added more functions from original code, added macro

src/macros/mod.rs

@@ -0,0 +1,21 @@
+// std::borrow::Cow
+// std::option::Option
+
+/// This macro extracts owned value from cow
+/// but if cow is borrowed it returns default given value
+/// 
+/// it's helpful when function returns `Cow<'_, T>` as result,
+/// where `Cow::Borrowed` option marks that value was not modified
+/// and we can use owned original instead of copying it.
+macro_rules! owned_from_cow_or {
+    ($getcow:expr, $default:expr) => {{
+        if let std::borrow::Cow::Owned(s) = $getcow {
+            s
+        } else {
+            $default
+        }
+    }};
+}
+
+pub(crate) use owned_from_cow_or;
+