fix: respect Arrow IPC offset buffer padding

packages/deck.gl-geoarrow/src/layers/path-layer.ts

@@ -28,6 +28,7 @@ import {
   getGeometryData,
   getInterleavedLineString,
   getMultiLineStringResolvedOffsets,
+  getValueOffsets,
   invertOffsets,
   isGeomSeparate,
 } from "../utils/utils";
@@ -170,7 +171,7 @@ export class GeoArrowPathLayer<
     if (isGeomSeparate(lineStringData)) {
       lineStringData = getInterleavedLineString(lineStringData);
     }
-    const geomOffsets = lineStringData.valueOffsets;
+    const geomOffsets = getValueOffsets(lineStringData);
     const pointData = ga.child.getLineStringChild(lineStringData);
     const nDim = pointData.type.listSize;
     const coordData = ga.child.getPointChild(pointData);
@@ -230,8 +231,8 @@ export class GeoArrowPathLayer<
     const pointData = ga.child.getLineStringChild(lineStringData);
     const coordData = ga.child.getPointChild(pointData);
 
-    const geomOffsets = multiLineStringData.valueOffsets;
-    const ringOffsets = lineStringData.valueOffsets;
+    const geomOffsets = getValueOffsets(multiLineStringData);
+    const ringOffsets = getValueOffsets(lineStringData);
 
     const nDim = pointData.type.listSize;
     const flatCoordinateArray = coordData.values;

packages/deck.gl-geoarrow/src/layers/polygon-layer.ts

@@ -22,7 +22,7 @@ import type {
   GeoArrowPickingInfo,
 } from "../types";
 import type { GeoArrowExtraPickingProps } from "../utils/picking";
-import { getGeometryData } from "../utils/utils";
+import { getGeometryData, getValueOffsets } from "../utils/utils";
 import { GeoArrowPathLayer } from "./path-layer";
 import { GeoArrowSolidPolygonLayer } from "./solid-polygon-layer";
 
@@ -78,7 +78,7 @@ export function getMultiPolygonExterior(
     );
   }
 
-  const geomOffsets: Int32Array = input.valueOffsets;
+  const geomOffsets: Int32Array = getValueOffsets(input);
   const polygonData = ga.child.getMultiPolygonChild(input);
   const polygonOffsets: Int32Array = polygonData.valueOffsets;
   const lineStringData = ga.child.getPolygonChild(polygonData);

packages/deck.gl-geoarrow/src/layers/scatterplot-layer.ts

@@ -27,6 +27,7 @@ import {
   convertStructToFixedSizeList,
   extractAccessorsFromProps,
   getGeometryData,
+  getValueOffsets,
   invertOffsets,
   isGeomSeparate,
 } from "../utils/utils";
@@ -219,7 +220,7 @@ export class GeoArrowScatterplotLayer<
     if (isGeomSeparate(pointData)) {
       pointData = convertStructToFixedSizeList(pointData);
     }
-    const geomOffsets = multiPointData.valueOffsets;
+    const geomOffsets = getValueOffsets(multiPointData);
     const flatCoordsData = ga.child.getPointChild(pointData);
     const flatCoordinateArray = flatCoordsData.values;
 

packages/deck.gl-geoarrow/src/layers/solid-polygon-layer.ts

@@ -34,6 +34,7 @@ import {
   getInterleavedPolygon,
   getMultiPolygonResolvedOffsets,
   getPolygonResolvedOffsets,
+  getValueOffsets,
   invertOffsets,
   isGeomSeparate,
 } from "../utils/utils";
@@ -553,7 +554,7 @@ export class GeoArrowSolidPolygonLayer<
 
     const nDim = pointData.type.listSize;
 
-    const geomOffsets = multiPolygonData.valueOffsets;
+    const geomOffsets = getValueOffsets(multiPolygonData);
     const flatCoordinateArray = coordData.values;
 
     if (!this.state.triangles) {

packages/deck.gl-geoarrow/src/layers/text-layer.ts

@@ -28,6 +28,7 @@ import {
   expandArrayToCoords,
   extractAccessorsFromProps,
   getGeometryData,
+  getValueOffsets,
   isGeomSeparate,
 } from "../utils/utils";
 import { validateAccessors } from "../utils/validate";
@@ -206,7 +207,7 @@ export class GeoArrowTextLayer<
 
     // console.log(textData);
     const textValues = textData.values;
-    const characterOffsets = textData.valueOffsets;
+    const characterOffsets = getValueOffsets(textData);
 
     const props: TextLayerProps = {
       // Note: because this is a composite layer and not doing the rendering

packages/deck.gl-geoarrow/src/layers/trips-layer.ts

@@ -20,6 +20,7 @@ import {
   extractAccessorsFromProps,
   getGeometryData,
   getInterleavedLineString,
+  getValueOffsets,
   isGeomSeparate,
 } from "../utils/utils";
 import { validateAccessors } from "../utils/validate";
@@ -137,7 +138,7 @@ export class GeoArrowTripsLayer<
     if (isGeomSeparate(lineStringData)) {
       lineStringData = getInterleavedLineString(lineStringData);
     }
-    const geomOffsets = lineStringData.valueOffsets;
+    const geomOffsets = getValueOffsets(lineStringData);
     const pointData = ga.child.getLineStringChild(lineStringData);
     const nDim = pointData.type.listSize;
     const coordData = ga.child.getPointChild(pointData);

packages/deck.gl-geoarrow/src/utils/utils.ts

@@ -142,6 +142,26 @@ export function convertStructToFixedSizeList(
   throw new Error(`Unsupported coordinate data type: ${coords.type}`);
 }
 
+/**
+ * Get the logical offsets buffer for a list- or Utf8-typed Data.
+ *
+ * Per the Arrow Columnar Format spec, IPC producers pad each buffer to a
+ * 64-byte boundary; `apache-arrow` JS exposes the offsets buffer at its
+ * on-wire byte length, so `data.valueOffsets.length` can exceed
+ * `data.length + 1` and the trailing entries are padding zeros that must not
+ * be read.
+ *
+ * Returns a zero-copy `subarray` view over the `data.length + 1` logical
+ * offsets — safe to iterate, index, and pass to `startIndices` /
+ * `invertOffsets` / `expandArrayToCoords`.
+ */
+export function getValueOffsets(data: {
+  readonly valueOffsets: Int32Array;
+  readonly length: number;
+}): Int32Array {
+  return data.valueOffsets.subarray(0, data.length + 1);
+}
+
 /**
  * Get LineString Data with interleaved coordinates
  * from the given LineString Data with separated (struct) coordinates.
@@ -370,7 +390,7 @@ export function getListNestingLevels(data: arrow.Data): number {
 export function getMultiLineStringResolvedOffsets(
   data: ga.data.MultiLineStringData,
 ): Int32Array {
-  const geomOffsets = data.valueOffsets;
+  const geomOffsets = getValueOffsets(data);
   const lineStringData = ga.child.getMultiLineStringChild(data);
   const ringOffsets = lineStringData.valueOffsets;
 
@@ -387,7 +407,7 @@ export function getMultiLineStringResolvedOffsets(
 export function getPolygonResolvedOffsets(
   data: ga.data.PolygonData,
 ): Int32Array {
-  const geomOffsets = data.valueOffsets;
+  const geomOffsets = getValueOffsets(data);
   const ringData = ga.child.getPolygonChild(data);
   const ringOffsets = ringData.valueOffsets;
 
@@ -407,7 +427,7 @@ export function getMultiPolygonResolvedOffsets(
   const polygonData = ga.child.getMultiPolygonChild(data);
   const ringData = ga.child.getPolygonChild(polygonData);
 
-  const geomOffsets = data.valueOffsets;
+  const geomOffsets = getValueOffsets(data);
   const polygonOffsets = polygonData.valueOffsets;
   const ringOffsets = ringData.valueOffsets;