/* Subtract two struct timespec values.
- Copyright (C) 2011-2012 Free Software Foundation, Inc.
+ Copyright (C) 2011-2016 Free Software Foundation, Inc.
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
/* Written by Paul Eggert. */
/* Return the difference between two timespec values A and B. On
- overflow, return an extremal value. This assumes 0 <= tv_nsec <=
- 999999999. */
+ overflow, return an extremal value. This assumes 0 <= tv_nsec <
+ TIMESPEC_RESOLUTION. */
#include <config.h>
#include "timespec.h"
struct timespec
timespec_sub (struct timespec a, struct timespec b)
{
- struct timespec r;
time_t rs = a.tv_sec;
time_t bs = b.tv_sec;
int ns = a.tv_nsec - b.tv_nsec;
int rns = ns;
+ time_t tmin = TYPE_MINIMUM (time_t);
+ time_t tmax = TYPE_MAXIMUM (time_t);
if (ns < 0)
{
- rns = ns + 1000000000;
- if (rs == TYPE_MINIMUM (time_t))
- {
- if (bs <= 0)
- goto low_overflow;
- bs--;
- }
- else
+ rns = ns + TIMESPEC_RESOLUTION;
+ if (bs < tmax)
+ bs++;
+ else if (- TYPE_SIGNED (time_t) < rs)
rs--;
+ else
+ goto low_overflow;
}
- if (INT_SUBTRACT_OVERFLOW (rs, bs))
+ /* INT_SUBTRACT_WRAPV is not appropriate since time_t might be unsigned.
+ In theory time_t might be narrower than int, so plain
+ INT_SUBTRACT_OVERFLOW does not suffice. */
+ if (! INT_SUBTRACT_OVERFLOW (rs, bs) && tmin <= rs - bs && rs - bs <= tmax)
+ rs -= bs;
+ else
{
if (rs < 0)
{
low_overflow:
- rs = TYPE_MINIMUM (time_t);
+ rs = tmin;
rns = 0;
}
else
{
- rs = TYPE_MAXIMUM (time_t);
- rns = 999999999;
+ rs = tmax;
+ rns = TIMESPEC_RESOLUTION - 1;
}
}
- else
- rs -= bs;
- r.tv_sec = rs;
- r.tv_nsec = rns;
- return r;
+ return make_timespec (rs, rns);
}