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69 lines
1.7 KiB
C
69 lines
1.7 KiB
C
/* Subtract two struct timespec values.
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Copyright (C) 2011-2015 Free Software Foundation, Inc.
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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(at your option) any later version.
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This program 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
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>. */
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/* Written by Paul Eggert. */
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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_RESOLUTION. */
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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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if (ns < 0)
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{
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rns = ns + TIMESPEC_RESOLUTION;
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if (rs == TYPE_MINIMUM (time_t))
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{
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if (bs <= 0)
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goto low_overflow;
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bs--;
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}
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else
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rs--;
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}
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if (INT_SUBTRACT_OVERFLOW (rs, bs))
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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 = TYPE_MINIMUM (time_t);
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rns = 0;
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}
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else
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{
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rs = TYPE_MAXIMUM (time_t);
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rns = TIMESPEC_RESOLUTION - 1;
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}
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}
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else
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rs -= bs;
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return make_timespec (rs, rns);
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}
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