1 files changed, 34 insertions, 2 deletions

diff --git a/source/blender/blenlib/BLI_index_range.hh b/source/blender/blenlib/BLI_index_range.hh
index 6fcc560d856..c259282ca64 100644
--- a/source/blender/blenlib/BLI_index_range.hh
+++ b/source/blender/blenlib/BLI_index_range.hh
@@ -90,10 +90,10 @@ class IndexRange {
       return *this;
     }
 
-    constexpr Iterator operator++(int) const
+    constexpr Iterator operator++(int)
     {
       Iterator copied_iterator = *this;
-      ++copied_iterator;
+      ++(*this);
       return copied_iterator;
     }
 
@@ -140,6 +140,10 @@ class IndexRange {
   {
     return (a.size_ == b.size_) && (a.start_ == b.start_ || a.size_ == 0);
   }
+  constexpr friend bool operator!=(IndexRange a, IndexRange b)
+  {
+    return !(a == b);
+  }
 
   /**
    * Get the amount of numbers in the range.
@@ -248,6 +252,19 @@ class IndexRange {
   }
 
   /**
+   * Returns a new IndexRange that contains the intersection of the current one with the given
+   * range. Returns empty range if there are no overlapping indices. The returned range is always
+   * a valid slice of this range.
+   */
+  constexpr IndexRange intersect(IndexRange other) const
+  {
+    const int64_t old_end = start_ + size_;
+    const int64_t new_start = std::min(old_end, std::max(start_, other.start_));
+    const int64_t new_end = std::max(new_start, std::min(old_end, other.start_ + other.size_));
+    return IndexRange(new_start, new_end - new_start);
+  }
+
+  /**
    * Returns a new IndexRange with n elements removed from the beginning of the range.
    * This invokes undefined behavior when n is negative.
    */
@@ -318,4 +335,19 @@ class IndexRange {
   Span<int64_t> as_span_internal() const;
 };
 
+struct AlignedIndexRanges {
+  IndexRange prefix;
+  IndexRange aligned;
+  IndexRange suffix;
+};
+
+/**
+ * Split a range into three parts so that the boundaries of the middle part are aligned to some
+ * power of two.
+ *
+ * This can be used when an algorithm can be optimized on aligned indices/memory. The algorithm
+ * then needs a slow path for the beginning and end, and a fast path for the aligned elements.
+ */
+AlignedIndexRanges split_index_range_by_alignment(const IndexRange range, const int64_t alignment);
+
 }  // namespace blender