diff options
Diffstat (limited to 'absl/synchronization/internal/kernel_timeout.h')
| -rw-r--r-- | absl/synchronization/internal/kernel_timeout.h | 28 |
1 files changed, 25 insertions, 3 deletions
diff --git a/absl/synchronization/internal/kernel_timeout.h b/absl/synchronization/internal/kernel_timeout.h index 952bd2c6..4e361a6a 100644 --- a/absl/synchronization/internal/kernel_timeout.h +++ b/absl/synchronization/internal/kernel_timeout.h @@ -15,6 +15,10 @@ #ifndef ABSL_SYNCHRONIZATION_INTERNAL_KERNEL_TIMEOUT_H_ #define ABSL_SYNCHRONIZATION_INTERNAL_KERNEL_TIMEOUT_H_ +#ifndef _WIN32 +#include <sys/types.h> +#endif + #include <algorithm> #include <chrono> // NOLINT(build/c++11) #include <cstdint> @@ -78,6 +82,18 @@ class KernelTimeout { // this method in the case of a spurious wakeup. struct timespec MakeRelativeTimespec() const; +#ifndef _WIN32 + // Convert to `struct timespec` for interfaces that expect an absolute timeout + // on a specific clock `c`. This is similar to `MakeAbsTimespec()`, but + // callers usually want to use this method with `CLOCK_MONOTONIC` when + // relative timeouts are requested, and when the appropriate interface expects + // an absolute timeout relative to a specific clock (for example, + // pthread_cond_clockwait() or sem_clockwait()). If !has_timeout(), attempts + // to convert to a reasonable absolute timeout, but callers should to test + // has_timeout() prefer to use a more appropriate interface. + struct timespec MakeClockAbsoluteTimespec(clockid_t c) const; +#endif + // Convert to unix epoch nanos for interfaces that expect an absolute timeout // in nanoseconds. If !has_timeout() or is_relative_timeout(), attempts to // convert to a reasonable absolute timeout, but callers should to test @@ -125,12 +141,18 @@ class KernelTimeout { // after the unix epoch. // - If the low bit is 1, then the high 63 bits is the number of nanoseconds // after the epoch used by SteadyClockNow(). + // + // In all cases the time is stored as an absolute time, the only difference is + // the clock epoch. The use of absolute times is important since in the case + // of a relative timeout with a spurious wakeup, the program would have to + // restart the wait, and thus needs a way of recomputing the remaining time. uint64_t rep_; // Returns the number of nanoseconds stored in the internal representation. - // Together with is_absolute_timeout() and is_relative_timeout(), the return - // value is used to compute when the timeout should occur. - int64_t RawNanos() const { return static_cast<int64_t>(rep_ >> 1); } + // When combined with the clock epoch indicated by the low bit (which is + // accessed through is_absolute_timeout() and is_relative_timeout()), the + // return value is used to compute when the timeout should occur. + int64_t RawAbsNanos() const { return static_cast<int64_t>(rep_ >> 1); } // Converts to nanoseconds from now. Since the return value is a relative // duration, it should be recomputed by calling this method in the case of a |