Limit the number of shrink to fit

This is not very important, but it seems a waste to do it for each stop
time. This reduce a bit the loading time, but not in a really important
way (tested on the Ile de france mobilité dataset).

Cargo.toml

@@ -1,7 +1,7 @@
 [package]
 description = "Read GTFS (public transit timetables) files"
 name = "gtfs-structures"
-version = "0.36.0"
+version = "0.36.1"
 authors = ["Tristram Gräbener <[email protected]>", "Antoine Desbordes <[email protected]>"]
 repository = "https://github.com/rust-transit/gtfs-structure"
 license = "MIT"

src/gtfs.rs

@@ -290,6 +290,10 @@ fn to_calendar_dates(cd: Vec<CalendarDate>) -> HashMap<String, Vec<CalendarDate>
     res
 }
 
+// Number of stoptimes to `pop` from the list before using shrink_to_fit to reduce the memory footprint
+// Hardcoded to what seems a sensible value, but if needed we could make this a parameter, feel free to open an issue if this could help
+const NB_STOP_TIMES_BEFORE_SHRINK: usize = 1_000_000;
+
 fn create_trips(
     raw_trips: Vec<RawTrip>,
     mut raw_stop_times: Vec<RawStopTime>,
@@ -311,15 +315,20 @@ fn create_trips(
         frequencies: vec![],
     }));
 
+    let mut st_idx = 0;
     while let Some(s) = raw_stop_times.pop() {
+        st_idx += 1;
         let trip = &mut trips
             .get_mut(&s.trip_id)
             .ok_or_else(|| Error::ReferenceError(s.trip_id.to_string()))?;
         let stop = stops
             .get(&s.stop_id)
             .ok_or_else(|| Error::ReferenceError(s.stop_id.to_string()))?;
         trip.stop_times.push(StopTime::from(s, Arc::clone(stop)));
-        raw_stop_times.shrink_to_fit();
+        if st_idx % NB_STOP_TIMES_BEFORE_SHRINK == 0 {
+            println!("hop on shrink = {}", st_idx);
+            raw_stop_times.shrink_to_fit();
+        }
     }
 
     for trip in &mut trips.values_mut() {