Commit | Line | Data |
1b289682 |
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 | } |