BLI: improve StringRef for C++17

Since C++17 there is also std::string_view, which is similar to StringRef.
This commit does a couple of things:
* New implicit conversions between StringRef and std::string_view.
* Support std::string_view in blender::DefaultHash.
* Support most of the methods that std::string_view has.
* Add StringRef::not_found which can be used instead of -1 in some places.
* Improve/fix the description at the top of BLI_string_ref.hh.

1 files changed, 24 insertions, 0 deletions

diff --git a/source/blender/blenlib/tests/BLI_string_ref_test.cc b/source/blender/blenlib/tests/BLI_string_ref_test.cc
index d08c8a77455..2d488feff71 100644
--- a/source/blender/blenlib/tests/BLI_string_ref_test.cc
+++ b/source/blender/blenlib/tests/BLI_string_ref_test.cc
@@ -254,6 +254,14 @@ TEST(string_ref, DropPrefix)
   EXPECT_EQ(ref2, "t");
 }
 
+TEST(string_ref, DropSuffix)
+{
+  StringRef ref("test");
+  StringRef ref2 = ref.drop_suffix(1);
+  EXPECT_EQ(ref2.size(), 3);
+  EXPECT_EQ(ref2, "tes");
+}
+
 TEST(string_ref, Substr)
 {
   StringRef ref("hello world");
@@ -261,6 +269,8 @@ TEST(string_ref, Substr)
   EXPECT_EQ(ref.substr(4, 0), "");
   EXPECT_EQ(ref.substr(3, 4), "lo w");
   EXPECT_EQ(ref.substr(6, 5), "world");
+  EXPECT_EQ(ref.substr(8), "rld");
+  EXPECT_EQ(ref.substr(8, 100), "rld");
 }
 
 TEST(string_ref, Copy)
@@ -274,4 +284,18 @@ TEST(string_ref, Copy)
   EXPECT_EQ(ref, dst);
 }
 
+TEST(string_ref, FromStringView)
+{
+  std::string_view view = "hello";
+  StringRef ref = view;
+  EXPECT_EQ(ref, "hello");
+}
+
+TEST(string_ref, ToStringView)
+{
+  StringRef ref = "hello";
+  std::string_view view = ref;
+  EXPECT_EQ(view, "hello");
+}
+
 }  // namespace blender::tests