Intern strings used as identifiers (for labels, constants, macros, charmaps, etc) (#1980)

include/asm/intern.hpp

@@ -0,0 +1,34 @@
+// SPDX-License-Identifier: MIT
+
+#ifndef RGBDS_ASM_INTERN_HPP
+#define RGBDS_ASM_INTERN_HPP
+
+#include <stddef.h>
+#include <string>
+#include <string_view>
+#include <utility> // hash
+
+class InternedStr {
+	size_t index;
+
+public:
+	constexpr InternedStr() : index(static_cast<size_t>(-1)) {}
+	explicit constexpr InternedStr(size_t index_) : index(index_) {}
+
+	std::string const &str() const;
+	char const *c_str() const { return str().c_str(); }
+
+	bool operator==(InternedStr const &rhs) const { return index == rhs.index; }
+
+	template<typename T>
+	friend struct std::hash;
+};
+
+template<>
+struct std::hash<InternedStr> {
+	size_t operator()(InternedStr const &str) const { return std::hash<size_t>{}(str.index); }
+};
+
+InternedStr intern(std::string_view str);
+
+#endif // RGBDS_ASM_INTERN_HPP