diff --git a/source/blender/blenkernel/intern/curves_geometry.cc b/source/blender/blenkernel/intern/curves_geometry.cc
index 7e3626da5ef..829bcfbf91b 100644
--- a/source/blender/blenkernel/intern/curves_geometry.cc
+++ b/source/blender/blenkernel/intern/curves_geometry.cc
@@ -549,13 +549,8 @@ IndexMask CurvesGeometry::indices_for_curve_type(const CurveType type,
 
 Array<int> CurvesGeometry::point_to_curve_map() const
 {
-  const OffsetIndices points_by_curve = this->points_by_curve();
   Array<int> map(this->points_num());
-  threading::parallel_for(this->curves_range(), 1024, [&](const IndexRange range) {
-    for (const int i_curve : range) {
-      map.as_mutable_span().slice(points_by_curve[i_curve]).fill(i_curve);
-    }
-  });
+  offset_indices::build_reverse_map(this->points_by_curve(), map);
   return map;
 }
 
diff --git a/source/blender/blenkernel/intern/mesh_mapping.cc b/source/blender/blenkernel/intern/mesh_mapping.cc
index b57164fae1e..1710c0b98bb 100644
--- a/source/blender/blenkernel/intern/mesh_mapping.cc
+++ b/source/blender/blenkernel/intern/mesh_mapping.cc
@@ -526,11 +526,7 @@ namespace blender::bke::mesh_topology {
 Array<int> build_loop_to_poly_map(const OffsetIndices<int> polys)
 {
   Array<int> map(polys.total_size());
-  threading::parallel_for(polys.index_range(), 1024, [&](IndexRange range) {
-    for (const int64_t poly_i : range) {
-      map.as_mutable_span().slice(polys[poly_i]).fill(int(poly_i));
-    }
-  });
+  offset_indices::build_reverse_map(polys, map);
   return map;
 }
 
diff --git a/source/blender/blenlib/BLI_offset_indices.hh b/source/blender/blenlib/BLI_offset_indices.hh
index b374be8c43b..3fa8ce9dd2a 100644
--- a/source/blender/blenlib/BLI_offset_indices.hh
+++ b/source/blender/blenlib/BLI_offset_indices.hh
@@ -97,6 +97,12 @@ template<typename T> class OffsetIndices {
  */
 void accumulate_counts_to_offsets(MutableSpan<int> counts_to_offsets, int start_offset = 0);
 
+/**
+ * Create a map from indexed elements to the source indices, in other words from the larger array
+ * to the smaller array.
+ */
+void build_reverse_map(OffsetIndices<int> offsets, MutableSpan<int> r_map);
+
 }  // namespace blender::offset_indices
 
 namespace blender {
diff --git a/source/blender/blenlib/intern/offset_indices.cc b/source/blender/blenlib/intern/offset_indices.cc
index 2ac11fe631e..8b38d630b05 100644
--- a/source/blender/blenlib/intern/offset_indices.cc
+++ b/source/blender/blenlib/intern/offset_indices.cc
@@ -1,6 +1,7 @@
 /* SPDX-License-Identifier: GPL-2.0-or-later */
 
 #include "BLI_offset_indices.hh"
+#include "BLI_task.hh"
 
 namespace blender::offset_indices {
 
@@ -16,4 +17,13 @@ void accumulate_counts_to_offsets(MutableSpan<int> counts_to_offsets, const int
   counts_to_offsets.last() = offset;
 }
 
+void build_reverse_map(OffsetIndices<int> offsets, MutableSpan<int> r_map)
+{
+  threading::parallel_for(offsets.index_range(), 1024, [&](const IndexRange range) {
+    for (const int64_t i : range) {
+      r_map.slice(offsets[i]).fill(i);
+    }
+  });
+}
+
 }  // namespace blender::offset_indices