src2 < 0L) && (dest >= 0L)) )
/*
* ChkMul evaluates to TRUE if dest = src1 * src2 has overflowed
*/
#define ChkMul(dest, src1, src2) ( src1 ? (dest/src1 != src2) : 0 )
/*
* Core function for both mktime() and _mkgmtime()
*/
static time_t _CRTAPI3 _make_time_t( struct tm *, int);
/***
*time_t mktime(tb) - Normalize user time block structure
*
*Purpose:
* Mktime converts a time structure, passed in as an argument, into a
* calendar time value in internal format (time_t). It also completes
* and updates the fields the of the passed in structure with 'normalized'
* values. There are three practical uses for this routine:
*
* (1) Convert broken-down time to internal time format (time_t).
* (2) To have mktime fill in the tm_wday, tm_yday, or tm_isdst fields.
* (3) To pass in a time structure with 'out of range' values for some
* fields and have mktime "normalize" them (e.g., pass in 1/35/87 and
* get back 2/4/87).
*Entry:
* struct tm *tb - pointer to a tm time structure to convert and
* normalize
*
*Exit:
* If successful, mktime returns the specified calender time encoded as
* a time_t value. Otherwise, (time_t)(-1) is returned to indicate an
* error.
*
*Exceptions:
* None.
*
*******************************************************************************/
time_t _CRTAPI1 mktime (
struct tm *tb
)
{
return( _make_time_t(tb, 1) );
}
/***
*time_t _mkgmtime(tb) - Convert broken down UTC time to time_t
*
*Purpose:
* Convert a tm structure, passed in as an argument, containing a UTC
* time value to internal format (time_t). It also completes and updates
* the fields the of the passed in structure with 'normalized' values.
*Entry:
* struct tm *tb - pointer to a tm time structure to convert and
* normalize
*
*Exit:
* If successful, _mkgmtime returns the calender time encoded as time_t
* Otherwise, (time_t)(-1) is returned to indicate an error.
*
*Exceptions:
* None.
*
*******************************************************************************/
time_t _CRTAPI1 _mkgmtime (
struct tm *tb
)
{
return( _make_time_t(tb, 0) );
}
/***
*static time_t make_time_t(tb, ultflag) -
*
*Purpose:
* Converts a struct tm value to a time_t value, then updates the struct
* tm value. Either local time or UTC is supported, based on ultflag.
* This is the routine that actually does the work for both mktime() and
* _mkgmtime().
*
*Entry:
* struct tm *tb - pointer to a tm time structure to convert and
* normalize
* int ultflag - use local time flag. the tb structure is assumed
* to represent a local date/time if ultflag > 0.
* otherwise, UTC is assumed.
*
*Exit:
* If successful, mktime returns the specified calender time encoded as
* a time_t value. Otherwise, (time_t)(-1) is returned to indicate an
* error.
*
*Exceptions:
* None.
*
*******************************************************************************/
static time_t _CRTAPI3 _make_time_t (
struct tm *tb,
int ultflag
)
{
long tmptm1, tmptm2, tmptm3;
struct tm *tbtemp;
/*
* First, make sure tm_year is reasonably close to being in range.
*/
if ( ((tmptm1 = tb->tm_year) < _BASE_YEAR - 1) || (tmptm1 > _MAX_YEAR
+ 1) )
goto err_mktime;
/*
* Adjust month value so it is in the range 0 - 11. This is because
* we don't know how many days are in months 12, 13, 14, etc.
*/
if ( (tmptm2 = tb->tm_mon/12) != 0L ) {
/*
* no danger of overflow because the range check above.
*/
tmptm1 += tmptm2;
if ( (tb->tm_mon %= 12) < 0 ) {
tb->tm_mon += 12;
tmptm1--;
}
/*
* Make sure year count is still in range.
*/
if ( (tmptm1 < _BASE_YEAR - 1) || (tmptm1 > _MAX_YEAR + 1) )
goto err_mktime;
}
/***** HERE: tmptm1 holds number of elapsed years *****/
/*
* Calculate days elapsed minus one, in the given year, to the given
* month. Check for leap year and adjust if necessary.
*/
tmptm2 = _days[tb->tm_mon];
if ( !(tmptm1 & 3) && (tb->tm_mon > 1) )
tmptm2++;
/*
* Calculate elapsed days since base date (midnight, 1/1/70, UTC)
*
*
* 365 days for each elapsed year since 1970, plus one more day for
* each elapsed leap year. no danger of overflow because of the range
* check (above) on tmptm1.
*/
tmptm3 = (tmptm1 - _BASE_YEAR) * 365L + ((tmptm1 - 1L) >> 2)
- _LEAP_YEAR_ADJUST;
/*
* elapsed days to current month (still no possible overflow)
*/
tmptm3 += tmptm2;
/*
* elapsed days to current date. overflow is now possible.
*/
tmptm1 = tmptm3 + (tmptm2 = (long)(tb->tm_mday));
if ( ChkAdd(tmptm1, tmptm3, tmptm2) )
goto err_mktime;
/***** HERE: tmptm1 holds number of elapsed days *****/
/*
* Calculate elapsed hours since base date
*/
tmptm2 = tmptm1 * 24L;
if ( ChkMul(tmptm2, tmptm1, 24L) )
goto err_mktime;
tmptm1 = tmptm2 + (tmptm3 = (long)tb->tm_hour);
if ( ChkAdd(tmptm1, tmptm2, tmptm3) )
goto err_mktime;
/***** HERE: tmptm1 holds number of elapsed hours *****/
/*
* Calculate elapsed minutes since base date
*/
tmptm2 = tmptm1 * 60L;
if ( ChkMul(tmptm2, tmptm1, 60L) )
goto err_mktime;
tmptm1 = tmptm2 + (tmptm3 = (long)tb->tm_min);
if ( ChkAdd(tmptm1, tmptm2, tmptm3) )
goto err_mktime;
/***** HERE: tmptm1 holds number of elapsed minutes *****/
/*
* Calculate elapsed seconds since base date
*/
tmptm2 = tmptm1 * 60L;
if ( ChkMul(tmptm2, tmptm1, 60L) )
goto err_mktime;
tmptm1 = tmptm2 + (tmptm3 = (long)tb->tm_sec);
if ( ChkAdd(tmptm1, tmptm2, tmptm3) )
goto err_mktime;
/***** HERE: tmptm1 holds number of elapsed seconds *****/
if ( ultflag ) {
/*
* Adjust for timezone. No need to check for overflow since
* localtime() will check its arg value
*/
#ifdef _POSIX_
tzset();
#else
__tzset();
#endif
tmptm1 += _timezone;
/*
* Convert this second count back into a time block structure.
* If localtime returns NULL, return an error.
*/
if ( (tbtemp = localtime(&tmptm1)) == NULL )
goto err_mktime;
/*
* Now must compensate for DST. The ANSI rules are to use the
* passed-in tm_isdst flag if it is non-negative. Otherwise,
* compute if DST applies. Recall that tbtemp has the time without
* DST compensation, but has set tm_isdst correctly.
*/
if ( (tb->tm_isdst > 0) || ((tb->tm_isdst < 0) &&
(tbtemp->tm_isdst > 0)) ) {
#ifdef _POSIX_
tmptm1 -= _timezone;
tmptm1 += _dstoffset;
#else
tmptm1 -= 3600L;
#endif
tbtemp = localtime(&tmptm1); /* reconvert, can't get NULL */
}
}
else {
if ( (tbtemp = gmtime(&tmptm1)) == NULL )
goto err_mktime;
}
/***** HERE: tmptm1 holds number of elapsed seconds, adjusted *****/
/***** for local time if requested *****/
*tb = *tbtemp;
return (time_t)tmptm1;
err_mktime:
/*
* All errors come to here
*/
return (time_t)(-1);
}
