Add comments on timestamp cast needs

EnricoMi · Nov 7, 2024 · 94a40b2 · 94a40b2
1 parent d2d7cab
commit 94a40b2
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Showing 2 changed files with 10 additions and 0 deletions.
diff --git a/python/pyarrow/_flight.pyx b/python/pyarrow/_flight.pyx
@@ -750,6 +750,9 @@ cdef class FlightEndpoint(_Weakrefable):
 
         if expiration_time is not None:
             if isinstance(expiration_time, lib.TimestampScalar):
+                # Convert into OS-dependent std::chrono::system_clock::time_point from
+                # std::chrono::time_point<std::chrono::system_clock, std::chrono::nanoseconds>
+                # See Timestamp in cpp/src/arrow/flight/types.h
                 self.endpoint.expiration_time = TimePoint_to_system_time(TimePoint_from_ns(
                     expiration_time.cast(timestamp("ns")).value))
             else:
@@ -784,6 +787,9 @@ cdef class FlightEndpoint(_Weakrefable):
             int64_t time_since_epoch
         if self.endpoint.expiration_time.has_value():
             time_since_epoch = TimePoint_to_ns(
+                # Convert from OS-dependent std::chrono::system_clock::time_point into
+                # std::chrono::time_point<std::chrono::system_clock, std::chrono::nanoseconds>
+                # See Timestamp in cpp/src/arrow/flight/types.h
                 TimePoint_from_system_time(self.endpoint.expiration_time.value()))
             return lib.scalar(time_since_epoch, timestamp("ns", "UTC"))
         return None

diff --git a/python/pyarrow/src/arrow/python/datetime.h b/python/pyarrow/src/arrow/python/datetime.h
@@ -145,11 +145,15 @@ inline TimePoint TimePoint_from_ns(int64_t val) {
 }
 
 ARROW_PYTHON_EXPORT
+// Note: Needed by FlightEndpoint.expiration_time, which is an OS-dependent
+// std::chrono::system_clock::time_point
 inline std::chrono::system_clock::time_point TimePoint_to_system_time(TimePoint val) {
   return std::chrono::time_point_cast<std::chrono::system_clock::duration>(val);
 }
 
 ARROW_PYTHON_EXPORT
+// Note: Needed by FlightEndpoint.expiration_time, which is an OS-dependent
+// std::chrono::system_clock::time_point
 inline TimePoint TimePoint_from_system_time(std::chrono::system_clock::time_point val) {
   return std::chrono::time_point_cast<TimePoint::duration>(val);
 }