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, 74 insertions, 0 deletions

diff --git a/tests/gtests/blenlib/BLI_optional_test.cc b/tests/gtests/blenlib/BLI_optional_test.cc
new file mode 100644
index 00000000000..2e672967680
--- /dev/null
+++ b/tests/gtests/blenlib/BLI_optional_test.cc
@@ -0,0 +1,74 @@
+#include "testing/testing.h"
+#include "BLI_optional.h"
+#include <string>
+
+using namespace BLI;
+
+TEST(optional, DefaultConstructor)
+{
+  Optional<int> a;
+  EXPECT_FALSE(a.has_value());
+}
+
+TEST(optional, ValueConstructor)
+{
+  Optional<int> a(5);
+  EXPECT_TRUE(a.has_value());
+  EXPECT_EQ(a.value(), 5);
+}
+
+TEST(optional, CopyConstructor)
+{
+  Optional<std::string> a("Hello");
+  Optional<std::string> b = a;
+  EXPECT_TRUE(a.has_value());
+  EXPECT_TRUE(b.has_value());
+  b.value()[0] = 'T';
+  EXPECT_EQ(a.value(), "Hello");
+  EXPECT_EQ(b.value(), "Tello");
+}
+
+TEST(optional, Reset)
+{
+  Optional<int> a(4);
+  EXPECT_TRUE(a.has_value());
+  a.reset();
+  EXPECT_FALSE(a.has_value());
+}
+
+TEST(optional, FromNullPointer)
+{
+  Optional<int> a = Optional<int>::FromPointer(nullptr);
+  EXPECT_FALSE(a.has_value());
+}
+
+TEST(optional, FromNonNullPointer)
+{
+  int value = 42;
+  Optional<int> a = Optional<int>::FromPointer(&value);
+  EXPECT_TRUE(a.has_value());
+  EXPECT_EQ(a.value(), 42);
+}
+
+TEST(optional, Extract)
+{
+  Optional<int> a(32);
+  EXPECT_TRUE(a.has_value());
+  EXPECT_EQ(a.extract(), 32);
+  EXPECT_FALSE(a.has_value());
+}
+
+TEST(optional, ArrowOperator)
+{
+  Optional<std::string> value = std::string("Hello");
+  EXPECT_TRUE(value.has_value());
+  EXPECT_EQ(value->size(), 5);
+}
+
+TEST(optional, StarOperator)
+{
+  Optional<std::string> value = std::string("Hello");
+  EXPECT_TRUE(value.has_value());
+  std::string &s = *value;
+  EXPECT_EQ(s.size(), 5);
+}