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Diffstat (limited to 'time/difftime.c')
| -rw-r--r-- | time/difftime.c | 121 |
1 files changed, 0 insertions, 121 deletions
diff --git a/time/difftime.c b/time/difftime.c deleted file mode 100644 index e5e3311744..0000000000 --- a/time/difftime.c +++ /dev/null @@ -1,121 +0,0 @@ -/* Copyright (C) 1991-2017 Free Software Foundation, Inc. - This file is part of the GNU C Library. - - The GNU C Library is free software; you can redistribute it and/or - modify it under the terms of the GNU Lesser General Public - License as published by the Free Software Foundation; either - version 2.1 of the License, or (at your option) any later version. - - The GNU C Library is distributed in the hope that it will be useful, - but WITHOUT ANY WARRANTY; without even the implied warranty of - MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU - Lesser General Public License for more details. - - You should have received a copy of the GNU Lesser General Public - License along with the GNU C Library; if not, see - <http://www.gnu.org/licenses/>. */ - -/* Written by Paul Eggert <eggert@cs.ucla.edu>. */ - -#include <time.h> - -#include <limits.h> -#include <float.h> -#include <stdint.h> - -#define TYPE_BITS(type) (sizeof (type) * CHAR_BIT) -#define TYPE_FLOATING(type) ((type) 0.5 == 0.5) -#define TYPE_SIGNED(type) ((type) -1 < 0) - -/* Return the difference between TIME1 and TIME0, where TIME0 <= TIME1. - time_t is known to be an integer type. */ - -static double -subtract (time_t time1, time_t time0) -{ - if (! TYPE_SIGNED (time_t)) - return time1 - time0; - else - { - /* Optimize the common special cases where time_t - can be converted to uintmax_t without losing information. */ - uintmax_t dt = (uintmax_t) time1 - (uintmax_t) time0; - double delta = dt; - - if (UINTMAX_MAX / 2 < INTMAX_MAX) - { - /* This is a rare host where uintmax_t has padding bits, and possibly - information was lost when converting time_t to uintmax_t. - Check for overflow by comparing dt/2 to (time1/2 - time0/2). - Overflow occurred if they differ by more than a small slop. - Thanks to Clive D.W. Feather for detailed technical advice about - hosts with padding bits. - - In the following code the "h" prefix means half. By range - analysis, we have: - - -0.5 <= ht1 - 0.5*time1 <= 0.5 - -0.5 <= ht0 - 0.5*time0 <= 0.5 - -1.0 <= dht - 0.5*(time1 - time0) <= 1.0 - - If overflow has not occurred, we also have: - - -0.5 <= hdt - 0.5*(time1 - time0) <= 0 - -1.0 <= dht - hdt <= 1.5 - - and since dht - hdt is an integer, we also have: - - -1 <= dht - hdt <= 1 - - or equivalently: - - 0 <= dht - hdt + 1 <= 2 - - In the above analysis, all the operators have their exact - mathematical semantics, not C semantics. However, dht - hdt + - 1 is unsigned in C, so it need not be compared to zero. */ - - uintmax_t hdt = dt / 2; - time_t ht1 = time1 / 2; - time_t ht0 = time0 / 2; - time_t dht = ht1 - ht0; - - if (2 < dht - hdt + 1) - { - /* Repair delta overflow. - - The following expression contains a second rounding, - so the result may not be the closest to the true answer. - This problem occurs only with very large differences. - It's too painful to fix this portably. */ - - delta = dt + 2.0L * (UINTMAX_MAX - UINTMAX_MAX / 2); - } - } - - return delta; - } -} - -/* Return the difference between TIME1 and TIME0. */ -double -__difftime (time_t time1, time_t time0) -{ - /* Convert to double and then subtract if no double-rounding error could - result. */ - - if (TYPE_BITS (time_t) <= DBL_MANT_DIG - || (TYPE_FLOATING (time_t) && sizeof (time_t) < sizeof (long double))) - return (double) time1 - (double) time0; - - /* Likewise for long double. */ - - if (TYPE_BITS (time_t) <= LDBL_MANT_DIG || TYPE_FLOATING (time_t)) - return (long double) time1 - (long double) time0; - - /* Subtract the smaller integer from the larger, convert the difference to - double, and then negate if needed. */ - - return time1 < time0 ? - subtract (time0, time1) : subtract (time1, time0); -} -strong_alias (__difftime, difftime) |