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72 lines
1.9 KiB
C
72 lines
1.9 KiB
C
/* Add two struct timespec values.
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Copyright (C) 2011-2017 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 sum of two timespec values A and B. On overflow, return
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an extremal value. This assumes 0 <= tv_nsec < 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_add (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 nsd = ns - TIMESPEC_RESOLUTION;
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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 (0 <= nsd)
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{
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rns = nsd;
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if (bs < tmax)
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bs++;
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else if (rs < 0)
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rs++;
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else
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goto high_overflow;
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}
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/* INT_ADD_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_ADD_OVERFLOW does not suffice. */
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if (! INT_ADD_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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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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high_overflow:
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rs = tmax;
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rns = TIMESPEC_RESOLUTION - 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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