RGBCube/serenity
1
Fork 0
mirror of https://github.com/RGBCube/serenity synced 2025-05-14 09:34:59 +00:00
Code Issues Activity Actions

LibC: Split time_t range validation to separate helper function

Browse source 
Right now, the tm_to_time helper invokes time_to_tm to validate the
time_t it creates. Soon, both tm_to_time and time_to_tm will perform
some TZDB lookups to handle DST. This isn't a huge cost, but let's
avoid the double lookup here.
This commit is contained in:
Timothy Flynn 2022-08-01 14:59:17 -04:00 • committed by Linus Groh
parent 91e3a2aaca
commit e683ca00cc
1 changed files with 13 additions and 3 deletions
Download patch file Download diff file Expand all files Collapse all files

16
Userland/Libraries/LibC/time.cpp
View file

@ -102,13 +102,19 @@ char* ctime_r(time_t const* t, char* buf)
static int const __seconds_per_day = 60 * 60 * 24;
static struct tm* time_to_tm(struct tm* tm, time_t t)
static bool is_valid_time(time_t timestamp)
{
// Note: these correspond to the number of seconds from epoch to the dates "Jan 1 00:00:00 -2147483648" and "Dec 31 23:59:59 2147483647",
// respectively, which are the smallest and biggest representable dates without overflowing tm->tm_year, if it is an int.
constexpr time_t smallest_possible_time = -67768040609740800;
constexpr time_t biggest_possible_time = 67768036191676799;
if (t < smallest_possible_time || t > biggest_possible_time) {
return (timestamp >= smallest_possible_time) && (timestamp <= biggest_possible_time);
}
static struct tm* time_to_tm(struct tm* tm, time_t t)
{
if (!is_valid_time(t)) {
errno = EOVERFLOW;
return nullptr;
}
@ -162,8 +168,12 @@ static time_t tm_to_time(struct tm* tm, long timezone_adjust_seconds)
tm->tm_yday = day_of_year(1900 + tm->tm_year, tm->tm_mon + 1, tm->tm_mday);
time_t days_since_epoch = years_to_days_since_epoch(1900 + tm->tm_year) + tm->tm_yday;
auto timestamp = ((days_since_epoch * 24 + tm->tm_hour) * 60 + tm->tm_min) * 60 + tm->tm_sec + timezone_adjust_seconds;
if (!time_to_tm(tm, timestamp))
if (!is_valid_time(timestamp)) {
errno = EOVERFLOW;
return -1;
}
return timestamp;
}