我编写了一个程序来探查系统的C时间.h函数的极限,并以JSON格式输出它们。那么依赖这些函数的其他东西就可以知道它们的限制。
# system time.h limits, as JSON
{
"gmtime": {
"max": 2147483647,
"min": -2147483648
},
"localtime": {
"max": 2147483647,
"min": -2147483648
},
"mktime": {
"max": {
"tm_sec": 7,
"tm_min": 14,
"tm_hour": 19,
"tm_mday": 18,
"tm_mon": 0,
"tm_year": 138,
"tm_wday": 1,
"tm_yday": 17,
"tm_isdst": 0
},
"min": {
"tm_sec": 52,
"tm_min": 45,
"tm_hour": 12,
"tm_mday": 13,
"tm_mon": 11,
"tm_year": 1,
"tm_wday": 5,
"tm_yday": 346,
"tm_isdst": 0
}
}
}
gmtime()和localtime()很简单,它们只需要数字,但是mktime()需要一个tm结构体。我编写了一个自定义函数来将tm struct转换为JSON哈希表。
/* Dump a tm struct as a json fragment */
char * tm_as_json(const struct tm* date) {
char *date_json = malloc(sizeof(char) * 512);
#ifdef HAS_TM_TM_ZONE
char zone_json[32];
#endif
#ifdef HAS_TM_TM_GMTOFF
char gmtoff_json[32];
#endif
sprintf(date_json,
"\"tm_sec\": %d, \"tm_min\": %d, \"tm_hour\": %d, \"tm_mday\": %d, \"tm_mon\": %d, \"tm_year\": %d, \"tm_wday\": %d, \"tm_yday\": %d, \"tm_isdst\": %d",
date->tm_sec, date->tm_min, date->tm_hour, date->tm_mday,
date->tm_mon, date->tm_year, date->tm_wday, date->tm_yday, date->tm_isdst
);
#ifdef HAS_TM_TM_ZONE
sprintf(&zone_json, ", \"tm_zone\": %s", date->tm_zone);
strcat(date_json, zone_json);
#endif
#ifdef HAS_TM_TM_GMTOFF
sprintf(&gmtoff_json", \"tm_gmtoff\": %ld", date->tm_gmtoff);
strcat(date_json, gmtoff_json);
#endif
return date_json;
}
有没有一种通用的方法,可以针对任何给定的结构体进行操作?
注意:这是C语言,不是C++。