本段落提供ACE_OS::mktime函数的源代码解析与详细说明。此函数为ACE（Adaptive Communication Environment）框架的一部分，用于将时间结构转换成日历时间值，是进行日期和时间处理的重要工具。
```c
static __time64_t _make__time64_t(struct tm *tb, int ultflag) {
__time64_t tmptm1, tmptm2, tmptm3;
struct tm tbtemp;
long dstbias = 0;
long timezone = 0;
// Validate input
_VALIDATE_RETURN(tb != NULL, EINVAL, (__time64_t)(-1));
if (((tmptm1 = tb->tm_year) < _BASE_YEAR - 1) || (tmptm1 > _MAX_YEAR64 + 1))
goto err_mktime;
// Adjust month value to be in range 0 - 11
if ((tb->tm_mon < 0) || (tb->tm_mon > 11)) {
tmptm1 += tb->tm_mon / 12;
tb->tm_mon %= 12;
if (tb->tm_mon < 0) {
tb->tm_mon += 12;
tmptm1--;
}
// Ensure year count is still in range
if ((tmptm1 < _BASE_YEAR - 1) || (tmptm1 > _MAX_YEAR64 + 1))
goto err_mktime;
}
// Calculate days elapsed minus one to the given month, adjust for leap years
tmptm2 = _days[tb->tm_mon];
if (_IS_LEAP_YEAR(tmptm1) && (tb->tm_mon > 1))
tmptm2++;
// Calculate total elapsed days since base date (midnight, 1170 UTC)
tmptm3 = ((tmptm1 - _BASE_YEAR) * 365 + _ELAPSED_LEAP_YEARS(tmptm1)) + tmptm2;
// Add current day
tmptm1 = tmptm3 + (__time64_t)(tb->tm_mday);
// Calculate elapsed hours since base date
tmptm2 = tmptm1 * 24;
tmptm1 = tmptm2 + (__time64_t)tb->tm_hour;
// Calculate elapsed minutes since base date
tmptm2 = tmptm1 * 60;
tmptm1 = tmptm2 + (__time64_t)tb->tm_min;
// Calculate elapsed seconds since base date
tmptm2 = tmptm1 * 60;
tmptm1 = tmptm2 + (__time64_t)tb->tm_sec;
if (ultflag) {
__tzset();
_ERRCHECK(_get_dstbias(&dstbias));
_ERRCHECK(_get_timezone(&timezone));
// Adjust for timezone
tmptm1 += timezone;
// Convert to time block structure and adjust for DST
if (_localtime64_s(&tbtemp, &tmptm1) != 0)
goto err_mktime;
if ((tb->tm_isdst > 0) || ((tb->tm_isdst < 0) && (tbtemp.tm_isdst > 0))) {
tmptm1 += dstbias;
if (_localtime64_s(&tbtemp, &tmptm1) != 0)
goto err_mktime;
}
} else {
if (_gmtime64_s(&tbtemp, &tmptm1) != 0)
goto err_mktime;
}
*tb = tbtemp;
return tmptm1;
err_mktime:
errno = EINVAL;
return (__time64_t)(-1);
}
```
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