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, 7 insertions, 0 deletions

diff --git a/source/blender/blenlib/BLI_hash.hh b/source/blender/blenlib/BLI_hash.hh
index 8301dbb8e3a..2e3212cc83b 100644
--- a/source/blender/blenlib/BLI_hash.hh
+++ b/source/blender/blenlib/BLI_hash.hh
@@ -180,6 +180,13 @@ template<> struct DefaultHash<StringRefNull> {
   }
 };
 
+template<> struct DefaultHash<std::string_view> {
+  uint64_t operator()(StringRef value) const
+  {
+    return hash_string(value);
+  }
+};
+
 /**
  * While we cannot guarantee that the lower 4 bits of a pointer are zero, it is often the case.
  */