mirror of
https://sourceware.org/git/glibc.git
synced 2024-09-19 16:10:01 +00:00
30891f35fa
We stopped adding "Contributed by" or similar lines in sources in 2012 in favour of git logs and keeping the Contributors section of the glibc manual up to date. Removing these lines makes the license header a bit more consistent across files and also removes the possibility of error in attribution when license blocks or files are copied across since the contributed-by lines don't actually reflect reality in those cases. Move all "Contributed by" and similar lines (Written by, Test by, etc.) into a new file CONTRIBUTED-BY to retain record of these contributions. These contributors are also mentioned in manual/contrib.texi, so we just maintain this additional record as a courtesy to the earlier developers. The following scripts were used to filter a list of files to edit in place and to clean up the CONTRIBUTED-BY file respectively. These were not added to the glibc sources because they're not expected to be of any use in future given that this is a one time task: https://gist.github.com/siddhesh/b5ecac94eabfd72ed2916d6d8157e7dc https://gist.github.com/siddhesh/15ea1f5e435ace9774f485030695ee02 Reviewed-by: Carlos O'Donell <carlos@redhat.com>
136 lines
4.1 KiB
C
136 lines
4.1 KiB
C
/* Copyright (C) 1991-2021 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
|
|
<https://www.gnu.org/licenses/>. */
|
|
|
|
|
|
#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 (__time64_t time1, __time64_t time0)
|
|
{
|
|
if (! TYPE_SIGNED (__time64_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;
|
|
__time64_t ht1 = time1 / 2;
|
|
__time64_t ht0 = time0 / 2;
|
|
__time64_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
|
|
__difftime64 (__time64_t time1, __time64_t time0)
|
|
{
|
|
/* Convert to double and then subtract if no double-rounding error could
|
|
result. */
|
|
|
|
if (TYPE_BITS (__time64_t) <= DBL_MANT_DIG
|
|
|| (TYPE_FLOATING (__time64_t) && sizeof (__time64_t) < sizeof (long double)))
|
|
return (double) time1 - (double) time0;
|
|
|
|
/* Likewise for long double. */
|
|
|
|
if (TYPE_BITS (__time64_t) <= LDBL_MANT_DIG || TYPE_FLOATING (__time64_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);
|
|
}
|
|
|
|
/* Provide a 32-bit wrapper if needed. */
|
|
|
|
#if __TIMESIZE != 64
|
|
|
|
libc_hidden_def (__difftime64)
|
|
|
|
double
|
|
__difftime (time_t time1, time_t time0)
|
|
{
|
|
return __difftime64 (time1, time0);
|
|
}
|
|
|
|
#endif
|
|
|
|
strong_alias (__difftime, difftime)
|