1/*
 2 * Copyright © 2018 Alexey Dobriyan <adobriyan@gmail.com>
 3 *
 4 * Permission to use, copy, modify, and distribute this software for any
 5 * purpose with or without fee is hereby granted, provided that the above
 6 * copyright notice and this permission notice appear in all copies.
 7 *
 8 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 9 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
10 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
11 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
12 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
13 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
14 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
15 */
16#undef NDEBUG
17#include <assert.h>
18#include <errno.h>
19#include <string.h>
20#include <stdlib.h>
21#include <unistd.h>
22
23static unsigned long long xstrtoull(const char *p, char **end)
24{
25	if (*p == '0') {
26		*end = (char *)p + 1;
27		return 0;
28	} else if ('1' <= *p && *p <= '9') {
29		unsigned long long val;
30
31		errno = 0;
32		val = strtoull(p, end, 10);
33		assert(errno == 0);
34		return val;
35	} else
36		assert(0);
37}
38
39static void proc_uptime(int fd, uint64_t *uptime, uint64_t *idle)
40{
41	uint64_t val1, val2;
42	char buf[64], *p;
43	ssize_t rv;
44
45	/* save "p < end" checks */
46	memset(buf, 0, sizeof(buf));
47	rv = pread(fd, buf, sizeof(buf), 0);
48	assert(0 <= rv && rv <= sizeof(buf));
49	buf[sizeof(buf) - 1] = '\0';
50
51	p = buf;
52
53	val1 = xstrtoull(p, &p);
54	assert(p[0] == '.');
55	assert('0' <= p[1] && p[1] <= '9');
56	assert('0' <= p[2] && p[2] <= '9');
57	assert(p[3] == ' ');
58
59	val2 = (p[1] - '0') * 10 + p[2] - '0';
60	*uptime = val1 * 100 + val2;
61
62	p += 4;
63
64	val1 = xstrtoull(p, &p);
65	assert(p[0] == '.');
66	assert('0' <= p[1] && p[1] <= '9');
67	assert('0' <= p[2] && p[2] <= '9');
68	assert(p[3] == '\n');
69
70	val2 = (p[1] - '0') * 10 + p[2] - '0';
71	*idle = val1 * 100 + val2;
72
73	assert(p + 4 == buf + rv);
74}