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3cfb933344
It wasn't tested and probably never worked, no platform used it, and the latest POSIX no longer allows it. * Makefile (typecheck): Don't check time_t being 'double'. * Theory: Document the change. * difftime.c (difftime): * localtime.c (differ_by_repeat, tzload, timesub, time2sub): * private.h (time_t_min, time_t_max): * zdump.c (absolute_min_time, absolute_max_time, tformat): Don't try to support floating-point time_t. * localtime.c, private.h, zdump.c: Don't include float.h. * localtime.c (truncate_time, double_to_time): * private.h (TYPE_INTEGRAL): * zdump.c (checkabsolutes): Remove; no longer needed. All uses removed. * zdump.8 (LIMITATIONS): Remove discussion of floating-point time_t.
49 lines
1.4 KiB
C
49 lines
1.4 KiB
C
/*
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** This file is in the public domain, so clarified as of
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** 1996-06-05 by Arthur David Olson.
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*/
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/*LINTLIBRARY*/
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#include "private.h" /* for time_t and TYPE_SIGNED */
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double ATTRIBUTE_CONST
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difftime(const time_t time1, const time_t time0)
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{
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/*
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** If (sizeof (double) > sizeof (time_t)) simply convert and subtract
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** (assuming that the larger type has more precision).
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*/
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if (sizeof (double) > sizeof (time_t))
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return (double) time1 - (double) time0;
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if (!TYPE_SIGNED(time_t)) {
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/*
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** The difference of two unsigned values can't overflow
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** if the minuend is greater than or equal to the subtrahend.
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*/
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if (time1 >= time0)
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return time1 - time0;
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else return -(double) (time0 - time1);
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}
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/*
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** Handle cases where both time1 and time0 have the same sign
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** (meaning that their difference cannot overflow).
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*/
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if ((time1 < 0) == (time0 < 0))
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return time1 - time0;
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/*
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** time1 and time0 have opposite signs.
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** Punt if uintmax_t is too narrow.
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** This suffers from double rounding; attempt to lessen that
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** by using long double temporaries.
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*/
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if (sizeof (uintmax_t) < sizeof (time_t))
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return (long double) time1 - (long double) time0;
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/*
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** Stay calm...decent optimizers will eliminate the complexity below.
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*/
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if (time1 >= 0 /* && time0 < 0 */)
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return (uintmax_t) time1 + (uintmax_t) (-1 - time0) + 1;
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return -(double) ((uintmax_t) time0 + (uintmax_t) (-1 - time1) + 1);
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}
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