diff options
Diffstat (limited to 'lib/libc/stdtime/difftime.c')
-rw-r--r-- | lib/libc/stdtime/difftime.c | 77 |
1 files changed, 0 insertions, 77 deletions
diff --git a/lib/libc/stdtime/difftime.c b/lib/libc/stdtime/difftime.c deleted file mode 100644 index f178524..0000000 --- a/lib/libc/stdtime/difftime.c +++ /dev/null @@ -1,77 +0,0 @@ -/* -** This file is in the public domain, so clarified as of -** June 5, 1996 by Arthur David Olson (arthur_david_olson@nih.gov). -*/ - -#ifndef lint -#ifndef NOID -static char elsieid[] = "@(#)difftime.c 7.7"; -#endif /* !defined NOID */ -#endif /* !defined lint */ - -/*LINTLIBRARY*/ - -#include "private.h" - -/* -** Algorithm courtesy Paul Eggert (eggert@twinsun.com). -*/ - -#ifdef HAVE_LONG_DOUBLE -#define long_double long double -#endif /* defined HAVE_LONG_DOUBLE */ -#ifndef HAVE_LONG_DOUBLE -#define long_double double -#endif /* !defined HAVE_LONG_DOUBLE */ - -double -difftime(time1, time0) -const time_t time1; -const time_t time0; -{ - time_t delta; - time_t hibit; - - if (sizeof(time_t) < sizeof(double)) - return (double) time1 - (double) time0; - if (sizeof(time_t) < sizeof(long_double)) - return (long_double) time1 - (long_double) time0; - if (time1 < time0) - return -difftime(time0, time1); - /* - ** As much as possible, avoid loss of precision - ** by computing the difference before converting to double. - */ - delta = time1 - time0; - if (delta >= 0) - return delta; - /* - ** Repair delta overflow. - */ - hibit = (~ (time_t) 0) << (TYPE_BIT(time_t) - 1); - /* - ** The following expression rounds twice, which means - ** the result may not be the closest to the true answer. - ** For example, suppose time_t is 64-bit signed int, - ** long_double is IEEE 754 double with default rounding, - ** time1 = 9223372036854775807 and time0 = -1536. - ** Then the true difference is 9223372036854777343, - ** which rounds to 9223372036854777856 - ** with a total error of 513. - ** But delta overflows to -9223372036854774273, - ** which rounds to -9223372036854774784, and correcting - ** this by subtracting 2 * (long_double) hibit - ** (i.e. by adding 2**64 = 18446744073709551616) - ** yields 9223372036854776832, which - ** rounds to 9223372036854775808 - ** with a total error of 1535 instead. - ** This problem occurs only with very large differences. - ** It's too painful to fix this portably. - ** We are not alone in this problem; - ** some C compilers round twice when converting - ** large unsigned types to small floating types, - ** so if time_t is unsigned the "return delta" above - ** has the same double-rounding problem with those compilers. - */ - return delta - 2 * (long_double) hibit; -} |