BLI: new C++ BitVector data structure

This adds a new `blender::BitVector` data structure that was requested
a couple of times. It also replaces usages of `BLI_bitmap` in C++ code.

See the comment in `BLI_bit_vector.hh` for more details about the
advantages and disadvantages of using a bit-vector and how the new
data structure compares to `std::vector<bool>` and `BLI_bitmap`.

Differential Revision: https://developer.blender.org/D14006

1 files changed, 30 insertions, 0 deletions

diff --git a/source/blender/blenlib/intern/BLI_index_range.cc b/source/blender/blenlib/intern/BLI_index_range.cc
index 398228ab461..624dcc39fc5 100644
--- a/source/blender/blenlib/intern/BLI_index_range.cc
+++ b/source/blender/blenlib/intern/BLI_index_range.cc
@@ -44,4 +44,34 @@ Span<int64_t> IndexRange::as_span_internal() const
   return Span<int64_t>(s_current_array + start_, size_);
 }
 
+AlignedIndexRanges split_index_range_by_alignment(const IndexRange range, const int64_t alignment)
+{
+  BLI_assert(is_power_of_2_i(alignment));
+  const int64_t mask = alignment - 1;
+
+  AlignedIndexRanges aligned_ranges;
+
+  const int64_t start_chunk = range.start() & ~mask;
+  const int64_t end_chunk = range.one_after_last() & ~mask;
+  if (start_chunk == end_chunk) {
+    aligned_ranges.prefix = range;
+  }
+  else {
+    int64_t prefix_size = 0;
+    int64_t suffix_size = 0;
+    if (range.start() != start_chunk) {
+      prefix_size = alignment - (range.start() & mask);
+    }
+    if (range.one_after_last() != end_chunk) {
+      suffix_size = range.one_after_last() - end_chunk;
+    }
+    aligned_ranges.prefix = IndexRange(range.start(), prefix_size);
+    aligned_ranges.suffix = IndexRange(end_chunk, suffix_size);
+    aligned_ranges.aligned = IndexRange(aligned_ranges.prefix.one_after_last(),
+                                        range.size() - prefix_size - suffix_size);
+  }
+
+  return aligned_ranges;
+}
+
 }  // namespace blender