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Guard antimeridian boundary vertex appends #205

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32 changes: 24 additions & 8 deletions h3_postgis/src/wkb_indexing.c
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Original file line number Diff line number Diff line change
Expand Up @@ -60,6 +60,22 @@ void
void
boundary_split_180_polar(const CellBoundary * boundary, CellBoundary * res);

/* Adds one vertex while preserving the fixed CellBoundary capacity. */
static void
boundary_add_vert(CellBoundary * boundary, const LatLng * vert);

static void
boundary_add_vert(CellBoundary * boundary, const LatLng * vert)
{
const int maxVerts = sizeof(boundary->verts) / sizeof(boundary->verts[0]);

SPLIT_ASSERT(
boundary->numVerts < maxVerts,

@chatgpt-codex-connector chatgpt-codex-connector Bot Jun 11, 2026

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P2 Badge Use a larger split buffer for seam vertices

When a valid H3 boundary already uses more than six of CellBoundary's fixed vertex slots, the polar splitter appends the original vertices plus four synthetic antimeridian/pole vertices; this new guard turns those cases into Cell boundary split exceeds CellBoundary vertex capacity errors for h3_cell_to_boundary_wkb/geometry instead of producing the boundary. The bounds check needs to be paired with a split representation sized for the extra seam vertices, otherwise high-resolution polar or distorted antimeridian cells remain unusable.

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"Cell boundary split exceeds CellBoundary vertex capacity");

boundary->verts[boundary->numVerts++] = *vert;
}

/*
* Serialize one H3 cell boundary to WKB.
*
Expand Down Expand Up @@ -166,7 +182,7 @@ boundary_split_180(const CellBoundary * boundary, CellBoundary * part1, CellBoun
part = (lon < 0) ? part1 : part2;

/* Add current vertex */
part->verts[part->numVerts++] = verts[v];
boundary_add_vert(part, &verts[v]);

if (SIGN(lon) != SIGN(nextLon))
{
Expand All @@ -182,11 +198,11 @@ boundary_split_180(const CellBoundary * boundary, CellBoundary * part1, CellBoun

/* Add split point */
/* current part */
part->verts[part->numVerts++] = vert;
boundary_add_vert(part, &vert);
/* next part */
vert.lng = -vert.lng;
part = (part == part1) ? part2 : part1;
part->verts[part->numVerts++] = vert;
boundary_add_vert(part, &vert);
}
}
}
Expand All @@ -205,7 +221,7 @@ boundary_split_180_polar(const CellBoundary * boundary, CellBoundary * res)
double nextLon;

/* Add current vertex */
res->verts[res->numVerts++] = verts[v];
boundary_add_vert(res, &verts[v]);

lon = verts[v].lng;
nextLon = verts[next].lng;
Expand All @@ -225,17 +241,17 @@ boundary_split_180_polar(const CellBoundary * boundary, CellBoundary * res)
/* Add intersection point */
vert.lat = splitLat;
vert.lng = (lon < 0) ? -M_PI : M_PI;
res->verts[res->numVerts++] = vert;
boundary_add_vert(res, &vert);

/* Add points on antimeridian near the pole */
vert.lat = SIGN(vert.lat) * ABS_LAT_MAX;
res->verts[res->numVerts++] = vert;
boundary_add_vert(res, &vert);
vert.lng = -vert.lng;
res->verts[res->numVerts++] = vert;
boundary_add_vert(res, &vert);

/* Add intersection point */
vert.lat = splitLat;
res->verts[res->numVerts++] = vert;
boundary_add_vert(res, &vert);
}
}
}
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