From 03e81f5553ef45bcae2e1ae78d4926bef617bfdd Mon Sep 17 00:00:00 2001
From: SeanOMik <seanomik@gmail.com>
Date: Tue, 6 Feb 2024 09:23:32 -0500
Subject: [PATCH] make it possible to provide references of rust types to lua

---
 src/chunk.rs                         |   4 +-
 src/function.rs                      |  21 +--
 src/main.rs                          | 174 ++++++++++++-----------
 src/state.rs                         |   9 +-
 src/table.rs                         |  74 ++++++----
 src/{userdata.rs => userdata/mod.rs} | 197 ++++++++++++++++++---------
 src/userdata/unsafe_ud.rs            | 180 ++++++++++++++++++++++++
 src/value.rs                         |  38 +++++-
 8 files changed, 503 insertions(+), 194 deletions(-)
 rename src/{userdata.rs => userdata/mod.rs} (69%)
 create mode 100755 src/userdata/unsafe_ud.rs

diff --git a/src/chunk.rs b/src/chunk.rs
index f686602..67cd57f 100755
--- a/src/chunk.rs
+++ b/src/chunk.rs
@@ -1,6 +1,6 @@
 use std::borrow::{Borrow, Cow};
 
-use crate::{AsLua, FromLua, Function, State};
+use crate::{FromLua, Function, IntoLuaVec, State};
 
 pub struct Chunk<'a> {
     state: &'a State,
@@ -38,7 +38,7 @@ impl<'a> Chunk<'a> {
     /// Execute the chunk in the Lua context
     pub fn execute<A, R>(&'a self, args: A) -> crate::Result<R>
     where
-        A: AsLua<'a>,
+        A: IntoLuaVec<'a>,
         R: FromLua<'a>
     {
         self.state.execute_chunk::<A, R>(self, args)
diff --git a/src/function.rs b/src/function.rs
index dbb5659..af74075 100755
--- a/src/function.rs
+++ b/src/function.rs
@@ -1,6 +1,6 @@
 use std::sync::Arc;
 
-use crate::{AsLua, FromLua, FromLuaStack,  LuaRef, PushToLuaStack, StackGuard, State, Value, ValueVec};
+use crate::{AsLua, FromLua, FromLuaStack, IntoLuaVec, LuaRef, PushToLuaStack, StackGuard, State, Value, ValueVec};
 
 use mlua_sys as lua;
 
@@ -38,19 +38,15 @@ impl<'a> Function<'a> {
 
     pub fn exec<A, R>(&self, args: A) -> crate::Result<R>
     where
-        A: AsLua<'a>,
+        A: IntoLuaVec<'a>,
         R: FromLua<'a>,
     {
         unsafe {
             let _g = StackGuard::new(self.state);
             let s = self.state.state_ptr();
             
-            let args_val = args.as_lua(self.state)?;
-            let args_len = match args_val {
-                Value::Variable(v) => v.len(),
-                Value::None => 0,
-                _ => 1,
-            } as _;
+            let args_val = args.into_lua_value_vec(self.state)?;
+            let args_len = args_val.len() as _;
 
             self.state.ensure_stack(2 + args_len)?;
 
@@ -64,7 +60,8 @@ impl<'a> Function<'a> {
 
             self.push_to_lua_stack(self.state)?;
 
-            let args_val = args.as_lua(self.state)?;
+            /* let args_val = args.into_lua_value_vec(self.state)?;
+            args_val.push_to_lua_stack(self.state)?; */
             args_val.push_to_lua_stack(self.state)?;
 
             match lua::lua_pcall(s, args_len, lua::LUA_MULTRET, handler_idx) {
@@ -100,4 +97,10 @@ impl<'a> AsLua<'a> for Function<'a> {
     fn as_lua(&self, _lua: &'a State) -> crate::Result<crate::Value<'a>> {
         Ok(crate::Value::Function(self.clone()))
     }
+}
+
+impl<'a> FromLua<'a> for Function<'a> {
+    fn from_lua(_lua: &'a State, val: Value<'a>) -> crate::Result<Self> {
+        val.into_function()
+    }
 }
\ No newline at end of file
diff --git a/src/main.rs b/src/main.rs
index b170659..71c113a 100755
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,4 +1,4 @@
-use std::{cell::Ref, marker::PhantomData, sync::Arc};
+use std::{cell::{Ref, RefCell}, marker::PhantomData, mem, sync::Arc};
 
 use mlua_sys as lua;
 
@@ -43,100 +43,63 @@ fn main() -> Result<()> {
     let f = lua.create_function(a)?;
     globals.set("native_test", f)?;
     
-    let ud = lua.create_userdata(UserdataProxy::<Vec2>::new())?;
-    globals.set("Vec2", ud)?;
+    /* let ud = lua.create_userdata(UserdataProxy::<Vec2>::new())?;
+    globals.set("Vec2", ud)?; */
 
-    let tbl = lua.create_table()?;
-    tbl.set("x", 10)?;
+    let cell = RefCell::new(Vec2 {
+        x: 50.0,
+        y: 5.0
+    });
 
-    //let globals = lua.globals()?;
-    globals.set("X", tbl)?;
+    {
+        let ud = lua.create_userdata(UserdataRef {
+            ud_ptr: unsafe {
+                mem::transmute::<Ref<Vec2>, Ref<Vec2>>(cell.borrow())
+            },
+        })?;
+        globals.set("vec2", ud)?;
+    }
 
     let chunk = lua.load("text.lua", r#"
         require "util"
 
-        --[[function dump_table(tbl)
-            for k, v in pairs(tbl) do
-                if type(v) == "table" then
-                    dump_table(v)
-                elseif type(v) == "function" then
-
-                else
-                    print(k .. "=" .. tostring(v))
-                end
-                
-            end
+        if vec2 ~= nil then
+            print("vec2: (" .. vec2.x .. ", " .. vec2.y .. ")")
         end
 
-        for k, v in pairs(_G) do
-            --print("Found global named " .. k)
-
-            if k == "X" then
-                --dump_table(v)
-            end
-        end]]--
-
-        function multiply_print(a, b)
-            print(a .. " * " .. b .. " = " .. a*b)
-        end
-
-        function multiply_ret(a, b)
-            return a * b
-        end
-
-        function say_number(a)
-            print("Lua says " .. a)
-        end
-
-        cool_num = 50
-
-        print("Lua is about to exec native_test")
-        local res = native_test(50)
-        print("Lua got " .. res .. " back from rust!")
-
-        print("Vec2: " .. dump_table(Vec2))
-        print("Meta Vec2: " .. dump_table(getmetatable(Vec2)))
-        
-        --print("Vec2 is (" .. Vec2.x .. ", " .. Vec2.y .. ")")
-
-        local v1 = Vec2.new(50, 50)
-        print("v1 is (" .. v1.x .. ", " .. v1.y .. ")")
-
-        local v2 = Vec2.new(500, 500)
-        print("v2 is (" .. v2.x .. ", " .. v2.y .. ")")
-
-        local v_add = v1 + v2
-        v_add.x = 90
-        print("v_add is (" .. v_add.x .. ", " .. v_add.y .. ")")
-
-        function f1(v1, v2)
-            --print("f1 tb: " .. debug.traceback(1))
-            local v_add = v1:add(v2)
-        end
-
-        function f2(v1, v2)
-            --print("f2 tb: " .. debug.traceback(1))
-            f1(v1, v2)
-        end
-
-        function f3(v1, v2)
-            --print("f3 tb: " .. debug.traceback(1))
-            f2(v1, v2)
-        end
-
-        --f3(v1, v2)
+        --print("vec2.x = " .. vec2.x)
+        --print("vec2.y = " .. vec2.y)
     "#)?;
 
-    // I don't care about the result of this execution, so I set the result as a
-    // Value which can be anything
-    //
-    // Chunks can also be executed with: `chunk.execute(())?;`
-    let res = lua.execute_chunk::<_, Value>(&chunk, ());
+    for _ in 0..2 {
+        // I don't care about the result of this execution, so I set the result as a
+        // Value which can be anything
+        //
+        // Chunks can also be executed with: `chunk.execute(())?;`
+        let res = lua.execute_chunk::<_, Value>(&chunk, ());
 
-    // if unwrapped, the new lines in the message would be escaped making
-    // the traceback in the error difficult to read.
-    if let Err(e) = res {
-        panic!("{}", e);
+        // if unwrapped, the new lines in the message would be escaped making
+        // the traceback in the error difficult to read.
+        if let Err(e) = res {
+            panic!("{}", e);
+        }
+
+        let vec2 = globals.get::<_, AnyUserdata>("vec2")?;
+        vec2.garbage_collect()?;
+        globals.set("vec2", Value::Nil)?;
+
+        let mut t = cell.borrow_mut();
+        t.x += 50.0;
+        t.y += 5.0;
+        drop(t);
+
+        let ud = lua.create_userdata(UserdataRef {
+            // TODO: avoid unsafe here
+            ud_ptr: unsafe {
+                mem::transmute::<Ref<Vec2>, Ref<Vec2>>(cell.borrow())
+            },
+        })?;
+        globals.raw_set("vec2", ud)?;
     }
 
     unsafe {
@@ -310,7 +273,7 @@ pub struct Vec3 {
 }
 
 impl Userdata for Vec3 {
-    fn build<'a>(_builder: &mut UserdataBuilder<'a, Self>) -> crate::Result<()> {
+    fn build<'a>(_state: &State, _builder: &mut UserdataBuilder<'a, Self>) -> crate::Result<()> {
         todo!()
     }
 
@@ -325,7 +288,7 @@ pub struct Vec2 {
 }
 
 impl Userdata for Vec2 {
-    fn build<'a>(builder: &mut UserdataBuilder<'a, Vec2>) -> crate::Result<()> {
+    fn build<'a>(_state: &State, builder: &mut UserdataBuilder<'a, Vec2>) -> crate::Result<()> {
         builder
             .field_getter("x", |_, this| Ok(this.x))
             .field_getter("y", |_, this| Ok(this.y))
@@ -381,9 +344,9 @@ impl<'a, T: Userdata> AsLua<'a> for UserdataProxy<T> {
 }
 
 impl<T: Userdata> Userdata for UserdataProxy<T> {
-    fn build<'a>(builder: &mut UserdataBuilder<'a, Self>) -> crate::Result<()> {
+    fn build<'a>(state: &State, builder: &mut UserdataBuilder<'a, Self>) -> crate::Result<()> {
         let mut other = UserdataBuilder::<T>::new();
-        T::build(&mut other)?;
+        T::build(state, &mut other)?;
 
         // only the functions need to be added since they're the only thing usable from a proxy
         builder.functions = other.functions;
@@ -395,4 +358,39 @@ impl<T: Userdata> Userdata for UserdataProxy<T> {
         let name = format!("{}Proxy", T::name());
         name
     }
+}
+
+pub struct UserdataRef<'a, T: Userdata> {
+    ud_ptr: Ref<'a, T>
+}
+
+impl<'a, T: Userdata + 'static> Userdata for UserdataRef<'a, T> {
+    fn build<'b>(state: &State, builder: &mut UserdataBuilder<'b, Self>) -> crate::Result<()> {
+        let mut other = UserdataBuilder::<T>::new();
+        T::build(state, &mut other)?;
+
+        builder.expand_with(other);
+
+        let getter: fn(AnyUserdata<'_>) -> Result<*const ()> = move |ud: AnyUserdata| {
+            let ud_ptr = {
+                let ud = ud.as_ref::<UserdataRef<T>>()?;
+                
+                let ud_ptr: *const T = &*ud.ud_ptr;
+                ud_ptr
+            };
+
+            Ok(ud_ptr.cast::<()>())
+        };
+
+        if builder.wrapped_getter.set(Box::new(getter)).is_err() {
+            panic!("Somehow the wrapped getter has already been set");
+        }
+
+        Ok(())
+    }
+
+    fn name() -> String {
+        let name = format!("{}Ref", T::name());
+        name
+    }
 }
\ No newline at end of file
diff --git a/src/state.rs b/src/state.rs
index a05aff4..e689c23 100755
--- a/src/state.rs
+++ b/src/state.rs
@@ -3,7 +3,7 @@ use std::{alloc::{self, Layout}, any::TypeId, cell::RefCell, collections::HashMa
 
 use mlua_sys as lua;
 
-use crate::{lua_error_guard, AnyUserdata, IntoChunkData, AsLua, Chunk, Error, FromLua, FromLuaStack, FromLuaVec, Function, LuaRef, MetaMethod, PushToLuaStack, Result, StackGuard, Table, Userdata, UserdataBuilder, Value, ValueVec};
+use crate::{lua_error_guard, AnyUserdata, AsLua, Chunk, Error, FromLua, FromLuaStack, FromLuaVec, Function, IntoChunkData, IntoLuaVec, LuaRef, MetaMethod, PushToLuaStack, Result, StackGuard, Table, Userdata, UserdataBuilder, Value, ValueVec};
 
 pub fn ptr_to_string(ptr: *const i8) -> std::result::Result<String, Utf8Error> {
     let c = unsafe { CStr::from_ptr(ptr) };
@@ -212,7 +212,7 @@ impl State {
 
     pub fn execute_chunk<'a, A, R>(&'a self, chunk: &'a Chunk, args: A) -> Result<R>
     where
-        A: AsLua<'a>,
+        A: IntoLuaVec<'a>,
         R: FromLua<'a>
     {
         let handler = self.create_function(|lua, msg: String| {
@@ -431,7 +431,7 @@ impl State {
 
     pub(crate) fn create_userdata_metatable<'a, T: Userdata + 'static>(&'a self) -> Result<Table<'a>> {
         let mut builder = UserdataBuilder::<T>::new();
-        T::build(&mut builder)?;
+        T::build(self, &mut builder)?;
 
         let getters = builder.field_getters;
         let setters = builder.field_setters;
@@ -502,10 +502,11 @@ impl State {
                     let ud_ptr = ud.as_ptr_unchecked::<T>().unwrap();
                     ud_ptr.drop_in_place();
 
-                    lua::luaL_unref(lua.state_ptr(), lua::LUA_REGISTRYINDEX, *ud.lref.0);
+                    lua::luaL_unref(lua.state_ptr(), lua::LUA_REGISTRYINDEX, *ud.unsafe_ud.lref.0);
 
                     let extra = lua.get_extra_space();
                     extra.userdata_metatables.remove(&TypeId::of::<T>());
+                    //todo!()
                 }
 
                 Ok(())
diff --git a/src/table.rs b/src/table.rs
index ceb810b..ffd592d 100755
--- a/src/table.rs
+++ b/src/table.rs
@@ -1,7 +1,7 @@
 
 use mlua_sys as lua;
 
-use crate::{ensure_type, FromLuaStack, LuaRef, PushToLuaStack, Result, StackGuard, State};
+use crate::{ensure_type, AsLua, FromLua, FromLuaStack, LuaRef, PushToLuaStack, Result, StackGuard, State, Value};
 
 #[derive(Clone)]
 pub struct Table<'a> {
@@ -83,8 +83,8 @@ impl<'a> Table<'a> {
     /// This may trigger the `__newindex` metamethod, see [`Table::raw_set`]
     pub fn set<K, V>(&self, key: K, val: V) -> Result<()>
     where
-        K: PushToLuaStack<'a>,
-        V: PushToLuaStack<'a>
+        K: AsLua<'a>,
+        V: AsLua<'a>
     {
         let s = self.state.state_ptr();
         unsafe {
@@ -97,8 +97,10 @@ impl<'a> Table<'a> {
             }
 
             self.lref.push_to_lua_stack(self.state)?;
-            key.push_to_lua_stack(self.state)?;
-            val.push_to_lua_stack(self.state)?;
+            key.as_lua(self.state)?
+                .push_to_lua_stack(self.state)?;
+            val.as_lua(self.state)?
+                .push_to_lua_stack(self.state)?;
 
             lua::lua_settable(s, -3);
         }
@@ -111,8 +113,8 @@ impl<'a> Table<'a> {
     /// This may trigger the `__index` metamethod, see [`Table::raw_get`]
     pub fn get<K, V>(&self, key: K) -> Result<V>
     where
-        K: PushToLuaStack<'a>,
-        V: FromLuaStack<'a>,
+        K: AsLua<'a>,
+        V: FromLua<'a>,
     {
         let s = self.state.state_ptr();
         unsafe {
@@ -120,10 +122,13 @@ impl<'a> Table<'a> {
             let _g = StackGuard::new(self.state);
             
             self.lref.push_to_lua_stack(self.state)?;
-            key.push_to_lua_stack(self.state)?;
+            let val = key.as_lua(self.state)?;
+            val.push_to_lua_stack(self.state)?;
+
             lua::lua_gettable(s, -2); // table[key] is at top of stack
             
-            let val = V::from_lua_stack(self.state)?;
+            let val = Value::from_lua_stack(self.state)?;
+            let val = V::from_lua(self.state, val)?;
 
             Ok(val)
         }
@@ -150,7 +155,7 @@ impl<'a> Table<'a> {
     /// Returns a boolean indicating if this table has a key
     pub fn has_key<K>(&self, key: K) -> Result<bool>
     where
-        K: PushToLuaStack<'a>,
+        K: AsLua<'a>,
     {
         let s = self.state.state_ptr();
         unsafe {
@@ -158,7 +163,8 @@ impl<'a> Table<'a> {
             let _g = StackGuard::new(self.state);
             
             self.lref.push_to_lua_stack(self.state)?;
-            key.push_to_lua_stack(self.state)?;
+            let key_val = key.as_lua(self.state)?;
+            key_val.push_to_lua_stack(self.state)?;
 
             // table[key] is at top of stack
             if lua::lua_gettable(s, -2) == lua::LUA_TNIL {
@@ -172,8 +178,8 @@ impl<'a> Table<'a> {
     /// Set a key to a value in the table without calling any meta methods.
     pub fn raw_set<K, V>(&self, key: K, val: V) -> Result<()>
     where
-        K: PushToLuaStack<'a>,
-        V: PushToLuaStack<'a>
+        K: AsLua<'a>,
+        V: AsLua<'a>
     {
         let s = self.state.state_ptr();
         unsafe {
@@ -181,8 +187,10 @@ impl<'a> Table<'a> {
             let _g = StackGuard::new(self.state);
             
             self.lref.push_to_lua_stack(self.state)?;
-            key.push_to_lua_stack(self.state)?;
-            val.push_to_lua_stack(self.state)?;
+            key.as_lua(self.state)?
+                .push_to_lua_stack(self.state)?;
+            val.as_lua(self.state)?
+                .push_to_lua_stack(self.state)?;
 
             lua::lua_rawset(s, -3);
         }
@@ -191,10 +199,10 @@ impl<'a> Table<'a> {
     }
 
     /// Get a value from the table without calling any meta methods.
-    pub fn raw_get<K, V>(&'a self, key: K) -> Result<V>
+    pub fn raw_get<K, V>(&self, key: K) -> Result<V>
     where
-        K: PushToLuaStack<'a>,
-        V: FromLuaStack<'a>,
+        K: AsLua<'a>,
+        V: FromLua<'a>,
     {
         let s = self.state.state_ptr();
         unsafe {
@@ -202,9 +210,13 @@ impl<'a> Table<'a> {
             let _g = StackGuard::new(self.state);
 
             self.lref.push_to_lua_stack(self.state)?;
-            key.push_to_lua_stack(self.state)?;
+            key.as_lua(self.state)?
+                .push_to_lua_stack(self.state)?;
+
             lua::lua_rawget(s, -2); // table[key] is at top of stack
-            V::from_lua_stack(self.state)
+            
+            let val = Value::from_lua_stack(self.state)?;
+            V::from_lua(self.state, val)
         }
     }
 
@@ -226,7 +238,7 @@ impl<'a> Table<'a> {
     /// Returns a boolean indicating if this table has a key without calling any meta methods.
     pub fn raw_has_key<K>(&self, key: K) -> Result<bool>
     where
-        K: PushToLuaStack<'a>,
+        K: AsLua<'a>,
     {
         let s = self.state.state_ptr();
         unsafe {
@@ -234,7 +246,9 @@ impl<'a> Table<'a> {
             let _g = StackGuard::new(self.state);
 
             self.lref.push_to_lua_stack(self.state)?;
-            key.push_to_lua_stack(self.state)?;
+            key.as_lua(self.state)?
+                .push_to_lua_stack(self.state)?;
+            
             // table[key] is at top of stack
             Ok(lua::lua_rawget(s, -2) != lua::LUA_TNIL)
         }
@@ -245,8 +259,8 @@ impl<'a> Table<'a> {
     /// Does nothing if this table is not a metatable
     pub fn set_meta<K, V>(&self, key: K, val: V) -> Result<()>
     where
-        K: PushToLuaStack<'a>,
-        V: PushToLuaStack<'a>
+        K: AsLua<'a>,
+        V: AsLua<'a>
     {
         if self.mt_marker {
             unsafe {
@@ -255,8 +269,10 @@ impl<'a> Table<'a> {
                 let _g = StackGuard::new(self.state);
 
                 self.lref.push_to_lua_stack(self.state)?;
-                key.push_to_lua_stack(self.state)?;
-                val.push_to_lua_stack(self.state)?;
+                key.as_lua(self.state)?
+                    .push_to_lua_stack(self.state)?;
+                val.as_lua(self.state)?
+                    .push_to_lua_stack(self.state)?;
                 lua::lua_settable(s, -3);
             }
         }
@@ -279,4 +295,10 @@ impl<'a> FromLuaStack<'a> for Table<'a> {
         ensure_type(state, lua::LUA_TTABLE, -1)?;
         Table::with_ref(state, LuaRef::from_stack(state)?, false)
     }
+}
+
+impl<'a> FromLua<'a> for Table<'a> {
+    fn from_lua(_lua: &'a State, val: Value<'a>) -> crate::Result<Self> {
+        val.into_table()
+    }
 }
\ No newline at end of file
diff --git a/src/userdata.rs b/src/userdata/mod.rs
similarity index 69%
rename from src/userdata.rs
rename to src/userdata/mod.rs
index c71fbe0..30bbbcb 100755
--- a/src/userdata.rs
+++ b/src/userdata/mod.rs
@@ -1,9 +1,12 @@
-use std::{cell::{Ref, RefCell, RefMut}, collections::HashMap, ffi::CStr, marker::PhantomData, ops::DerefMut};
+use std::{cell::{OnceCell, Ref, RefCell, RefMut}, collections::HashMap, ffi::CStr, marker::PhantomData, mem, ops::{Deref, DerefMut}, sync::Arc};
 
-use crate::{ensure_type, AsLua, FromLua, FromLuaStack, FromLuaVec, LuaRef, PushToLuaStack, StackGuard, State, Value, ValueVec};
+use crate::{ensure_type, AsLua, FromLua, FromLuaStack, FromLuaVec, Function, IntoLuaVec, LuaRef, PushToLuaStack, StackGuard, State, Table, Value, ValueVec};
 
 use mlua_sys as lua;
 
+pub mod unsafe_ud;
+pub use unsafe_ud::*;
+
 /// An enum representing all Lua MetaMethods
 /// https://gist.github.com/oatmealine/655c9e64599d0f0dd47687c1186de99f
 pub enum MetaMethod {
@@ -89,7 +92,7 @@ impl<'a> PushToLuaStack<'a> for MetaMethod {
     }
 }
 
-type UserdataFn<'a> = Box<dyn Fn(&'a State, ValueVec<'a>) -> crate::Result<Value<'a>>>;
+pub type UserdataFn<'a> = Box<dyn Fn(&'a State, ValueVec<'a>) -> crate::Result<Value<'a>>>;
 
 pub struct UserdataBuilder<'a, T> {
     pub(crate) name: String,
@@ -97,6 +100,9 @@ pub struct UserdataBuilder<'a, T> {
     pub(crate) field_setters: HashMap<String, UserdataFn<'a>>,
     pub(crate) functions: HashMap<String, UserdataFn<'a>>,
     pub(crate) meta_methods: HashMap<String, UserdataFn<'a>>,
+
+    pub(crate) wrapped_getter: Arc<OnceCell<Box<dyn Fn(AnyUserdata<'a>) -> crate::Result<*const ()>>>>,
+
     _marker: PhantomData<T>,
 }
 
@@ -108,6 +114,7 @@ impl<'a, T: Userdata> UserdataBuilder<'a, T> {
             field_setters: HashMap::new(),
             functions: HashMap::new(),
             meta_methods: HashMap::new(),
+            wrapped_getter: Arc::new(OnceCell::new()),
             _marker: PhantomData,
         }
     }
@@ -118,11 +125,34 @@ impl<'a, T: Userdata> UserdataBuilder<'a, T> {
         R: AsLua<'a>,
         T: Userdata + 'static
     {
+        let wrapped = self.wrapped_getter.clone();
+        let wrapped: Arc<OnceCell<Box<dyn Fn(AnyUserdata<'_>) -> Result<*const (), crate::Error>>>> = unsafe { mem::transmute(wrapped) };
+        let fn_name = Arc::new(name.to_string());
+
         let wrap = move |lua: &'a State, mut val: ValueVec<'a>| {
             let val = val.pop_front().unwrap();
             let this = val.as_userdata().unwrap(); // if this panics, its a bug
-            let this = this.as_ref::<T>()?;
-            f(lua, &*this).and_then(|r| r.as_lua(lua))
+
+            if let Some(getter) = wrapped.get() {
+                let this_ptr = match getter(this.clone()) {
+                    Ok(v) => v,
+                    Err(e) => {
+                        return Err(crate::Error::BadArgument {
+                            func: Some(fn_name.deref().clone()),
+                            arg_index: 1,
+                            arg_name: Some("self".to_string()),
+                            error: Arc::new(e),
+                        });
+                    }
+                };
+                let this_ptr = this_ptr.cast::<T>();
+                let this = unsafe { &*this_ptr };
+
+                f(lua, this).and_then(|r| r.as_lua(lua))
+            } else {
+                let this = this.as_ref::<T>()?;
+                f(lua, &*this).and_then(|r| r.as_lua(lua))
+            }
         };
         self.field_getters.insert(name.to_string(), Box::new(wrap));
 
@@ -192,6 +222,7 @@ impl<'a, T: Userdata> UserdataBuilder<'a, T> {
         let wrap = move |lua: &'a State, mut val: ValueVec<'a>| {
             let this_val = val.pop_front().unwrap();
             let this = this_val.as_userdata().unwrap(); // if this panics, its a bug
+            //this.unsafe_ud.as_ptr_unchecked()
             let this = this.as_ref::<T>()?;
             
             let this_name = T::name();
@@ -233,78 +264,60 @@ impl<'a, T: Userdata> UserdataBuilder<'a, T> {
 
         self
     }
+
+    //fn append_fields_from<S>(&mut self, other: UserDataRegistry<'lua, S>) {
+    pub fn expand_with<U>(&mut self, other: UserdataBuilder<'a, U>) {
+        self.field_getters = other.field_getters;
+        self.field_setters = other.field_setters;
+        self.functions = other.functions;
+        self.meta_methods = other.meta_methods;
+        self.wrapped_getter = other.wrapped_getter;
+    }
 }
 
 pub trait Userdata: Sized {
     fn name() -> String;
 
-    fn build<'a>(builder: &mut UserdataBuilder<'a, Self>) -> crate::Result<()>;
+    fn build<'a>(state: &State, builder: &mut UserdataBuilder<'a, Self>) -> crate::Result<()>;
 }
 
 /// A handle to some userdata on the stack
-#[derive(Clone)]
+//#[derive(Clone)]
 pub struct AnyUserdata<'a> {
-    pub(crate) lref: LuaRef<'a>,
+    pub(crate) unsafe_ud: UnsafeUserdata<'a>,
     state: &'a State,
 }
 
+impl<'a> Clone for AnyUserdata<'a> {
+    fn clone(&self) -> Self {
+        Self {
+            state: self.state,
+            unsafe_ud: self.unsafe_ud.clone()
+        }
+    }
+}
+
 impl<'a> AnyUserdata<'a> {
     pub fn from_ref(state: &'a State, lref: LuaRef<'a>) -> Self {
         Self {
-            lref,
             state,
+            unsafe_ud: UnsafeUserdata::from_ref(state, lref)
         }
     }
 
     /// Returns a borrow to the userdata.
     pub fn as_ref<T: Userdata + 'static>(&self) -> crate::Result<Ref<'a, T>> {
         unsafe {
-            self.state.ensure_stack(3)?;
-            let _g = StackGuard::new(self.state);
-            let s = self.state.state_ptr();
-
-            self.lref.push_to_lua_stack(self.state)?;
-            
-            if lua::lua_getmetatable(s, -1) == 0 {
-                return Err(crate::Error::UserdataMismatch);
-            }
-
-            self.state.get_userdata_metatable::<T>()
-                .push_to_lua_stack(self.state)?;
-
-            if lua::lua_rawequal(s, -2, -1) == 1 {
-                let cptr = lua::lua_touserdata(s, -3);
-                let cell = &*cptr.cast::<RefCell<T>>();
-                Ok(cell.borrow())
-            } else {
-                return Err(crate::Error::UserdataMismatch);
-            }
+            let cell = &*self.unsafe_ud.as_ptr_unchecked::<RefCell<T>>()?;
+            Ok(cell.borrow())
         }
     }
 
     /// Returns a mutable reference to the userdata.
     pub fn as_mut<T: Userdata + 'static>(&self) -> crate::Result<RefMut<'a, T>> {
         unsafe {
-            self.state.ensure_stack(3)?;
-            let _g = StackGuard::new(self.state);
-            let s = self.state.state_ptr();
-
-            self.lref.push_to_lua_stack(self.state)?;
-            
-            if lua::lua_getmetatable(s, -1) == 0 {
-                return Err(crate::Error::MissingMetatable);
-            }
-
-            self.state.get_userdata_metatable::<T>()
-                .push_to_lua_stack(self.state)?;
-
-            if lua::lua_rawequal(s, -2, -1) == 1 {
-                let cptr = lua::lua_touserdata(s, -3);
-                let cell = &*cptr.cast::<RefCell<T>>();
-                Ok(cell.borrow_mut())
-            } else {
-                Err(crate::Error::UserdataMismatch)
-            }
+            let cell = &*self.unsafe_ud.as_ptr_unchecked::<RefCell<T>>()?;
+            Ok(cell.borrow_mut())
         }
     }
 
@@ -317,14 +330,8 @@ impl<'a> AnyUserdata<'a> {
     /// If there is a possibility that these types do not match, use [`AnyUserdata::as_ptr`]
     /// which does verify the types.
     pub unsafe fn as_ptr_unchecked<T: Userdata + 'static>(&self) -> crate::Result<*mut RefCell<T>> {
-        self.state.ensure_stack(1)?;
-        let _g = StackGuard::new(self.state);
-        let s = self.state.state_ptr();
-
-        self.lref.push_to_lua_stack(self.state)?;
-        let cptr = lua::lua_touserdata(s, -3);
-
-        Ok(cptr.cast())
+        let cell = self.unsafe_ud.as_ptr_unchecked::<RefCell<T>>()?;
+        Ok(cell)
     }
 
     /// Returns a mutable pointer of the [`RefCell`] storing the userdata.
@@ -335,7 +342,7 @@ impl<'a> AnyUserdata<'a> {
         let _g = StackGuard::new(self.state);
         let s = self.state.state_ptr();
 
-        self.lref.push_to_lua_stack(self.state)?;
+        self.unsafe_ud.lref.push_to_lua_stack(self.state)?;
         
         if lua::lua_getmetatable(s, -1) == 0 {
             return Err(crate::Error::MissingMetatable);
@@ -345,8 +352,9 @@ impl<'a> AnyUserdata<'a> {
             .push_to_lua_stack(self.state)?;
 
         if lua::lua_rawequal(s, -2, -1) == 1 {
-            let cptr = lua::lua_touserdata(s, -3);
-            Ok(cptr.cast())
+            drop(_g);
+            let cell = self.unsafe_ud.as_ptr_unchecked::<RefCell<T>>()?;
+            Ok(cell)
         } else {
             Err(crate::Error::UserdataMismatch)
         }
@@ -358,7 +366,7 @@ impl<'a> AnyUserdata<'a> {
             self.state.ensure_stack(3)?;
             let _g = StackGuard::new(self.state);
 
-            self.lref.push_to_lua_stack(self.state)?;
+            self.unsafe_ud.lref.push_to_lua_stack(self.state)?;
             let s = self.state.state_ptr();
 
             if lua::lua_getmetatable(s, -1) == 0 {
@@ -378,6 +386,69 @@ impl<'a> AnyUserdata<'a> {
             Ok(cstr.to_string())
         }
     }
+
+    /// Returns the metatable of this userdata
+    pub fn get_metatable(&self) -> crate::Result<Table<'a>> {
+        unsafe {
+            self.state.ensure_stack(2)?;
+            let _g = StackGuard::new(self.state);
+
+            self.unsafe_ud.lref.push_to_lua_stack(self.state)?;
+            let s = self.state.state_ptr();
+
+            if lua::lua_getmetatable(s, -1) == 0 {
+                Err(crate::Error::MissingMetatable)
+            } else {
+                Ok(Table::from_lua_stack(self.state)?)
+            }
+        }
+    }
+
+    /// Gets something from the userdata.
+    /// 
+    /// Will trigger a call to the `__index` metamethod. Use [`AnyUserdata::raw_get`] if you
+    /// don't want to call it.
+    pub fn get<K, V>(&'a self, key: K) -> crate::Result<V>
+    where
+        K: AsLua<'a>,
+        V: FromLua<'a>,
+    {
+        let mt = self.get_metatable()?;
+        mt.get::<K, V>(key)
+    }
+
+    /// Gets something from the userdata. Will **not** trigger a call to the `__index` metamethod.
+    pub fn raw_get<K, V>(&'a self, key: K) -> crate::Result<V>
+    where
+        K: AsLua<'a>,
+        V: FromLua<'a>,
+    {
+        let mt = self.get_metatable()?;
+        mt.raw_get::<K, V>(key)
+    }
+
+    /// Execute a method on this userdata. This finds a function with `name` and executes it
+    /// with the userdata as the first argument.
+    pub fn execute_method<A, R>(&self, name: &str, args: A) -> crate::Result<R>
+    where
+        A: IntoLuaVec<'a>,
+        R: FromLua<'a>,
+    {
+        //let s: &Self = unsafe { mem::transmute(self) };
+        let name = name.to_string();
+        let mt = self.get_metatable()?;
+        let f = mt.get::<_, Function>(name)?;
+
+        let mut args = args.into_lua_value_vec(self.state)?;
+        args.push_front(self.clone().as_lua(self.state)?);
+
+        f.exec(args)
+    }
+
+    /// Trigger garbage collection on the userdata.
+    pub fn garbage_collect(self) -> crate::Result<()> {
+        self.execute_method("__gc", ()).into()
+    }
 }
 
 impl<'a> FromLuaStack<'a> for AnyUserdata<'a> {
@@ -385,15 +456,15 @@ impl<'a> FromLuaStack<'a> for AnyUserdata<'a> {
         ensure_type(state, lua::LUA_TUSERDATA, -1)?;
 
         Ok(AnyUserdata {
-            lref: LuaRef::from_stack(state)?,
             state,
+            unsafe_ud: UnsafeUserdata::from_lua_stack(state)?,
         })
     }
 }
 
 impl<'a> PushToLuaStack<'a> for AnyUserdata<'a> {
     unsafe fn push_to_lua_stack(&self, state: &'a State) -> crate::Result<()> {
-        self.lref.push_to_lua_stack(state)
+        self.unsafe_ud.lref.push_to_lua_stack(state)
     }
 }
 
diff --git a/src/userdata/unsafe_ud.rs b/src/userdata/unsafe_ud.rs
new file mode 100755
index 0000000..e067bd6
--- /dev/null
+++ b/src/userdata/unsafe_ud.rs
@@ -0,0 +1,180 @@
+use std::ffi::CStr;
+
+use crate::{ensure_type, FromLuaStack, LuaRef, PushToLuaStack, StackGuard, State, Userdata};
+
+use mlua_sys as lua;
+
+pub struct UnsafeUserdata<'a> {
+    pub(crate) lref: LuaRef<'a>,
+    state: &'a State,
+}
+
+impl<'a> Clone for UnsafeUserdata<'a> {
+    fn clone(&self) -> Self {
+        Self {
+            lref: self.lref.clone(),
+            state: self.state,
+        }
+    }
+}
+
+impl<'a> UnsafeUserdata<'a> {
+    pub fn from_ref(state: &'a State, lref: LuaRef<'a>) -> Self {
+        Self {
+            lref,
+            state,
+        }
+    }
+
+    /// Returns a borrow to the userdata.
+    pub fn as_ref<T: Userdata + 'static>(&self) -> crate::Result<&'a T> {
+        unsafe {
+            self.state.ensure_stack(3)?;
+            let _g = StackGuard::new(self.state);
+            let s = self.state.state_ptr();
+
+            self.lref.push_to_lua_stack(self.state)?;
+            
+            if lua::lua_getmetatable(s, -1) == 0 {
+                return Err(crate::Error::UserdataMismatch);
+            }
+
+            self.state.get_userdata_metatable::<T>()
+                .push_to_lua_stack(self.state)?;
+
+            if lua::lua_rawequal(s, -2, -1) == 1 {
+                let cptr = lua::lua_touserdata(s, -3);
+                let t = &*cptr.cast::<T>();
+                Ok(t)
+            } else {
+                return Err(crate::Error::UserdataMismatch);
+            }
+        }
+    }
+
+    /// Returns a mutable reference to the userdata.
+    pub fn as_mut<T: Userdata + 'static>(&self) -> crate::Result<&'a mut T> {
+        unsafe {
+            self.state.ensure_stack(3)?;
+            let _g = StackGuard::new(self.state);
+            let s = self.state.state_ptr();
+
+            self.lref.push_to_lua_stack(self.state)?;
+            
+            if lua::lua_getmetatable(s, -1) == 0 {
+                return Err(crate::Error::MissingMetatable);
+            }
+
+            self.state.get_userdata_metatable::<T>()
+                .push_to_lua_stack(self.state)?;
+
+            if lua::lua_rawequal(s, -2, -1) == 1 {
+                let cptr = lua::lua_touserdata(s, -3);
+                let t = &mut *cptr.cast::<T>();
+                Ok(t)
+            } else {
+                Err(crate::Error::UserdataMismatch)
+            }
+        }
+    }
+
+    /// Returns a mutable pointer of the [`RefCell`] of userdata **WITHOUT verifying the type of it**.
+    /// 
+    /// # Safety
+    /// * You must be certain that the type `T` is the same type that this userdata has a handle to.
+    ///   There is a blind cast from `void*` to `T*`
+    /// 
+    /// If there is a possibility that these types do not match, use [`UnsafeUserdata::as_ptr`]
+    /// which does verify the types.
+    pub unsafe fn as_ptr_unchecked<T>(&self) -> crate::Result<*mut T> {
+        self.state.ensure_stack(1)?;
+        let _g = StackGuard::new(self.state);
+        let s = self.state.state_ptr();
+
+        self.lref.push_to_lua_stack(self.state)?;
+        let cptr = lua::lua_touserdata(s, -1);
+
+        Ok(cptr.cast())
+    }
+
+    /// Returns a mutable pointer of the data stored.
+    /// 
+    /// This function ensures that the type of the userdata this struct has a handle to is the
+    /// same as `T`. If it isn't, a `UserdataMismatch` error will be returned.
+    pub unsafe fn as_ptr<T: Userdata + 'static>(&self) -> crate::Result<*mut T> {
+        let _g = StackGuard::new(self.state);
+        let s = self.state.state_ptr();
+
+        self.lref.push_to_lua_stack(self.state)?;
+        
+        if lua::lua_getmetatable(s, -1) == 0 {
+            return Err(crate::Error::MissingMetatable);
+        }
+
+        self.state.get_userdata_metatable::<T>()
+            .push_to_lua_stack(self.state)?;
+
+        if lua::lua_rawequal(s, -2, -1) == 1 {
+            let cptr = lua::lua_touserdata(s, -3);
+            Ok(cptr.cast())
+        } else {
+            Err(crate::Error::UserdataMismatch)
+        }
+    }
+
+    /// Returns the name of the userdata by accessing the metatable
+    pub fn name(&self) -> crate::Result<String> {
+        unsafe {
+            self.state.ensure_stack(3)?;
+            let _g = StackGuard::new(self.state);
+
+            self.lref.push_to_lua_stack(self.state)?;
+            let s = self.state.state_ptr();
+
+            if lua::lua_getmetatable(s, -1) == 0 {
+                return Err(crate::Error::MissingMetatable);
+            }
+
+            lua::lua_pushliteral(s, "__name");
+            lua::lua_rawget(s, -2);
+            
+            ensure_type(self.state, lua::LUA_TSTRING, -1)?;
+
+            let cstr = CStr::from_ptr(lua::lua_tostring(s, -1));
+            let cstr = cstr.to_str()
+                // on panic, this should be considered a bug
+                .expect("Metatable name has invalid utf8 bytes!");
+
+            Ok(cstr.to_string())
+        }
+    }
+}
+
+impl<'a> FromLuaStack<'a> for UnsafeUserdata<'a> {
+    unsafe fn from_lua_stack(state: &'a State) -> crate::Result<Self> {
+        ensure_type(state, lua::LUA_TUSERDATA, -1)?;
+
+        Ok(UnsafeUserdata {
+            lref: LuaRef::from_stack(state)?,
+            state,
+        })
+    }
+}
+
+impl<'a> PushToLuaStack<'a> for UnsafeUserdata<'a> {
+    unsafe fn push_to_lua_stack(&self, state: &'a State) -> crate::Result<()> {
+        self.lref.push_to_lua_stack(state)
+    }
+}
+
+/* impl<'a> AsLua<'a> for UnsafeUserdata<'a> {
+    fn as_lua(&self, _lua: &'a State) -> crate::Result<Value<'a>> {
+        Ok(Value::Userdata(self.clone()))
+    }
+}
+
+impl<'a> FromLua<'a> for UnsafeUserdata<'a> {
+    fn from_lua(_lua: &State, val: Value<'a>) -> crate::Result<Self> {
+        val.into_userdata()
+    }
+} */
\ No newline at end of file
diff --git a/src/value.rs b/src/value.rs
index 4258529..6d97ba8 100755
--- a/src/value.rs
+++ b/src/value.rs
@@ -36,7 +36,7 @@ impl<'a> Value<'a> {
         }
     }
 
-    pub fn as_userdata(&self) -> crate::Result<&AnyUserdata> {
+    pub fn as_userdata(&self) -> crate::Result<&AnyUserdata<'a>> {
         match self {
             Value::Userdata(ud) => Ok(ud),
             _ => {
@@ -74,10 +74,28 @@ impl<'a> Value<'a> {
             }
         }
     }
+
+    pub fn into_table(self) -> crate::Result<Table<'a>> {
+        match self {
+            Value::Table(v) => Ok(v),
+            _ => {
+                Err(crate::Error::UnexpectedType("Table".to_string(), self.type_name().to_string()))
+            }
+        }
+    }
+
+    pub fn into_function(self) -> crate::Result<Function<'a>> {
+        match self {
+            Value::Function(v) => Ok(v),
+            _ => {
+                Err(crate::Error::UnexpectedType("Function".to_string(), self.type_name().to_string()))
+            }
+        }
+    }
 }
 
 impl<'a> PushToLuaStack<'a> for Value<'a> {
-    unsafe fn push_to_lua_stack(&self, state: &crate::State) -> crate::Result<()> {
+    unsafe fn push_to_lua_stack(&self, state: &'a crate::State) -> crate::Result<()> {
         let s = state.state_ptr();
 
         match self {
@@ -304,6 +322,16 @@ impl<'a> FromLuaVec<'a> for ValueVec<'a> {
     }
 }
 
+impl<'a> PushToLuaStack<'a> for ValueVec<'a> {
+    unsafe fn push_to_lua_stack(&self, state: &'a State) -> crate::Result<()> {
+        for v in self.iter() {
+            v.push_to_lua_stack(state)?;
+        }
+
+        Ok(())
+    }
+}
+
 impl<'a, T: FromLua<'a>> FromLuaVec<'a> for T {
     fn from_lua_value_vec(state: &'a State, mut values: ValueVec<'a>) -> crate::Result<Self> {
         if let Some(val) = values.pop_front() {
@@ -317,6 +345,12 @@ impl<'a, T: FromLua<'a>> FromLuaVec<'a> for T {
     }
 }
 
+impl<'a> IntoLuaVec<'a> for () {
+    fn into_lua_value_vec(self, _state: &'a State) -> crate::Result<ValueVec<'a>> {
+        Ok(ValueVec::new())
+    }
+}
+
 macro_rules! impl_from_lua_vec_tuple {
     ( $count: expr, $first: tt, $( $name: tt ),+ ) => (
         #[allow(non_snake_case)]