Commit | Line | Data |
---|---|---|
1b289682 MB |
1 | /* A little program to test the limits of your system's time functions */ |
2 | ||
3 | #include <time.h> | |
4 | #include <stdio.h> | |
5 | #include <math.h> | |
6 | ||
7 | time_t Time_Zero = 0; | |
8 | ||
9 | /* Visual C++ 2008's difftime() can't do negative times */ | |
10 | double my_difftime(time_t left, time_t right) { | |
11 | double diff = (double)left - (double)right; | |
12 | return diff; | |
13 | } | |
14 | ||
15 | void check_date_max( struct tm * (*date_func)(const time_t *), char *func_name ) { | |
16 | struct tm *date; | |
17 | time_t time = 0; | |
18 | time_t last_time = 0; | |
19 | time_t time_change; | |
20 | int i; | |
21 | ||
22 | for (i = 0; i <= 63; i++) { | |
23 | date = (*date_func)(&time); | |
24 | ||
25 | /* date_func() broke or tm_year overflowed */ | |
26 | if(date == NULL || date->tm_year < 69) | |
27 | break; | |
28 | ||
29 | last_time = time; | |
30 | time += time + 1; | |
31 | ||
32 | /* time_t overflowed */ | |
33 | if( time < last_time ) | |
34 | break; | |
35 | } | |
36 | ||
37 | /* Binary search for the exact failure point */ | |
38 | time = last_time; | |
39 | time_change = last_time / 2; | |
40 | ||
41 | do { | |
42 | time += time_change; | |
43 | ||
44 | date = (*date_func)(&time); | |
45 | ||
46 | /* date_func() broke or tm_year overflowed or time_t overflowed */ | |
47 | if(date == NULL || date->tm_year < 69 || time < last_time) { | |
48 | time = last_time; | |
49 | time_change = time_change / 2; | |
50 | } | |
51 | else { | |
52 | last_time = time; | |
53 | } | |
54 | } while(time_change > 0); | |
55 | ||
56 | printf("%20s max %.0f\n", func_name, my_difftime(last_time, Time_Zero)); | |
57 | } | |
58 | ||
59 | ||
60 | void check_date_min( struct tm * (*date_func)(const time_t *), char *func_name ) { | |
61 | struct tm *date; | |
62 | time_t time = -1; | |
63 | time_t last_time = 0; | |
64 | time_t time_change; | |
65 | int i; | |
66 | ||
67 | for (i = 1; i <= 63; i++) { | |
68 | date = (*date_func)(&time); | |
69 | ||
70 | /* date_func() broke or tm_year underflowed */ | |
71 | if(date == NULL || date->tm_year > 70) | |
72 | break; | |
73 | ||
74 | last_time = time; | |
75 | time += time; | |
76 | ||
77 | /* time_t underflowed */ | |
78 | if( time > last_time ) | |
79 | break; | |
80 | } | |
81 | ||
82 | /* Binary search for the exact failure point */ | |
83 | time = last_time; | |
84 | time_change = last_time / 2; | |
85 | ||
86 | do { | |
87 | time += time_change; | |
88 | ||
89 | date = (*date_func)(&time); | |
90 | ||
91 | /* gmtime() broke or tm_year overflowed or time_t overflowed */ | |
92 | if(date == NULL || date->tm_year > 70 || time > last_time) { | |
93 | time = last_time; | |
94 | time_change = time_change / 2; | |
95 | } | |
96 | else { | |
97 | last_time = time; | |
98 | } | |
99 | } while(time_change < 0); | |
100 | ||
101 | printf("%20s min %.0f\n", func_name, my_difftime(last_time, Time_Zero)); | |
102 | } | |
103 | ||
104 | ||
105 | int main(void) { | |
106 | check_date_max(gmtime, "gmtime"); | |
107 | check_date_max(localtime, "localtime"); | |
108 | check_date_min(gmtime, "gmtime"); | |
109 | check_date_min(localtime, "localtime"); | |
110 | ||
111 | return 0; | |
112 | } |