BLI: improve various C++ data structures

The changes come from the `functions` branch, where I'm using
these structures a lot.

This also includes a new `BLI::Optional<T>` type, which is similar
to `std::Optional<T>` which can be used when Blender starts using
C++17.

1 files changed, 15 insertions, 0 deletions

diff --git a/source/blender/blenlib/BLI_index_range.h b/source/blender/blenlib/BLI_index_range.h
index a1fed5bd97c..f67cc259227 100644
--- a/source/blender/blenlib/BLI_index_range.h
+++ b/source/blender/blenlib/BLI_index_range.h
@@ -31,6 +31,11 @@
 
 #include "BLI_utildefines.h"
 
+/* Forward declare tbb::blocked_range for conversion operations. */
+namespace tbb {
+template<typename Value> class blocked_range;
+}
+
 namespace BLI {
 
 template<typename T> class ArrayRef;
@@ -51,6 +56,11 @@ class IndexRange {
   {
   }
 
+  template<typename T>
+  IndexRange(const tbb::blocked_range<T> &range) : m_start(range.begin()), m_size(range.size())
+  {
+  }
+
   class Iterator {
    private:
     uint m_current;
@@ -179,6 +189,11 @@ class IndexRange {
     return IndexRange(new_start, size);
   }
 
+  IndexRange slice(IndexRange range) const
+  {
+    return this->slice(range.start(), range.size());
+  }
+
   /**
    * Get read-only access to a memory buffer that contains the range as actual numbers.
    */