utf8.char

components/lua/utf8.cpp

@@ -1,11 +1,27 @@
+#include <codecvt>
+
 #include "utf8.hpp"
-#include "luastate.hpp"
 
 namespace
 {
     static constexpr std::string_view UTF8PATT = "[%z\x01-\x7F\xC2-\xF4][\x80-\xBF]*"; // %z is deprecated in Lua5.2
     static constexpr uint32_t MAXUTF = 0x7FFFFFFFu;
     static constexpr uint32_t MAXUNICODE = 0x10FFFFu;
+
+    inline static double getInteger(const sol::stack_proxy arg, const size_t& n, const std::string_view& name)
+    {
+        double integer;
+        if (!arg.is<double>())
+            throw std::runtime_error(std::format("bad argument #{} to '{}' (number expected, got {})", n, name,
+                sol::type_name(arg.lua_state(), arg.get_type())));
+
+        if (std::modf(arg, &integer) != 0)
+            throw std::runtime_error(
+                std::format("bad argument #{} to '{}' (number has no integer representation)", n, name));
+
+        return integer;
+    }
+
 }
 
 namespace LuaUtf8
@@ -16,6 +32,19 @@ namespace LuaUtf8
 
         utf8["charpattern"] = UTF8PATT;
 
+        utf8["char"] = [](const sol::variadic_args args) -> std::string {
+            std::string result{};
+            std::wstring_convert<std::codecvt_utf8<wchar_t>> converter;
+            for (size_t i = 0; i < args.size(); ++i)
+            {
+                int64_t codepoint = getInteger(args[i], (i + 1), "char");
+                if (codepoint < 0 || codepoint > MAXUTF)
+                    throw std::runtime_error(std::format("bad argument #{} to 'char' (value out of range)", (i + 1)));
+
+                result += converter.to_bytes(codepoint);
+            }
+            return result;
+        };
         return utf8;
     }
 }

components/lua/utf8.hpp

@@ -1,6 +1,8 @@
 #ifndef COMPONENTS_LUA_UTF8_H
 #define COMPONENTS_LUA_UTF8_H
 
+#include <sol/sol.hpp>
+
 namespace LuaUtf8
 {
     sol::table initUtf8Package(sol::state_view&);