Move fengari specific things to src/fengaricore.js

String manipulation functions now get exposed on 'fengari' object itself at top level

16 files changed, 359 insertions, 325 deletions

diff --git a/src/defs.js b/src/defs.js
index fc18707..c1720c3 100644
--- a/src/defs.js
+++ b/src/defs.js
@@ -22,16 +22,6 @@ const LUA_RELEASE             = LUA_VERSION + "." + LUA_VERSION_RELEASE;
 const LUA_COPYRIGHT           = LUA_RELEASE + "  Copyright (C) 1994-2017 Lua.org, PUC-Rio";
 const LUA_AUTHORS             = "R. Ierusalimschy, L. H. de Figueiredo, W. Celes";
 
-const FENGARI_VERSION_MAJOR   = "0";
-const FENGARI_VERSION_MINOR   = "0";
-const FENGARI_VERSION_NUM     = 1;
-const FENGARI_VERSION_RELEASE = "1";
-
-const FENGARI_VERSION         = "Fengari " + FENGARI_VERSION_MAJOR + "." + FENGARI_VERSION_MINOR;
-const FENGARI_RELEASE         = FENGARI_VERSION + "." + FENGARI_VERSION_RELEASE;
-const FENGARI_AUTHORS         = "B. Giannangeli, Daurnimator";
-const FENGARI_COPYRIGHT       = FENGARI_RELEASE + "  Copyright (C) 2017-2018 " + FENGARI_AUTHORS + "\nBased on: " + LUA_COPYRIGHT;
-
 const LUA_VERSUFFIX           = "_" + LUA_VERSION_MAJOR + "_" + LUA_VERSION_MINOR;
 
 const LUA_INIT_VAR            = "LUA_INIT";
@@ -437,14 +427,6 @@ if (typeof process === "undefined") {
 }
 
 module.exports.CT                      = CT;
-module.exports.FENGARI_AUTHORS         = FENGARI_AUTHORS;
-module.exports.FENGARI_COPYRIGHT       = FENGARI_COPYRIGHT;
-module.exports.FENGARI_RELEASE         = FENGARI_RELEASE;
-module.exports.FENGARI_VERSION         = FENGARI_VERSION;
-module.exports.FENGARI_VERSION_MAJOR   = FENGARI_VERSION_MAJOR;
-module.exports.FENGARI_VERSION_MINOR   = FENGARI_VERSION_MINOR;
-module.exports.FENGARI_VERSION_NUM     = FENGARI_VERSION_NUM;
-module.exports.FENGARI_VERSION_RELEASE = FENGARI_VERSION_RELEASE;
 module.exports.LUA_AUTHORS             = LUA_AUTHORS;
 module.exports.LUA_COPYRIGHT           = LUA_COPYRIGHT;
 module.exports.LUA_HOOKCALL            = LUA_HOOKCALL;
diff --git a/src/fengari.js b/src/fengari.js
index 3d35334..b37f7d6 100644
--- a/src/fengari.js
+++ b/src/fengari.js
@@ -1,5 +1,23 @@
 "use strict";
 
+const core = require("./fengaricore.js");
+
+module.exports.FENGARI_AUTHORS         = core.FENGARI_AUTHORS;
+module.exports.FENGARI_COPYRIGHT       = core.FENGARI_COPYRIGHT;
+module.exports.FENGARI_RELEASE         = core.FENGARI_RELEASE;
+module.exports.FENGARI_VERSION         = core.FENGARI_VERSION;
+module.exports.FENGARI_VERSION_MAJOR   = core.FENGARI_VERSION_MAJOR;
+module.exports.FENGARI_VERSION_MINOR   = core.FENGARI_VERSION_MINOR;
+module.exports.FENGARI_VERSION_NUM     = core.FENGARI_VERSION_NUM;
+module.exports.FENGARI_VERSION_RELEASE = core.FENGARI_VERSION_RELEASE;
+
+module.exports.luastring_eq      = core.luastring_eq;
+module.exports.luastring_indexOf = core.luastring_indexOf;
+module.exports.luastring_of      = core.luastring_of;
+module.exports.to_jsstring       = core.to_jsstring;
+module.exports.to_luastring      = core.to_luastring;
+module.exports.to_uristring      = core.to_uristring;
+
 const lua      = require('./lua.js');
 const lauxlib  = require('./lauxlib.js');
 const lualib   = require('./lualib.js');
diff --git a/src/fengaricore.js b/src/fengaricore.js
new file mode 100644
index 0000000..1fd0354
--- /dev/null
+++ b/src/fengaricore.js
@@ -0,0 +1,36 @@
+/* Fengari specific functions
+ *
+ * This file includes fengari-specific data or and functionality for users to
+ * manipulate fengari's string type.
+ * The fields are exposed to the user on the 'fengari' entry point; however to
+ * avoid a dependency on defs.js from lauxlib.js they are defined in this file.
+ */
+
+const defs = require("./defs.js");
+
+const FENGARI_VERSION_MAJOR   = "0";
+const FENGARI_VERSION_MINOR   = "0";
+const FENGARI_VERSION_NUM     = 1;
+const FENGARI_VERSION_RELEASE = "1";
+const FENGARI_VERSION         = "Fengari " + FENGARI_VERSION_MAJOR + "." + FENGARI_VERSION_MINOR;
+const FENGARI_RELEASE         = FENGARI_VERSION + "." + FENGARI_VERSION_RELEASE;
+const FENGARI_AUTHORS         = "B. Giannangeli, Daurnimator";
+const FENGARI_COPYRIGHT       = FENGARI_RELEASE + "  Copyright (C) 2017-2018 " + FENGARI_AUTHORS + "\nBased on: " + defs.LUA_COPYRIGHT;
+
+module.exports.FENGARI_AUTHORS         = FENGARI_AUTHORS;
+module.exports.FENGARI_COPYRIGHT       = FENGARI_COPYRIGHT;
+module.exports.FENGARI_RELEASE         = FENGARI_RELEASE;
+module.exports.FENGARI_VERSION         = FENGARI_VERSION;
+module.exports.FENGARI_VERSION_MAJOR   = FENGARI_VERSION_MAJOR;
+module.exports.FENGARI_VERSION_MINOR   = FENGARI_VERSION_MINOR;
+module.exports.FENGARI_VERSION_NUM     = FENGARI_VERSION_NUM;
+module.exports.FENGARI_VERSION_RELEASE = FENGARI_VERSION_RELEASE;
+module.exports.is_luastring            = defs.is_luastring;
+module.exports.luastring_eq            = defs.luastring_eq;
+module.exports.luastring_from          = defs.luastring_from;
+module.exports.luastring_indexOf       = defs.luastring_indexOf;
+module.exports.luastring_of            = defs.luastring_of;
+module.exports.to_jsstring             = defs.to_jsstring;
+module.exports.to_luastring            = defs.to_luastring;
+module.exports.to_uristring            = defs.to_uristring;
+module.exports.from_userstring         = defs.from_userstring;
diff --git a/src/lauxlib.js b/src/lauxlib.js
index 52ea3a2..5dc42c2 100644
--- a/src/lauxlib.js
+++ b/src/lauxlib.js
@@ -1,22 +1,23 @@
 "use strict";
 
-const lua     = require('./lua.js');
+const lua = require('./lua.js');
+const {luastring_eq, to_luastring, to_uristring} = require("./fengaricore.js");
 
 /* extra error code for 'luaL_loadfilex' */
 const LUA_ERRFILE = lua.LUA_ERRERR+1;
 
 /* key, in the registry, for table of loaded modules */
-const LUA_LOADED_TABLE = lua.to_luastring("_LOADED");
+const LUA_LOADED_TABLE = to_luastring("_LOADED");
 
 /* key, in the registry, for table of preloaded loaders */
-const LUA_PRELOAD_TABLE = lua.to_luastring("_PRELOAD");
+const LUA_PRELOAD_TABLE = to_luastring("_PRELOAD");
 
-const LUA_FILEHANDLE = lua.to_luastring("FILE*");
+const LUA_FILEHANDLE = to_luastring("FILE*");
 
 const LUAL_NUMSIZES  = 4*16 + 8;
 
-const __name = lua.to_luastring("__name");
-const __tostring = lua.to_luastring("__tostring");
+const __name = to_luastring("__name");
+const __tostring = to_luastring("__tostring");
 
 const empty = new Uint8Array(0);
 
@@ -65,7 +66,7 @@ const findfield = function(L, objidx, level) {
 */
 const pushglobalfuncname = function(L, ar) {
     let top = lua.lua_gettop(L);
-    lua.lua_getinfo(L, lua.to_luastring("f"), ar);  /* push function */
+    lua.lua_getinfo(L, to_luastring("f"), ar);  /* push function */
     lua.lua_getfield(L, lua.LUA_REGISTRYINDEX, LUA_LOADED_TABLE);
     if (findfield(L, top + 1, 2)) {
         let name = lua.lua_tostring(L, -1);
@@ -84,15 +85,15 @@ const pushglobalfuncname = function(L, ar) {
 
 const pushfuncname = function(L, ar) {
     if (pushglobalfuncname(L, ar)) {  /* try first a global name */
-        lua.lua_pushfstring(L, lua.to_luastring("function '%s'"), lua.lua_tostring(L, -1));
+        lua.lua_pushfstring(L, to_luastring("function '%s'"), lua.lua_tostring(L, -1));
         lua.lua_remove(L, -2);  /* remove name */
     }
     else if (ar.namewhat.length !== 0)  /* is there a name from code? */
-        lua.lua_pushfstring(L, lua.to_luastring("%s '%s'"), ar.namewhat, ar.name);  /* use it */
+        lua.lua_pushfstring(L, to_luastring("%s '%s'"), ar.namewhat, ar.name);  /* use it */
     else if (ar.what && ar.what[0] === 'm'.charCodeAt(0))  /* main? */
         lua.lua_pushliteral(L, "main chunk");
     else if (ar.what && ar.what[0] === 'L'.charCodeAt(0))  /* for Lua functions, use <file:line> */
-        lua.lua_pushfstring(L, lua.to_luastring("function <%s:%d>"), ar.short_src, ar.linedefined);
+        lua.lua_pushfstring(L, to_luastring("function <%s:%d>"), ar.short_src, ar.linedefined);
     else  /* nothing left... */
         lua.lua_pushliteral(L, "?");
 };
@@ -118,7 +119,7 @@ const luaL_traceback = function(L, L1, msg, level) {
     let last = lastlevel(L1);
     let n1 = last - level > LEVELS1 + LEVELS2 ? LEVELS1 : -1;
     if (msg)
-        lua.lua_pushfstring(L, lua.to_luastring("%s\n"), msg);
+        lua.lua_pushfstring(L, to_luastring("%s\n"), msg);
     luaL_checkstack(L, 10, null);
     lua.lua_pushliteral(L, "stack traceback:");
     while (lua.lua_getstack(L1, level++, ar)) {
@@ -126,8 +127,8 @@ const luaL_traceback = function(L, L1, msg, level) {
             lua.lua_pushliteral(L, "\n\t...");  /* add a '...' */
             level = last - LEVELS2 + 1;  /* and skip to last ones */
         } else {
-            lua.lua_getinfo(L1, lua.to_luastring("Slnt", true), ar);
-            lua.lua_pushfstring(L, lua.to_luastring("\n\t%s:"), ar.short_src);
+            lua.lua_getinfo(L1, to_luastring("Slnt", true), ar);
+            lua.lua_pushfstring(L, to_luastring("\n\t%s:"), ar.short_src);
             if (ar.currentline > 0)
                 lua.lua_pushliteral(L, `${ar.currentline}:`);
             lua.lua_pushliteral(L, " in ");
@@ -153,20 +154,20 @@ const luaL_argerror = function(L, arg, extramsg) {
     let ar = new lua.lua_Debug();
 
     if (!lua.lua_getstack(L, 0, ar))  /* no stack frame? */
-        return luaL_error(L, lua.to_luastring("bad argument #%d (%s)"), arg, extramsg);
+        return luaL_error(L, to_luastring("bad argument #%d (%s)"), arg, extramsg);
 
-    lua.lua_getinfo(L, lua.to_luastring("n"), ar);
+    lua.lua_getinfo(L, to_luastring("n"), ar);
 
-    if (lua.luastring_eq(ar.namewhat, lua.to_luastring("method"))) {
+    if (luastring_eq(ar.namewhat, to_luastring("method"))) {
         arg--;  /* do not count 'self' */
         if (arg === 0)  /* error is in the self argument itself? */
-            return luaL_error(L, lua.to_luastring("calling '%s' on bad self (%s)"), ar.name, extramsg);
+            return luaL_error(L, to_luastring("calling '%s' on bad self (%s)"), ar.name, extramsg);
     }
 
     if (ar.name === null)
-        ar.name = pushglobalfuncname(L, ar) ? lua.lua_tostring(L, -1) : lua.to_luastring("?");
+        ar.name = pushglobalfuncname(L, ar) ? lua.lua_tostring(L, -1) : to_luastring("?");
 
-    return luaL_error(L, lua.to_luastring("bad argument #%d to '%s' (%s)"), arg, ar.name, extramsg);
+    return luaL_error(L, to_luastring("bad argument #%d to '%s' (%s)"), arg, ar.name, extramsg);
 };
 
 const typeerror = function(L, arg, tname) {
@@ -174,24 +175,24 @@ const typeerror = function(L, arg, tname) {
     if (luaL_getmetafield(L, arg, __name) === lua.LUA_TSTRING)
         typearg = lua.lua_tostring(L, -1);
     else if (lua.lua_type(L, arg) === lua.LUA_TLIGHTUSERDATA)
-        typearg = lua.to_luastring("light userdata", true);
+        typearg = to_luastring("light userdata", true);
     else
         typearg = luaL_typename(L, arg);
 
-    let msg = lua.lua_pushfstring(L, lua.to_luastring("%s expected, got %s"), tname, typearg);
+    let msg = lua.lua_pushfstring(L, to_luastring("%s expected, got %s"), tname, typearg);
     return luaL_argerror(L, arg, msg);
 };
 
 const luaL_where = function(L, level) {
     let ar = new lua.lua_Debug();
     if (lua.lua_getstack(L, level, ar)) {
-        lua.lua_getinfo(L, lua.to_luastring("Sl", true), ar);
+        lua.lua_getinfo(L, to_luastring("Sl", true), ar);
         if (ar.currentline > 0) {
-            lua.lua_pushfstring(L, lua.to_luastring("%s:%d: "), ar.short_src, ar.currentline);
+            lua.lua_pushfstring(L, to_luastring("%s:%d: "), ar.short_src, ar.currentline);
             return;
         }
     }
-    lua.lua_pushstring(L, lua.to_luastring(""));
+    lua.lua_pushstring(L, to_luastring(""));
 };
 
 const luaL_error = function(L, fmt, ...argp) {
@@ -209,9 +210,9 @@ const luaL_fileresult = function(L, stat, fname, e) {
     } else {
         lua.lua_pushnil(L);
         if (fname)
-            lua.lua_pushfstring(L, lua.to_luastring("%s: %s"), fname, lua.to_luastring(e.message));
+            lua.lua_pushfstring(L, to_luastring("%s: %s"), fname, to_luastring(e.message));
         else
-            lua.lua_pushstring(L, lua.to_luastring(e.message));
+            lua.lua_pushstring(L, to_luastring(e.message));
         lua.lua_pushinteger(L, -e.errno);
         return 3;
     }
@@ -288,7 +289,7 @@ const luaL_checkoption = function(L, arg, def, lst) {
     for (let i = 0; lst[i]; i++)
         if (lst[i].join('|') === name.join('|'))
             return i;
-    return luaL_argerror(L, arg, lua.lua_pushfstring(L, lua.to_luastring("invalid option '%s'"), name));
+    return luaL_argerror(L, arg, lua.lua_pushfstring(L, to_luastring("invalid option '%s'"), name));
 };
 
 const tag_error = function(L, arg, tag) {
@@ -312,7 +313,7 @@ const luaL_argcheck = function(L, cond, arg, extramsg) {
 
 const luaL_checkany = function(L, arg) {
     if (lua.lua_type(L, arg) === lua.LUA_TNONE)
-        luaL_argerror(L, arg, lua.to_luastring("value expected", true));
+        luaL_argerror(L, arg, to_luastring("value expected", true));
 };
 
 const luaL_checktype = function(L, arg, t) {
@@ -340,7 +341,7 @@ const luaL_optstring = luaL_optlstring;
 
 const interror = function(L, arg) {
     if (lua.lua_isnumber(L, arg))
-        luaL_argerror(L, arg, lua.to_luastring("number has no integer representation", true));
+        luaL_argerror(L, arg, to_luastring("number has no integer representation", true));
     else
         tag_error(L, arg, lua.LUA_TNUMBER);
 };
@@ -489,17 +490,17 @@ const luaL_len = function(L, idx) {
     lua.lua_len(L, idx);
     let l = lua.lua_tointegerx(L, -1);
     if (l === false)
-        luaL_error(L, lua.to_luastring("object length is not an integer", true));
+        luaL_error(L, to_luastring("object length is not an integer", true));
     lua.lua_pop(L, 1);  /* remove object */
     return l;
 };
 
-const p_I = lua.to_luastring("%I");
-const p_f = lua.to_luastring("%f");
+const p_I = to_luastring("%I");
+const p_f = to_luastring("%f");
 const luaL_tolstring = function(L, idx) {
     if (luaL_callmeta(L, idx, __tostring)) {
         if (!lua.lua_isstring(L, -1))
-            luaL_error(L, lua.to_luastring("'__tostring' must return a string"));
+            luaL_error(L, to_luastring("'__tostring' must return a string"));
     } else {
         let t = lua.lua_type(L, idx);
         switch(t) {
@@ -522,7 +523,7 @@ const luaL_tolstring = function(L, idx) {
             default: {
                 let tt = luaL_getmetafield(L, idx, __name);
                 let kind = tt === lua.LUA_TSTRING ? lua.lua_tostring(L, -1) : luaL_typename(L, idx);
-                lua.lua_pushfstring(L, lua.to_luastring("%s: %p"), kind, lua.lua_topointer(L, idx));
+                lua.lua_pushfstring(L, to_luastring("%s: %p"), kind, lua.lua_topointer(L, idx));
                 if (tt !== lua.LUA_TNIL)
                     lua.lua_remove(L, -2);
                 break;
@@ -608,12 +609,12 @@ const luaL_getsubtable = function(L, idx, fname) {
 ** Returns with only the table at the stack.
 */
 const luaL_setfuncs = function(L, l, nup) {
-    luaL_checkstack(L, nup, lua.to_luastring("too many upvalues", true));
+    luaL_checkstack(L, nup, to_luastring("too many upvalues", true));
     for (let lib in l) {  /* fill the table with given functions */
         for (let i = 0; i < nup; i++)  /* copy upvalues to the top */
             lua.lua_pushvalue(L, -nup);
         lua.lua_pushcclosure(L, l[lib], nup);  /* closure with those upvalues */
-        lua.lua_setfield(L, -(nup + 2), lua.to_luastring(lib));
+        lua.lua_setfield(L, -(nup + 2), to_luastring(lib));
     }
     lua.lua_pop(L, nup);  /* remove upvalues */
 };
@@ -628,9 +629,9 @@ const luaL_setfuncs = function(L, l, nup) {
 const luaL_checkstack = function(L, space, msg) {
     if (!lua.lua_checkstack(L, space)) {
         if (msg)
-            luaL_error(L, lua.to_luastring("stack overflow (%s)"), msg);
+            luaL_error(L, to_luastring("stack overflow (%s)"), msg);
         else
-            luaL_error(L, lua.to_luastring('stack overflow', true));
+            luaL_error(L, to_luastring('stack overflow', true));
     }
 };
 
@@ -682,7 +683,7 @@ const luaL_unref = function(L, t, ref) {
 const errfile = function(L, what, fnameindex, error) {
     let serr = error.message;
     let filename = lua.lua_tostring(L, fnameindex).subarray(1);
-    lua.lua_pushfstring(L, lua.to_luastring("cannot %s %s: %s"), lua.to_luastring(what), filename, lua.to_luastring(serr));
+    lua.lua_pushfstring(L, to_luastring("cannot %s %s: %s"), to_luastring(what), filename, to_luastring(serr));
     lua.lua_remove(L, fnameindex);
     return LUA_ERRFILE;
 };
@@ -768,8 +769,8 @@ if (typeof process === "undefined") {
         if (filename === null) {
             throw new Error("Can't read stdin in the browser");
         } else {
-            lua.lua_pushfstring(L, lua.to_luastring("@%s"), filename);
-            let path = lua.to_uristring(filename);
+            lua.lua_pushfstring(L, to_luastring("@%s"), filename);
+            let path = to_uristring(filename);
             let xhr = new XMLHttpRequest();
             xhr.open("GET", path, false);
             /* XXX: Synchronous xhr in main thread always returns a js string
@@ -781,7 +782,7 @@ if (typeof process === "undefined") {
             xhr.send();
             if (xhr.status >= 200 && xhr.status <= 299) {
                 if (typeof xhr.response === "string") {
-                    lf.f = lua.to_luastring(xhr.response);
+                    lf.f = to_luastring(xhr.response);
                 } else {
                     lf.f = new Uint8Array(xhr.response);
                 }
@@ -851,7 +852,7 @@ if (typeof process === "undefined") {
             lua.lua_pushliteral(L, "=stdin");
             lf.f = process.stdin.fd;
         } else {
-            lua.lua_pushfstring(L, lua.to_luastring("@%s"), filename);
+            lua.lua_pushfstring(L, to_luastring("@%s"), filename);
             try {
                 lf.f = fs.openSync(filename, "r");
             } catch (e) {
@@ -910,11 +911,11 @@ const luaL_checkversion = function(L) {
     let sz = LUAL_NUMSIZES;
     let v = lua.lua_version(L);
     if (sz != LUAL_NUMSIZES)  /* check numeric types */
-        luaL_error(L, lua.to_luastring("core and library have incompatible numeric types"));
+        luaL_error(L, to_luastring("core and library have incompatible numeric types"));
     if (v != lua.lua_version(null))
-        luaL_error(L, lua.to_luastring("multiple Lua VMs detected"));
+        luaL_error(L, to_luastring("multiple Lua VMs detected"));
     else if (v !== ver)
-        luaL_error(L, lua.to_luastring("version mismatch: app. needs %f, Lua core provides %f"), ver, v);
+        luaL_error(L, to_luastring("version mismatch: app. needs %f, Lua core provides %f"), ver, v);
 };
 
 module.exports.LUA_ERRFILE          = LUA_ERRFILE;
diff --git a/src/lbaselib.js b/src/lbaselib.js
index ca03b7f..78a32ed 100644
--- a/src/lbaselib.js
+++ b/src/lbaselib.js
@@ -2,6 +2,7 @@
 
 const lua     = require('./lua.js');
 const lauxlib = require('./lauxlib.js');
+const {to_jsstring, to_luastring} = require("./fengaricore.js");
 
 let lua_writestring;
 let lua_writeline;
@@ -23,7 +24,7 @@ if (typeof process === "undefined") {
         lua_writestring = function(s) {
             try {
                 /* If the string is valid utf8, then we can use to_jsstring */
-                s = lua.to_jsstring(s);
+                s = to_jsstring(s);
             } catch(e) {
                 /* otherwise push copy of raw array */
                 let copy = new Uint8Array(s.length);
@@ -47,15 +48,15 @@ if (typeof process === "undefined") {
 }
 const luaB_print = function(L) {
     let n = lua.lua_gettop(L); /* number of arguments */
-    lua.lua_getglobal(L, lua.to_luastring("tostring", true));
+    lua.lua_getglobal(L, to_luastring("tostring", true));
     for (let i = 1; i <= n; i++) {
         lua.lua_pushvalue(L, -1);  /* function to be called */
         lua.lua_pushvalue(L, i);  /* value to print */
         lua.lua_call(L, 1, 1);
         let s = lua.lua_tolstring(L, -1);
         if (s === null)
-            return lauxlib.luaL_error(L, lua.to_luastring("'tostring' must return a string to 'print'", true));
-        if (i > 1) lua_writestring(lua.to_luastring("\t"));
+            return lauxlib.luaL_error(L, to_luastring("'tostring' must return a string to 'print'", true));
+        if (i > 1) lua_writestring(to_luastring("\t"));
         lua_writestring(s);
         lua.lua_pop(L, 1);
     }
@@ -76,16 +77,16 @@ const luaB_getmetatable = function(L) {
         lua.lua_pushnil(L);
         return 1;  /* no metatable */
     }
-    lauxlib.luaL_getmetafield(L, 1, lua.to_luastring("__metatable", true));
+    lauxlib.luaL_getmetafield(L, 1, to_luastring("__metatable", true));
     return 1;  /* returns either __metatable field (if present) or metatable */
 };
 
 const luaB_setmetatable = function(L) {
     let t = lua.lua_type(L, 2);
     lauxlib.luaL_checktype(L, 1, lua.LUA_TTABLE);
-    lauxlib.luaL_argcheck(L, t === lua.LUA_TNIL || t === lua.LUA_TTABLE, 2, lua.to_luastring("nil or table expected", true));
-    if (lauxlib.luaL_getmetafield(L, 1, lua.to_luastring("__metatable", true)) !== lua.LUA_TNIL)
-        return lauxlib.luaL_error(L, lua.to_luastring("cannot change a protected metatable", true));
+    lauxlib.luaL_argcheck(L, t === lua.LUA_TNIL || t === lua.LUA_TTABLE, 2, to_luastring("nil or table expected", true));
+    if (lauxlib.luaL_getmetafield(L, 1, to_luastring("__metatable", true)) !== lua.LUA_TNIL)
+        return lauxlib.luaL_error(L, to_luastring("cannot change a protected metatable", true));
     lua.lua_settop(L, 2);
     lua.lua_setmetatable(L, 1);
     return 1;
@@ -100,7 +101,7 @@ const luaB_rawequal = function(L) {
 
 const luaB_rawlen = function(L) {
     let t = lua.lua_type(L, 1);
-    lauxlib.luaL_argcheck(L, t === lua.LUA_TTABLE || t === lua.LUA_TSTRING, 1, lua.to_luastring("table or string expected", true));
+    lauxlib.luaL_argcheck(L, t === lua.LUA_TTABLE || t === lua.LUA_TSTRING, 1, to_luastring("table or string expected", true));
     lua.lua_pushinteger(L, lua.lua_rawlen(L, 1));
     return 1;
 };
@@ -126,16 +127,16 @@ const opts = [
     "stop", "restart", "collect",
     "count", "step", "setpause", "setstepmul",
     "isrunning"
-].map((e) => lua.to_luastring(e));
+].map((e) => to_luastring(e));
 const luaB_collectgarbage = function(L) {
-    lauxlib.luaL_checkoption(L, 1, lua.to_luastring("collect"), opts);
+    lauxlib.luaL_checkoption(L, 1, to_luastring("collect"), opts);
     lauxlib.luaL_optinteger(L, 2, 0);
-    lauxlib.luaL_error(L, lua.to_luastring("lua_gc not implemented"));
+    lauxlib.luaL_error(L, to_luastring("lua_gc not implemented"));
 };
 
 const luaB_type = function(L) {
     let t = lua.lua_type(L, 1);
-    lauxlib.luaL_argcheck(L, t !== lua.LUA_TNONE, 1, lua.to_luastring("value expected", true));
+    lauxlib.luaL_argcheck(L, t !== lua.LUA_TNONE, 1, to_luastring("value expected", true));
     lua.lua_pushstring(L, lua.lua_typename(L, t));
     return 1;
 };
@@ -166,7 +167,7 @@ const luaB_next = function(L) {
 };
 
 const luaB_pairs = function(L) {
-    return pairsmeta(L, lua.to_luastring("__pairs", true), 0, luaB_next);
+    return pairsmeta(L, to_luastring("__pairs", true), 0, luaB_next);
 };
 
 /*
@@ -195,7 +196,7 @@ const luaB_ipairs = function(L) {
 
 const b_str2int = function(s, base) {
     try {
-        s = lua.to_jsstring(s);
+        s = to_jsstring(s);
     } catch (e) {
         return null;
     }
@@ -229,7 +230,7 @@ const luaB_tonumber = function(L) {
         let base = lauxlib.luaL_checkinteger(L, 2);
         lauxlib.luaL_checktype(L, 1, lua.LUA_TSTRING);  /* no numbers as strings */
         let s = lua.lua_tostring(L, 1);
-        lauxlib.luaL_argcheck(L, 2 <= base && base <= 36, 2, lua.to_luastring("base out of range", true));
+        lauxlib.luaL_argcheck(L, 2 <= base && base <= 36, 2, to_luastring("base out of range", true));
         let n = b_str2int(s, base);
         if (n !== null) {
             lua.lua_pushinteger(L, n);
@@ -273,7 +274,7 @@ const luaB_select = function(L) {
         let i = lauxlib.luaL_checkinteger(L, 1);
         if (i < 0) i = n + i;
         else if (i > n) i = n;
-        lauxlib.luaL_argcheck(L, 1 <= i, 1, lua.to_luastring("index out of range", true));
+        lauxlib.luaL_argcheck(L, 1 <= i, 1, to_luastring("index out of range", true));
         return n - i;
     }
 };
@@ -347,28 +348,28 @@ const RESERVEDSLOT = 5;
 ** reserved slot inside the stack.
 */
 const generic_reader = function(L, ud) {
-    lauxlib.luaL_checkstack(L, 2, lua.to_luastring("too many nested functions", true));
+    lauxlib.luaL_checkstack(L, 2, to_luastring("too many nested functions", true));
     lua.lua_pushvalue(L, 1);  /* get function */
     lua.lua_call(L, 0, 1);  /* call it */
     if (lua.lua_isnil(L, -1)) {
         lua.lua_pop(L, 1);  /* pop result */
         return null;
     } else if (!lua.lua_isstring(L, -1))
-        lauxlib.luaL_error(L, lua.to_luastring("reader function must return a string", true));
+        lauxlib.luaL_error(L, to_luastring("reader function must return a string", true));
     lua.lua_replace(L, RESERVEDSLOT);  /* save string in reserved slot */
     return lua.lua_tostring(L, RESERVEDSLOT);
 };
 
 const luaB_load = function(L) {
     let s = lua.lua_tostring(L, 1);
-    let mode = lauxlib.luaL_optstring(L, 3, lua.to_luastring("bt", true));
+    let mode = lauxlib.luaL_optstring(L, 3, to_luastring("bt", true));
     let env = !lua.lua_isnone(L, 4) ? 4 : 0;  /* 'env' index or 0 if no 'env' */
     let status;
     if (s !== null) {  /* loading a string? */
         let chunkname = lauxlib.luaL_optstring(L, 2, s);
         status = lauxlib.luaL_loadbufferx(L, s, s.length, chunkname, mode);
     } else {  /* loading from a reader function */
-        let chunkname = lauxlib.luaL_optstring(L, 2, lua.to_luastring("=(load)", true));
+        let chunkname = lauxlib.luaL_optstring(L, 2, to_luastring("=(load)", true));
         lauxlib.luaL_checktype(L, 1, lua.LUA_TFUNCTION);
         lua.lua_settop(L, RESERVEDSLOT);  /* create reserved slot */
         status = lua.lua_load(L, generic_reader, null, chunkname, mode);
@@ -428,10 +429,10 @@ const luaopen_base = function(L) {
     lauxlib.luaL_setfuncs(L, base_funcs, 0);
     /* set global _G */
     lua.lua_pushvalue(L, -1);
-    lua.lua_setfield(L, -2, lua.to_luastring("_G", true));
+    lua.lua_setfield(L, -2, to_luastring("_G", true));
     /* set global _VERSION */
     lua.lua_pushliteral(L, lua.LUA_VERSION);
-    lua.lua_setfield(L, -2, lua.to_luastring("_VERSION", true));
+    lua.lua_setfield(L, -2, to_luastring("_VERSION", true));
     return 1;
 };
 
diff --git a/src/lcorolib.js b/src/lcorolib.js
index a72d22b..bcdae8b 100644
--- a/src/lcorolib.js
+++ b/src/lcorolib.js
@@ -2,10 +2,11 @@
 
 const lua     = require('./lua.js');
 const lauxlib = require('./lauxlib.js');
+const {to_luastring} = require("./fengaricore.js");
 
 const getco = function(L) {
     let co = lua.lua_tothread(L, 1);
-    lauxlib.luaL_argcheck(L, co, 1, lua.to_luastring("thread expected", true));
+    lauxlib.luaL_argcheck(L, co, 1, to_luastring("thread expected", true));
     return co;
 };
 
diff --git a/src/ldblib.js b/src/ldblib.js
index 7e08dc5..9698f7a 100644
--- a/src/ldblib.js
+++ b/src/ldblib.js
@@ -4,6 +4,7 @@ const assert  = require('assert');
 
 const lua     = require('./lua.js');
 const lauxlib = require('./lauxlib.js');
+const {luastring_indexOf, to_luastring} = require("./fengaricore.js");
 
 /*
 ** If L1 != L, L1 can be in any state, and therefore there are no
@@ -12,7 +13,7 @@ const lauxlib = require('./lauxlib.js');
 */
 const checkstack = function(L, L1, n) {
     if (L !== L1 && !lua.lua_checkstack(L1, n))
-        lauxlib.luaL_error(L, lua.to_luastring("stack overflow", true));
+        lauxlib.luaL_error(L, to_luastring("stack overflow", true));
 };
 
 const db_getregistry = function(L) {
@@ -30,7 +31,7 @@ const db_getmetatable = function(L) {
 
 const db_setmetatable = function(L) {
     const t = lua.lua_type(L, 2);
-    lauxlib.luaL_argcheck(L, t == lua.LUA_TNIL || t == lua.LUA_TTABLE, 2, lua.to_luastring("nil or table expected", true));
+    lauxlib.luaL_argcheck(L, t == lua.LUA_TNIL || t == lua.LUA_TTABLE, 2, to_luastring("nil or table expected", true));
     lua.lua_settop(L, 2);
     lua.lua_setmetatable(L, 1);
     return 1;  /* return 1st argument */
@@ -120,10 +121,10 @@ const db_getinfo = function(L) {
     let thread = getthread(L);
     let arg = thread.arg;
     let L1 = thread.thread;
-    let options = lauxlib.luaL_optstring(L, arg + 2, lua.to_luastring("flnStu", true));
+    let options = lauxlib.luaL_optstring(L, arg + 2, to_luastring("flnStu", true));
     checkstack(L, L1, 3);
     if (lua.lua_isfunction(L, arg + 1)) {  /* info about a function? */
-        options = lua.lua_pushfstring(L, lua.to_luastring(">%s"), options);  /* add '>' to 'options' */
+        options = lua.lua_pushfstring(L, to_luastring(">%s"), options);  /* add '>' to 'options' */
         lua.lua_pushvalue(L, arg + 1);  /* move function to 'L1' stack */
         lua.lua_xmove(L, L1, 1);
     } else {  /* stack level */
@@ -134,32 +135,32 @@ const db_getinfo = function(L) {
     }
 
     if (!lua.lua_getinfo(L1, options, ar))
-        lauxlib.luaL_argerror(L, arg + 2, lua.to_luastring("invalid option", true));
+        lauxlib.luaL_argerror(L, arg + 2, to_luastring("invalid option", true));
     lua.lua_newtable(L);  /* table to collect results */
-    if (lua.luastring_indexOf(options, 'S'.charCodeAt(0)) > -1) {
-        settabss(L, lua.to_luastring("source", true), ar.source);
-        settabss(L, lua.to_luastring("short_src", true), ar.short_src);
-        settabsi(L, lua.to_luastring("linedefined", true), ar.linedefined);
-        settabsi(L, lua.to_luastring("lastlinedefined", true), ar.lastlinedefined);
-        settabss(L, lua.to_luastring("what", true), ar.what);
+    if (luastring_indexOf(options, 'S'.charCodeAt(0)) > -1) {
+        settabss(L, to_luastring("source", true), ar.source);
+        settabss(L, to_luastring("short_src", true), ar.short_src);
+        settabsi(L, to_luastring("linedefined", true), ar.linedefined);
+        settabsi(L, to_luastring("lastlinedefined", true), ar.lastlinedefined);
+        settabss(L, to_luastring("what", true), ar.what);
     }
-    if (lua.luastring_indexOf(options, 'l'.charCodeAt(0)) > -1)
-        settabsi(L, lua.to_luastring("currentline", true), ar.currentline);
-    if (lua.luastring_indexOf(options, 'u'.charCodeAt(0)) > -1) {
-        settabsi(L, lua.to_luastring("nups", true), ar.nups);
-        settabsi(L, lua.to_luastring("nparams", true), ar.nparams);
-        settabsb(L, lua.to_luastring("isvararg", true), ar.isvararg);
+    if (luastring_indexOf(options, 'l'.charCodeAt(0)) > -1)
+        settabsi(L, to_luastring("currentline", true), ar.currentline);
+    if (luastring_indexOf(options, 'u'.charCodeAt(0)) > -1) {
+        settabsi(L, to_luastring("nups", true), ar.nups);
+        settabsi(L, to_luastring("nparams", true), ar.nparams);
+        settabsb(L, to_luastring("isvararg", true), ar.isvararg);
     }
-    if (lua.luastring_indexOf(options, 'n'.charCodeAt(0)) > -1) {
-        settabss(L, lua.to_luastring("name", true), ar.name);
-        settabss(L, lua.to_luastring("namewhat", true), ar.namewhat);
+    if (luastring_indexOf(options, 'n'.charCodeAt(0)) > -1) {
+        settabss(L, to_luastring("name", true), ar.name);
+        settabss(L, to_luastring("namewhat", true), ar.namewhat);
     }
-    if (lua.luastring_indexOf(options, 't'.charCodeAt(0)) > -1)
-        settabsb(L, lua.to_luastring("istailcall", true), ar.istailcall);
-    if (lua.luastring_indexOf(options, 'L'.charCodeAt(0)) > -1)
-        treatstackoption(L, L1, lua.to_luastring("activelines", true));
-    if (lua.luastring_indexOf(options, 'f'.charCodeAt(0)) > -1)
-        treatstackoption(L, L1, lua.to_luastring("func", true));
+    if (luastring_indexOf(options, 't'.charCodeAt(0)) > -1)
+        settabsb(L, to_luastring("istailcall", true), ar.istailcall);
+    if (luastring_indexOf(options, 'L'.charCodeAt(0)) > -1)
+        treatstackoption(L, L1, to_luastring("activelines", true));
+    if (luastring_indexOf(options, 'f'.charCodeAt(0)) > -1)
+        treatstackoption(L, L1, to_luastring("func", true));
     return 1;  /* return table */
 };
 
@@ -176,7 +177,7 @@ const db_getlocal = function(L) {
     } else {  /* stack-level argument */
         let level = lauxlib.luaL_checkinteger(L, arg + 1);
         if (!lua.lua_getstack(L1, level, ar))  /* out of range? */
-            return lauxlib.luaL_argerror(L, arg+1, lua.to_luastring("level out of range", true));
+            return lauxlib.luaL_argerror(L, arg+1, to_luastring("level out of range", true));
         checkstack(L, L1, 1);
         let name = lua.lua_getlocal(L1, ar, nvar);
         if (name) {
@@ -200,7 +201,7 @@ const db_setlocal = function(L) {
     let level = lauxlib.luaL_checkinteger(L, arg + 1);
     let nvar = lauxlib.luaL_checkinteger(L, arg + 2);
     if (!lua.lua_getstack(L1, level, ar))  /* out of range? */
-        return lauxlib.luaL_argerror(L, arg + 1, lua.to_luastring("level out of range", true));
+        return lauxlib.luaL_argerror(L, arg + 1, to_luastring("level out of range", true));
     lauxlib.luaL_checkany(L, arg + 3);
     lua.lua_settop(L, arg + 3);
     checkstack(L, L1, 1);
@@ -242,7 +243,7 @@ const db_setupvalue = function(L) {
 const checkupval = function(L, argf, argnup) {
     let nup = lauxlib.luaL_checkinteger(L, argnup);  /* upvalue index */
     lauxlib.luaL_checktype(L, argf, lua.LUA_TFUNCTION);  /* closure */
-    lauxlib.luaL_argcheck(L, (lua.lua_getupvalue(L, argf, nup) !== null), argnup, lua.to_luastring("invalid upvalue index", true));
+    lauxlib.luaL_argcheck(L, (lua.lua_getupvalue(L, argf, nup) !== null), argnup, to_luastring("invalid upvalue index", true));
     return nup;
 };
 
@@ -255,8 +256,8 @@ const db_upvalueid = function(L) {
 const db_upvaluejoin = function(L) {
     let n1 = checkupval(L, 1, 2);
     let n2 = checkupval(L, 3, 4);
-    lauxlib.luaL_argcheck(L, !lua.lua_iscfunction(L, 1), 1, lua.to_luastring("Lua function expected", true));
-    lauxlib.luaL_argcheck(L, !lua.lua_iscfunction(L, 3), 3, lua.to_luastring("Lua function expected", true));
+    lauxlib.luaL_argcheck(L, !lua.lua_iscfunction(L, 1), 1, to_luastring("Lua function expected", true));
+    lauxlib.luaL_argcheck(L, !lua.lua_iscfunction(L, 3), 3, to_luastring("Lua function expected", true));
     lua.lua_upvaluejoin(L, 1, n1, 3, n2);
     return 0;
 };
@@ -265,9 +266,9 @@ const db_upvaluejoin = function(L) {
 ** The hook table at registry[HOOKKEY] maps threads to their current
 ** hook function. (We only need the unique address of 'HOOKKEY'.)
 */
-const HOOKKEY = lua.to_luastring("__hooks__", true);
+const HOOKKEY = to_luastring("__hooks__", true);
 
-const hooknames = ["call", "return", "line", "count", "tail call"].map(e => lua.to_luastring(e));
+const hooknames = ["call", "return", "line", "count", "tail call"].map(e => to_luastring(e));
 
 /*
 ** Call hook function registered at hook table for the current
@@ -281,7 +282,7 @@ const hookf = function(L, ar) {
         if (ar.currentline >= 0)
             lua.lua_pushinteger(L, ar.currentline);  /* push current line */
         else lua.lua_pushnil(L);
-        assert(lua.lua_getinfo(L, lua.to_luastring("lS"), ar));
+        assert(lua.lua_getinfo(L, to_luastring("lS"), ar));
         lua.lua_call(L, 2, 0);  /* call hook function */
     }
 };
@@ -291,9 +292,9 @@ const hookf = function(L, ar) {
 */
 const makemask = function(smask, count) {
     let mask = 0;
-    if (lua.luastring_indexOf(smask, "c".charCodeAt(0)) > -1) mask |= lua.LUA_MASKCALL;
-    if (lua.luastring_indexOf(smask, "r".charCodeAt(0)) > -1) mask |= lua.LUA_MASKRET;
-    if (lua.luastring_indexOf(smask, "l".charCodeAt(0)) > -1) mask |= lua.LUA_MASKLINE;
+    if (luastring_indexOf(smask, "c".charCodeAt(0)) > -1) mask |= lua.LUA_MASKCALL;
+    if (luastring_indexOf(smask, "r".charCodeAt(0)) > -1) mask |= lua.LUA_MASKRET;
+    if (luastring_indexOf(smask, "l".charCodeAt(0)) > -1) mask |= lua.LUA_MASKLINE;
     if (count > 0) mask |= lua.LUA_MASKCOUNT;
     return mask;
 };
@@ -328,8 +329,8 @@ const db_sethook = function(L) {
         lua.lua_createtable(L, 0, 2);  /* create a hook table */
         lua.lua_pushvalue(L, -1);
         lua.lua_rawsetp(L, lua.LUA_REGISTRYINDEX, HOOKKEY);  /* set it in position */
-        lua.lua_pushstring(L, lua.to_luastring("k"));
-        lua.lua_setfield(L, -2, lua.to_luastring("__mode", true));  /** hooktable.__mode = "k" */
+        lua.lua_pushstring(L, to_luastring("k"));
+        lua.lua_setfield(L, -2, to_luastring("__mode", true));  /** hooktable.__mode = "k" */
         lua.lua_pushvalue(L, -1);
         lua.lua_setmetatable(L, -2);  /* setmetatable(hooktable) = hooktable */
     }
@@ -424,8 +425,8 @@ if (getinput) {
             if (input.length === 0)
                 continue;
 
-            let buffer = lua.to_luastring(input);
-            if (lauxlib.luaL_loadbuffer(L, buffer, buffer.length, lua.to_luastring("=(debug command)", true))
+            let buffer = to_luastring(input);
+            if (lauxlib.luaL_loadbuffer(L, buffer, buffer.length, to_luastring("=(debug command)", true))
                 || lua.lua_pcall(L, 0, 0, 0)) {
                 lauxlib.lua_writestringerror(lua.lua_tojsstring(L, -1), "\n");
             }
diff --git a/src/linit.js b/src/linit.js
index 97cbfc9..5656bae 100644
--- a/src/linit.js
+++ b/src/linit.js
@@ -2,6 +2,8 @@
 
 const lua      = require('./lua.js');
 const lauxlib  = require('./lauxlib.js');
+const {to_luastring} = require("./fengaricore.js");
+
 const lbaselib = require('./lbaselib.js');
 const lcorolib = require('./lcorolib.js');
 const lmathlib = require('./lmathlib.js');
@@ -30,7 +32,7 @@ const luaL_openlibs = function(L) {
 
     /* "require" functions from 'loadedlibs' and set results to global table */
     for (let lib in loadedlibs) {
-        lauxlib.luaL_requiref(L, lua.to_luastring(lib), loadedlibs[lib], 1);
+        lauxlib.luaL_requiref(L, to_luastring(lib), loadedlibs[lib], 1);
         lua.lua_pop(L, 1); /* remove lib */
     }
 };
diff --git a/src/liolib.js b/src/liolib.js
index 66ef3db..462e7ed 100644
--- a/src/liolib.js
+++ b/src/liolib.js
@@ -5,11 +5,12 @@ const fs      = require('fs');
 
 const lua     = require('./lua.js');
 const lauxlib = require('./lauxlib.js');
+const {to_luastring} = require("./fengaricore.js");
 
 const IO_PREFIX = "_IO_";
 const IOPREF_LEN = IO_PREFIX.length;
-const IO_INPUT = lua.to_luastring(IO_PREFIX + "input");
-const IO_OUTPUT = lua.to_luastring(IO_PREFIX + "output");
+const IO_INPUT = to_luastring(IO_PREFIX + "input");
+const IO_OUTPUT = to_luastring(IO_PREFIX + "output");
 
 const tolstream = function(L) {
     return lauxlib.luaL_checkudata(L, 1, lauxlib.LUA_FILEHANDLE);
@@ -36,14 +37,14 @@ const f_tostring = function(L) {
     if (isclosed(p))
         lua.lua_pushliteral(L, "file (closed)");
     else
-        lua.lua_pushstring(L, lua.to_luastring(`file (${p.f.toString()})`));
+        lua.lua_pushstring(L, to_luastring(`file (${p.f.toString()})`));
     return 1;
 };
 
 const tofile = function(L) {
     let p = tolstream(L);
     if (isclosed(p))
-        lauxlib.luaL_error(L, lua.to_luastring("attempt to use a closed file"));
+        lauxlib.luaL_error(L, to_luastring("attempt to use a closed file"));
     assert(p.f);
     return p.f;
 };
@@ -74,7 +75,7 @@ const getiofile = function(L, findex) {
     lua.lua_getfield(L, lua.LUA_REGISTRYINDEX, findex);
     let p = lua.lua_touserdata(L, -1);
     if (isclosed(p))
-        lauxlib.luaL_error(L, lua.to_luastring("standard %s file is closed"), findex.subarray(IOPREF_LEN));
+        lauxlib.luaL_error(L, to_luastring("standard %s file is closed"), findex.subarray(IOPREF_LEN));
     return p.f;
 };
 
@@ -82,7 +83,7 @@ const g_iofile = function(L, f, mode) {
     if (!lua.lua_isnoneornil(L, 1)) {
         let filename = lua.lua_tostring(L, 1);
         if (filename)
-            lauxlib.luaL_error(L, lua.to_luastring("opening files not yet implemented"));
+            lauxlib.luaL_error(L, to_luastring("opening files not yet implemented"));
         else {
             tofile(L);  /* check that it's a valid file handle */
             lua.lua_pushvalue(L, 1);
@@ -160,7 +161,7 @@ const flib = {
 const createmeta = function(L) {
     lauxlib.luaL_newmetatable(L, lauxlib.LUA_FILEHANDLE);  /* create metatable for file handles */
     lua.lua_pushvalue(L, -1);  /* push metatable */
-    lua.lua_setfield(L, -2, lua.to_luastring("__index", true));  /* metatable.__index = metatable */
+    lua.lua_setfield(L, -2, to_luastring("__index", true));  /* metatable.__index = metatable */
     lauxlib.luaL_setfuncs(L, flib, 0);  /* add file methods to new metatable */
     lua.lua_pop(L, 1);  /* pop new metatable */
 };
@@ -188,9 +189,9 @@ const luaopen_io = function(L) {
     lauxlib.luaL_newlib(L, iolib);
     createmeta(L);
     /* create (and set) default files */
-    createstdfile(L, process.stdin, IO_INPUT, lua.to_luastring("stdin"));
-    createstdfile(L, process.stdout, IO_OUTPUT, lua.to_luastring("stdout"));
-    createstdfile(L, process.stderr, null, lua.to_luastring("stderr"));
+    createstdfile(L, process.stdin, IO_INPUT, to_luastring("stdin"));
+    createstdfile(L, process.stdout, IO_OUTPUT, to_luastring("stdout"));
+    createstdfile(L, process.stderr, null, to_luastring("stderr"));
     return 1;
 };
 
diff --git a/src/lmathlib.js b/src/lmathlib.js
index e056fd8..328356b 100644
--- a/src/lmathlib.js
+++ b/src/lmathlib.js
@@ -3,6 +3,7 @@
 const lua     = require('./lua.js');
 const lauxlib = require('./lauxlib.js');
 const luaconf = require('./luaconf.js');
+const {to_luastring} = require("./fengaricore.js");
 
 const math_random = function(L) {
     let low, up;
@@ -21,13 +22,13 @@ const math_random = function(L) {
             up = lauxlib.luaL_checkinteger(L, 2);
             break;
         }
-        default: return lauxlib.luaL_error(L, lua.to_luastring("wrong number of arguments", true));
+        default: return lauxlib.luaL_error(L, to_luastring("wrong number of arguments", true));
     }
 
     /* random integer in the interval [low, up] */
-    lauxlib.luaL_argcheck(L, low <= up, 1, lua.to_luastring("interval is empty", true));
+    lauxlib.luaL_argcheck(L, low <= up, 1, to_luastring("interval is empty", true));
     lauxlib.luaL_argcheck(L, low >= 0 || up <= luaconf.LUA_MAXINTEGER + low, 1,
-        lua.to_luastring("interval too large", true));
+        to_luastring("interval too large", true));
 
     r *= (up - low) + 1;
     lua.lua_pushinteger(L, Math.floor(r) + low);
@@ -162,7 +163,7 @@ const math_rad = function(L) {
 const math_min = function(L) {
     let n = lua.lua_gettop(L);  /* number of arguments */
     let imin = 1;  /* index of current minimum value */
-    lauxlib.luaL_argcheck(L, n >= 1, 1, lua.to_luastring("value expected", true));
+    lauxlib.luaL_argcheck(L, n >= 1, 1, to_luastring("value expected", true));
     for (let i = 2; i <= n; i++){
         if (lua.lua_compare(L, i, imin, lua.LUA_OPLT))
             imin = i;
@@ -174,7 +175,7 @@ const math_min = function(L) {
 const math_max = function(L) {
     let n = lua.lua_gettop(L);  /* number of arguments */
     let imax = 1;  /* index of current minimum value */
-    lauxlib.luaL_argcheck(L, n >= 1, 1, lua.to_luastring("value expected", true));
+    lauxlib.luaL_argcheck(L, n >= 1, 1, to_luastring("value expected", true));
     for (let i = 2; i <= n; i++){
         if (lua.lua_compare(L, imax, i, lua.LUA_OPLT))
             imax = i;
@@ -201,7 +202,7 @@ const math_fmod = function(L) {
         let d = lua.lua_tointeger(L, 2);
         /* no special case needed for -1 in javascript */
         if (d === 0) {
-            lauxlib.luaL_argerror(L, 2, lua.to_luastring("zero", true));
+            lauxlib.luaL_argerror(L, 2, to_luastring("zero", true));
         } else
             lua.lua_pushinteger(L, (lua.lua_tointeger(L, 1) % d)|0);
     } else {
@@ -253,13 +254,13 @@ const mathlib = {
 const luaopen_math = function(L) {
     lauxlib.luaL_newlib(L, mathlib);
     lua.lua_pushnumber(L, Math.PI);
-    lua.lua_setfield(L, -2, lua.to_luastring("pi", true));
+    lua.lua_setfield(L, -2, to_luastring("pi", true));
     lua.lua_pushnumber(L, Infinity);
-    lua.lua_setfield(L, -2, lua.to_luastring("huge", true));
+    lua.lua_setfield(L, -2, to_luastring("huge", true));
     lua.lua_pushinteger(L, luaconf.LUA_MAXINTEGER);
-    lua.lua_setfield(L, -2, lua.to_luastring("maxinteger", true));
+    lua.lua_setfield(L, -2, to_luastring("maxinteger", true));
     lua.lua_pushinteger(L, luaconf.LUA_MININTEGER);
-    lua.lua_setfield(L, -2, lua.to_luastring("mininteger", true));
+    lua.lua_setfield(L, -2, to_luastring("mininteger", true));
     return 1;
 };
 
diff --git a/src/loadlib.js b/src/loadlib.js
index 2e68ffd..2dc6d73 100644
--- a/src/loadlib.js
+++ b/src/loadlib.js
@@ -3,6 +3,7 @@
 const fengari  = require('./fengari.js');
 const lua      = require('./lua.js');
 const lauxlib  = require('./lauxlib.js');
+const {luastring_indexOf, to_jsstring, to_luastring, to_uristring} = require("./fengaricore.js");
 
 const global_env = (function() {
     /* global WorkerGlobalScope */ /* see https://github.com/sindresorhus/globals/issues/127 */
@@ -21,7 +22,7 @@ const global_env = (function() {
     }
 })();
 
-const CLIBS         = lua.to_luastring("__CLIBS__", true);
+const CLIBS         = to_luastring("__CLIBS__", true);
 const LUA_PATH_VAR  = "LUA_PATH";
 const LUA_CPATH_VAR = "LUA_CPATH";
 
@@ -37,13 +38,13 @@ const LUA_CSUBSEP   = lua.LUA_DIRSEP;
 const LUA_LSUBSEP   = lua.LUA_DIRSEP;
 
 /* prefix for open functions in C libraries */
-const LUA_POF       = lua.to_luastring("luaopen_");
+const LUA_POF       = to_luastring("luaopen_");
 
 /* separator for open functions in C libraries */
-const LUA_OFSEP     = lua.to_luastring("_");
+const LUA_OFSEP     = to_luastring("_");
 const LIB_FAIL      = "open";
 
-const AUXMARK       = lua.to_luastring("\x01");
+const AUXMARK       = to_luastring("\x01");
 
 
 /*
@@ -55,13 +56,13 @@ const AUXMARK       = lua.to_luastring("\x01");
 let lsys_load;
 if (typeof process === "undefined") {
     lsys_load = function(L, path, seeglb) {
-        path = lua.to_uristring(path);
+        path = to_uristring(path);
         let xhr = new XMLHttpRequest();
         xhr.open("GET", path, false);
         xhr.send();
 
         if (xhr.status < 200 || xhr.status >= 300) {
-            lua.lua_pushstring(L, lua.to_luastring(`${xhr.status}: ${xhr.statusText}`));
+            lua.lua_pushstring(L, to_luastring(`${xhr.status}: ${xhr.statusText}`));
             return null;
         }
 
@@ -73,7 +74,7 @@ if (typeof process === "undefined") {
         try {
             func = Function("fengari", code);
         } catch (e) {
-            lua.lua_pushstring(L, lua.to_luastring(`${e.name}: ${e.message}`));
+            lua.lua_pushstring(L, to_luastring(`${e.name}: ${e.message}`));
             return null;
         }
         let res = func(fengari);
@@ -82,20 +83,20 @@ if (typeof process === "undefined") {
         } else if (res === void 0) { /* assume library added symbols to global environment */
             return global_env;
         } else {
-            lua.lua_pushstring(L, lua.to_luastring(`library returned unexpected type (${typeof res})`));
+            lua.lua_pushstring(L, to_luastring(`library returned unexpected type (${typeof res})`));
             return null;
         }
     };
 } else {
     const pathlib = require('path');
     lsys_load = function(L, path, seeglb) {
-        path = lua.to_jsstring(path);
+        path = to_jsstring(path);
         /* relative paths should be relative to cwd, not this js file */
         path = pathlib.resolve(process.cwd(), path);
         try {
             return require(path);
         } catch (e) {
-            lua.lua_pushstring(L, lua.to_luastring(e.message));
+            lua.lua_pushstring(L, to_luastring(e.message));
             return null;
         }
     };
@@ -107,12 +108,12 @@ if (typeof process === "undefined") {
 ** error string in the stack.
 */
 const lsys_sym = function(L, lib, sym) {
-    let f = lib[lua.to_jsstring(sym)];
+    let f = lib[to_jsstring(sym)];
 
     if (f && typeof f === 'function')
         return f;
     else {
-        lua.lua_pushfstring(L, lua.to_luastring("undefined symbol: %s"), sym);
+        lua.lua_pushfstring(L, to_luastring("undefined symbol: %s"), sym);
         return null;
     }
 };
@@ -121,7 +122,7 @@ const lsys_sym = function(L, lib, sym) {
 ** return registry.LUA_NOENV as a boolean
 */
 const noenv = function(L) {
-    lua.lua_getfield(L, lua.LUA_REGISTRYINDEX, lua.to_luastring("LUA_NOENV"));
+    lua.lua_getfield(L, lua.LUA_REGISTRYINDEX, to_luastring("LUA_NOENV"));
     let b = lua.lua_toboolean(L, -1);
     lua.lua_pop(L, 1);  /* remove value */
     return b;
@@ -143,7 +144,7 @@ if (typeof process !== "undefined") { // Only with Node
 } else {
     /* TODO: use async/await ? */
     readable = function(path) {
-        path = lua.to_uristring(path);
+        path = to_uristring(path);
         let xhr = new XMLHttpRequest();
         /* Following GET request done by searcher_Web will be cached */
         xhr.open("GET", path, false);
@@ -217,21 +218,21 @@ const env = (function() {
 */
 const setpath = function(L, fieldname, envname, dft) {
     let nver = `${envname}${lua.LUA_VERSUFFIX}`;
-    lua.lua_pushstring(L, lua.to_luastring(nver));
+    lua.lua_pushstring(L, to_luastring(nver));
     let path = env[nver];  /* use versioned name */
     if (path === undefined)  /* no environment variable? */
         path = env[envname];  /* try unversioned name */
     if (path === undefined || noenv(L))  /* no environment variable? */
-        lua.lua_pushstring(L, lua.to_luastring(dft));  /* use default */
+        lua.lua_pushstring(L, to_luastring(dft));  /* use default */
     else {
         /* replace ";;" by ";AUXMARK;" and then AUXMARK by default path */
         path = lauxlib.luaL_gsub(
             L,
-            lua.to_luastring(path),
-            lua.to_luastring(lua.LUA_PATH_SEP + lua.LUA_PATH_SEP, true),
-            lua.to_luastring(lua.LUA_PATH_SEP + lua.to_jsstring(AUXMARK) + lua.LUA_PATH_SEP, true)
+            to_luastring(path),
+            to_luastring(lua.LUA_PATH_SEP + lua.LUA_PATH_SEP, true),
+            to_luastring(lua.LUA_PATH_SEP + to_jsstring(AUXMARK) + lua.LUA_PATH_SEP, true)
         );
-        lauxlib.luaL_gsub(L, path, AUXMARK, lua.to_luastring(dft));
+        lauxlib.luaL_gsub(L, path, AUXMARK, to_luastring(dft));
         lua.lua_remove(L, -2); /* remove result from 1st 'gsub' */
     }
     lua.lua_setfield(L, -3, fieldname);  /* package[fieldname] = path value */
@@ -265,7 +266,7 @@ const addtoclib = function(L, path, plib) {
 const pushnexttemplate = function(L, path) {
     while (path[0] === lua.LUA_PATH_SEP.charCodeAt(0)) path = path.subarray(1);  /* skip separators */
     if (path.length === 0) return null;  /* no more templates */
-    let l = lua.luastring_indexOf(path, lua.LUA_PATH_SEP.charCodeAt(0));  /* find next separator */
+    let l = luastring_indexOf(path, lua.LUA_PATH_SEP.charCodeAt(0));  /* find next separator */
     if (l < 0) l = path.length;
     lua.lua_pushlstring(L, path, l);  /* template */
     return path.subarray(l);
@@ -277,11 +278,11 @@ const searchpath = function(L, name, path, sep, dirsep) {
     if (sep[0] !== 0)  /* non-empty separator? */
         name = lauxlib.luaL_gsub(L, name, sep, dirsep);  /* replace it by 'dirsep' */
     while ((path = pushnexttemplate(L, path)) !== null) {
-        let filename = lauxlib.luaL_gsub(L, lua.lua_tostring(L, -1), lua.to_luastring(lua.LUA_PATH_MARK, true), name);
+        let filename = lauxlib.luaL_gsub(L, lua.lua_tostring(L, -1), to_luastring(lua.LUA_PATH_MARK, true), name);
         lua.lua_remove(L, -2);  /* remove path template */
         if (readable(filename))  /* does file exist and is readable? */
             return filename;  /* return that file name */
-        lua.lua_pushfstring(L, lua.to_luastring("\n\tno file '%s'"), filename);
+        lua.lua_pushfstring(L, to_luastring("\n\tno file '%s'"), filename);
         lua.lua_remove(L, -2);  /* remove file name */
         lauxlib.luaL_addvalue(msg);
     }
@@ -294,8 +295,8 @@ const ll_searchpath = function(L) {
         L,
         lauxlib.luaL_checkstring(L, 1),
         lauxlib.luaL_checkstring(L, 2),
-        lauxlib.luaL_optstring(L, 3, lua.to_luastring(".")),
-        lauxlib.luaL_optstring(L, 4, lua.to_luastring(lua.LUA_DIRSEP))
+        lauxlib.luaL_optstring(L, 3, to_luastring(".")),
+        lauxlib.luaL_optstring(L, 4, to_luastring(lua.LUA_DIRSEP))
     );
     if (f !== null) return 1;
     else {  /* error message is on top of the stack */
@@ -309,8 +310,8 @@ const findfile = function(L, name, pname, dirsep) {
     lua.lua_getfield(L, lua.lua_upvalueindex(1), pname);
     let path = lua.lua_tostring(L, -1);
     if (path === null)
-        lauxlib.luaL_error(L, lua.to_luastring("'package.%s' must be a string"), pname);
-    return searchpath(L, name, path, lua.to_luastring("."), dirsep);
+        lauxlib.luaL_error(L, to_luastring("'package.%s' must be a string"), pname);
+    return searchpath(L, name, path, to_luastring("."), dirsep);
 };
 
 const checkload = function(L, stat, filename) {
@@ -318,13 +319,13 @@ const checkload = function(L, stat, filename) {
         lua.lua_pushstring(L, filename);  /* will be 2nd argument to module */
         return 2;  /* return open function and file name */
     } else
-        return lauxlib.luaL_error(L, lua.to_luastring("error loading module '%s' from file '%s':\n\t%s"),
+        return lauxlib.luaL_error(L, to_luastring("error loading module '%s' from file '%s':\n\t%s"),
             lua.lua_tostring(L, 1), filename, lua.lua_tostring(L, -1));
 };
 
 const searcher_Lua = function(L) {
     let name = lauxlib.luaL_checkstring(L, 1);
-    let filename = findfile(L, name, lua.to_luastring("path", true), lua.to_luastring(LUA_LSUBSEP, true));
+    let filename = findfile(L, name, to_luastring("path", true), to_luastring(LUA_LSUBSEP, true));
     if (filename === null) return 1;  /* module not found in this path */
     return checkload(L, lauxlib.luaL_loadfile(L, filename) === lua.LUA_OK, filename);
 };
@@ -339,39 +340,39 @@ const searcher_Lua = function(L) {
 */
 const loadfunc = function(L, filename, modname) {
     let openfunc;
-    modname = lauxlib.luaL_gsub(L, modname, lua.to_luastring("."), LUA_OFSEP);
-    let mark = lua.luastring_indexOf(modname, LUA_IGMARK.charCodeAt(0));
+    modname = lauxlib.luaL_gsub(L, modname, to_luastring("."), LUA_OFSEP);
+    let mark = luastring_indexOf(modname, LUA_IGMARK.charCodeAt(0));
     if (mark >= 0) {
         openfunc = lua.lua_pushlstring(L, modname, mark);
-        openfunc = lua.lua_pushfstring(L, lua.to_luastring("%s%s"), LUA_POF, openfunc);
+        openfunc = lua.lua_pushfstring(L, to_luastring("%s%s"), LUA_POF, openfunc);
         let stat = lookforfunc(L, filename, openfunc);
         if (stat !== ERRFUNC) return stat;
         modname = mark + 1;  /* else go ahead and try old-style name */
     }
-    openfunc = lua.lua_pushfstring(L, lua.to_luastring("%s%s"), LUA_POF, modname);
+    openfunc = lua.lua_pushfstring(L, to_luastring("%s%s"), LUA_POF, modname);
     return lookforfunc(L, filename, openfunc);
 };
 
 const searcher_C = function(L) {
     let name = lauxlib.luaL_checkstring(L, 1);
-    let filename = findfile(L, name, lua.to_luastring("cpath", true), lua.to_luastring(LUA_CSUBSEP, true));
+    let filename = findfile(L, name, to_luastring("cpath", true), to_luastring(LUA_CSUBSEP, true));
     if (filename === null) return 1;  /* module not found in this path */
     return checkload(L, (loadfunc(L, filename, name) === 0), filename);
 };
 
 const searcher_Croot = function(L) {
     let name = lauxlib.luaL_checkstring(L, 1);
-    let p = lua.luastring_indexOf(name, '.'.charCodeAt(0));
+    let p = luastring_indexOf(name, '.'.charCodeAt(0));
     let stat;
     if (p < 0) return 0;  /* is root */
     lua.lua_pushlstring(L, name, p);
-    let filename = findfile(L, lua.lua_tostring(L, -1), lua.to_luastring("cpath", true), lua.to_luastring(LUA_CSUBSEP, true));
+    let filename = findfile(L, lua.lua_tostring(L, -1), to_luastring("cpath", true), to_luastring(LUA_CSUBSEP, true));
     if (filename === null) return 1;  /* root not found */
     if ((stat = loadfunc(L, filename, name)) !== 0) {
         if (stat != ERRFUNC)
             return checkload(L, 0, filename);  /* real error */
         else {  /* open function not found */
-            lua.lua_pushstring(L, lua.to_luastring("\n\tno module '%s' in file '%s'"), name, filename);
+            lua.lua_pushstring(L, to_luastring("\n\tno module '%s' in file '%s'"), name, filename);
             return 1;
         }
     }
@@ -383,7 +384,7 @@ const searcher_preload = function(L) {
     let name = lauxlib.luaL_checkstring(L, 1);
     lua.lua_getfield(L, lua.LUA_REGISTRYINDEX, lauxlib.LUA_PRELOAD_TABLE);
     if (lua.lua_getfield(L, -1, name) === lua.LUA_TNIL)  /* not found? */
-        lua.lua_pushfstring(L, lua.to_luastring("\n\tno field package.preload['%s']"), name);
+        lua.lua_pushfstring(L, to_luastring("\n\tno field package.preload['%s']"), name);
     return 1;
 };
 
@@ -391,8 +392,8 @@ const findloader = function(L, name, ctx, k) {
     let msg = new lauxlib.luaL_Buffer();  /* to build error message */
     lauxlib.luaL_buffinit(L, msg);
     /* push 'package.searchers' to index 3 in the stack */
-    if (lua.lua_getfield(L, lua.lua_upvalueindex(1), lua.to_luastring("searchers", true)) !== lua.LUA_TTABLE)
-        lauxlib.luaL_error(L, lua.to_luastring("'package.searchers' must be a table"));
+    if (lua.lua_getfield(L, lua.lua_upvalueindex(1), to_luastring("searchers", true)) !== lua.LUA_TTABLE)
+        lauxlib.luaL_error(L, to_luastring("'package.searchers' must be a table"));
     let ctx2 = {name: name, i: 1, msg: msg, ctx: ctx, k: k};
     return findloader_cont(L, lua.LUA_OK, ctx2);
 };
@@ -404,7 +405,7 @@ const findloader_cont = function(L, status, ctx) {
             if (lua.lua_rawgeti(L, 3, ctx.i) === lua.LUA_TNIL) {  /* no more searchers? */
                 lua.lua_pop(L, 1);  /* remove nil */
                 lauxlib.luaL_pushresult(ctx.msg);  /* create error message */
-                lauxlib.luaL_error(L, lua.to_luastring("module '%s' not found:%s"), ctx.name, lua.lua_tostring(L, -1));
+                lauxlib.luaL_error(L, to_luastring("module '%s' not found:%s"), ctx.name, lua.lua_tostring(L, -1));
             }
             lua.lua_pushstring(L, ctx.name);
             lua.lua_callk(L, 1, 2, ctx, findloader_cont);  /* call it */
@@ -475,7 +476,7 @@ const createsearcherstable = function(L) {
         lua.lua_pushcclosure(L, searchers[i], 1);
         lua.lua_rawseti(L, -2, i+1);
     }
-    lua.lua_setfield(L, -2, lua.to_luastring("searchers", true));  /* put it in field 'searchers' */
+    lua.lua_setfield(L, -2, to_luastring("searchers", true));  /* put it in field 'searchers' */
 };
 
 /*
@@ -494,18 +495,18 @@ const luaopen_package = function(L) {
     lauxlib.luaL_newlib(L, pk_funcs);  /* create 'package' table */
     createsearcherstable(L);
     /* set paths */
-    setpath(L, lua.to_luastring("path", true), LUA_PATH_VAR, lua.LUA_PATH_DEFAULT);
-    setpath(L, lua.to_luastring("cpath", true), LUA_CPATH_VAR, lua.LUA_CPATH_DEFAULT);
+    setpath(L, to_luastring("path", true), LUA_PATH_VAR, lua.LUA_PATH_DEFAULT);
+    setpath(L, to_luastring("cpath", true), LUA_CPATH_VAR, lua.LUA_CPATH_DEFAULT);
     /* store config information */
     lua.lua_pushliteral(L, lua.LUA_DIRSEP + "\n" + lua.LUA_PATH_SEP + "\n" + lua.LUA_PATH_MARK + "\n" +
                         lua.LUA_EXEC_DIR + "\n" + LUA_IGMARK + "\n");
-    lua.lua_setfield(L, -2, lua.to_luastring("config", true));
+    lua.lua_setfield(L, -2, to_luastring("config", true));
     /* set field 'loaded' */
     lauxlib.luaL_getsubtable(L, lua.LUA_REGISTRYINDEX, lauxlib.LUA_LOADED_TABLE);
-    lua.lua_setfield(L, -2, lua.to_luastring("loaded", true));
+    lua.lua_setfield(L, -2, to_luastring("loaded", true));
     /* set field 'preload' */
     lauxlib.luaL_getsubtable(L, lua.LUA_REGISTRYINDEX, lauxlib.LUA_PRELOAD_TABLE);
-    lua.lua_setfield(L, -2, lua.to_luastring("preload", true));
+    lua.lua_setfield(L, -2, to_luastring("preload", true));
     lua.lua_pushglobaltable(L);
     lua.lua_pushvalue(L, -2);  /* set 'package' as upvalue for next lib */
     lauxlib.luaL_setfuncs(L, ll_funcs, 1);  /* open lib into global table */
diff --git a/src/loslib.js b/src/loslib.js
index b5f3ddb..2266e53 100644
--- a/src/loslib.js
+++ b/src/loslib.js
@@ -2,25 +2,26 @@
 
 const lua      = require('./lua.js');
 const lauxlib  = require('./lauxlib.js');
+const {luastring_indexOf, to_jsstring, to_luastring} = require("./fengaricore.js");
 
 const strftime = require('strftime');
 
 /* options for ANSI C 89 (only 1-char options) */
-const L_STRFTIMEC89 = lua.to_luastring("aAbBcdHIjmMpSUwWxXyYZ%");
+const L_STRFTIMEC89 = to_luastring("aAbBcdHIjmMpSUwWxXyYZ%");
 const LUA_STRFTIMEOPTIONS = L_STRFTIMEC89;
 
 /* options for ISO C 99 and POSIX */
-// const L_STRFTIMEC99 = lua.to_luastring("aAbBcCdDeFgGhHIjmMnprRStTuUVwWxXyYzZ%||EcECExEXEyEYOdOeOHOIOmOMOSOuOUOVOwOWOy");  /* two-char options */
+// const L_STRFTIMEC99 = to_luastring("aAbBcCdDeFgGhHIjmMnprRStTuUVwWxXyYzZ%||EcECExEXEyEYOdOeOHOIOmOMOSOuOUOVOwOWOy");  /* two-char options */
 // const LUA_STRFTIMEOPTIONS = L_STRFTIMEC99;
 
 /* options for Windows */
-// const L_STRFTIMEWIN = lua.to_luastring("aAbBcdHIjmMpSUwWxXyYzZ%||#c#x#d#H#I#j#m#M#S#U#w#W#y#Y");  /* two-char options */
+// const L_STRFTIMEWIN = to_luastring("aAbBcdHIjmMpSUwWxXyYzZ%||#c#x#d#H#I#j#m#M#S#U#w#W#y#Y");  /* two-char options */
 // const LUA_STRFTIMEOPTIONS = L_STRFTIMEWIN;
 
 
 const setfield = function(L, key, value) {
     lua.lua_pushinteger(L, value);
-    lua.lua_setfield(L, -2, lua.to_luastring(key, true));
+    lua.lua_setfield(L, -2, to_luastring(key, true));
 };
 
 const setallfields = function(L, time, utc) {
@@ -39,18 +40,18 @@ const setallfields = function(L, time, utc) {
 const L_MAXDATEFIELD = (Number.MAX_SAFE_INTEGER / 2);
 
 const getfield = function(L, key, d, delta) {
-    let t = lua.lua_getfield(L, -1, lua.to_luastring(key, true));  /* get field and its type */
+    let t = lua.lua_getfield(L, -1, to_luastring(key, true));  /* get field and its type */
     let res = lua.lua_tointegerx(L, -1);
     if (res === false) {  /* field is not an integer? */
         if (t !== lua.LUA_TNIL)  /* some other value? */
-            return lauxlib.luaL_error(L, lua.to_luastring("field '%s' is not an integer"), key);
+            return lauxlib.luaL_error(L, to_luastring("field '%s' is not an integer"), key);
         else if (d < 0)  /* absent field; no default? */
-            return lauxlib.luaL_error(L, lua.to_luastring("field '%s' missing in date table"), key);
+            return lauxlib.luaL_error(L, to_luastring("field '%s' missing in date table"), key);
         res = d;
     }
     else {
         if (!(-L_MAXDATEFIELD <= res && res <= L_MAXDATEFIELD))
-            return lauxlib.luaL_error(L, lua.to_luastring("field '%s' is out-of-bound"), key);
+            return lauxlib.luaL_error(L, to_luastring("field '%s' is out-of-bound"), key);
         res -= delta;
     }
     lua.lua_pop(L, 1);
@@ -78,7 +79,7 @@ const checkoption = function(L, conv, i, buff) {
         }
     }
     lauxlib.luaL_argerror(L, 1,
-        lua.lua_pushfstring(L, lua.to_luastring("invalid conversion specifier '%%%s'"), conv));
+        lua.lua_pushfstring(L, to_luastring("invalid conversion specifier '%%%s'"), conv));
 };
 
 /* maximum size for an individual 'strftime' item */
@@ -86,7 +87,7 @@ const checkoption = function(L, conv, i, buff) {
 
 
 const os_date = function(L) {
-    let s = lauxlib.luaL_optlstring(L, 1, lua.to_luastring("%c"));
+    let s = lauxlib.luaL_optlstring(L, 1, to_luastring("%c"));
     let t = lauxlib.luaL_opt(L, l_checktime, 2, new Date().getTime() / 1000) * 1000;
     let stm = new Date(t);
     let utc = false;
@@ -97,7 +98,7 @@ const os_date = function(L) {
     }
 
     if (stm === null)  /* invalid date? */
-        lauxlib.luaL_error(L, lua.to_luastring("time result cannot be represented in this installation", true));
+        lauxlib.luaL_error(L, to_luastring("time result cannot be represented in this installation", true));
     if (s[i] === "*".charCodeAt(0) && s[i+1] === "t".charCodeAt(0)) {
         lua.lua_createtable(L, 0, 9);  /* 9 = number of fields */
         setallfields(L, stm, utc);
@@ -112,11 +113,11 @@ const os_date = function(L) {
             } else {
                 i++;  /* skip '%' */
                 i = checkoption(L, s, i, cc.subarray(1));  /* copy specifier to 'cc' */
-                let len = lua.luastring_indexOf(cc, 0);
+                let len = luastring_indexOf(cc, 0);
                 if (len !== -1)
                     cc = cc.subarray(0, len);
-                let buff = strftime(lua.to_jsstring(cc), stm);
-                lauxlib.luaL_addstring(b, lua.to_luastring(buff));
+                let buff = strftime(to_jsstring(cc), stm);
+                lauxlib.luaL_addstring(b, to_luastring(buff));
             }
         }
         lauxlib.luaL_pushresult(b);
@@ -144,7 +145,7 @@ const os_time = function(L) {
 
 const l_checktime = function(L, arg) {
     let t = lauxlib.luaL_checkinteger(L, arg);
-    // lauxlib.luaL_argcheck(L, t, arg, lua.to_luastring("time out-of-bounds"));
+    // lauxlib.luaL_argcheck(L, t, arg, to_luastring("time out-of-bounds"));
     return t;
 };
 
@@ -186,7 +187,7 @@ if (typeof process === "undefined") {
 
     syslib.getenv = function(L) {
         let key = lauxlib.luaL_checkstring(L, 1);
-        key = lua.to_jsstring(key); /* https://github.com/nodejs/node/issues/16961 */
+        key = to_jsstring(key); /* https://github.com/nodejs/node/issues/16961 */
         if (Object.prototype.hasOwnProperty.call(process.env, key)) {
             lua.lua_pushliteral(L, process.env[key]);
         } else {
@@ -233,8 +234,8 @@ if (typeof process === "undefined") {
     syslib.tmpname = function(L) {
         let name = lua_tmpname();
         if (!name)
-            return lauxlib.luaL_error(L, lua.to_luastring("unable to generate a unique filename"));
-        lua.lua_pushstring(L, lua.to_luastring(name));
+            return lauxlib.luaL_error(L, to_luastring("unable to generate a unique filename"));
+        lua.lua_pushstring(L, to_luastring(name));
         return 1;
     };
 
diff --git a/src/lstrlib.js b/src/lstrlib.js
index 6986411..5477750 100644
--- a/src/lstrlib.js
+++ b/src/lstrlib.js
@@ -6,6 +6,7 @@ const sprintf = require('sprintf-js').sprintf;
 const lauxlib = require('./lauxlib.js');
 const lua     = require('./lua.js');
 const luaconf = require('./luaconf.js');
+const {luastring_indexOf, to_jsstring, to_luastring} = require("./fengaricore.js");
 
 const sL_ESC  = '%';
 const L_ESC   = sL_ESC.charCodeAt(0);
@@ -22,7 +23,7 @@ const MAXSIZE = 2147483647;
 
 /* Give natural (i.e. strings end at the first \0) length of a string represented by an array of bytes */
 const strlen = function(s) {
-    let len = lua.luastring_indexOf(s, 0);
+    let len = luastring_indexOf(s, 0);
     return len > -1 ? len : s.length;
 };
 
@@ -76,7 +77,7 @@ const str_dump = function(L) {
     lua.lua_settop(L, 1);
     lauxlib.luaL_buffinit(L, b);
     if (lua.lua_dump(L, writer, b, strip) !== 0)
-        return lauxlib.luaL_error(L, lua.to_luastring("unable to dump given function"));
+        return lauxlib.luaL_error(L, to_luastring("unable to dump given function"));
     lauxlib.luaL_pushresult(b);
     return 1;
 };
@@ -88,17 +89,17 @@ const L_NBFD = 1;
 const num2straux = function(x) {
     /* if 'inf' or 'NaN', format it like '%g' */
     if (Object.is(x, Infinity))
-        return lua.to_luastring('inf');
+        return to_luastring('inf');
     else if (Object.is(x, -Infinity))
-        return lua.to_luastring('-inf');
+        return to_luastring('-inf');
     else if (Number.isNaN(x))
-        return lua.to_luastring('nan');
+        return to_luastring('nan');
     else if (x === 0) {  /* can be -0... */
         /* create "0" or "-0" followed by exponent */
         let zero = sprintf(luaconf.LUA_NUMBER_FMT + "x0p+0", x);
         if (Object.is(x, -0))
             zero = "-" + zero;
-        return lua.to_luastring(zero);
+        return to_luastring(zero);
     } else {
         let buff = "";
         let fe = luaconf.frexp(x);  /* 'x' fraction and exponent */
@@ -112,7 +113,7 @@ const num2straux = function(x) {
         buff += (m * (1<<L_NBFD)).toString(16);
         e -= L_NBFD;  /* this digit goes before the radix point */
         buff += sprintf("p%+d", e);  /* add exponent */
-        return lua.to_luastring(buff);
+        return to_luastring(buff);
     }
 };
 
@@ -122,7 +123,7 @@ const lua_number2strx = function(L, fmt, x) {
         for (let i = 0; i < buff.length; i++)
             buff[i] = String.fromCharCode(buff[i]).toUpperCase().charCodeAt(0);
     } else if (fmt[SIZELENMOD] !== 'a'.charCodeAt(0))
-        lauxlib.luaL_error(L, lua.to_luastring("modifiers for format '%%a'/'%%A' not implemented"));
+        lauxlib.luaL_error(L, to_luastring("modifiers for format '%%a'/'%%A' not implemented"));
     return buff;
 };
 
@@ -166,9 +167,9 @@ const addquoted = function(b, s, len) {
         } else if (iscntrl(s[i])) {
             let buff;
             if (!isdigit(s[i+1]))
-                buff = lua.to_luastring(sprintf("\\%d", s[i]));
+                buff = to_luastring(sprintf("\\%d", s[i]));
             else
-                buff = lua.to_luastring(sprintf("\\%03d", s[i]));
+                buff = to_luastring(sprintf("\\%03d", s[i]));
             lauxlib.luaL_addstring(b, buff);
         } else
             lauxlib.luaL_addchar(b, s[i]);
@@ -181,9 +182,9 @@ const addquoted = function(b, s, len) {
 ** Ensures the 'buff' string uses a dot as the radix character.
 */
 const checkdp = function(buff) {
-    if (lua.luastring_indexOf(buff, '.'.charCodeAt(0)) < 0) {  /* no dot? */
+    if (luastring_indexOf(buff, '.'.charCodeAt(0)) < 0) {  /* no dot? */
         let point = luaconf.lua_getlocaledecpoint().charCodeAt(0);  /* try locale point */
-        let ppoint = lua.luastring_indexOf(buff, point);
+        let ppoint = luastring_indexOf(buff, point);
         if (ppoint) buff[ppoint] = '.';  /* change it to a dot */
     }
 };
@@ -199,14 +200,14 @@ const addliteral = function(L, b, arg) {
             let buff;
             if (!lua.lua_isinteger(L, arg)) {  /* float? */
                 let n = lua.lua_tonumber(L, arg);  /* write as hexa ('%a') */
-                buff = lua_number2strx(L, lua.to_luastring(`%${luaconf.LUA_INTEGER_FRMLEN}a`), n);
+                buff = lua_number2strx(L, to_luastring(`%${luaconf.LUA_INTEGER_FRMLEN}a`), n);
                 checkdp(buff);  /* ensure it uses a dot */
             } else {  /* integers */
                 let n = lua.lua_tointeger(L, arg);
                 let format = (n === luaconf.LUA_MININTEGER)  /* corner case? */
                     ? "0x%" + luaconf.LUA_INTEGER_FRMLEN + "x"  /* use hexa */
                     : luaconf.LUA_INTEGER_FMT;  /* else use default format */
-                buff = lua.to_luastring(sprintf(format, n));
+                buff = to_luastring(sprintf(format, n));
             }
             lauxlib.luaL_addstring(b, buff);
             break;
@@ -217,16 +218,16 @@ const addliteral = function(L, b, arg) {
             break;
         }
         default: {
-            lauxlib.luaL_argerror(L, arg, lua.to_luastring("value has no literal form", true));
+            lauxlib.luaL_argerror(L, arg, to_luastring("value has no literal form", true));
         }
     }
 };
 
 const scanformat = function(L, strfrmt, i, form) {
     let p = i;
-    while (strfrmt[p] !== 0 && lua.luastring_indexOf(FLAGS, strfrmt[p]) >= 0) p++;  /* skip flags */
+    while (strfrmt[p] !== 0 && luastring_indexOf(FLAGS, strfrmt[p]) >= 0) p++;  /* skip flags */
     if (p - i >= FLAGS.length)
-        lauxlib.luaL_error(L, lua.to_luastring("invalid format (repeated flags)", true));
+        lauxlib.luaL_error(L, to_luastring("invalid format (repeated flags)", true));
     if (isdigit(strfrmt[p])) p++;  /* skip width */
     if (isdigit(strfrmt[p])) p++;  /* (2 digits at most) */
     if (strfrmt[p] === '.'.charCodeAt(0)) {
@@ -235,7 +236,7 @@ const scanformat = function(L, strfrmt, i, form) {
         if (isdigit(strfrmt[p])) p++;  /* (2 digits at most) */
     }
     if (isdigit(strfrmt[p]))
-        lauxlib.luaL_error(L, lua.to_luastring("invalid format (width or precision too long)", true));
+        lauxlib.luaL_error(L, to_luastring("invalid format (width or precision too long)", true));
     form[0] = "%".charCodeAt(0);
     for (let j = 0; j < p - i + 1; j++)
         form[j+1] = strfrmt[i+j];
@@ -270,7 +271,7 @@ const str_format = function(L) {
         } else { /* format item */
             let form = [];  /* to store the format ('%...') */
             if (++arg > top)
-                lauxlib.luaL_argerror(L, arg, lua.to_luastring("no value", true));
+                lauxlib.luaL_argerror(L, arg, to_luastring("no value", true));
             i = scanformat(L, strfrmt, i, form);
             switch (String.fromCharCode(strfrmt[i++])) {
                 case 'c': {
@@ -282,7 +283,7 @@ const str_format = function(L) {
                 case 'o': case 'u': case 'x': case 'X': {
                     let n = lauxlib.luaL_checkinteger(L, arg);
                     addlenmod(form, luaconf.LUA_INTEGER_FRMLEN.split('').map(e => e.charCodeAt(0)));
-                    lauxlib.luaL_addstring(b, lua.to_luastring(sprintf(String.fromCharCode(...form), n)));
+                    lauxlib.luaL_addstring(b, to_luastring(sprintf(String.fromCharCode(...form), n)));
                     break;
                 }
                 case 'a': case 'A': {
@@ -294,7 +295,7 @@ const str_format = function(L) {
                 case 'g': case 'G': {
                     let n = lauxlib.luaL_checknumber(L, arg);
                     addlenmod(form, luaconf.LUA_INTEGER_FRMLEN.split('').map(e => e.charCodeAt(0)));
-                    lauxlib.luaL_addstring(b, lua.to_luastring(sprintf(String.fromCharCode(...form), n)));
+                    lauxlib.luaL_addstring(b, to_luastring(sprintf(String.fromCharCode(...form), n)));
                     break;
                 }
                 case 'q': {
@@ -306,20 +307,20 @@ const str_format = function(L) {
                     if (form.length <= 2 || form[2] === 0) {  /* no modifiers? */
                         lauxlib.luaL_addvalue(b);  /* keep entire string */
                     } else {
-                        lauxlib.luaL_argcheck(L, s.length === strlen(s), arg, lua.to_luastring("string contains zeros", true));
-                        if (lua.luastring_indexOf(form, '.'.charCodeAt(0)) < 0 && s.length >= 100) {
+                        lauxlib.luaL_argcheck(L, s.length === strlen(s), arg, to_luastring("string contains zeros", true));
+                        if (luastring_indexOf(form, '.'.charCodeAt(0)) < 0 && s.length >= 100) {
                             /* no precision and string is too long to be formatted */
                             lauxlib.luaL_addvalue(b);  /* keep entire string */
                         } else {  /* format the string into 'buff' */
                             // TODO: will fail if s is not valid UTF-8
-                            lauxlib.luaL_addstring(b, lua.to_luastring(sprintf(String.fromCharCode(...form), lua.to_jsstring(s))));
+                            lauxlib.luaL_addstring(b, to_luastring(sprintf(String.fromCharCode(...form), to_jsstring(s))));
                             lua.lua_pop(L, 1);  /* remove result from 'luaL_tolstring' */
                         }
                     }
                     break;
                 }
                 default: {  /* also treat cases 'pnLlh' */
-                    return lauxlib.luaL_error(L, lua.to_luastring("invalid option '%%%c' to 'format'"), strfrmt[i-1]);
+                    return lauxlib.luaL_error(L, to_luastring("invalid option '%%%c' to 'format'"), strfrmt[i-1]);
                 }
             }
         }
@@ -393,7 +394,7 @@ const getnum = function(fmt, df) {
 const getnumlimit = function(h, fmt, df) {
     let sz = getnum(fmt, df);
     if (sz > MAXINTSIZE || sz <= 0)
-        lauxlib.luaL_error(h.L, lua.to_luastring("integral size (%d) out of limits [1,%d]"), sz, MAXINTSIZE);
+        lauxlib.luaL_error(h.L, to_luastring("integral size (%d) out of limits [1,%d]"), sz, MAXINTSIZE);
     return sz;
 };
 
@@ -427,7 +428,7 @@ const getoption = function(h, fmt) {
         case 'c'.charCodeAt(0): {
             r.size = getnum(fmt, -1);
             if (r.size === -1)
-                lauxlib.luaL_error(h.L, lua.to_luastring("missing size for format option 'c'"));
+                lauxlib.luaL_error(h.L, to_luastring("missing size for format option 'c'"));
             r.opt = KOption.Kchar;
             return r;
         }
@@ -439,7 +440,7 @@ const getoption = function(h, fmt) {
         case '>'.charCodeAt(0): h.islittle = false; break;
         case '='.charCodeAt(0): h.islittle = true; break;
         case '!'.charCodeAt(0): h.maxalign = getnumlimit(h, fmt, MAXALIGN); break;
-        default: lauxlib.luaL_error(h.L, lua.to_luastring("invalid format option '%c'"), r.opt);
+        default: lauxlib.luaL_error(h.L, to_luastring("invalid format option '%c'"), r.opt);
     }
 
     r.opt = KOption.Knop;
@@ -468,13 +469,13 @@ const getdetails = function(h, totalsize, fmt) {
     let align = r.size;  /* usually, alignment follows size */
     if (r.opt === KOption.Kpaddalign) {  /* 'X' gets alignment from following option */
         if (fmt.off >= fmt.s.length || fmt.s[fmt.off] === 0)
-            lauxlib.luaL_argerror(h.L, 1, lua.to_luastring("invalid next option for option 'X'", true));
+            lauxlib.luaL_argerror(h.L, 1, to_luastring("invalid next option for option 'X'", true));
         else {
             let o = getoption(h, fmt);
             align = o.size;
             o = o.opt;
             if (o === KOption.Kchar || align === 0)
-                lauxlib.luaL_argerror(h.L, 1, lua.to_luastring("invalid next option for option 'X'", true));
+                lauxlib.luaL_argerror(h.L, 1, to_luastring("invalid next option for option 'X'", true));
         }
     }
     if (align <= 1 || r.opt === KOption.Kchar)  /* need no alignment? */
@@ -483,7 +484,7 @@ const getdetails = function(h, totalsize, fmt) {
         if (align > h.maxalign)  /* enforce maximum alignment */
             align = h.maxalign;
         if ((align & (align -1)) !== 0)  /* is 'align' not a power of 2? */
-            lauxlib.luaL_argerror(h.L, 1, lua.to_luastring("format asks for alignment not power of 2", true));
+            lauxlib.luaL_argerror(h.L, 1, to_luastring("format asks for alignment not power of 2", true));
         r.ntoalign = (align - (totalsize & (align - 1))) & (align - 1);
     }
     return r;
@@ -534,7 +535,7 @@ const str_pack = function(L) {
                 let n = lauxlib.luaL_checkinteger(L, arg);
                 if (size < SZINT) {  /* need overflow check? */
                     let lim = 1 << (size * 8) - 1;
-                    lauxlib.luaL_argcheck(L, -lim <= n && n < lim, arg, lua.to_luastring("integer overflow", true));
+                    lauxlib.luaL_argcheck(L, -lim <= n && n < lim, arg, to_luastring("integer overflow", true));
                 }
                 packint(b, n, h.islittle, size, n < 0);
                 break;
@@ -542,7 +543,7 @@ const str_pack = function(L) {
             case KOption.Kuint: {  /* unsigned integers */
                 let n = lauxlib.luaL_checkinteger(L, arg);
                 if (size < SZINT)
-                    lauxlib.luaL_argcheck(L, (n>>>0) < (1 << (size * NB)), arg, lua.to_luastring("unsigned overflow", true));
+                    lauxlib.luaL_argcheck(L, (n>>>0) < (1 << (size * NB)), arg, to_luastring("unsigned overflow", true));
                 packint(b, n>>>0, h.islittle, size, false);
                 break;
             }
@@ -558,7 +559,7 @@ const str_pack = function(L) {
             case KOption.Kchar: {  /* fixed-size string */
                 let s = lauxlib.luaL_checkstring(L, arg);
                 let len = s.length;
-                lauxlib.luaL_argcheck(L, len <= size, arg, lua.to_luastring("string longer than given size", true));
+                lauxlib.luaL_argcheck(L, len <= size, arg, to_luastring("string longer than given size", true));
                 lauxlib.luaL_addlstring(b, s, len);  /* add string */
                 while (len++ < size)  /* pad extra space */
                     lauxlib.luaL_addchar(b, LUAL_PACKPADBYTE);
@@ -569,7 +570,7 @@ const str_pack = function(L) {
                 let len = s.length;
                 lauxlib.luaL_argcheck(L,
                     size >= 4 /* sizeof(size_t) */ || len < (1 << (size * NB)),
-                    arg, lua.to_luastring("string length does not fit in given size", true));
+                    arg, to_luastring("string length does not fit in given size", true));
                 packint(b, len, h.islittle, size, 0);  /* pack length */
                 lauxlib.luaL_addlstring(b, s, len);
                 totalsize += len;
@@ -578,7 +579,7 @@ const str_pack = function(L) {
             case KOption.Kzstr: {  /* zero-terminated string */
                 let s = lauxlib.luaL_checkstring(L, arg);
                 let len = s.length;
-                lauxlib.luaL_argcheck(L, lua.luastring_indexOf(s, 0) < 0, arg, lua.to_luastring("strings contains zeros", true));
+                lauxlib.luaL_argcheck(L, luastring_indexOf(s, 0) < 0, arg, to_luastring("strings contains zeros", true));
                 lauxlib.luaL_addlstring(b, s, len);
                 lauxlib.luaL_addchar(b, 0);  /* add zero at the end */
                 totalsize += len + 1;
@@ -607,14 +608,14 @@ const str_reverse = function(L) {
 const str_lower = function(L) {
     let s = lauxlib.luaL_checkstring(L, 1);
     // TODO: will fail on invalid UTF-8
-    lua.lua_pushstring(L, lua.to_luastring(lua.to_jsstring(s).toLowerCase()));
+    lua.lua_pushstring(L, to_luastring(to_jsstring(s).toLowerCase()));
     return 1;
 };
 
 const str_upper = function(L) {
     let s = lauxlib.luaL_checkstring(L, 1);
     // TODO: will fail on invalid UTF-8
-    lua.lua_pushstring(L, lua.to_luastring(lua.to_jsstring(s).toUpperCase()));
+    lua.lua_pushstring(L, to_luastring(to_jsstring(s).toUpperCase()));
     return 1;
 };
 
@@ -622,11 +623,11 @@ const str_rep = function(L) {
     let s = lauxlib.luaL_checkstring(L, 1);
     let l = s.length;
     let n = lauxlib.luaL_checkinteger(L, 2);
-    let sep = lauxlib.luaL_optstring(L, 3, lua.to_luastring(""));
+    let sep = lauxlib.luaL_optstring(L, 3, to_luastring(""));
     let lsep = sep.length;
     if (n <= 0) lua.lua_pushliteral(L, "");
     else if (l + lsep < l || l + lsep > MAXSIZE / n)  /* may overflow? */
-        return lauxlib.luaL_error(L, lua.to_luastring("resulting string too large"));
+        return lauxlib.luaL_error(L, to_luastring("resulting string too large"));
     else {
         let totallen = n * l + (n - 1) * lsep;
         let b = new lauxlib.luaL_Buffer();
@@ -656,10 +657,10 @@ const str_byte = function(L) {
     if (pose > l) pose = l;
     if (posi > pose) return 0;  /* empty interval; return no values */
     if (pose - posi >= Number.MAX_SAFE_INTEGER)  /* arithmetic overflow? */
-        return lauxlib.luaL_error(L, lua.to_luastring("string slice too long", true));
+        return lauxlib.luaL_error(L, to_luastring("string slice too long", true));
 
     let n = (pose - posi) + 1;
-    lauxlib.luaL_checkstack(L, n, lua.to_luastring("string slice too long", true));
+    lauxlib.luaL_checkstack(L, n, to_luastring("string slice too long", true));
     for (let i = 0; i < n; i++)
         lua.lua_pushinteger(L, s[posi + i - 1]);
     return n;
@@ -678,12 +679,12 @@ const str_packsize = function(L) {
         let size = details.size;
         let ntoalign = details.ntoalign;
         size += ntoalign;  /* total space used by option */
-        lauxlib.luaL_argcheck(L, totalsize <= MAXSIZE - size, 1, lua.to_luastring("format result too large", true));
+        lauxlib.luaL_argcheck(L, totalsize <= MAXSIZE - size, 1, to_luastring("format result too large", true));
         totalsize += size;
         switch (opt) {
             case KOption.Kstring:  /* strings with length count */
             case KOption.Kzstr:    /* zero-terminated string */
-                lauxlib.luaL_argerror(L, 1, lua.to_luastring("variable-length format", true));
+                lauxlib.luaL_argerror(L, 1, to_luastring("variable-length format", true));
                 /* call never return, but to avoid warnings: *//* fall through */
             default:  break;
         }
@@ -716,7 +717,7 @@ const unpackint = function(L, str, islittle, size, issigned) {
         let mask = !issigned || res >= 0 ? 0 : MC;
         for (let i = limit; i < size; i++) {
             if (str[islittle ? i : size - 1 - i] !== mask)
-                lauxlib.luaL_error(L, lua.to_luastring("%d-byte integer does not fit into Lua Integer"), size);
+                lauxlib.luaL_error(L, to_luastring("%d-byte integer does not fit into Lua Integer"), size);
         }
     }
     return res;
@@ -743,17 +744,17 @@ const str_unpack = function(L) {
     let ld = data.length;
     let pos = posrelat(lauxlib.luaL_optinteger(L, 3, 1), ld) - 1;
     let n = 0;  /* number of results */
-    lauxlib.luaL_argcheck(L, pos <= ld && pos >= 0, 3, lua.to_luastring("initial position out of string", true));
+    lauxlib.luaL_argcheck(L, pos <= ld && pos >= 0, 3, to_luastring("initial position out of string", true));
     while (fmt.off < fmt.s.length) {
         let details = getdetails(h, pos, fmt);
         let opt = details.opt;
         let size = details.size;
         let ntoalign = details.ntoalign;
         if (/*ntoalign + size > ~pos ||*/ pos + ntoalign + size > ld)
-            lauxlib.luaL_argerror(L, 2, lua.to_luastring("data string too short", true));
+            lauxlib.luaL_argerror(L, 2, to_luastring("data string too short", true));
         pos += ntoalign;  /* skip alignment */
         /* stack space for item + next position */
-        lauxlib.luaL_checkstack(L, 2, lua.to_luastring("too many results", true));
+        lauxlib.luaL_checkstack(L, 2, to_luastring("too many results", true));
         n++;
         switch (opt) {
             case KOption.Kint:
@@ -773,13 +774,13 @@ const str_unpack = function(L) {
             }
             case KOption.Kstring: {
                 let len = unpackint(L, data.subarray(pos), h.islittle, size, 0);
-                lauxlib.luaL_argcheck(L, pos + len + size <= ld, 2, lua.to_luastring("data string too short", true));
+                lauxlib.luaL_argcheck(L, pos + len + size <= ld, 2, to_luastring("data string too short", true));
                 lua.lua_pushstring(L, data.subarray(pos + size, pos + size + len));
                 pos += len;  /* skip string */
                 break;
             }
             case KOption.Kzstr: {
-                let e = lua.luastring_indexOf(data, 0, pos);
+                let e = luastring_indexOf(data, 0, pos);
                 if (e === -1) e = data.length - pos;
                 lua.lua_pushstring(L, data.subarray(pos, e));
                 pos = e + 1;  /* skip string plus final '\0' */
@@ -817,7 +818,7 @@ class MatchState {
 const check_capture = function(ms, l) {
     l = l - '1'.charCodeAt(0);
     if (l < 0 || l >= ms.level || ms.capture[l].len === CAP_UNFINISHED)
-        return lauxlib.luaL_error(ms.L, lua.to_luastring("invalid capture index %%%d"), l + 1);
+        return lauxlib.luaL_error(ms.L, to_luastring("invalid capture index %%%d"), l + 1);
     return l;
 };
 
@@ -825,21 +826,21 @@ const capture_to_close = function(ms) {
     let level = ms.level;
     for (level--; level >= 0; level--)
         if (ms.capture[level].len === CAP_UNFINISHED) return level;
-    return lauxlib.luaL_error(ms.L, lua.to_luastring("invalid pattern capture"));
+    return lauxlib.luaL_error(ms.L, to_luastring("invalid pattern capture"));
 };
 
 const classend = function(ms, p) {
     switch(ms.p[p++]) {
         case L_ESC: {
             if (p === ms.p_end)
-                lauxlib.luaL_error(ms.L, lua.to_luastring("malformed pattern (ends with '%%')"));
+                lauxlib.luaL_error(ms.L, to_luastring("malformed pattern (ends with '%%')"));
             return p + 1;
         }
         case '['.charCodeAt(0): {
             if (ms.p[p] === '^'.charCodeAt(0)) p++;
             do {  /* look for a ']' */
                 if (p === ms.p_end)
-                    lauxlib.luaL_error(ms.L, lua.to_luastring("malformed pattern (missing ']')"));
+                    lauxlib.luaL_error(ms.L, to_luastring("malformed pattern (missing ']')"));
                 if (ms.p[p++] === L_ESC && p < ms.p_end)
                     p++;  /* skip escapes (e.g. '%]') */
             } while (ms.p[p] !== ']'.charCodeAt(0));
@@ -906,7 +907,7 @@ const singlematch = function(ms, s, p, ep) {
 
 const matchbalance = function(ms, s, p) {
     if (p >= ms.p_end - 1)
-        lauxlib.luaL_error(ms.L, lua.to_luastring("malformed pattern (missing arguments to '%%b'"));
+        lauxlib.luaL_error(ms.L, to_luastring("malformed pattern (missing arguments to '%%b'"));
     if (ms.src[s] !== ms.p[p])
         return null;
     else {
@@ -949,7 +950,7 @@ const min_expand = function(ms, s, p, ep) {
 
 const start_capture = function(ms, s, p, what) {
     let level = ms.level;
-    if (level >= LUA_MAXCAPTURES) lauxlib.luaL_error(ms.L, lua.to_luastring("too many captures", true));
+    if (level >= LUA_MAXCAPTURES) lauxlib.luaL_error(ms.L, to_luastring("too many captures", true));
     ms.capture[level] = ms.capture[level] ? ms.capture[level] : {};
     ms.capture[level].init = s;
     ms.capture[level].len = what;
@@ -975,7 +976,7 @@ const array_cmp = function(a, ai, b, bi, len) {
         return true;
     let aj = ai+len;
     loop: for (;;) {
-        ai = lua.luastring_indexOf(a, b[bi], ai);
+        ai = luastring_indexOf(a, b[bi], ai);
         if (ai === -1 || ai >= aj)
             return false;
         for (let j = 1; j < len; j++) {
@@ -1001,7 +1002,7 @@ const match = function(ms, s, p) {
     let gotoinit = true;
 
     if (ms.matchdepth-- === 0)
-        lauxlib.luaL_error(ms.L, lua.to_luastring("pattern too complex", true));
+        lauxlib.luaL_error(ms.L, to_luastring("pattern too complex", true));
 
     while (gotoinit || gotodefault) {
         gotoinit = false;
@@ -1039,7 +1040,7 @@ const match = function(ms, s, p) {
                         case 'f'.charCodeAt(0): {  /* frontier? */
                             p += 2;
                             if (ms.p[p] !== '['.charCodeAt(0))
-                                lauxlib.luaL_error(ms.L, lua.to_luastring("missing '[' after '%%f' in pattern"));
+                                lauxlib.luaL_error(ms.L, to_luastring("missing '[' after '%%f' in pattern"));
                             let ep = classend(ms, p);  /* points to what is next */
                             let previous = s === ms.src_init ? 0 : ms.src[s-1];
                             if (!matchbracketclass(ms, previous, p, ep - 1) && matchbracketclass(ms, (s===ms.src_end)?0:ms.src[s], p, ep - 1)) {
@@ -1108,10 +1109,10 @@ const push_onecapture = function(ms, i, s, e) {
         if (i === 0)
             lua.lua_pushlstring(ms.L, ms.src.subarray(s, e), e - s);  /* add whole match */
         else
-            lauxlib.luaL_error(ms.L, lua.to_luastring("invalid capture index %%%d"), i + 1);
+            lauxlib.luaL_error(ms.L, to_luastring("invalid capture index %%%d"), i + 1);
     } else {
         let l = ms.capture[i].len;
-        if (l === CAP_UNFINISHED) lauxlib.luaL_error(ms.L, lua.to_luastring("unfinished capture", true));
+        if (l === CAP_UNFINISHED) lauxlib.luaL_error(ms.L, to_luastring("unfinished capture", true));
         if (l === CAP_POSITION)
             lua.lua_pushinteger(ms.L, ms.capture[i].init - ms.src_init + 1);
         else
@@ -1121,7 +1122,7 @@ const push_onecapture = function(ms, i, s, e) {
 
 const push_captures = function(ms, s, e) {
     let nlevels = ms.level === 0 && ms.src.subarray(s) ? 1 : ms.level;
-    lauxlib.luaL_checkstack(ms.L, nlevels, lua.to_luastring("too many catpures", true));
+    lauxlib.luaL_checkstack(ms.L, nlevels, to_luastring("too many catpures", true));
     for (let i = 0; i < nlevels; i++)
         push_onecapture(ms, i, s, e);
     return nlevels;  /* number of strings pushed */
@@ -1275,7 +1276,7 @@ const add_s = function(ms, b, s, e) {
             i++;  /* skip ESC */
             if (!isdigit(news[i])) {
                 if (news[i] !== L_ESC)
-                    lauxlib.luaL_error(L, lua.to_luastring("invalid use of '%c' in replacement string"), L_ESC);
+                    lauxlib.luaL_error(L, to_luastring("invalid use of '%c' in replacement string"), L_ESC);
                 lauxlib.luaL_addchar(b, news[i]);
             } else if (news[i] === '0'.charCodeAt(0))
                 lauxlib.luaL_addlstring(b, ms.src.subarray(s, e), e - s);
@@ -1312,7 +1313,7 @@ const add_value = function(ms, b, s, e, tr) {
         lua.lua_pop(L, 1);
         lua.lua_pushlstring(L, ms.src.subarray(s, e), e - s);  /* keep original text */
     } else if (!lua.lua_isstring(L, -1))
-        lauxlib.luaL_error(L, lua.to_luastring("invalid replacement value (a %s)"), lauxlib.luaL_typename(L, -1));
+        lauxlib.luaL_error(L, to_luastring("invalid replacement value (a %s)"), lauxlib.luaL_typename(L, -1));
     lauxlib.luaL_addvalue(b);  /* add result to accumulator */
 };
 
@@ -1329,7 +1330,7 @@ const str_gsub = function(L) {
     let ms = new MatchState(L);
     let b = new lauxlib.luaL_Buffer();
     lauxlib.luaL_argcheck(L, tr === lua.LUA_TNUMBER || tr === lua.LUA_TSTRING || tr === lua.LUA_TFUNCTION || tr === lua.LUA_TTABLE, 3,
-        lua.to_luastring("string/function/table expected", true));
+        to_luastring("string/function/table expected", true));
     lauxlib.luaL_buffinit(L, b);
     if (anchor) {
         p = p.subarray(1); lp--;  /* skip anchor character */
@@ -1381,7 +1382,7 @@ const createmetatable = function(L) {
     lua.lua_setmetatable(L, -2);  /* set table as metatable for strings */
     lua.lua_pop(L, 1);  /* pop dummy string */
     lua.lua_pushvalue(L, -2);  /* get string library */
-    lua.lua_setfield(L, -2, lua.to_luastring("__index", true));  /* metatable.__index = string */
+    lua.lua_setfield(L, -2, to_luastring("__index", true));  /* metatable.__index = string */
     lua.lua_pop(L, 1);  /* pop metatable */
 };
 
diff --git a/src/ltablib.js b/src/ltablib.js
index 9998f3c..a24a275 100644
--- a/src/ltablib.js
+++ b/src/ltablib.js
@@ -5,7 +5,7 @@ const assert  = require('assert');
 const lua     = require('./lua.js');
 const lauxlib = require('./lauxlib.js');
 const luaconf = require('./luaconf.js');
-
+const {to_luastring} = require("./fengaricore.js");
 
 /*
 ** Operations that an object must define to mimic a table
@@ -29,9 +29,9 @@ const checktab = function(L, arg, what) {
     if (lua.lua_type(L, arg) !== lua.LUA_TTABLE) {  /* is it not a table? */
         let n = 1;
         if (lua.lua_getmetatable(L, arg) &&  /* must have metatable */
-            (!(what & TAB_R) || checkfield(L, lua.to_luastring("__index", true), ++n)) &&
-            (!(what & TAB_W) || checkfield(L, lua.to_luastring("__newindex", true), ++n)) &&
-            (!(what & TAB_L) || checkfield(L, lua.to_luastring("__len", true), ++n))) {
+            (!(what & TAB_R) || checkfield(L, to_luastring("__index", true), ++n)) &&
+            (!(what & TAB_W) || checkfield(L, to_luastring("__newindex", true), ++n)) &&
+            (!(what & TAB_L) || checkfield(L, to_luastring("__len", true), ++n))) {
             lua.lua_pop(L, n);  /* pop metatable and tested metamethods */
         }
         else
@@ -47,7 +47,7 @@ const aux_getn = function(L, n, w) {
 const addfield = function(L, b, i) {
     lua.lua_geti(L, 1, i);
     if (!lua.lua_isstring(L, -1))
-        lauxlib.luaL_error(L, lua.to_luastring("invalid value (%s) at index %d in table for 'concat'"),
+        lauxlib.luaL_error(L, to_luastring("invalid value (%s) at index %d in table for 'concat'"),
             lauxlib.luaL_typename(L, -1), i);
 
     lauxlib.luaL_addvalue(b);
@@ -62,7 +62,7 @@ const tinsert = function(L) {
             break;
         case 3: {
             pos = lauxlib.luaL_checkinteger(L, 2);  /* 2nd argument is the position */
-            lauxlib.luaL_argcheck(L, 1 <= pos && pos <= e, 2, lua.to_luastring("position out of bounds", true));
+            lauxlib.luaL_argcheck(L, 1 <= pos && pos <= e, 2, to_luastring("position out of bounds", true));
             for (let i = e; i > pos; i--) {  /* move up elements */
                 lua.lua_geti(L, 1, i - 1);
                 lua.lua_seti(L, 1, i);  /* t[i] = t[i - 1] */
@@ -70,7 +70,7 @@ const tinsert = function(L) {
             break;
         }
         default: {
-            return lauxlib.luaL_error(L, lua.to_luastring("wrong number of arguments to 'insert'", true));
+            return lauxlib.luaL_error(L, to_luastring("wrong number of arguments to 'insert'", true));
         }
     }
 
@@ -82,7 +82,7 @@ const tremove = function(L) {
     let size = aux_getn(L, 1, TAB_RW);
     let pos = lauxlib.luaL_optinteger(L, 2, size);
     if (pos !== size)  /* validate 'pos' if given */
-        lauxlib.luaL_argcheck(L, 1 <= pos && pos <= size + 1, 1, lua.to_luastring("position out of bounds", true));
+        lauxlib.luaL_argcheck(L, 1 <= pos && pos <= size + 1, 1, to_luastring("position out of bounds", true));
     lua.lua_geti(L, 1, pos);  /* result = t[pos] */
     for (; pos < size; pos++) {
         lua.lua_geti(L, 1, pos + 1);
@@ -107,9 +107,9 @@ const tmove = function(L) {
     checktab(L, 1, TAB_R);
     checktab(L, tt, TAB_W);
     if (e >= f) {  /* otherwise, nothing to move */
-        lauxlib.luaL_argcheck(L, f > 0 || e < luaconf.LUA_MAXINTEGER + f, 3, lua.to_luastring("too many elements to move", true));
+        lauxlib.luaL_argcheck(L, f > 0 || e < luaconf.LUA_MAXINTEGER + f, 3, to_luastring("too many elements to move", true));
         let n = e - f + 1;  /* number of elements to move */
-        lauxlib.luaL_argcheck(L, t <= luaconf.LUA_MAXINTEGER - n + 1, 4, lua.to_luastring("destination wrap around", true));
+        lauxlib.luaL_argcheck(L, t <= luaconf.LUA_MAXINTEGER - n + 1, 4, to_luastring("destination wrap around", true));
 
         if (t > e || t <= f || (tt !== 1 && lua.lua_compare(L, 1, tt, lua.LUA_OPEQ) !== 1)) {
             for (let i = 0; i < n; i++) {
@@ -130,7 +130,7 @@ const tmove = function(L) {
 
 const tconcat = function(L) {
     let last = aux_getn(L, 1, TAB_R);
-    let sep = lauxlib.luaL_optlstring(L, 2, lua.to_luastring(""));
+    let sep = lauxlib.luaL_optlstring(L, 2, to_luastring(""));
     let lsep = sep.length;
     let i = lauxlib.luaL_optinteger(L, 3, 1);
     last = lauxlib.luaL_optinteger(L, 4, last);
@@ -158,7 +158,7 @@ const pack = function(L) {
     for (let i = n; i >= 1; i--)  /* assign elements */
         lua.lua_seti(L, 1, i);
     lua.lua_pushinteger(L, n);
-    lua.lua_setfield(L, 1, lua.to_luastring("n"));  /* t.n = number of elements */
+    lua.lua_setfield(L, 1, to_luastring("n"));  /* t.n = number of elements */
     return 1;  /* return table */
 };
 
@@ -168,7 +168,7 @@ const unpack = function(L) {
     if (i > e) return 0;  /* empty range */
     let n = e - i;  /* number of elements minus 1 (avoid overflows) */
     if (n >= Number.MAX_SAFE_INTEGER || !lua.lua_checkstack(L, ++n))
-        return lauxlib.luaL_error(L, lua.to_luastring("too many results to unpack", true));
+        return lauxlib.luaL_error(L, to_luastring("too many results to unpack", true));
     for (; i < e; i++)  /* push arg[i..e - 1] (to avoid overflows) */
         lua.lua_geti(L, 1, i);
     lua.lua_geti(L, 1, e);  /* push last element */
@@ -208,14 +208,14 @@ const partition = function(L, lo, up) {
         /* next loop: repeat ++i while a[i] < P */
         while (lua.lua_geti(L, 1, ++i), sort_comp(L, -1, -2)) {
             if (i == up - 1)  /* a[i] < P  but a[up - 1] == P  ?? */
-                lauxlib.luaL_error(L, lua.to_luastring("invalid order function for sorting"));
+                lauxlib.luaL_error(L, to_luastring("invalid order function for sorting"));
             lua.lua_pop(L, 1);  /* remove a[i] */
         }
         /* after the loop, a[i] >= P and a[lo .. i - 1] < P */
         /* next loop: repeat --j while P < a[j] */
         while (lua.lua_geti(L, 1, --j), sort_comp(L, -3, -1)) {
             if (j < i)  /* j < i  but  a[j] > P ?? */
-                lauxlib.luaL_error(L, lua.to_luastring("invalid order function for sorting"));
+                lauxlib.luaL_error(L, to_luastring("invalid order function for sorting"));
             lua.lua_pop(L, 1);  /* remove a[j] */
         }
         /* after the loop, a[j] <= P and a[j + 1 .. up] >= P */
@@ -292,7 +292,7 @@ const auxsort = function(L, lo, up, rnd) {
 const sort = function(L) {
     let n = aux_getn(L, 1, TAB_RW);
     if (n > 1) {  /* non-trivial interval? */
-        lauxlib.luaL_argcheck(L, n < luaconf.LUA_MAXINTEGER, 1, lua.to_luastring("array too big", true));
+        lauxlib.luaL_argcheck(L, n < luaconf.LUA_MAXINTEGER, 1, to_luastring("array too big", true));
         if (!lua.lua_isnoneornil(L, 2))  /* is there a 2nd argument? */
             lauxlib.luaL_checktype(L, 2, lua.LUA_TFUNCTION);  /* must be a function */
         lua.lua_settop(L, 2);  /* make sure there are two arguments */
diff --git a/src/lua.js b/src/lua.js
index a5b290c..6bbb1a0 100644
--- a/src/lua.js
+++ b/src/lua.js
@@ -6,14 +6,6 @@ const ldebug = require("./ldebug.js");
 const ldo    = require("./ldo.js");
 const lstate = require("./lstate.js");
 
-module.exports.FENGARI_AUTHORS         = defs.FENGARI_AUTHORS;
-module.exports.FENGARI_COPYRIGHT       = defs.FENGARI_COPYRIGHT;
-module.exports.FENGARI_RELEASE         = defs.FENGARI_RELEASE;
-module.exports.FENGARI_VERSION         = defs.FENGARI_VERSION;
-module.exports.FENGARI_VERSION_MAJOR   = defs.FENGARI_VERSION_MAJOR;
-module.exports.FENGARI_VERSION_MINOR   = defs.FENGARI_VERSION_MINOR;
-module.exports.FENGARI_VERSION_NUM     = defs.FENGARI_VERSION_NUM;
-module.exports.FENGARI_VERSION_RELEASE = defs.FENGARI_VERSION_RELEASE;
 module.exports.LUA_AUTHORS             = defs.LUA_AUTHORS;
 module.exports.LUA_COPYRIGHT           = defs.LUA_COPYRIGHT;
 module.exports.LUA_ERRERR              = defs.thread_status.LUA_ERRERR;
@@ -78,12 +70,6 @@ module.exports.LUA_VERSUFFIX           = defs.LUA_VERSUFFIX;
 module.exports.LUA_YIELD               = defs.thread_status.LUA_YIELD;
 module.exports.lua_Debug               = defs.lua_Debug;
 module.exports.lua_upvalueindex        = defs.lua_upvalueindex;
-module.exports.luastring_eq            = defs.luastring_eq;
-module.exports.luastring_indexOf       = defs.luastring_indexOf;
-module.exports.luastring_of            = defs.luastring_of;
-module.exports.to_jsstring             = defs.to_jsstring;
-module.exports.to_luastring            = defs.to_luastring;
-module.exports.to_uristring            = defs.to_uristring;
 module.exports.LUA_CDIR                = defs.LUA_CDIR;
 module.exports.LUA_CPATH_DEFAULT       = defs.LUA_CPATH_DEFAULT;
 module.exports.LUA_EXEC_DIR            = defs.LUA_EXEC_DIR;
diff --git a/src/lutf8lib.js b/src/lutf8lib.js
index 58533cf..9cf7f14 100644
--- a/src/lutf8lib.js
+++ b/src/lutf8lib.js
@@ -2,6 +2,7 @@
 
 const lua     = require('./lua.js');
 const lauxlib = require('./lauxlib.js');
+const {luastring_of, to_luastring} = require("./fengaricore.js");
 
 const MAXUNICODE = 0x10FFFF;
 
@@ -59,8 +60,8 @@ const utflen = function(L) {
     let posi = u_posrelat(lauxlib.luaL_optinteger(L, 2, 1), len);
     let posj = u_posrelat(lauxlib.luaL_optinteger(L, 3, -1), len);
 
-    lauxlib.luaL_argcheck(L, 1 <= posi && --posi <= len, 2, lua.to_luastring("initial position out of string"));
-    lauxlib.luaL_argcheck(L, --posj < len, 3, lua.to_luastring("final position out of string"));
+    lauxlib.luaL_argcheck(L, 1 <= posi && --posi <= len, 2, to_luastring("initial position out of string"));
+    lauxlib.luaL_argcheck(L, --posj < len, 3, to_luastring("final position out of string"));
 
     while (posi <= posj) {
         let dec = utf8_decode(s, posi);
@@ -76,10 +77,10 @@ const utflen = function(L) {
     return 1;
 };
 
-const p_U = lua.to_luastring("%U");
+const p_U = to_luastring("%U");
 const pushutfchar = function(L, arg) {
     let code = lauxlib.luaL_checkinteger(L, arg);
-    lauxlib.luaL_argcheck(L, 0 <= code && code <= MAXUNICODE, arg, lua.to_luastring("value out of range", true));
+    lauxlib.luaL_argcheck(L, 0 <= code && code <= MAXUNICODE, arg, to_luastring("value out of range", true));
     lua.lua_pushfstring(L, p_U, code);
 };
 
@@ -112,14 +113,14 @@ const byteoffset = function(L) {
     let posi = n >= 0 ? 1 : s.length + 1;
     posi = u_posrelat(lauxlib.luaL_optinteger(L, 3, posi), s.length);
 
-    lauxlib.luaL_argcheck(L, 1 <= posi && --posi <= s.length, 3, lua.to_luastring("position out of range", true));
+    lauxlib.luaL_argcheck(L, 1 <= posi && --posi <= s.length, 3, to_luastring("position out of range", true));
 
     if (n === 0) {
         /* find beginning of current byte sequence */
         while (posi > 0 && iscont(s[posi])) posi--;
     } else {
         if (iscont(s[posi]))
-            lauxlib.luaL_error(L, lua.to_luastring("initial position is a continuation byte", true));
+            lauxlib.luaL_error(L, to_luastring("initial position is a continuation byte", true));
 
         if (n < 0) {
             while (n < 0 && posi > 0) {  /* move back */
@@ -156,19 +157,19 @@ const codepoint = function(L) {
     let posi = u_posrelat(lauxlib.luaL_optinteger(L, 2, 1), s.length);
     let pose = u_posrelat(lauxlib.luaL_optinteger(L, 3, posi), s.length);
 
-    lauxlib.luaL_argcheck(L, posi >= 1, 2, lua.to_luastring("out of range", true));
-    lauxlib.luaL_argcheck(L, pose <= s.length, 3, lua.to_luastring("out of range", true));
+    lauxlib.luaL_argcheck(L, posi >= 1, 2, to_luastring("out of range", true));
+    lauxlib.luaL_argcheck(L, pose <= s.length, 3, to_luastring("out of range", true));
 
     if (posi > pose) return 0;  /* empty interval; return no values */
     if (pose - posi >= Number.MAX_SAFE_INTEGER)
-        return lauxlib.luaL_error(L, lua.to_luastring("string slice too long", true));
+        return lauxlib.luaL_error(L, to_luastring("string slice too long", true));
     let n = (pose - posi) + 1;
-    lauxlib.luaL_checkstack(L, n, lua.to_luastring("string slice too long", true));
+    lauxlib.luaL_checkstack(L, n, to_luastring("string slice too long", true));
     n = 0;
     for (posi -= 1; posi < pose;) {
         let dec = utf8_decode(s, posi);
         if (dec === null)
-            return lauxlib.luaL_error(L, lua.to_luastring("invalid UTF-8 code", true));
+            return lauxlib.luaL_error(L, to_luastring("invalid UTF-8 code", true));
         lua.lua_pushinteger(L, dec.code);
         posi = dec.pos;
         n++;
@@ -193,7 +194,7 @@ const iter_aux = function(L) {
     else {
         let dec = utf8_decode(s, n);
         if (dec === null || iscont(s[dec.pos]))
-            return lauxlib.luaL_error(L, lua.to_luastring("invalid UTF-8 code", true));
+            return lauxlib.luaL_error(L, to_luastring("invalid UTF-8 code", true));
         lua.lua_pushinteger(L, n + 1);
         lua.lua_pushinteger(L, dec.code);
         return 2;
@@ -217,12 +218,12 @@ const funcs = {
 };
 
 /* pattern to match a single UTF-8 character */
-const UTF8PATT = lua.luastring_of(91, 0, 45, 127, 194, 45, 244, 93, 91, 128, 45, 191, 93, 42);
+const UTF8PATT = luastring_of(91, 0, 45, 127, 194, 45, 244, 93, 91, 128, 45, 191, 93, 42);
 
 const luaopen_utf8 = function(L) {
     lauxlib.luaL_newlib(L, funcs);
     lua.lua_pushstring(L, UTF8PATT);
-    lua.lua_setfield(L, -2, lua.to_luastring("charpattern", true));
+    lua.lua_setfield(L, -2, to_luastring("charpattern", true));
     return 1;
 };