72 lines
2.0 KiB
C
72 lines
2.0 KiB
C
/* Subtract two struct timespec values.
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Copyright (C) 2011-2019 Free Software Foundation, Inc.
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This file is part of the GNU C Library and is also part of gnulib.
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Patches to this file should be submitted to both projects.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<http://www.gnu.org/licenses/>. */
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/* Return the difference between two timespec values A and B. On
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overflow, return an extremal value. This assumes 0 <= tv_nsec <
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TIMESPEC_HZ. */
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#include <config.h>
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#include "timespec.h"
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#include "intprops.h"
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struct timespec
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timespec_sub (struct timespec a, struct timespec b)
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{
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time_t rs = a.tv_sec;
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time_t bs = b.tv_sec;
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int ns = a.tv_nsec - b.tv_nsec;
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int rns = ns;
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time_t tmin = TYPE_MINIMUM (time_t);
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time_t tmax = TYPE_MAXIMUM (time_t);
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if (ns < 0)
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{
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rns = ns + TIMESPEC_HZ;
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if (bs < tmax)
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bs++;
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else if (- TYPE_SIGNED (time_t) < rs)
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rs--;
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else
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goto low_overflow;
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}
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/* INT_SUBTRACT_WRAPV is not appropriate since time_t might be unsigned.
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In theory time_t might be narrower than int, so plain
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INT_SUBTRACT_OVERFLOW does not suffice. */
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if (! INT_SUBTRACT_OVERFLOW (rs, bs) && tmin <= rs - bs && rs - bs <= tmax)
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rs -= bs;
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else
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{
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if (rs < 0)
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{
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low_overflow:
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rs = tmin;
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rns = 0;
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}
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else
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{
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rs = tmax;
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rns = TIMESPEC_HZ - 1;
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}
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}
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return make_timespec (rs, rns);
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}
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