sumtimespec.c


1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50

/* See LICENSE file for copyright and license details. */
#include "libsimple.h"


int
libsimple_sumtimespec(struct timespec *sum, const struct timespec *augend, const struct timespec *addend)
{
	long int ns = augend->tv_nsec + addend->tv_nsec;
	time_t s;
	int ret = 0;

	s = augend->tv_sec + addend->tv_sec;
	if ((augend->tv_sec < 0) == (addend->tv_sec < 0)) {
		if (augend->tv_sec >= 0 && augend->tv_sec > TIME_MAX - addend->tv_sec) {
			s = TIME_MAX;
			ns = 999999999L;
			errno = ERANGE;
			ret = -1;
		} else if (augend->tv_sec < 0 && augend->tv_sec + addend->tv_sec < TIME_MIN) {
			s = TIME_MIN;
			ns = 0;
			errno = ERANGE;
			ret = -1;
		}
	}

	if (ns < 0) {
		if (s == TIME_MIN) {
			ns = 0L;
			errno = ERANGE;
			ret = -1;
		} else {
			s -= 1;
			ns += 1000000000L;
		}
	} else if (ns >= 1000000000L) {
		if (s == TIME_MAX) {
			ns = 999999999L;
			errno = ERANGE;
			ret = -1;
		} else {
			s += 1;
			ns -= 1000000000L;
		}
	}

	sum->tv_sec = s;
	sum->tv_nsec = ns;
	return ret;
}