reduce data exchanges across boundary

gpx-rs/engine/src/engine/derived/statistics_buffer.rs

@@ -10,6 +10,9 @@ pub const NO_TIME: i64 = i64::MIN;
 /// trackpoints are the difference between its two ends: see [`StatisticsBuffer::slice`].
 /// Times are in milliseconds, distances in kilometers, speeds in km/h. Missing times are
 /// [`NO_TIME`], missing measures are NaN.
+///
+/// The optional values (`time`, `hr`, `cad`, `atemp`, `power`) are `None` when no trackpoint of the
+/// selection has one, and the OSM attributes are stored as [`Intervals`].
 #[derive(Debug, Default)]
 pub struct StatisticsBuffer {
     /// Statistics of the whole selection.
@@ -28,20 +31,47 @@ pub struct StatisticsBuffer {
     pub lat: Vec<f64>,
     pub ele: Vec<f64>,
     /// Timestamps, in milliseconds since the epoch.
-    pub time: Vec<i64>,
+    pub time: Option<Vec<i64>>,
-    pub hr: Vec<f64>,
+    pub hr: Option<Vec<f64>>,
-    pub cad: Vec<f64>,
+    pub cad: Option<Vec<f64>>,
-    pub atemp: Vec<f64>,
+    pub atemp: Option<Vec<f64>>,
-    pub power: Vec<f64>,
+    pub power: Option<Vec<f64>>,
-    /// Surface of the trackpoints: 0 when unknown, else 1 + its code in the categories of the
+    /// Surface of the trackpoints, see [`Intervals`].
-    /// engine (so that it is never 0 for a known surface).
+    pub surface: Intervals,
-    pub surface: Vec<u8>,
     /// Highway of the trackpoints, as the surface.
-    pub highway: Vec<u8>,
+    pub highway: Intervals,
     /// SAC hiking scale of the trackpoints, as the surface.
-    pub sac_scale: Vec<u8>,
+    pub sac_scale: Intervals,
     /// Mountain biking scale of the trackpoints, as the surface.
-    pub mtb_scale: Vec<u8>,
+    pub mtb_scale: Intervals,
+}
+
+/// A value per trackpoint that rarely changes from one trackpoint to the next, stored as the
+/// intervals of trackpoints that share it.
+///
+/// The values are 0 when unknown, else 1 + the code in the categories of the engine (so that it
+/// is never 0 for a known value). `starts[i]` is the index of the first trackpoint of the
+/// interval `i`, which ends where the next one starts, or at the last trackpoint for the last one.
+/// Both are empty when there are no trackpoints.
+#[derive(Debug, Default, PartialEq, Eq)]
+pub struct Intervals {
+    pub starts: Vec<u32>,
+    pub values: Vec<u8>,
+}
+
+impl Intervals {
+    fn clear(&mut self) {
+        self.starts.clear();
+        self.values.clear();
+    }
+
+    /// Adds the value of the trackpoint at `index`, the indices being pushed in order.
+    fn push(&mut self, index: usize, value: u8) {
+        if self.values.last() != Some(&value) {
+            self.starts.push(index as u32);
+            self.values.push(value);
+        }
+    }
 }
 
 /// 0 for an unknown value, else the code plus one. The categories hold at most 255 values, so it
@@ -50,6 +80,21 @@ fn unknown_or_next(code: Option<u8>) -> u8 {
     code.and_then(|code| code.checked_add(1)).unwrap_or(0)
 }
 
+/// Adds the value of the trackpoint at `index` to an optional column, the indices being pushed in
+/// order. The column is created at the first present value, the previous trackpoints getting
+/// `missing`.
+fn push_optional<T: Copy>(column: &mut Option<Vec<T>>, index: usize, value: Option<T>, missing: T) {
+    match (column.as_mut(), value) {
+        (Some(column), value) => column.push(value.unwrap_or(missing)),
+        (None, Some(value)) => {
+            let mut new_column = vec![missing; index];
+            new_column.push(value);
+            *column = Some(new_column);
+        }
+        (None, None) => {}
+    }
+}
+
 impl StatisticsBuffer {
     pub fn len(&self) -> usize {
         self.total_distance.len()
@@ -75,20 +120,19 @@ impl StatisticsBuffer {
         self.lng.clear();
         self.lat.clear();
         self.ele.clear();
-        self.time.clear();
+        self.time = None;
-        self.hr.clear();
+        self.hr = None;
-        self.cad.clear();
+        self.cad = None;
-        self.atemp.clear();
+        self.atemp = None;
-        self.power.clear();
+        self.power = None;
         self.surface.clear();
         self.highway.clear();
         self.sac_scale.clear();
         self.mtb_scale.clear();
 
-        let optional = |value: Option<f64>| value.unwrap_or(f64::NAN);
-
         for (segment, stats) in selected {
             for (trkpt, trkpt_stats) in segment.iter().zip(stats.local.iter()) {
+                let index = self.total_distance.len();
                 let cumul_stats = &self.global;
                 self.total_distance
                     .push(cumul_stats.total_distance + trkpt_stats.total_distance);
@@ -116,15 +160,15 @@ impl StatisticsBuffer {
                 self.lng.push(trkpt.coordinates.lng);
                 self.lat.push(trkpt.coordinates.lat);
                 self.ele.push(trkpt.ele);
-                self.time.push(trkpt.time.unwrap_or(NO_TIME));
+                push_optional(&mut self.time, index, trkpt.time, NO_TIME);
-                self.hr.push(optional(trkpt.hr.map(f64::from)));
+                push_optional(&mut self.hr, index, trkpt.hr.map(f64::from), f64::NAN);
-                self.cad.push(optional(trkpt.cad.map(f64::from)));
+                push_optional(&mut self.cad, index, trkpt.cad.map(f64::from), f64::NAN);
-                self.atemp.push(optional(trkpt.atemp.map(f64::from)));
+                push_optional(&mut self.atemp, index, trkpt.atemp.map(f64::from), f64::NAN);
-                self.power.push(optional(trkpt.power.map(f64::from)));
+                push_optional(&mut self.power, index, trkpt.power.map(f64::from), f64::NAN);
-                self.surface.push(unknown_or_next(trkpt.surface));
+                self.surface.push(index, unknown_or_next(trkpt.surface));
-                self.highway.push(unknown_or_next(trkpt.highway));
+                self.highway.push(index, unknown_or_next(trkpt.highway));
-                self.sac_scale.push(unknown_or_next(trkpt.sac_scale));
+                self.sac_scale.push(index, unknown_or_next(trkpt.sac_scale));
-                self.mtb_scale.push(unknown_or_next(trkpt.mtb_scale));
+                self.mtb_scale.push(index, unknown_or_next(trkpt.mtb_scale));
             }
             self.global.merge(&stats.global);
         }
@@ -143,7 +187,10 @@ impl StatisticsBuffer {
 
         let delta = |values: &[f64]| values[end] - values[start];
         let delta_time = |values: &[i64]| values[end] - values[start];
-        let time = |i: usize| (self.time[i] != NO_TIME).then_some(self.time[i]);
+        let time = |i: usize| {
+            let time = self.time.as_ref()?[i];
+            (time != NO_TIME).then_some(time)
+        };
         Some(GlobalStatistics {
             total_distance: delta(&self.total_distance),
             moving_distance: self
@@ -182,6 +229,17 @@ mod tests {
         (segment, stats)
     }
 
+    /// The value of the trackpoint at `index`, 0 before the first interval.
+    fn value_at(intervals: &Intervals, index: usize) -> u8 {
+        match intervals
+            .starts
+            .partition_point(|start| *start as usize <= index)
+        {
+            0 => 0,
+            next => intervals.values[next - 1],
+        }
+    }
+
     fn all_lengths(buffer: &StatisticsBuffer) -> Vec<usize> {
         vec![
             buffer.total_distance.len(),
@@ -197,15 +255,6 @@ mod tests {
             buffer.lng.len(),
             buffer.lat.len(),
             buffer.ele.len(),
-            buffer.time.len(),
-            buffer.hr.len(),
-            buffer.cad.len(),
-            buffer.atemp.len(),
-            buffer.power.len(),
-            buffer.surface.len(),
-            buffer.highway.len(),
-            buffer.sac_scale.len(),
-            buffer.mtb_scale.len(),
         ]
     }
 
@@ -290,33 +339,121 @@ mod tests {
         assert_eq!(buffer.total_time[n], duration);
         assert_eq!(buffer.total_time[2 * n - 1], 2 * duration);
         assert!(buffer.total_time.windows(2).all(|w| w[0] <= w[1]));
-        assert!(buffer.time.iter().all(|t| *t != NO_TIME));
+        assert!(buffer.time.unwrap().iter().all(|t| *t != NO_TIME));
     }
 
     #[test]
-    fn test_missing_times_and_measures_are_nan() {
+    fn test_absent_optional_values_have_no_buffer() {
         let (segment, s) = computed("data/simple.gpx");
         assert!(segment.iter().all(|trkpt| trkpt.time.is_none()));
         let mut buffer = StatisticsBuffer::default();
         buffer.update(&[(&segment, &s)]);
-        assert!(buffer.time.iter().all(|t| *t == NO_TIME));
+        assert!(buffer.time.is_none());
-        assert!(buffer.hr.iter().all(|v| v.is_nan()));
+        assert!(buffer.hr.is_none());
+        assert!(buffer.cad.is_none());
+        assert!(buffer.atemp.is_none());
+        assert!(buffer.power.is_none());
         assert_eq!(buffer.global.hr.count, 0);
         assert_eq!(buffer.global.total_time, None);
+        assert_eq!(buffer.len(), s.local.len());
+        // the slices do not need them
+        let slice = buffer.slice(0, 2).unwrap();
+        assert_eq!((slice.start_time, slice.end_time), (None, None));
     }
 
     #[test]
-    fn test_surface_and_highway_codes() {
+    fn test_present_optional_values_have_one_entry_per_trackpoint() {
+        let (segment, s) = computed("data/with_time.gpx");
+        let mut buffer = StatisticsBuffer::default();
+        buffer.update(&[(&segment, &s)]);
+        assert_eq!(buffer.time.as_ref().unwrap().len(), buffer.len());
+        assert!(buffer.hr.is_none());
+
+        let data = std::fs::read("data/with_hr.gpx").unwrap();
+        let file = parse(&data, &mut Default::default()).unwrap();
+        let segment = file.trk[0].trkseg[0].clone();
+        let s = Statistics::compute(&segment);
+        buffer.update(&[(&segment, &s)]);
+        let hr = buffer.hr.as_ref().unwrap();
+        assert_eq!(hr.len(), buffer.len());
+        assert!(hr.iter().any(|v| !v.is_nan()));
+    }
+
+    #[test]
+    fn test_a_value_missing_for_some_trackpoints_is_a_sentinel() {
+        let (mut segment, _) = computed("data/with_time.gpx");
+        let n = segment.len();
+        let mut point = segment[1].clone();
+        point.time = None;
+        point.hr = Some(120);
+        segment.splice(1, 2, vec![point]);
+        let s = Statistics::compute(&segment);
+        let mut buffer = StatisticsBuffer::default();
+        buffer.update(&[(&segment, &s)]);
+        let time = buffer.time.as_ref().unwrap();
+        assert_eq!(time.len(), n);
+        assert_eq!(time[1], NO_TIME);
+        assert_ne!(time[0], NO_TIME);
+        // the first trackpoint has no heart rate: it is filled once the first one is found
+        let hr = buffer.hr.as_ref().unwrap();
+        assert_eq!(hr.len(), n);
+        assert_eq!(hr[1], 120.0);
+        assert!(hr[0].is_nan() && hr[2].is_nan());
+        assert!(buffer.cad.is_none());
+    }
+
+    #[test]
+    fn test_surface_and_highway_intervals() {
         let (segment, s) = computed("data/with_highway.gpx");
         let mut buffer = StatisticsBuffer::default();
         buffer.update(&[(&segment, &s)]);
 
         // 0 for the trackpoints that have none, else the code of the engine plus one
-        assert_eq!(buffer.surface, [1, 1, 0, 2, 2]);
+        let surface = &buffer.surface;
-        assert_eq!(buffer.highway, [1, 1, 0, 2, 0]);
+        assert_eq!(surface.starts, [0, 2, 3]);
-        assert_eq!(buffer.sac_scale, [0, 0, 0, 1, 2]);
+        assert_eq!(surface.values, [1, 0, 2]);
-        assert_eq!(buffer.mtb_scale, [0, 0, 0, 1, 1]);
+        let highway = &buffer.highway;
+        assert_eq!(
+            (&highway.starts[..], &highway.values[..]),
+            (&[0, 2, 3, 4][..], &[1, 0, 2, 0][..])
+        );
+        let sac_scale = &buffer.sac_scale;
+        assert_eq!(
+            (&sac_scale.starts[..], &sac_scale.values[..]),
+            (&[0, 3, 4][..], &[0, 1, 2][..])
+        );
+        let mtb_scale = &buffer.mtb_scale;
+        assert_eq!(
+            (&mtb_scale.starts[..], &mtb_scale.values[..]),
+            (&[0, 3][..], &[0, 1][..])
+        );
         assert!(all_lengths(&buffer).iter().all(|len| *len == 5));
+
+        // and they can be looked up
+        let values: Vec<u8> = (0..6).map(|i| value_at(&buffer.surface, i)).collect();
+        assert_eq!(values, [1, 1, 0, 2, 2, 2]);
+    }
+
+    #[test]
+    fn test_intervals_merge_equal_neighbours_across_segments() {
+        let (mut segment, _) = computed("data/simple.gpx");
+        let points: Vec<_> = segment
+            .iter()
+            .map(|trkpt| {
+                let mut trkpt = trkpt.clone();
+                trkpt.surface = Some(4);
+                trkpt
+            })
+            .collect();
+        segment.splice(0, points.len(), points);
+        let s = Statistics::compute(&segment);
+        let mut buffer = StatisticsBuffer::default();
+        buffer.update(&[(&segment, &s), (&segment, &s)]);
+        // one interval for the two segments
+        assert_eq!(buffer.surface.starts, [0]);
+        assert_eq!(buffer.surface.values, [5]);
+        // and a single one of unknown values when nothing is known
+        assert_eq!(buffer.highway.values, [0]);
     }
 
     #[test]
@@ -331,26 +468,37 @@ mod tests {
         let s = Statistics::compute(&segment);
         let mut buffer = StatisticsBuffer::default();
         buffer.update(&[(&segment, &s)]);
-        assert_eq!((buffer.surface[0], buffer.highway[0]), (8, 255));
+        let at = |i: usize| {
-        assert_eq!((buffer.sac_scale[0], buffer.mtb_scale[0]), (1, 4));
+            (
-        assert_eq!((buffer.surface[1], buffer.highway[1]), (0, 0));
+                value_at(&buffer.surface, i),
-        assert_eq!((buffer.sac_scale[1], buffer.mtb_scale[1]), (0, 0));
+                value_at(&buffer.highway, i),
+                value_at(&buffer.sac_scale, i),
+                value_at(&buffer.mtb_scale, i),
+            )
+        };
+        assert_eq!(at(0), (8, 255, 1, 4));
+        assert_eq!(at(1), (0, 0, 0, 0));
     }
 
     #[test]
-    fn test_no_codes_without_surface_and_highway() {
+    fn test_unknown_intervals_without_surface_and_highway() {
         let (segment, s) = computed("data/simple.gpx");
         let mut buffer = StatisticsBuffer::default();
         buffer.update(&[(&segment, &s)]);
-        assert_eq!(buffer.surface.len(), s.local.len());
+        // a single interval of unknown values
-        assert!(buffer.surface.iter().all(|c| *c == 0));
+        assert_eq!(buffer.surface.starts, [0]);
-        assert!(buffer.highway.iter().all(|c| *c == 0));
+        assert_eq!(buffer.surface.values, [0]);
-        assert!(buffer.sac_scale.iter().all(|c| *c == 0));
+        assert_eq!(buffer.highway.starts, [0]);
-        assert!(buffer.mtb_scale.iter().all(|c| *c == 0));
+        assert_eq!(buffer.highway.values, [0]);
+        assert_eq!(buffer.sac_scale.values, [0]);
+        assert_eq!(buffer.mtb_scale.values, [0]);
         // and they are reset by the next update
         buffer.update(&[]);
-        assert!(buffer.surface.is_empty() && buffer.highway.is_empty());
+        assert_eq!(buffer.surface, Intervals::default());
-        assert!(buffer.sac_scale.is_empty() && buffer.mtb_scale.is_empty());
+        assert_eq!(buffer.highway, Intervals::default());
+        assert_eq!(buffer.sac_scale, Intervals::default());
+        assert_eq!(buffer.mtb_scale, Intervals::default());
+        assert_eq!(value_at(&buffer.surface, 0), 0);
     }
 
     #[test]
@@ -405,8 +553,8 @@ mod tests {
             slice.moving_time,
             Some(buffer.moving_time[end] - buffer.moving_time[start])
         );
-        assert_eq!(slice.start_time, Some(buffer.time[start]));
+        assert_eq!(slice.start_time, Some(buffer.time.as_ref().unwrap()[start]));
-        assert_eq!(slice.end_time, Some(buffer.time[end]));
+        assert_eq!(slice.end_time, Some(buffer.time.as_ref().unwrap()[end]));
         assert!(slice.total_distance < buffer.global.total_distance);
         assert!(slice.total_speed().is_some());
 

gpx-rs/engine/src/engine/engine.rs

@@ -269,6 +269,15 @@ mod tests {
 
     use super::*;
 
+    fn expand(intervals: &crate::Intervals, len: usize) -> Vec<u8> {
+        let mut values = Vec::new();
+        for (i, value) in intervals.values.iter().enumerate() {
+            let end = intervals.starts.get(i + 1).map_or(len, |end| *end as usize);
+            values.resize(end, *value);
+        }
+        values
+    }
+
     fn edit(engine: &mut Engine, command: Command) -> bool {
         engine.execute(Action::Edit(command))
     }
@@ -1250,14 +1259,14 @@ mod tests {
             ["residential", "track"]
         );
         // the trackpoints of the selection refer to them
-        assert_eq!(engine.statistics().surface, [1, 1, 0, 2, 2]);
+        assert_eq!(expand(&engine.statistics().surface, 5), [1, 1, 0, 2, 2]);
-        assert_eq!(engine.statistics().highway, [1, 1, 0, 2, 0]);
+        assert_eq!(expand(&engine.statistics().highway, 5), [1, 1, 0, 2, 0]);
         assert_eq!(
             engine.categories().sac_scale.names(),
             ["mountain_hiking", "hiking"]
         );
-        assert_eq!(engine.statistics().sac_scale, [0, 0, 0, 1, 2]);
+        assert_eq!(expand(&engine.statistics().sac_scale, 5), [0, 0, 0, 1, 2]);
-        assert_eq!(engine.statistics().mtb_scale, [0, 0, 0, 1, 1]);
+        assert_eq!(expand(&engine.statistics().mtb_scale, 5), [0, 0, 0, 1, 1]);
 
         // a second file goes on with the same table
         load(&mut engine, "data/with_surface.gpx");
@@ -1265,17 +1274,10 @@ mod tests {
             engine.categories().surface.names(),
             ["asphalt", "gravel", "cobblestone"]
         );
-        assert_eq!(engine.statistics().surface.len(), 80);
+        assert_eq!(engine.statistics().len(), 80);
-        assert_eq!(engine.statistics().surface[0], 1);
+        let surface = expand(&engine.statistics().surface, 80);
-        assert_eq!(
+        assert_eq!(surface[0], 1);
-            engine
+        assert_eq!(surface.iter().filter(|c| **c == 3).count(), 1);
-                .statistics()
-                .surface
-                .iter()
-                .filter(|c| **c == 3)
-                .count(),
-            1
-        );
 
         // undoing does not forget what was learned: the codes stay valid in every state
         assert!(engine.execute(Action::Undo));
@@ -1287,7 +1289,7 @@ mod tests {
         assert!(engine.execute(Action::Redo));
         let first = engine.order()[0];
         select_files(&mut engine, &[first]);
-        assert_eq!(engine.statistics().surface, [1, 1, 0, 2, 2]);
+        assert_eq!(expand(&engine.statistics().surface, 5), [1, 1, 0, 2, 2]);
     }
 
     #[test]

gpx-rs/wasm/src/lib.rs

@@ -14,7 +14,7 @@ use std::cell::RefCell;
 use wasm_bindgen::prelude::*;
 
 use gpx_engine::{self as engine, Action, Command, Engine, FileId, LngLat, LngLatBounds};
-use js_sys::{Array, BigInt64Array, Float64Array, Object, Reflect, Uint8Array};
+use js_sys::{Array, BigInt64Array, Float64Array, Object, Reflect, Uint8Array, Uint32Array};
 
 #[wasm_bindgen]
 #[derive(Clone, Copy)]
@@ -146,32 +146,63 @@ stats_getter!(lng, Float64Array);
 stats_getter!(lat, Float64Array);
 stats_getter!(ele, Float64Array);
 
-/// Timestamps in milliseconds since the epoch (`NO_TIME`, the smallest i64, when missing).
+// The optional values are `undefined` when no trackpoint of the selection has one, else they have
-#[wasm_bindgen]
+// an entry per trackpoint, the missing ones being NaN (`NO_TIME` for the timestamps).
-pub fn timestamps() -> BigInt64Array {
+macro_rules! optional_stats_getter {
-    with_stats(|s| unsafe { BigInt64Array::view(&s.time) })
+    ($name:ident, $field:ident, $array:ident) => {
-        .unwrap_or_else(|| BigInt64Array::new_with_length(0))
+        #[wasm_bindgen]
+        pub fn $name() -> Option<$array> {
+            with_stats(|s| {
+                s.$field
+                    .as_ref()
+                    .map(|values| unsafe { $array::view(values) })
+            })
+            .flatten()
+        }
+    };
 }
 
+// Timestamps in milliseconds since the epoch (`NO_TIME`, the smallest i64, when missing).
+optional_stats_getter!(timestamps, time, BigInt64Array);
+
 /// Value of the timestamps of the trackpoints that have none.
 #[wasm_bindgen]
 pub fn no_time() -> i64 {
     engine::NO_TIME
 }
 
-stats_getter!(hr, Float64Array);
+optional_stats_getter!(hr, hr, Float64Array);
-stats_getter!(cad, Float64Array);
+optional_stats_getter!(cad, cad, Float64Array);
-stats_getter!(atemp, Float64Array);
+optional_stats_getter!(atemp, atemp, Float64Array);
-stats_getter!(power, Float64Array);
+optional_stats_getter!(power, power, Float64Array);
 
-// Surface, highway, SAC scale and MTB scale of the trackpoints: 0 when unknown, else 1 + the index
+// Surface, highway, SAC scale and MTB scale of the trackpoints, as intervals of trackpoints that
-// in `surfaces()`, `highways()`, `sac_scales()` or `mtb_scales()`.
+// have the same value: `<name>_starts` holds the index of the first trackpoint of each interval,
-stats_getter!(surface, Uint8Array);
+// and `<name>_values` its value (0 when unknown, else 1 + the index in `surfaces()`,
-stats_getter!(highway, Uint8Array);
+// `highways()`, `sac_scales()` or `mtb_scales()`). A value that is unknown for every trackpoint is
-stats_getter!(sac_scale, Uint8Array);
+// a single interval.
-stats_getter!(mtb_scale, Uint8Array);
+macro_rules! intervals_getters {
+    ($starts:ident, $values:ident, $field:ident) => {
+        #[wasm_bindgen]
+        pub fn $starts() -> Uint32Array {
+            with_stats(|s| unsafe { Uint32Array::view(&s.$field.starts) })
+                .unwrap_or_else(|| Uint32Array::new_with_length(0))
+        }
 
-/// The names of the surfaces, in the order of their codes (see `surface`). The list only grows:
+        #[wasm_bindgen]
+        pub fn $values() -> Uint8Array {
+            with_stats(|s| unsafe { Uint8Array::view(&s.$field.values) })
+                .unwrap_or_else(|| Uint8Array::new_with_length(0))
+        }
+    };
+}
+
+intervals_getters!(surface_starts, surface_values, surface);
+intervals_getters!(highway_starts, highway_values, highway);
+intervals_getters!(sac_scale_starts, sac_scale_values, sac_scale);
+intervals_getters!(mtb_scale_starts, mtb_scale_values, mtb_scale);
+
+/// The names of the surfaces, in the order of their codes (see `surface_values`). The list only grows:
 /// a name keeps its index.
 #[wasm_bindgen]
 pub fn surfaces() -> StringList {
@@ -180,7 +211,7 @@ pub fn surfaces() -> StringList {
         .unchecked_into()
 }
 
-/// The names of the highways, in the order of their codes (see `highway`).
+/// The names of the highways, in the order of their codes (see `highway_values`).
 #[wasm_bindgen]
 pub fn highways() -> StringList {
     with_engine(|e| array(e.categories().highway.names(), |name| name.as_str().into()))
@@ -188,7 +219,7 @@ pub fn highways() -> StringList {
         .unchecked_into()
 }
 
-/// The names of the SAC scales, in the order of their codes (see `sac_scale`).
+/// The names of the SAC scales, in the order of their codes (see `sac_scale_values`).
 #[wasm_bindgen]
 pub fn sac_scales() -> StringList {
     with_engine(|e| {
@@ -200,7 +231,7 @@ pub fn sac_scales() -> StringList {
     .unchecked_into()
 }
 
-/// The names of the MTB scales, in the order of their codes (see `mtb_scale`).
+/// The names of the MTB scales, in the order of their codes (see `mtb_scale_values`).
 #[wasm_bindgen]
 pub fn mtb_scales() -> StringList {
     with_engine(|e| {

website/src/lib/components/elevation-profile/elevation-profile.ts

@@ -22,10 +22,16 @@ import Chart, {
 } from 'chart.js/auto';
 import { get, type Readable, type Writable } from 'svelte/store';
 import type { Coordinates } from 'gpx';
-import { NO_TIME, type SelectionStatistics } from '$lib/engine';
+import {
+    engine,
+    NO_TIME,
+    type SelectionStatistics,
+    type StatisticsMetric,
+    type StatisticsRequest,
+} from '$lib/engine';
 import type { SlicedStatistics } from '$lib/logic/selection-statistics';
 import { mode } from 'mode-watcher';
-import { categoryAt } from '$lib/trackpoint-categories';
+import { categoryValues } from '$lib/trackpoint-categories';
 import { getHighwayColor, getSlopeColor, getSurfaceColor } from '$lib/assets/colors';
 
 const { distanceUnits, velocityUnits, temperatureUnits } = settings;
@@ -62,6 +68,8 @@ export class ElevationProfile {
     private _hoveredPoint: Writable<Coordinates | null>;
     private _additionalDatasets: Readable<string[]>;
     private _elevationFill: Readable<'slope' | 'surface' | 'highway' | undefined>;
+    /** The statistics that are only read from the engine while the profile shows them. */
+    private _request: StatisticsRequest;
 
     constructor(
         statistics: Readable<SelectionStatistics>,
@@ -79,6 +87,8 @@ export class ElevationProfile {
         this._elevationFill = elevationFill;
         this._canvas = canvas;
         this._overlay = overlay;
+        this._request = engine.requestStatistics();
+        this.updateRequest();
 
         import('chartjs-plugin-zoom').then((module) => {
             Chart.register(module.default);
@@ -100,14 +110,34 @@ export class ElevationProfile {
                 this.updateData();
             });
             this._additionalDatasets.subscribe(() => {
+                // requesting a missing metric updates the data, and then the visibility
+                this.updateRequest();
                 this.updateDataVisibility();
             });
             this._elevationFill.subscribe(() => {
+                this.updateRequest();
                 this.updateFill();
             });
         });
     }
 
+    /** Asks the engine for what the profile currently shows, and nothing more. */
+    updateRequest() {
+        const metrics = new Set<StatisticsMetric>();
+        for (const dataset of get(this._additionalDatasets)) {
+            if (['speed', 'hr', 'cad', 'atemp', 'power'].includes(dataset)) {
+                metrics.add(dataset as StatisticsMetric);
+            }
+        }
+        const elevationFill = get(this._elevationFill);
+        if (elevationFill === 'slope') {
+            metrics.add('slopeSegment');
+        } else if (elevationFill) {
+            metrics.add(elevationFill);
+        }
+        this._request.set(metrics);
+    }
+
     initialize() {
         let options: ChartOptions<'line'> = {
             animation: false,
@@ -400,47 +430,51 @@ export class ElevationProfile {
 
         const datasets: Array<Array<any>> = [[], [], [], [], [], []];
         const { global } = data;
+        const surfaces = categoryValues(data.surface, data.length);
+        const highways = categoryValues(data.highway, data.length);
+        const sacScales = categoryValues(data.sacScale, data.length);
+        const mtbScales = categoryValues(data.mtbScale, data.length);
         for (let index = 0; index < data.length; index++) {
             const x = getConvertedDistance(data.totalDistance[index], units.distance);
             const ele = data.ele[index];
-            const timestamp = data.timestamps[index];
+            const timestamp = data.timestamps?.[index] ?? NO_TIME;
             datasets[0].push({
                 x,
                 y: ele ? getConvertedElevation(ele, units.distance) : 0,
                 time: timestamp === NO_TIME ? undefined : new Date(Number(timestamp)),
                 slope: {
                     at: data.slope[index],
-                    segment: data.slopeSegmentSlope[index],
+                    segment: data.slopeSegmentSlope?.[index] ?? NaN,
-                    length: data.slopeSegmentDistance[index],
+                    length: data.slopeSegmentDistance?.[index] ?? NaN,
                 },
-                surface: categoryAt(data.surface, data.surfaces, index),
+                surface: surfaces[index],
-                highway: categoryAt(data.highway, data.highways, index),
+                highway: highways[index],
-                sacScale: categoryAt(data.sacScale, data.sacScales, index),
+                sacScale: sacScales[index],
-                mtbScale: categoryAt(data.mtbScale, data.mtbScales, index),
+                mtbScale: mtbScales[index],
                 coordinates: { lat: data.lat[index], lon: data.lng[index] },
                 index,
             });
-            if ((global.totalTime ?? 0) > 0) {
+            if (data.speed && (global.totalTime ?? 0) > 0) {
                 datasets[1].push({
                     x,
                     y: getConvertedVelocity(data.speed[index], units.velocity, units.distance),
                     index,
                 });
             }
-            if (global.hr) {
+            if (data.hr) {
                 datasets[2].push({ x, y: data.hr[index], index });
             }
-            if (global.cad) {
+            if (data.cad) {
                 datasets[3].push({ x, y: data.cad[index], index });
             }
-            if (global.atemp) {
+            if (data.atemp) {
                 datasets[4].push({
                     x,
                     y: getConvertedTemperature(data.atemp[index], units.temperature),
                     index,
                 });
             }
-            if (global.power) {
+            if (data.power) {
                 datasets[5].push({ x, y: data.power[index], index });
             }
         }
@@ -613,6 +647,7 @@ export class ElevationProfile {
     }
 
     destroy() {
+        this._request.release();
         if (this._chart) {
             this._chart.destroy();
             this._chart = null;

website/src/lib/engine.ts

@@ -2,6 +2,7 @@ import { browser } from '$app/environment';
 import { get, writable, type Readable, type Writable } from 'svelte/store';
 import { FileColorAllocator, normalizeColor } from '$lib/file-colors';
 import { setHidden, type Visibility } from '$lib/file-visibility';
+import type { CategoryIntervals } from '$lib/trackpoint-categories';
 import { selectedElementIds, type FileTreeNode } from '$lib/selection-helpers';
 import type { Feature, FeatureCollection, LineString, Point } from 'geojson';
 import type {
@@ -106,56 +107,62 @@ const EMPTY_STATISTICS: GlobalStatistics = { totalDistance: 0, elevationGain: 0,
  */
 export const NO_TIME = -(2n ** 63n);
 
+/**
+ * Statistics of the selection that are only read from the engine when something asks for them
+ * (see `Engine.requestStatistics`). A metric can bring several arrays.
+ */
+export type StatisticsMetric =
+    | 'speed'
+    | 'hr'
+    | 'cad'
+    | 'atemp'
+    | 'power'
+    /** `slopeSegmentSlope` and `slopeSegmentDistance`. */
+    | 'slopeSegment'
+    | 'surface'
+    /** `highway`, `sacScale` and `mtbScale`. */
+    | 'highway';
+
 /**
  * The statistics of the selection: its global statistics, and the values at each of its
  * trackpoints (all the selected segments, one after the other). The arrays are copies.
  *
- * Distances, times, moving values and elevation gain / loss are cumulative over the whole
+ * Distances are cumulative over the whole selection. Distances are in km, speeds in km/h, times in
- * selection. Distances are in km, speeds in km/h, times in ms (timestamps since the epoch, as
+ * ms (timestamps since the epoch, as 64-bit integers), elevations in m and slopes in %.
- * 64-bit integers), elevations in m and slopes in %. Missing timestamps are `NO_TIME`, missing
+ *
- * measures are NaN.
+ * The values of the trackpoints that the selection does not have at all (for example the heart
+ * rates, when no trackpoint has any) are `undefined`, and so are the ones that were not requested
+ * (see `StatisticsMetric`). Otherwise they have one entry per trackpoint: missing timestamps are
+ * `NO_TIME`, missing measures are NaN.
  */
 export type SelectionStatistics = {
     global: GlobalStatistics;
     /** Number of trackpoints. */
     length: number;
     totalDistance: Float64Array;
-    movingDistance: Float64Array;
-    /** Duration since the start of the selection, in ms. */
-    totalTime: BigInt64Array;
-    movingTime: BigInt64Array;
-    speed: Float64Array;
-    elevationGain: Float64Array;
-    elevationLoss: Float64Array;
     /** Slope at the trackpoint. */
     slope: Float64Array;
-    /** Slope and length (km) of the smoothed elevation segment the trackpoint belongs to. */
-    slopeSegmentSlope: Float64Array;
-    slopeSegmentDistance: Float64Array;
     lng: Float64Array;
     lat: Float64Array;
     ele: Float64Array;
-    timestamps: BigInt64Array;
+    timestamps?: BigInt64Array;
-    hr: Float64Array;
+
-    cad: Float64Array;
+    // the following need to be requested
-    atemp: Float64Array;
+    speed?: Float64Array;
-    power: Float64Array;
+    hr?: Float64Array;
-    /** Surface of the trackpoints: 0 when unknown, else 1 + the index in `surfaces`. */
+    cad?: Float64Array;
-    surface: Uint8Array;
+    atemp?: Float64Array;
-    /** Names of the surfaces, by code: a name keeps its index. */
+    power?: Float64Array;
-    surfaces: string[];
+    /** Slope and length (km) of the smoothed elevation segment the trackpoint belongs to. */
-    /** Highway of the trackpoints: 0 when unknown, else 1 + the index in `highways`. */
+    slopeSegmentSlope?: Float64Array;
-    highway: Uint8Array;
+    slopeSegmentDistance?: Float64Array;
-    /** Names of the highways, by code. */
+    surface?: CategoryIntervals;
-    highways: string[];
+    highway?: CategoryIntervals;
-    /** SAC hiking scale of the trackpoints: 0 when unknown, else 1 + the index in `sacScales`. */
+    /** SAC hiking scale. */
-    sacScale: Uint8Array;
+    sacScale?: CategoryIntervals;
-    /** Names of the SAC scales, by code. */
+    /** Mountain biking scale. */
-    sacScales: string[];
+    mtbScale?: CategoryIntervals;
-    /** Mountain biking scale of the trackpoints: 0 when unknown, else 1 + the index in `mtbScales`. */
+
-    mtbScale: Uint8Array;
-    /** Names of the mountain biking scales, by code. */
-    mtbScales: string[];
     /**
      * Global statistics of the trackpoints from `start` to `end` (both included), for example
      * the part of the elevation profile that was dragged over. `undefined` if the range is not
@@ -168,34 +175,21 @@ const EMPTY_SELECTION_STATISTICS: SelectionStatistics = {
     global: EMPTY_STATISTICS,
     length: 0,
     totalDistance: new Float64Array(),
-    movingDistance: new Float64Array(),
-    totalTime: new BigInt64Array(),
-    movingTime: new BigInt64Array(),
-    speed: new Float64Array(),
-    elevationGain: new Float64Array(),
-    elevationLoss: new Float64Array(),
     slope: new Float64Array(),
-    slopeSegmentSlope: new Float64Array(),
-    slopeSegmentDistance: new Float64Array(),
     lng: new Float64Array(),
     lat: new Float64Array(),
     ele: new Float64Array(),
-    timestamps: new BigInt64Array(),
-    hr: new Float64Array(),
-    cad: new Float64Array(),
-    atemp: new Float64Array(),
-    power: new Float64Array(),
-    surface: new Uint8Array(),
-    surfaces: [],
-    highway: new Uint8Array(),
-    highways: [],
-    sacScale: new Uint8Array(),
-    sacScales: [],
-    mtbScale: new Uint8Array(),
-    mtbScales: [],
     slice: () => undefined,
 };
 
+/** What a consumer of the statistics needs, see `Engine.requestStatistics`. */
+export type StatisticsRequest = {
+    /** Replaces the metrics needed by this consumer. */
+    set(metrics: Iterable<StatisticsMetric>): void;
+    /** The consumer does not need any metric anymore. */
+    release(): void;
+};
+
 function toPositions(flat: Float64Array): [number, number][] {
     const positions: [number, number][] = new Array(flat.length / 2);
     for (let i = 0; i < positions.length; i++) {
@@ -245,6 +239,10 @@ class Engine {
     private _statistics = writable<SelectionStatistics>(EMPTY_SELECTION_STATISTICS);
     /** Identifies the statistics currently in the engine's buffers. */
     private _statisticsVersion = 0;
+    /** What each consumer of the statistics asked for. */
+    private _statisticsRequests = new Set<Set<StatisticsMetric>>();
+    /** The metrics that were read for the current statistics. */
+    private _loadedMetrics = new Set<StatisticsMetric>();
 
     /** Ids of the files in display order. */
     readonly order: Readable<string[]> = { subscribe: this._order.subscribe };
@@ -641,42 +639,141 @@ class Engine {
         }
     }
 
-    /** Copies the statistics buffers of the engine (they are overwritten by the next action). */
+    /**
+     * Copies the statistics buffers of the engine (they are overwritten by the next action), but
+     * only the metrics that were requested.
+     */
     private readStatistics(wasm: Wasm): SelectionStatistics {
         const version = ++this._statisticsVersion;
+        this._loadedMetrics.clear();
         const totalDistance = wasm.total_distance().slice();
-        return {
+        const statistics: SelectionStatistics = {
             global: wasm.selection_statistics() ?? EMPTY_STATISTICS,
             length: totalDistance.length,
             totalDistance,
-            movingDistance: wasm.moving_distance().slice(),
-            totalTime: wasm.total_time().slice(),
-            movingTime: wasm.moving_time().slice(),
-            speed: wasm.speed().slice(),
-            elevationGain: wasm.elevation_gain().slice(),
-            elevationLoss: wasm.elevation_loss().slice(),
             slope: wasm.slope().slice(),
-            slopeSegmentSlope: wasm.slope_segment_slope().slice(),
-            slopeSegmentDistance: wasm.slope_segment_distance().slice(),
             lng: wasm.lng().slice(),
             lat: wasm.lat().slice(),
             ele: wasm.ele().slice(),
-            timestamps: wasm.timestamps().slice(),
+            timestamps: wasm.timestamps()?.slice(),
-            hr: wasm.hr().slice(),
-            cad: wasm.cad().slice(),
-            atemp: wasm.atemp().slice(),
-            power: wasm.power().slice(),
-            surface: wasm.surface().slice(),
-            surfaces: wasm.surfaces(),
-            highway: wasm.highway().slice(),
-            highways: wasm.highways(),
-            sacScale: wasm.sac_scale().slice(),
-            sacScales: wasm.sac_scales(),
-            mtbScale: wasm.mtb_scale().slice(),
-            mtbScales: wasm.mtb_scales(),
             slice: (start, end) =>
                 version === this._statisticsVersion ? wasm.slice_statistics(start, end) : undefined,
         };
+        this.readMetrics(wasm, statistics, this.requestedMetrics());
+        return statistics;
+    }
+
+    private requestedMetrics(): Set<StatisticsMetric> {
+        const metrics = new Set<StatisticsMetric>();
+        this._statisticsRequests.forEach((request) => request.forEach((m) => metrics.add(m)));
+        return metrics;
+    }
+
+    /** Reads the metrics that were not read yet into `statistics`, which is the current one. */
+    private readMetrics(
+        wasm: Wasm,
+        statistics: SelectionStatistics,
+        metrics: Set<StatisticsMetric>
+    ) {
+        const categories = (
+            starts: Uint32Array,
+            values: Uint8Array,
+            names: () => string[]
+        ): CategoryIntervals => ({
+            starts: starts.slice(),
+            values: values.slice(),
+            names: names(),
+        });
+
+        for (const metric of metrics) {
+            if (this._loadedMetrics.has(metric)) {
+                continue;
+            }
+            this._loadedMetrics.add(metric);
+            switch (metric) {
+                case 'speed':
+                    statistics.speed = wasm.speed().slice();
+                    break;
+                case 'hr':
+                    statistics.hr = wasm.hr()?.slice();
+                    break;
+                case 'cad':
+                    statistics.cad = wasm.cad()?.slice();
+                    break;
+                case 'atemp':
+                    statistics.atemp = wasm.atemp()?.slice();
+                    break;
+                case 'power':
+                    statistics.power = wasm.power()?.slice();
+                    break;
+                case 'slopeSegment':
+                    statistics.slopeSegmentSlope = wasm.slope_segment_slope().slice();
+                    statistics.slopeSegmentDistance = wasm.slope_segment_distance().slice();
+                    break;
+                case 'surface':
+                    statistics.surface = categories(
+                        wasm.surface_starts(),
+                        wasm.surface_values(),
+                        wasm.surfaces
+                    );
+                    break;
+                case 'highway':
+                    statistics.highway = categories(
+                        wasm.highway_starts(),
+                        wasm.highway_values(),
+                        wasm.highways
+                    );
+                    statistics.sacScale = categories(
+                        wasm.sac_scale_starts(),
+                        wasm.sac_scale_values(),
+                        wasm.sac_scales
+                    );
+                    statistics.mtbScale = categories(
+                        wasm.mtb_scale_starts(),
+                        wasm.mtb_scale_values(),
+                        wasm.mtb_scales
+                    );
+                    break;
+            }
+        }
+    }
+
+    /**
+     * Registers a consumer of the statistics that needs some of the metrics that are not part of
+     * them by default (see `StatisticsMetric`). The metrics asked for by all the consumers are
+     * added to `statistics`: the ones that are missing are read right away, and then after each
+     * change of the selection or of the files, and the store is updated. Call `release` when the
+     * consumer goes away.
+     */
+    requestStatistics(): StatisticsRequest {
+        const wanted = new Set<StatisticsMetric>();
+        this._statisticsRequests.add(wanted);
+        return {
+            set: (metrics) => {
+                wanted.clear();
+                for (const metric of metrics) {
+                    wanted.add(metric);
+                }
+                this.loadMissingMetrics();
+            },
+            release: () => {
+                this._statisticsRequests.delete(wanted);
+            },
+        };
+    }
+
+    /** Reads the requested metrics that are not in the current statistics yet. */
+    private loadMissingMetrics() {
+        const wasm = this.wasm;
+        const metrics = this.requestedMetrics();
+        if (!wasm || [...metrics].every((metric) => this._loadedMetrics.has(metric))) {
+            return;
+        }
+        // the buffers of the engine still are the ones of the current statistics, as they are
+        // read after every action
+        const statistics = { ...get(this._statistics) };
+        this.readMetrics(wasm, statistics, metrics);
+        this._statistics.set(statistics);
     }
 
     /** Reads the state of a file, reusing from `previous` what did not change. */

website/src/lib/trackpoint-categories.test.ts

@@ -1,24 +1,45 @@
 import { describe, it } from 'node:test';
 import assert from 'node:assert/strict';
-import { categoryAt } from './trackpoint-categories';
+import { categoryValues, type CategoryIntervals } from './trackpoint-categories';
 
-describe('categoryAt', () => {
+describe('categoryValues', () => {
-    const codes = new Uint8Array([1, 1, 0, 2, 0]);
+    // asphalt, asphalt, unknown, gravel, gravel, gravel, unknown
-    const names = ['asphalt', 'gravel'];
+    const intervals: CategoryIntervals = {
+        starts: new Uint32Array([0, 2, 3, 6]),
+        values: new Uint8Array([1, 0, 2, 0]),
+        names: ['asphalt', 'gravel'],
+    };
 
-    it('is the name of the code', () => {
+    it('is the name of the value of the interval of each trackpoint', () => {
-        assert.equal(categoryAt(codes, names, 0), 'asphalt');
+        assert.deepEqual(categoryValues(intervals, 7), [
-        assert.equal(categoryAt(codes, names, 3), 'gravel');
+            'asphalt',
+            'asphalt',
+            undefined,
+            'gravel',
+            'gravel',
+            'gravel',
+            undefined,
+        ]);
     });
 
-    it('is undefined when the value is unknown', () => {
+    it('goes on with the last interval until the last trackpoint', () => {
-        assert.equal(categoryAt(codes, names, 2), undefined);
+        const last = { ...intervals, values: new Uint8Array([1, 0, 2, 2]) };
-        assert.equal(categoryAt(codes, names, 4), undefined);
+        assert.deepEqual(categoryValues(last, 9).slice(5), [
+            'gravel',
+            'gravel',
+            'gravel',
+            'gravel',
+        ]);
     });
 
-    it('is undefined out of the trackpoints, or for a code without name', () => {
+    it('does not go past the trackpoints', () => {
-        assert.equal(categoryAt(codes, names, 5), undefined);
+        assert.deepEqual(categoryValues(intervals, 3), ['asphalt', 'asphalt', undefined]);
-        assert.equal(categoryAt(new Uint8Array([3]), names, 0), undefined);
+        assert.deepEqual(categoryValues(intervals, 0), []);
-        assert.equal(categoryAt(new Uint8Array(), [], 0), undefined);
+    });
+
+    it('is undefined without intervals, or for a code without name', () => {
+        assert.deepEqual(categoryValues(undefined, 2), [undefined, undefined]);
+        const unnamed = { starts: new Uint32Array([0]), values: new Uint8Array([3]), names: [] };
+        assert.deepEqual(categoryValues(unnamed, 2), [undefined, undefined]);
     });
 });

website/src/lib/trackpoint-categories.ts

@@ -1,12 +1,37 @@
 /**
- * The value of a trackpoint for a category of the engine (surface, highway): `codes` has one entry
+ * A category of the engine (surface, highway...) for each trackpoint, as the intervals of
- * per trackpoint, 0 when the value is unknown, else 1 + the index of the value in `names`.
+ * consecutive trackpoints that share the same value: `starts[i]` is the index of the first
+ * trackpoint of the interval `i`, which lasts until the next start (or the last trackpoint). Its
+ * `values[i]` is 0 when the value is unknown, else 1 + the index of the value in `names`.
  */
-export function categoryAt(
+export type CategoryIntervals = {
-    codes: ArrayLike<number>,
+    starts: Uint32Array;
-    names: readonly string[],
+    values: Uint8Array;
-    index: number
+    /** Names of the values, by code: a name keeps its index. */
-): string | undefined {
+    names: string[];
-    const code = codes[index];
+};
-    return code ? names[code - 1] : undefined;
+
+/**
+ * The value of each of the `length` trackpoints for a category of the engine, `undefined` when it
+ * is unknown, or when the category is missing (it is unknown for every trackpoint). The intervals
+ * are scanned once, so it takes a time linear in `length`.
+ */
+export function categoryValues(
+    intervals: CategoryIntervals | undefined,
+    length: number
+): (string | undefined)[] {
+    const result: (string | undefined)[] = new Array(length).fill(undefined);
+    if (!intervals) {
+        return result;
+    }
+    const { starts, values, names } = intervals;
+    for (let i = 0; i < starts.length; i++) {
+        if (!values[i]) {
+            continue; // unknown, already `undefined`
+        }
+        const name = names[values[i] - 1];
+        const end = i + 1 < starts.length ? Math.min(starts[i + 1], length) : length;
+        result.fill(name, starts[i], end);
+    }
+    return result;
 }

website/src/routes/[[language]]/+page.svelte

@@ -17,6 +17,7 @@
         ExternalLink,
     } from '@lucide/svelte';
     import { i18n } from '$lib/i18n.svelte';
+    import type { SelectionStatistics } from '$lib/engine';
     import { getURLForLanguage } from '$lib/utils';
     import { writable } from 'svelte/store';
     import Scissors from '$lib/components/toolbar/tools/scissors/Scissors.svelte';
@@ -24,35 +25,14 @@
     import { onDestroy, onMount } from 'svelte';
 
     // TODO the example comes from the previous implementation
-    let statistics = writable({
+    let statistics = writable<SelectionStatistics>({
         global: { totalDistance: 0, elevationGain: 0, elevationLoss: 0 },
         length: 0,
         totalDistance: new Float64Array(),
-        movingDistance: new Float64Array(),
-        totalTime: new BigInt64Array(),
-        movingTime: new BigInt64Array(),
-        speed: new Float64Array(),
-        elevationGain: new Float64Array(),
-        elevationLoss: new Float64Array(),
         slope: new Float64Array(),
-        slopeSegmentSlope: new Float64Array(),
-        slopeSegmentDistance: new Float64Array(),
         lng: new Float64Array(),
         lat: new Float64Array(),
         ele: new Float64Array(),
-        timestamps: new BigInt64Array(),
-        hr: new Float64Array(),
-        cad: new Float64Array(),
-        atemp: new Float64Array(),
-        power: new Float64Array(),
-        surface: new Uint8Array(),
-        surfaces: [],
-        highway: new Uint8Array(),
-        highways: [],
-        sacScale: new Uint8Array(),
-        sacScales: [],
-        mtbScale: new Uint8Array(),
-        mtbScales: [],
         slice: () => undefined,
     });
     let slicedStatistics = writable(undefined);