IndexRange: Add new `intersect` method

Returns a new range, that contains the intersection of the current one
with the given range.

This is helpful to select a portion of a range without having to deal with
all the asserts of other functions. The resulting range being always a
valid subrange, it can be used to iterate or copy a part of a vector.

1 files changed, 11 insertions, 0 deletions

diff --git a/source/blender/blenlib/tests/BLI_index_range_test.cc b/source/blender/blenlib/tests/BLI_index_range_test.cc
index 955691b3430..8ec7ad85d9c 100644
--- a/source/blender/blenlib/tests/BLI_index_range_test.cc
+++ b/source/blender/blenlib/tests/BLI_index_range_test.cc
@@ -126,6 +126,17 @@ TEST(index_range, Slice)
   EXPECT_EQ(slice.last(), 12);
 }
 
+TEST(index_range, Intersect)
+{
+  IndexRange range = IndexRange(5, 15);
+  EXPECT_EQ(range.intersect(IndexRange(2, 2)), IndexRange(5, 0));
+  EXPECT_EQ(range.intersect(IndexRange(4, 2)), IndexRange(5, 1));
+  EXPECT_EQ(range.intersect(IndexRange(3, 20)), IndexRange(5, 15));
+  EXPECT_EQ(range.intersect(IndexRange(5, 15)), IndexRange(5, 15));
+  EXPECT_EQ(range.intersect(IndexRange(15, 10)), IndexRange(15, 5));
+  EXPECT_EQ(range.intersect(IndexRange(22, 2)), IndexRange(20, 0));
+}
+
 TEST(index_range, SliceRange)
 {
   IndexRange range = IndexRange(5, 15);