copy on wasm side to avoid any data corruption

gpx-rs/wasm/src/lib.rs

@@ -114,8 +114,7 @@ pub fn start() {
 
 // Statistics buffers
 //
-// These are views into wasm memory: they are invalidated by the next command (and any
+// Each getter returns a copy of the buffer, as a new JS typed array.
-// allocation), so read or copy them right away.
 
 fn with_stats<T>(f: impl FnOnce(&engine::StatisticsBuffer) -> T) -> Option<T> {
     ENGINE.with(|engine| engine.borrow().as_ref().map(|e| f(e.statistics())))
@@ -125,8 +124,7 @@ macro_rules! stats_getter {
     ($name:ident, $array:ident) => {
         #[wasm_bindgen]
         pub fn $name() -> $array {
-            with_stats(|s| unsafe { $array::view(&s.$name) })
+            with_stats(|s| $array::from(&s.$name[..])).unwrap_or_else(|| $array::new_with_length(0))
-                .unwrap_or_else(|| $array::new_with_length(0))
         }
     };
 }
@@ -152,12 +150,7 @@ macro_rules! optional_stats_getter {
     ($name:ident, $field:ident, $array:ident) => {
         #[wasm_bindgen]
         pub fn $name() -> Option<$array> {
-            with_stats(|s| {
+            with_stats(|s| s.$field.as_deref().map($array::from)).flatten()
-                s.$field
-                    .as_ref()
-                    .map(|values| unsafe { $array::view(values) })
-            })
-            .flatten()
         }
     };
 }
@@ -185,13 +178,13 @@ macro_rules! intervals_getters {
     ($starts:ident, $values:ident, $field:ident) => {
         #[wasm_bindgen]
         pub fn $starts() -> Uint32Array {
-            with_stats(|s| unsafe { Uint32Array::view(&s.$field.starts) })
+            with_stats(|s| Uint32Array::from(&s.$field.starts[..]))
                 .unwrap_or_else(|| Uint32Array::new_with_length(0))
         }
 
         #[wasm_bindgen]
         pub fn $values() -> Uint8Array {
-            with_stats(|s| unsafe { Uint8Array::view(&s.$field.values) })
+            with_stats(|s| Uint8Array::from(&s.$field.values[..]))
                 .unwrap_or_else(|| Uint8Array::new_with_length(0))
         }
     };
@@ -1214,14 +1207,12 @@ pub fn last_update() -> FilesUpdate {
 
 // Coordinates buffers
 //
-// Like the statistics buffers, these are views into wasm memory, invalidated by the next
+// Like the statistics buffers, these are copies. They are flat `[lng, lat, ...]` arrays. Compare `rev` / `waypointsRev` of the file structures with the previous ones to know which
-// command (and any allocation): read or copy them right away. They are flat `[lng, lat, ...]`
-// arrays. Compare `rev` / `waypointsRev` of the file structures with the previous ones to know which
 // buffers actually changed.
 
-fn coordinates_view(f: impl FnOnce(&Engine) -> Option<&[f64]>) -> Float64Array {
+fn coordinates_array(f: impl FnOnce(&Engine) -> Option<&[f64]>) -> Float64Array {
     ENGINE.with(|engine| match engine.borrow().as_ref().and_then(f) {
-        Some(coordinates) => unsafe { Float64Array::view(coordinates) },
+        Some(coordinates) => Float64Array::from(coordinates),
         None => Float64Array::new_with_length(0),
     })
 }
@@ -1230,7 +1221,7 @@ fn coordinates_view(f: impl FnOnce(&Engine) -> Option<&[f64]>) -> Float64Array {
 #[wasm_bindgen]
 pub fn segment_coordinates(segment_id: &str) -> Float64Array {
     match uuid::Uuid::parse_str(segment_id) {
-        Ok(id) => coordinates_view(|e| Some(e.segment_coordinates(&engine::TrackSegmentId(id)))),
+        Ok(id) => coordinates_array(|e| Some(e.segment_coordinates(&engine::TrackSegmentId(id)))),
         Err(_) => Float64Array::new_with_length(0),
     }
 }
@@ -1239,7 +1230,7 @@ pub fn segment_coordinates(segment_id: &str) -> Float64Array {
 #[wasm_bindgen]
 pub fn waypoint_coordinates(file_id: &str) -> Float64Array {
     match uuid::Uuid::parse_str(file_id) {
-        Ok(id) => coordinates_view(|e| Some(e.waypoint_coordinates(&FileId(id)))),
+        Ok(id) => coordinates_array(|e| Some(e.waypoint_coordinates(&FileId(id)))),
         Err(_) => Float64Array::new_with_length(0),
     }
 }

website/src/lib/engine.ts

@@ -566,15 +566,15 @@ class Engine {
         store.update((state) => ({ ...state, visibility }));
     }
 
-    // Coordinates, as flat [lng, lat, ...] arrays. They are copied out of the WASM memory.
+    // Coordinates, as flat [lng, lat, ...] arrays. The getters copy them out of the WASM memory.
     // Refetch them when the `rev` of the segment (or the `waypointsRev` of the file) changed.
 
     segmentCoordinates(segmentId: string): Float64Array {
-        return this.wasm?.segment_coordinates(segmentId).slice() ?? new Float64Array();
+        return this.wasm?.segment_coordinates(segmentId) ?? new Float64Array();
     }
 
     waypointCoordinates(fileId: string): Float64Array {
-        return this.wasm?.waypoint_coordinates(fileId).slice() ?? new Float64Array();
+        return this.wasm?.waypoint_coordinates(fileId) ?? new Float64Array();
     }
 
     private async run(action: (wasm: Wasm) => boolean): Promise<boolean> {
@@ -640,22 +640,22 @@ class Engine {
     }
 
     /**
-     * Copies the statistics buffers of the engine (they are overwritten by the next action), but
+     * Reads the statistics buffers of the engine (the getters copy them), but only the metrics
-     * only the metrics that were requested.
+     * that were requested.
      */
     private readStatistics(wasm: Wasm): SelectionStatistics {
         const version = ++this._statisticsVersion;
         this._loadedMetrics.clear();
-        const totalDistance = wasm.total_distance().slice();
+        const totalDistance = wasm.total_distance();
         const statistics: SelectionStatistics = {
             global: wasm.selection_statistics() ?? EMPTY_STATISTICS,
             length: totalDistance.length,
             totalDistance,
-            slope: wasm.slope().slice(),
+            slope: wasm.slope(),
-            lng: wasm.lng().slice(),
+            lng: wasm.lng(),
-            lat: wasm.lat().slice(),
+            lat: wasm.lat(),
-            ele: wasm.ele().slice(),
+            ele: wasm.ele(),
-            timestamps: wasm.timestamps()?.slice(),
+            timestamps: wasm.timestamps(),
             slice: (start, end) =>
                 version === this._statisticsVersion ? wasm.slice_statistics(start, end) : undefined,
         };
@@ -680,8 +680,8 @@ class Engine {
             values: Uint8Array,
             names: () => string[]
         ): CategoryIntervals => ({
-            starts: starts.slice(),
+            starts,
-            values: values.slice(),
+            values,
             names: names(),
         });
 
@@ -692,23 +692,23 @@ class Engine {
             this._loadedMetrics.add(metric);
             switch (metric) {
                 case 'speed':
-                    statistics.speed = wasm.speed().slice();
+                    statistics.speed = wasm.speed();
                     break;
                 case 'hr':
-                    statistics.hr = wasm.hr()?.slice();
+                    statistics.hr = wasm.hr();
                     break;
                 case 'cad':
-                    statistics.cad = wasm.cad()?.slice();
+                    statistics.cad = wasm.cad();
                     break;
                 case 'atemp':
-                    statistics.atemp = wasm.atemp()?.slice();
+                    statistics.atemp = wasm.atemp();
                     break;
                 case 'power':
-                    statistics.power = wasm.power()?.slice();
+                    statistics.power = wasm.power();
                     break;
                 case 'slopeSegment':
-                    statistics.slopeSegmentSlope = wasm.slope_segment_slope().slice();
+                    statistics.slopeSegmentSlope = wasm.slope_segment_slope();
-                    statistics.slopeSegmentDistance = wasm.slope_segment_distance().slice();
+                    statistics.slopeSegmentDistance = wasm.slope_segment_distance();
                     break;
                 case 'surface':
                     statistics.surface = categories(