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, 10 insertions, 0 deletions

diff --git a/source/blender/blenlib/tests/BLI_set_test.cc b/source/blender/blenlib/tests/BLI_set_test.cc
index 7bd0b258df8..df3f7ab544c 100644
--- a/source/blender/blenlib/tests/BLI_set_test.cc
+++ b/source/blender/blenlib/tests/BLI_set_test.cc
@@ -452,6 +452,16 @@ TEST(set, LookupKeyPtr)
   EXPECT_EQ(set.lookup_key_ptr({3, 50}), nullptr);
 }
 
+TEST(set, StringViewKeys)
+{
+  Set<std::string_view> set;
+  set.add("hello");
+  set.add("world");
+  EXPECT_FALSE(set.contains("worlds"));
+  EXPECT_TRUE(set.contains("world"));
+  EXPECT_TRUE(set.contains("hello"));
+}
+
 /**
  * Set this to 1 to activate the benchmark. It is disabled by default, because it prints a lot.
  */