add utf8.upper, utf8.lower

doc/en/scripting/builtins/libutf8.md

@@ -18,4 +18,10 @@ utf8.codepoint(chars: str) -> int
 
 -- Returns a substring from position startchar to endchar inclusive
 utf8.sub(text: str, startchar: int, [optional] endchar: int) -> str
+
+-- Converts a string to uppercase
+utf8.upper(text: str) -> str
+
+-- Converts a string to lowercase
+utf8.lower(text: str) -> str
 ```

doc/ru/scripting/builtins/libutf8.md

@@ -18,4 +18,10 @@ utf8.codepoint(chars: str) -> int
 
 -- Возвращает подстроку от позиции startchar до endchar включительно
 utf8.sub(text: str, startchar: int, [опционально] endchar: int) -> str
+
+-- Переводит строку в вверхний регистр
+utf8.upper(text: str) -> str
+
+-- Переводит строку в нижний регистр
+utf8.lower(text: str) -> str
 ```

src/logic/scripting/lua/libs/libutf8.cpp

@@ -63,11 +63,29 @@ static int l_sub(lua::State* L) {
     return lua::pushstring(L, util::u32str2str_utf8(string.substr(start, end)));
 }
 
+static int l_upper(lua::State* L) {
+    auto string = util::str2u32str_utf8(lua::require_string(L, 1));
+    for (auto& c : string) {
+        c = std::towupper(c);
+    }
+    return lua::pushstring(L, util::u32str2str_utf8(string));
+}
+
+static int l_lower(lua::State* L) {
+    auto string = util::str2u32str_utf8(lua::require_string(L, 1));
+    for (auto& c : string) {
+        c = std::towlower(c);
+    }
+    return lua::pushstring(L, util::u32str2str_utf8(string));
+}
+
 const luaL_Reg utf8lib[] = {
     {"tobytes", lua::wrap<l_encode>},
     {"tostring", lua::wrap<l_decode>},
     {"length", lua::wrap<l_length>},
     {"codepoint", lua::wrap<l_codepoint>},
     {"sub", lua::wrap<l_sub>},
+    {"upper", lua::wrap<l_upper>},
+    {"lower", lua::wrap<l_lower>},
     {NULL, NULL}
 };