BLI: Add generic utlity for gathering values with indices

Add new functions to `array_utils` namespace called `gather(..)`.
Versions of `GVArray::materialize_compressed_to_uninitialized(..)` with
threading have been reimplemented locally in multiple geometry node
contexts. The purpose of this patch is therefore to:
 * Assemble these implementations in a single file.
 * Provide a naming convention that is easier to recognize.

Differential Revision: https://developer.blender.org/D15786

1 files changed, 12 insertions, 1 deletions

diff --git a/source/blender/blenlib/intern/array_utils.cc b/source/blender/blenlib/intern/array_utils.cc
index a0fc8810199..a837d6aceec 100644
--- a/source/blender/blenlib/intern/array_utils.cc
+++ b/source/blender/blenlib/intern/array_utils.cc
@@ -1,7 +1,6 @@
 /* SPDX-License-Identifier: GPL-2.0-or-later */
 
 #include "BLI_array_utils.hh"
-#include "BLI_task.hh"
 
 namespace blender::array_utils {
 
@@ -17,4 +16,16 @@ void copy(const GVArray &src,
   });
 }
 
+void gather(const GVArray &src,
+            const IndexMask indices,
+            GMutableSpan dst,
+            const int64_t grain_size)
+{
+  BLI_assert(src.type() == dst.type());
+  BLI_assert(indices.size() == dst.size());
+  threading::parallel_for(indices.index_range(), grain_size, [&](const IndexRange range) {
+    src.materialize_compressed_to_uninitialized(indices.slice(range), dst.slice(range).data());
+  });
+}
+
 }  // namespace blender::array_utils