diff options
Diffstat (limited to 'src/common')
| -rw-r--r-- | src/common/compat_libevent.c | 30 | ||||
| -rw-r--r-- | src/common/compat_libevent.h | 1 |
2 files changed, 31 insertions, 0 deletions
diff --git a/src/common/compat_libevent.c b/src/common/compat_libevent.c index b7987bc99a..61cbe91488 100644 --- a/src/common/compat_libevent.c +++ b/src/common/compat_libevent.c @@ -673,3 +673,33 @@ tor_gettimeofday_cache_set(const struct timeval *tv) #endif #endif +/** + * As tor_gettimeofday_cached, but can never move backwards in time. + * + * The returned value may diverge from wall-clock time, since wall-clock time + * can trivially be adjusted backwards, and this can't. Don't mix wall-clock + * time with these values in the same calculation. + * + * Depending on implementation, this function may or may not "smooth out" huge + * jumps forward in wall-clock time. It may or may not keep its results + * advancing forward (as opposed to stalling) if the wall-clock time goes + * backwards. The current implementation does neither of of these. + * + * This function is not thread-safe; do not call it outside the main thread. + * + * In future versions of Tor, this may return a time does not have its + * origin at the Unix epoch. + */ +void +tor_gettimeofday_cached_monotonic(struct timeval *tv) +{ + struct timeval last_tv = { 0, 0 }; + + tor_gettimeofday_cached(tv); + if (timercmp(tv, &last_tv, <)) { + memcpy(tv, &last_tv, sizeof(struct timeval)); + } else { + memcpy(&last_tv, tv, sizeof(struct timeval)); + } +} + diff --git a/src/common/compat_libevent.h b/src/common/compat_libevent.h index 17e0523789..f0d1828b7b 100644 --- a/src/common/compat_libevent.h +++ b/src/common/compat_libevent.h @@ -94,6 +94,7 @@ void tor_gettimeofday_cache_clear(void); #ifdef TOR_UNIT_TESTS void tor_gettimeofday_cache_set(const struct timeval *tv); #endif +void tor_gettimeofday_cached_monotonic(struct timeval *tv); #endif |