1 #include <stdlib.h>
2 #include <stdio.h>
3 #include <unistd.h>
4 #include <sys/limits.h>
5 #include <sys/time.h>
6 #include <time.h>
7 #include <errno.h>
8
9 #include <string.h>
10
11
12
nanotime(void)13 long long nanotime(void)
14 {
15 struct timespec t;
16
17 if(clock_gettime(CLOCK_MONOTONIC, &t)) {
18 fprintf(stderr,"clock failure\n");
19 exit(1);
20 }
21
22 return (((long long) t.tv_sec) * 1000000000LL) +
23 ((long long) t.tv_nsec);
24 }
25
ts_sub(struct timespec a,struct timespec b)26 static struct timespec ts_sub(struct timespec a, struct timespec b)
27 {
28 struct timespec r;
29 r.tv_sec = a.tv_sec - b.tv_sec;
30 r.tv_nsec = a.tv_nsec - b.tv_nsec;
31 if(r.tv_nsec < 0) {
32 r.tv_sec--;
33 r.tv_nsec += 1000 * 1000 * 1000;
34 }
35 if(r.tv_sec < 0 && r.tv_nsec > 0) {
36 r.tv_sec++;
37 r.tv_nsec -= 1000 * 1000 * 1000;
38 }
39 return r;
40 }
41
ts_min(struct timespec a,struct timespec b)42 static struct timespec ts_min(struct timespec a, struct timespec b)
43 {
44 if(a.tv_sec < b.tv_sec || (a.tv_sec == b.tv_sec && a.tv_nsec < b.tv_nsec))
45 return a;
46 else
47 return b;
48 }
49
ts_max(struct timespec a,struct timespec b)50 static struct timespec ts_max(struct timespec a, struct timespec b)
51 {
52 if(a.tv_sec < b.tv_sec || (a.tv_sec == b.tv_sec && a.tv_nsec < b.tv_nsec))
53 return b;
54 else
55 return a;
56 }
57
main(int argc,char ** argv)58 int main(int argc, char **argv)
59 {
60 long long tnow, tlast;
61 struct timespec t1, dtmin, dtminp, dtmax;
62 int print_interval = 50000;
63 int print_countdown = 1;
64 int clock_id = CLOCK_MONOTONIC;
65 dtmin.tv_sec = INT_MAX;
66 dtmin.tv_nsec = 0;
67 dtminp.tv_sec = INT_MAX;
68 dtminp.tv_nsec = 0;
69 dtmax.tv_sec = 0;
70 dtmax.tv_nsec = 0;
71 tlast = 0;
72
73 if(argc == 2) {
74 clock_id = atoi(argv[1]);
75 printf("using clock %d\n", clock_id);
76 }
77 clock_gettime(clock_id, &t1);
78
79 for(;;) {
80 struct timespec t, dt;
81 clock_gettime(clock_id, &t);
82 dt = ts_sub(t, t1);
83 t1 = t;
84 dtmin = ts_min(dtmin, dt);
85 if(dt.tv_sec > 0 || dt.tv_nsec > 0)
86 dtminp = ts_min(dtminp, dt);
87 if(print_countdown != print_interval)
88 dtmax = ts_max(dtmax, dt);
89 if(--print_countdown == 0) {
90 fprintf(stderr,"%09ld.%09ld, dt %ld.%09ld, min %ld.%09ld, minp %ld.%09ld, max %ld.%09ld\n",
91 t.tv_sec, t.tv_nsec, dt.tv_sec, dt.tv_nsec,
92 dtmin.tv_sec, dtmin.tv_nsec, dtminp.tv_sec, dtminp.tv_nsec,
93 dtmax.tv_sec, dtmax.tv_nsec);
94 print_countdown = print_interval;
95 }
96 }
97 for(;;) {
98 tnow = nanotime();
99 if(tnow < tlast) {
100 #if 0
101 fprintf(stderr,"time went backwards: %lld -> %lld\n",
102 tlast, tnow);
103 exit(1);
104 #endif
105 fprintf(stderr,"%lld ROLLBACK\n", tnow);
106 } else {
107 fprintf(stderr,"%lld\n", tnow);
108 }
109 tlast = tnow;
110 }
111
112 return 0;
113 }
114