added crow

include/crow/ci_map.h

@@ -0,0 +1,43 @@
+#pragma once
+
+#include <string_view>
+#include <locale>
+#include <unordered_map>
+
+#include "crow/utility.h"
+
+namespace crow
+{
+    /// Hashing function for ci_map (unordered_multimap).
+    struct ci_hash
+    {
+        size_t operator()(const std::string_view key) const
+        {
+            std::size_t seed = 0;
+            std::locale locale;
+
+            for (auto c : key)
+                hash_combine(seed, std::toupper(c, locale));
+
+            return seed;
+        }
+
+    private:
+        static inline void hash_combine(std::size_t& seed, char v)
+        {
+            std::hash<char> hasher;
+            seed ^= hasher(v) + 0x9e3779b9 + (seed << 6) + (seed >> 2);
+        }
+    };
+
+    /// Equals function for ci_map (unordered_multimap).
+    struct ci_key_eq
+    {
+        bool operator()(const std::string_view l, const std::string_view r) const
+        {
+            return utility::string_equals(l, r);
+        }
+    };
+
+    using ci_map = std::unordered_multimap<std::string, std::string, ci_hash, ci_key_eq>;
+} // namespace crow