Implements Zero-Copy String Views onto Contiguous Memory, resolves #3265.

- http://www.boost.org/doc/libs/1_61_0/libs/utility/doc/html/string_ref.html
- http://en.cppreference.com/w/cpp/string/basic_string_view

include/extractor/suffix_table.hpp

@@ -4,6 +4,8 @@
 #include <string>
 #include <unordered_set>
 
+#include "util/string_view.hpp"
+
 namespace osrm
 {
 namespace extractor
@@ -21,9 +23,20 @@ class SuffixTable final
 
     // check whether a string is part of the know suffix list
     bool isSuffix(const std::string &possible_suffix) const;
+    bool isSuffix(util::StringView possible_suffix) const;
 
   private:
-    std::unordered_set<std::string> suffix_set;
+    // Store lower-cased strings in SuffixTable and a set of StringViews for quick membership
+    // checks.
+    //
+    // Why not uset<StringView>? StringView is non-owning, the vector<string> holds the string
+    // contents, the set<StringView> only holds [first,last) pointers into the vector.
+    //
+    // Then why not simply uset<string>? Because membership tests against StringView keys would
+    // require us to first convert StringViews into strings (allocation), do the membership,
+    // and destroy the StringView again.
+    std::vector<std::string> suffixes;
+    std::unordered_set<util::StringView> suffix_set;
 };
 
 } /* namespace extractor */