setmetatable, getmetatable

3 files changed, 94 insertions, 8 deletions

diff --git a/src/lapi.js b/src/lapi.js
index ece02e0..e1e548d 100644
--- a/src/lapi.js
+++ b/src/lapi.js
@@ -260,6 +260,33 @@ const lua_setglobal = function(L, name) {
     auxsetstr(L, L.l_G.l_registry.value.array[lua.LUA_RIDX_GLOBALS - 1], name);
 };
 
+const lua_setmetatable = function(L, objindex) {
+    assert(1 < L.top - L.ci.funcOff, "not enough elements in the stack");
+    let mt;
+    let obj = index2addr(L, objindex);
+    if (L.stack[L.top - 1].ttisnil())
+        mt = null;
+    else {
+        assert(L.stack[L.top - 1].ttistable(), "table expected");
+        mt = L.stack[L.top - 1];
+    }
+
+    switch (obj.ttnov()) {
+        case CT.LUA_TUSERDATA:
+        case CT.LUA_TTABLE: {
+            obj.metatable = mt;
+            break;
+        }
+        default: {
+            L.l_G.mt[obj.ttnov()] = mt;
+            break;
+        }
+    }
+
+    L.top--;
+    return true;
+};
+
 const lua_settable = function(L, idx) {
     assert(2 < L.top - L.ci.funcOff, "not enough elements in the stack");
 
@@ -562,4 +589,6 @@ module.exports.lua_pushglobaltable = lua_pushglobaltable;
 module.exports.lua_setfield        = lua_setfield;
 module.exports.lua_getfield        = lua_getfield;
 module.exports.lua_getglobal       = lua_getglobal;
-module.exports.lua_getmetatable    = lua_getmetatable;
\ No newline at end of file
+module.exports.lua_getmetatable    = lua_getmetatable;
+module.exports.lua_setmetatable    = lua_setmetatable;
+module.exports.lua_settop          = lua_settop;
\ No newline at end of file
diff --git a/src/lauxlib.js b/src/lauxlib.js
index 6db0aae..a1f9d64 100644
--- a/src/lauxlib.js
+++ b/src/lauxlib.js
@@ -13,7 +13,27 @@ const LUA_LOADED_TABLE = "_LOADED"
 const panic = function(L) {
     console.log(`PANIC: unprotected error in call to Lua API (...)`);
     return 0;
-}
+};
+
+const typeerror = function(L, arg, tname) {
+    let typearg;
+    if (luaL_getmetafield(L, arg, "__name") === CT.LUA_TSTRING)
+        typearg = lapi.lua_tostring(L, -1);
+    else if (lapi.lua_type(L, arg) === CT.LUA_TLIGHTUSERDATA)
+        typearg = "light userdata";
+    else
+        typearg = luaL_typename(L, arg);
+
+    throw new Error(`${tname} expected, got ${typearg}`);
+
+    // TODO:
+    // let msg = lua_pushstring(L, `${tname} expected, got ${typearg}`);
+    // return luaL_argerror(L, arg, msg);
+};
+
+const tag_error = function(L, arg, tag) {
+    typeerror(L, arg, lapi.lua_typename(L, tag));
+};
 
 const luaL_newstate = function() {
     let L = lstate.lua_newstate();
@@ -26,11 +46,20 @@ const luaL_typename = function(L, i) {
     return lapi.lua_typename(L, lapi.lua_type(L, i));
 };
 
+const luaL_argcheck = function(L, cond, arg, extramsg) {
+    if (!cond) throw new Error("bad argument"); // TODO: luaL_argerror
+};
+
 const luaL_checkany = function(L, arg) {
     if (lapi.lua_type(L, arg) === CT.LUA_TNONE)
         throw new Error("value expected"); // TODO: luaL_argerror(L, arg, "value expected");
 };
 
+const luaL_checktype = function(L, arg, t) {
+    if (lapi.lua_type(L, arg) !== t)
+        tag_error(L, arg, t);
+};
+
 const luaL_getmetafield = function(L, obj, event) {
     if (!lapi.lua_getmetatable(L, obj))
         return CT.LUA_TNIL;
@@ -157,6 +186,7 @@ const luaL_checkstack = function(L, space, msg) {
 module.exports.luaL_newstate     = luaL_newstate;
 module.exports.luaL_typename     = luaL_typename;
 module.exports.luaL_checkany     = luaL_checkany;
+module.exports.luaL_checktype    = luaL_checktype;
 module.exports.luaL_callmeta     = luaL_callmeta;
 module.exports.luaL_getmetafield = luaL_getmetafield;
 module.exports.luaL_requiref     = luaL_requiref;
@@ -164,4 +194,5 @@ module.exports.luaL_getsubtable  = luaL_getsubtable;
 module.exports.luaL_setfuncs     = luaL_setfuncs;
 module.exports.luaL_checkstack   = luaL_checkstack;
 module.exports.LUA_LOADED_TABLE  = LUA_LOADED_TABLE;
-module.exports.luaL_tolstring    = luaL_tolstring;
\ No newline at end of file
+module.exports.luaL_tolstring    = luaL_tolstring;
+module.exports.luaL_argcheck     = luaL_argcheck;
\ No newline at end of file
diff --git a/src/lbaselib.js b/src/lbaselib.js
index b046f67..12c28fe 100644
--- a/src/lbaselib.js
+++ b/src/lbaselib.js
@@ -6,6 +6,7 @@ const assert  = require('assert');
 const lua     = require('./lua.js');
 const lapi    = require('./lapi.js');
 const lauxlib = require('./lauxlib.js');
+const CT      = lua.constant_types;
 
 const luaB_print = function(L) {
     let n = lapi.lua_gettop(L); /* number of arguments */
@@ -35,9 +36,32 @@ const luaB_tostring = function(L) {
     return true;
 };
 
+const luaB_getmetatable = function(L) {
+    lauxlib.luaL_checkany(L, 1);
+    if (!lapi.lua_getmetatable(L, 1)) {
+        lapi.lua_pushnil(L);
+        return true;  /* no metatable */
+    }
+    lauxlib.luaL_getmetafield(L, 1, "__metatable");
+    return true;  /* returns either __metatable field (if present) or metatable */
+};
+
+const luaB_setmetatable = function(L) {
+    let t = lapi.lua_type(L, 2);
+    lauxlib.luaL_checktype(L, 1, CT.LUA_TTABLE);
+    lauxlib.luaL_argcheck(L, t === CT.LUA_TNIL || t === CT.LUA_TTABLE, 2, "nil or table expected");
+    if (lauxlib.luaL_getmetafield(L, 1, "__metatable") !== CT.LUA_TNIL)
+        throw new Error("cannot change a protected metatable");
+    lapi.lua_settop(L, 2);
+    lapi.lua_setmetatable(L, 1);
+    return true;
+};
+
 const base_funcs = {
-    "print":    luaB_print,
-    "tostring": luaB_tostring,
+    "print":        luaB_print,
+    "tostring":     luaB_tostring,
+    "getmetatable": luaB_getmetatable,
+    "setmetatable": luaB_setmetatable,
 };
 
 const luaopen_base = function(L) {
@@ -53,6 +77,8 @@ const luaopen_base = function(L) {
     return true;
 };
 
-module.exports.luaB_tostring = luaB_tostring;
-module.exports.luaB_print    = luaB_print;
-module.exports.luaopen_base  = luaopen_base;
+module.exports.luaB_tostring     = luaB_tostring;
+module.exports.luaB_print        = luaB_print;
+module.exports.luaB_getmetatable = luaB_getmetatable;
+module.exports.luaB_setmetatable = luaB_setmetatable;
+module.exports.luaopen_base      = luaopen_base;