BLI: add reverse iterators, iterator constructor and Vector.insert/prepend

The new reverse iterators behave as the reverse iterators for contains from
the standard library. Have a look at the tests to see how to use them.
Using them will hopefully become easier with ranges in C++20.

A Vector can now be constructed from two iterators, which is very common
in the standard library.

New Vector.insert methods allow adding elements in the middle of a vector.
These methods should not be used often in practice, because they has a linear running time.

New Vector.prepend methods allow adding elements to the beginning of a vector.
These methods are O(n) as well.

1 files changed, 15 insertions, 0 deletions

diff --git a/source/blender/blenlib/tests/BLI_array_test.cc b/source/blender/blenlib/tests/BLI_array_test.cc
index 7348a6f93f3..38ab695d238 100644
--- a/source/blender/blenlib/tests/BLI_array_test.cc
+++ b/source/blender/blenlib/tests/BLI_array_test.cc
@@ -2,6 +2,7 @@
 
 #include "BLI_array.hh"
 #include "BLI_strict_flags.h"
+#include "BLI_vector.hh"
 #include "testing/testing.h"
 
 namespace blender::tests {
@@ -173,4 +174,18 @@ TEST(array, Fill)
   EXPECT_EQ(array[4], 3);
 }
 
+TEST(array, ReverseIterator)
+{
+  Array<int> array = {3, 4, 5, 6};
+  Vector<int> reversed_vec;
+
+  for (auto it = array.rbegin(); it != array.rend(); ++it) {
+    reversed_vec.append(*it);
+    *it += 10;
+  }
+
+  EXPECT_EQ_ARRAY(reversed_vec.data(), Span({6, 5, 4, 3}).data(), 4);
+  EXPECT_EQ_ARRAY(array.data(), Span({13, 14, 15, 16}).data(), 4);
+}
+
 }  // namespace blender::tests