Make cb map as hash table

src/hash.hpp

@@ -0,0 +1,20 @@
+#pragma once
+
+#include <utility>
+
+namespace {
+	template<typename T, typename... Rest>
+	void hash_combine(std::size_t& seed, const T& v, const Rest&... rest) {
+		seed ^= std::hash<T>{}(v) + 0x9e3779b9 + (seed << 6) + (seed >> 2);
+		(hash_combine(seed, rest), ...);
+	}
+}
+
+template<typename T1, typename T2>
+struct std::hash<std::pair<T1, T2>> {
+	std::size_t operator()(std::pair<T1, T2> const& p) const noexcept {
+		std::size_t seed{};
+		hash_combine(seed, p.first, p.second);
+		return seed;
+	}
+};

src/plugin.hpp

@@ -1,6 +1,7 @@
 #pragma once
 
 #include "callback.hpp"
+#include "hash.hpp"
 
 #include <plugify/cpp_plugin.hpp>
 #include <plugin_export.h>