112 lines
3.0 KiB
C
112 lines
3.0 KiB
C
/*
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* Copyright (c) 2013, 2021 Jonas 'Sortie' Termansen.
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*
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* Permission to use, copy, modify, and distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*
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* timespec/timespec.c
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* Utility functions for manipulation of struct timespec.
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*/
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#include <sys/types.h>
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#include <assert.h>
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#include <timespec.h>
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static const long NANOSECONDS_PER_SECOND = 1000000000L;
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// The C modulo operator doesn't do exactly what we desire.
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static long proper_modulo(long a, long b)
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{
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if ( 0 <= a )
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return a % b;
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long tmp = - (unsigned long) a % b;
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return tmp ? tmp : 0;
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}
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struct timespec timespec_canonalize(struct timespec t)
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{
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t.tv_sec += t.tv_nsec / NANOSECONDS_PER_SECOND;
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t.tv_nsec = proper_modulo(t.tv_nsec, NANOSECONDS_PER_SECOND);
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return t;
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}
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bool timespec_add_overflow(struct timespec a,
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struct timespec b,
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struct timespec* res)
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{
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assert(timespec_is_canonical(a) && timespec_is_canonical(b));
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struct timespec ret;
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ret.tv_nsec = a.tv_nsec + b.tv_nsec;
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if ( NANOSECONDS_PER_SECOND <= ret.tv_nsec )
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{
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ret.tv_nsec -= NANOSECONDS_PER_SECOND;
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if ( a.tv_sec != TIME_MAX )
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a.tv_sec++;
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else if ( b.tv_sec != TIME_MAX )
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b.tv_sec++;
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else
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goto overflow;
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}
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if ( __builtin_add_overflow(a.tv_sec, b.tv_sec, &ret.tv_sec) )
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goto overflow;
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*res = ret;
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return false;
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overflow:
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*res = b.tv_sec < 0 ?
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timespec_make(TIME_MIN, 0) :
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timespec_make(TIME_MAX, NANOSECONDS_PER_SECOND - 1);
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return true;
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}
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struct timespec timespec_add(struct timespec a, struct timespec b)
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{
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struct timespec ret;
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timespec_add_overflow(a, b, &ret);
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return ret;
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}
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bool timespec_sub_overflow(struct timespec a,
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struct timespec b,
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struct timespec* res)
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{
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assert(timespec_is_canonical(a) && timespec_is_canonical(b));
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struct timespec ret;
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ret.tv_nsec = a.tv_nsec - b.tv_nsec;
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if ( ret.tv_nsec < 0 )
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{
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ret.tv_nsec += NANOSECONDS_PER_SECOND;
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if ( a.tv_sec != TIME_MIN )
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a.tv_sec--;
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else if ( b.tv_sec != TIME_MAX )
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b.tv_sec++;
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else
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goto overflow;
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}
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if ( __builtin_sub_overflow(a.tv_sec, b.tv_sec, &ret.tv_sec) )
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goto overflow;
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*res = ret;
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return false;
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overflow:
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*res = b.tv_sec >= 0 ?
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timespec_make(TIME_MIN, 0) :
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timespec_make(TIME_MAX, NANOSECONDS_PER_SECOND - 1);
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return true;
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}
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struct timespec timespec_sub(struct timespec a, struct timespec b)
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{
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struct timespec ret;
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timespec_sub_overflow(a, b, &ret);
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return ret;
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}
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