stevemk14ebr · June 10, 2022 20:35 · Jun 10, 2022 · Jun 9, 2022
diff --git a/typdef_args_to_typeids b/typdef_args_to_typeids
@@ -23,4 +23,54 @@ int main()
     {
         std::cout << t.hash_code() << std::endl;
     }
-}
+}
+
+// ALTERNATIVE (free standing, no typeid). Also fixes bug with function types with 0 args by using std::array
+using hash_t = std::uint64_t;
+
+// FNV-1a 64 bit hash
+consteval hash_t fnv1a_hash(std::size_t n, const char* str, hash_t hash = 14695981039346656037ull)
+{
+    return n > 0 ? fnv1a_hash(n - 1, str + 1, (hash ^ *str) * 1099511628211ull) : hash;
+}
+
+template<std::size_t N>
+consteval hash_t fnv1a_hash(const char(&array)[N])
+{
+    return fnv1a_hash(N - 1, &array[0]);
+}
+
+struct string_view
+{
+    char const* data;
+    std::size_t size;
+
+    consteval uint64_t hash() {
+        return fnv1a_hash(size, data);
+    }
+};
+
+template<size_t N>
+consteval size_t length(char const (&)[N])
+{
+    return N - 1;
+}
+
+template<class T>
+consteval string_view get_unique_name_for_type()
+{
+    return { __FUNCSIG__, length(__FUNCSIG__)};
+}
+
+template<typename T>
+consteval uint64_t get_type_id() {
+    return get_unique_name_for_type<T>().hash();
+}
+
+template<typename T>
+struct arg_types {};
+
+template<typename R, typename... A>
+struct arg_types<R(*)(A...)> {
+    static constexpr std::array<uint64_t, sizeof...(A)> value = {get_type_id<A>()...};
+};
diff --git a/typdef_args_to_typeids b/typdef_args_to_typeids
@@ -0,0 +1,26 @@
+#include <iostream>
+#include <typeinfo>
+#include <typeindex>
+#include <span>
+
+typedef int (*tExample) (int a, bool b, char* c, long long d);
+
+template<typename T>
+struct arg_types {};
+
+template<typename R, typename... A>
+struct arg_types<R(*)(A...)> {
+    inline static const std::type_index value[] = {typeid(A)...};
+};
+
+template<typename T>
+static constexpr std::span<const std::type_index> arg_types_v = arg_types<T>::value;
+
+int main()
+{
+    auto vec = arg_types_v<tExample>;
+    for (const auto& t : vec)
+    {
+        std::cout << t.hash_code() << std::endl;
+    }
+}