BLI: Add functions to IndexRange to mirror Span

Adds functions for special cases of slicing and an `is_empty` method.

1 files changed, 73 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 7f0d2e6c22a..10f6784cd44 100644
--- a/source/blender/blenlib/tests/BLI_index_range_test.cc
+++ b/source/blender/blenlib/tests/BLI_index_range_test.cc
@@ -129,6 +129,79 @@ TEST(index_range, SliceRange)
   EXPECT_EQ(slice.last(), 12);
 }
 
+TEST(index_range, DropBack)
+{
+  IndexRange a(4, 4);
+  auto slice = a.drop_back(2);
+  EXPECT_EQ(slice.size(), 2);
+  EXPECT_EQ(slice.start(), 4);
+  EXPECT_EQ(slice[1], 5);
+}
+
+TEST(index_range, DropBackAll)
+{
+  IndexRange a(4, 4);
+  auto slice = a.drop_back(a.size());
+  EXPECT_TRUE(slice.is_empty());
+}
+
+TEST(index_range, DropFront)
+{
+  IndexRange a(4, 4);
+  auto slice = a.drop_front(1);
+  EXPECT_EQ(slice.size(), 3);
+  EXPECT_EQ(slice[0], 5);
+  EXPECT_EQ(slice[1], 6);
+  EXPECT_EQ(slice.last(), 7);
+}
+
+TEST(index_range, DropFrontLargeN)
+{
+  IndexRange a(1, 5);
+  IndexRange slice = a.drop_front(100);
+  EXPECT_TRUE(slice.is_empty());
+}
+
+TEST(index_range, DropFrontAll)
+{
+  IndexRange a(50);
+  IndexRange slice = a.drop_front(a.size());
+  EXPECT_TRUE(slice.is_empty());
+}
+
+TEST(index_range, TakeFront)
+{
+  IndexRange a(4, 4);
+  IndexRange slice = a.take_front(2);
+  EXPECT_EQ(slice.size(), 2);
+  EXPECT_EQ(slice[0], 4);
+  EXPECT_EQ(slice[1], 5);
+}
+
+TEST(index_range, TakeFrontLargeN)
+{
+  IndexRange a(4, 4);
+  IndexRange slice = a.take_front(100);
+  EXPECT_EQ(slice.size(), 4);
+}
+
+TEST(index_range, TakeBack)
+{
+  IndexRange a(4, 4);
+  auto slice = a.take_back(2);
+  EXPECT_EQ(slice.size(), 2);
+  EXPECT_EQ(slice[0], 6);
+  EXPECT_EQ(slice[1], 7);
+}
+
+TEST(index_range, TakeBackLargeN)
+{
+  IndexRange a(3, 4);
+  IndexRange slice = a.take_back(100);
+  EXPECT_EQ(slice.size(), 4);
+  EXPECT_EQ(slice.size(), 4);
+}
+
 TEST(index_range, AsSpan)
 {
   IndexRange range = IndexRange(4, 6);