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
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
|
/**
* @file pthread-timedwait.c
* @brief Demonstrates the effects on pthread_timedwait upon system wall clock
* change
*/
#define _POSIX_C_SOURCE 199309L
#include <stdio.h>
#include <stdbool.h>
#include <string.h>
#include <time.h>
#include <errno.h>
#include <pthread.h>
#define ARG0 "pthread_timedwait"
struct {
// desired sleep time
struct timespec t;
} opts;
/**
* @brief Raise nanosecond fraction part
* @details "05" -> 50000000, "123" -> 123000000, "005" -> 5000000
* @note used to preserve precision
*
* @param str fraction part, excluding the leading decimal point
* @param len length of \param str
* @return long the fraction part raised to nanosecond scale
*/
long raise_nsec_frac (const char *str, const size_t len) {
char m[] = { '0', '0', '0', '0', '0', '0', '0', '0', '0', 0 };
char *p;
long ret = -1;
memcpy(m, str, len > 9 ? 9 : len);
for (p = m; *p != 0 && *p == '0'; p += 1);
if (*p == 0 && m[0] == '0') {
return 0;
}
if (sscanf(p, "%ld", &ret) != 1) {
return -1;
}
return ret;
}
/**
* @brief Parse timespec from string, preserving precision
*
* @param str string to parse
* @param ts_out (optional) pointer to timespec struct
* @return true if parsed successfully and \param ts_out is set if non-null
* @return false otherwise. errno set to EINVAL if \param str is NULL. errno set
* to EBADMSG on format error
*/
bool parse_ts (const char *str, struct timespec *ts_out) {
long long sec = 0;
long nsec = 0;
int fr;
const char *frac, *ipart;
if (str == NULL) {
errno = EINVAL;
return false;
}
if (str[0] == '.' || str[0] == ',') {
ipart = NULL;
frac = str + 1;
}
else {
ipart = str;
frac = strchr(str, '.');
if (frac == NULL) {
frac = strchr(str, ',');
}
}
if (ipart != NULL) {
fr = sscanf(ipart, "%lld", &sec);
if (fr < 1) {
errno = EBADMSG;
return false;
}
}
if (frac != NULL) {
frac += 1;
nsec = raise_nsec_frac(frac, strlen(frac));
if (nsec < 0) {
errno = EBADMSG;
return false;
}
}
if (ts_out != NULL) {
ts_out->tv_sec = sec;
ts_out->tv_nsec = nsec;
}
return true;
}
bool parse_args (const int argc, const char **argv) {
if (argc <= 1) {
fprintf(stderr, ARG0" <TIME>\n");
return false;
}
if (!parse_ts(argv[1], &opts.t)) {
perror(ARG0);
return false;
}
return true;
}
int main (const int argc, const char **argv) {
pthread_cond_t cond = PTHREAD_COND_INITIALIZER;
pthread_mutex_t mtx = PTHREAD_MUTEX_INITIALIZER;
struct timespec ts[2];
struct timespec tp_deadline;
if (!parse_args(argc, argv)) {
return 1;
}
clock_gettime(CLOCK_REALTIME, &tp_deadline);
tp_deadline.tv_nsec += opts.t.tv_nsec;
tp_deadline.tv_sec += opts.t.tv_sec + (tp_deadline.tv_nsec / 1000000000);
tp_deadline.tv_nsec %= 1000000000;
clock_gettime(CLOCK_MONOTONIC, ts);
pthread_mutex_lock(&mtx);
pthread_cond_timedwait(&cond, &mtx, &tp_deadline);
clock_gettime(CLOCK_MONOTONIC, ts + 1);
ts[1].tv_nsec -= ts[0].tv_nsec;
ts[1].tv_sec -= ts[0].tv_sec;
if (ts[1].tv_nsec < 0) {
ts[1].tv_sec -= 1;
ts[1].tv_nsec += 1000000000;
}
printf("%lld.%03ld\n", (long long)ts[1].tv_sec, ts[1].tv_nsec / 1000000);
return 0;
}
|
