Code cleanup, separate things to other source files

Cargo.lock

@@ -17,16 +17,6 @@ version = "1.0.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "baf1de4339761588bc0619e3cbc0120ee582ebb74b53b4efbf79117bd2da40fd"
 
-[[package]]
-name = "cstr"
-version = "0.2.11"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "8aa998c33a6d3271e3678950a22134cd7dd27cef86dee1b611b5b14207d1d90b"
-dependencies = [
- "proc-macro2",
- "quote",
-]
-
 [[package]]
 name = "libc"
 version = "0.2.152"
@@ -37,7 +27,6 @@ checksum = "13e3bf6590cbc649f4d1a3eefc9d5d6eb746f5200ffb04e5e142700b8faa56e7"
 name = "lua-ffi"
 version = "0.1.0"
 dependencies = [
- "cstr",
  "mlua-sys",
  "thiserror",
 ]

Cargo.toml

@@ -6,6 +6,5 @@ edition = "2021"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
-cstr = "0.2.11"
 mlua-sys = { version = "0.5.0", features = ["lua54"] }
 thiserror = "1.0.56"

src/lib.rs

@@ -0,0 +1,200 @@
+use mlua_sys as lua;
+
+pub mod state;
+use state::*;
+
+pub mod table;
+use table::*;
+
+pub mod function;
+use function::*;
+
+pub mod value;
+use value::*;
+
+pub mod guard;
+use guard::*;
+
+pub mod userdata;
+use userdata::*;
+
+pub mod util;
+use util::*;
+
+pub mod chunk;
+use chunk::*;
+
+pub mod error;
+use error::*;
+
+pub mod lref;
+use lref::*;
+
+#[cfg(test)]
+pub mod tests;
+
+/* fn main() -> Result<()> {
+    let lua = State::new();
+    lua.expose_libraries(&[StdLibrary::Debug, StdLibrary::Package]);
+
+    let globals = lua.globals()?;
+
+    let v1 = RefCell::new(Vec2 { x: 50.0, y: 5.0 });
+    let ud = lua.create_userdata(UserdataRef::from(v1.borrow()))?;
+    globals.set("v1", ud)?;
+
+    let v2 = Vec2 { x: 10.0, y: 15.0 };
+    let ud = lua.create_userdata(UserdataRef::from(&v2))?;
+    globals.set("v2", ud)?;
+
+    //lua.gc_stop()?;
+    let chunk = lua.load(
+        "text.lua",
+        r#"
+        require "util"
+
+        --if vec2 ~= nil then
+        print("v1: (" .. v1.x .. ", " .. v1.y .. ")")
+        --print("v2: (" .. v2.x .. ", " .. v2.y .. ")")
+        --end
+
+        --print("vec2.x = " .. vec2.x)
+        --print("vec2.y = " .. vec2.y)
+    "#,
+    )?;
+
+    const MAX_RUNS: i32 = 400;
+    for i in 0..MAX_RUNS {
+        // 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);
+        }
+        
+        //print_refs(&lua).unwrap();
+        println!("i = {}", i);
+        globals.set("v1", Value::Nil)?;
+        lua.gc_collect()?;
+
+        let mut t = v1.borrow_mut();
+        t.x += 50.0;
+        t.y += 5.0;
+        drop(t); 
+
+        let ud = lua.create_userdata(UserdataRef::from(v1.borrow()))?;
+        globals.raw_set("v1", ud)?;
+    }
+
+    unsafe {
+        assert_eq!(lua::lua_gettop(lua.state_ptr()), 0); // ensure that nothing is left on the stack
+    }
+
+    Ok(())
+} */
+
+pub trait PushToLuaStack<'a> {
+    unsafe fn push_to_lua_stack(&self, state: &'a State) -> Result<()>;
+}
+
+pub trait FromLuaStack<'a>: Sized {
+    unsafe fn from_lua_stack(state: &'a State) -> Result<Self>;
+}
+
+impl<'a> PushToLuaStack<'a> for () {
+    unsafe fn push_to_lua_stack(&self, _state: &'a State) -> Result<()> {
+        Ok(())
+    }
+}
+
+impl<'a, T: PushToLuaStack<'a>> PushToLuaStack<'a> for Option<T> {
+    unsafe fn push_to_lua_stack(&self, state: &'a State) -> Result<()> {
+        if let Some(v) = self {
+            v.push_to_lua_stack(state)?;
+        } else {
+            unsafe {
+                lua::lua_pushnil(state.state_ptr());
+            }
+        }
+
+        Ok(())
+    }
+}
+
+/// Implements PushToLuaStack for a number
+macro_rules! impl_as_lua_number {
+    ($ty: ident) => {
+        impl<'a> AsLua<'a> for $ty {
+            fn as_lua(&self, _lua: &'a State) -> crate::Result<Value<'a>> {
+                Ok(Value::Number(*self as f64))
+            }
+        }
+
+        impl<'a> FromLua<'a> for $ty {
+            fn from_lua(_lua: &State, val: Value) -> crate::Result<Self> {
+                match val {
+                    Value::Number(v) => Ok(v as $ty),
+                    _ => Err(Error::UnexpectedType(
+                        "Number".to_string(),
+                        val.type_name().to_string(),
+                    )),
+                }
+            }
+        }
+
+        impl<'a> PushToLuaStack<'a> for $ty {
+            unsafe fn push_to_lua_stack(&self, state: &'a State) -> crate::Result<()> {
+                let v = self.as_lua(state)?;
+                v.push_to_lua_stack(state)
+            }
+        }
+    };
+}
+
+impl_as_lua_number!(i8);
+impl_as_lua_number!(i16);
+impl_as_lua_number!(i32);
+impl_as_lua_number!(i64);
+
+impl_as_lua_number!(u8);
+impl_as_lua_number!(u16);
+impl_as_lua_number!(u32);
+impl_as_lua_number!(u64);
+
+impl_as_lua_number!(f32);
+impl_as_lua_number!(f64);
+
+impl<'a> PushToLuaStack<'a> for String {
+    unsafe fn push_to_lua_stack(&self, state: &State) -> Result<()> {
+        state.ensure_stack(1)?;
+
+        self.as_str()
+            .push_to_lua_stack(state)?;
+
+        Ok(())
+    }
+}
+
+impl<'a> FromLua<'a> for String {
+    fn from_lua(_lua: &State, val: Value) -> crate::Result<Self> {
+        val.as_string().cloned()
+    }
+}
+
+impl<'a> PushToLuaStack<'a> for &str {
+    unsafe fn push_to_lua_stack(&self, state: &State) -> Result<()> {
+        state.ensure_stack(1)?;
+
+        let s = format!("{}\0", self);
+        let cstr = s.as_ptr() as *const i8;
+        // lua copies the string, so its okay if the string pointer is dropped
+        lua::lua_pushstring(state.state_ptr(), cstr);
+
+        Ok(())
+    }
+}

src/lref.rs

@@ -0,0 +1,65 @@
+use std::sync::Arc;
+
+use crate::{Error, PushToLuaStack, Result, State};
+
+use mlua_sys as lua;
+
+/// A LuaRef is a a handle to something in Lua.
+///
+/// These are created with `luaL_ref`, they can be created from anything on the top of the stack
+/// with [`LuaRef::from_stack`]. The references are automatically freed with `luaL_unref` when
+/// the inner Arc detects a single strong count.
+#[derive(Clone)]
+pub struct LuaRef<'a> {
+    lref: Arc<i32>,
+    state: &'a State,
+}
+
+impl<'a> Drop for LuaRef<'a> {
+    fn drop(&mut self) {
+        unsafe {
+            let s = self.state.state_ptr();
+
+            if Arc::strong_count(&self.lref) == 1 {
+                lua::luaL_unref(s, lua::LUA_REGISTRYINDEX, *self.lref);
+            }
+        }
+    }
+}
+
+impl<'a> LuaRef<'a> {
+    pub fn new(lua_ref: i32, state: &'a State) -> Self {
+        Self {
+            lref: Arc::new(lua_ref),
+            state,
+        }
+    }
+
+    /// Creates a reference to what is at the top of the stack.
+    pub unsafe fn from_stack(state: &'a State) -> Result<Self> {
+        let s = state.state_ptr();
+        let r = lua::luaL_ref(s, lua::LUA_REGISTRYINDEX);
+        if r == lua::LUA_REFNIL {
+            Err(Error::Nil)
+        } else {
+            Ok(LuaRef::new(r, state))
+        } 
+    }
+}
+
+impl<'a> PushToLuaStack<'a> for LuaRef<'a> {
+    unsafe fn push_to_lua_stack(&self, state: &State) -> Result<()> {
+        let s = state.state_ptr();
+
+        state.ensure_stack(1)?;
+        let top = lua::lua_gettop(s);
+        let ty = lua::lua_rawgeti(s, lua::LUA_REGISTRYINDEX, *self.lref as i64);
+        let new_top = lua::lua_gettop(s);
+
+        if ty == lua::LUA_TNIL || ty == lua::LUA_TNONE || top == new_top {
+            return Err(Error::Nil);
+        }
+
+        Ok(())
+    }
+}

src/main.rs

@@ -1,463 +0,0 @@
-use std::{
-    cell::{Ref, RefCell}, ffi::CStr, marker::PhantomData, mem, ops::Deref, sync::Arc
-};
-
-use mlua_sys as lua;
-
-pub mod state;
-use state::*;
-
-pub mod table;
-use table::*;
-
-pub mod function;
-use function::*;
-
-pub mod value;
-use value::*;
-
-pub mod guard;
-use guard::*;
-
-pub mod userdata;
-use userdata::*;
-
-pub mod util;
-use util::*;
-
-pub mod chunk;
-use chunk::*;
-
-pub mod error;
-use error::*;
-
-fn main() -> Result<()> {
-    let lua = State::new();
-    lua.expose_libraries(&[StdLibrary::Debug, StdLibrary::Package]);
-
-    let globals = lua.globals()?;
-
-    let v1 = RefCell::new(Vec2 { x: 50.0, y: 5.0 });
-    let ud = lua.create_userdata(UserdataRef::from(v1.borrow()))?;
-    globals.set("v1", ud)?;
-
-    let v2 = Vec2 { x: 10.0, y: 15.0 };
-    let ud = lua.create_userdata(UserdataRef::from(&v2))?;
-    globals.set("v2", ud)?;
-
-    //lua.gc_stop()?;
-    let chunk = lua.load(
-        "text.lua",
-        r#"
-        require "util"
-
-        --if vec2 ~= nil then
-        print("v1: (" .. v1.x .. ", " .. v1.y .. ")")
-        --print("v2: (" .. v2.x .. ", " .. v2.y .. ")")
-        --end
-
-        --print("vec2.x = " .. vec2.x)
-        --print("vec2.y = " .. vec2.y)
-    "#,
-    )?;
-
-    const MAX_RUNS: i32 = 400;
-    for i in 0..MAX_RUNS {
-        // 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);
-        }
-        
-        //print_refs(&lua).unwrap();
-        println!("i = {}", i);
-        globals.set("v1", Value::Nil)?;
-        lua.gc_collect()?;
-
-        let mut t = v1.borrow_mut();
-        t.x += 50.0;
-        t.y += 5.0;
-        drop(t); 
-
-        let ud = lua.create_userdata(UserdataRef::from(v1.borrow()))?;
-        globals.raw_set("v1", ud)?;
-    }
-
-    unsafe {
-        assert_eq!(lua::lua_gettop(lua.state_ptr()), 0); // ensure that nothing is left on the stack
-    }
-
-    Ok(())
-}
-
-/// Prints the types of the registry
-pub fn print_refs(lua: &State) -> Result<()> {
-    unsafe {
-        let _g = StackGuard::new(&lua);
-        let s = lua.state_ptr();
-
-        Value::String(String::from("Hello World")).push_to_lua_stack(&lua)?;
-        let r = lua::luaL_ref(s, lua::LUA_REGISTRYINDEX);
-        
-        for i in 0..r {
-            let ty = lua::lua_rawgeti(s, lua::LUA_REGISTRYINDEX, i as i64);
-            
-            match ty {
-                lua::LUA_TUSERDATA => {
-                    lua::lua_getmetatable(s, -1);
-                    lua::lua_pushliteral(s, "__name");
-                    lua::lua_rawget(s, -2);
-                    
-                    let v = Value::from_lua_stack(&lua)?;
-                    println!("{}: {}", i, v.as_string().unwrap());
-                },
-                _ => {
-                    let tyname = CStr::from_ptr(lua::lua_typename(s, ty));
-                    let tyname = tyname.to_str().unwrap();
-                    println!("{}: {}", i, tyname);
-                }
-            }
-            
-            lua::lua_pop(s, 1);
-        }
-        lua::luaL_unref(s, lua::LUA_REGISTRYINDEX, r);
-    }
-    Ok(())
-}
-
-/// A LuaRef is a a handle to something in Lua.
-///
-/// These are created with `luaL_ref`, they can be created from anything on the top of the stack
-/// with [`LuaRef::from_stack`]. The references are automatically freed with `luaL_unref` when
-/// the inner Arc detects a single strong count.
-#[derive(Clone)]
-pub struct LuaRef<'a> {
-    lref: Arc<i32>,
-    state: &'a State,
-}
-
-impl<'a> Drop for LuaRef<'a> {
-    fn drop(&mut self) {
-        unsafe {
-            let s = self.state.state_ptr();
-
-            if Arc::strong_count(&self.lref) == 1 {
-                lua::luaL_unref(s, lua::LUA_REGISTRYINDEX, *self.lref);
-            }
-        }
-    }
-}
-
-impl<'a> LuaRef<'a> {
-    pub fn new(lua_ref: i32, state: &'a State) -> Self {
-        Self {
-            lref: Arc::new(lua_ref),
-            state,
-        }
-    }
-
-    /// Creates a reference to what is at the top of the stack.
-    pub unsafe fn from_stack(state: &'a State) -> Result<Self> {
-        let s = state.state_ptr();
-        let r = lua::luaL_ref(s, lua::LUA_REGISTRYINDEX);
-        if r == lua::LUA_REFNIL {
-            Err(Error::Nil)
-        } else {
-            Ok(LuaRef::new(r, state))
-        } 
-    }
-}
-
-impl<'a> PushToLuaStack<'a> for LuaRef<'a> {
-    unsafe fn push_to_lua_stack(&self, state: &State) -> Result<()> {
-        let s = state.state_ptr();
-
-        state.ensure_stack(1)?;
-        let top = lua::lua_gettop(s);
-        let ty = lua::lua_rawgeti(s, lua::LUA_REGISTRYINDEX, *self.lref as i64);
-        let new_top = lua::lua_gettop(s);
-
-        if ty == lua::LUA_TNIL || ty == lua::LUA_TNONE || top == new_top {
-            return Err(Error::Nil);
-        }
-
-        Ok(())
-    }
-}
-
-pub trait PushToLuaStack<'a> {
-    unsafe fn push_to_lua_stack(&self, state: &'a State) -> Result<()>;
-}
-
-pub trait FromLuaStack<'a>: Sized {
-    unsafe fn from_lua_stack(state: &'a State) -> Result<Self>;
-}
-
-impl<'a> PushToLuaStack<'a> for () {
-    unsafe fn push_to_lua_stack(&self, _state: &'a State) -> Result<()> {
-        Ok(())
-    }
-}
-
-impl<'a, T: PushToLuaStack<'a>> PushToLuaStack<'a> for Option<T> {
-    unsafe fn push_to_lua_stack(&self, state: &'a State) -> Result<()> {
-        if let Some(v) = self {
-            v.push_to_lua_stack(state)?;
-        } else {
-            unsafe {
-                lua::lua_pushnil(state.state_ptr());
-            }
-        }
-
-        Ok(())
-    }
-}
-
-/// Implements PushToLuaStack for a number
-macro_rules! impl_as_lua_number {
-    ($ty: ident) => {
-        impl<'a> AsLua<'a> for $ty {
-            fn as_lua(&self, _lua: &'a State) -> crate::Result<Value<'a>> {
-                Ok(Value::Number(*self as f64))
-            }
-        }
-
-        impl<'a> FromLua<'a> for $ty {
-            fn from_lua(_lua: &State, val: Value) -> crate::Result<Self> {
-                match val {
-                    Value::Number(v) => Ok(v as $ty),
-                    _ => Err(Error::UnexpectedType(
-                        "Number".to_string(),
-                        val.type_name().to_string(),
-                    )),
-                }
-            }
-        }
-
-        impl<'a> PushToLuaStack<'a> for $ty {
-            unsafe fn push_to_lua_stack(&self, state: &'a State) -> crate::Result<()> {
-                let v = self.as_lua(state)?;
-                v.push_to_lua_stack(state)
-            }
-        }
-    };
-}
-
-impl_as_lua_number!(i8);
-impl_as_lua_number!(i16);
-impl_as_lua_number!(i32);
-impl_as_lua_number!(i64);
-
-impl_as_lua_number!(u8);
-impl_as_lua_number!(u16);
-impl_as_lua_number!(u32);
-impl_as_lua_number!(u64);
-
-impl_as_lua_number!(f32);
-impl_as_lua_number!(f64);
-
-impl<'a> PushToLuaStack<'a> for String {
-    unsafe fn push_to_lua_stack(&self, state: &State) -> Result<()> {
-        state.ensure_stack(1)?;
-
-        let s = format!("{}\0", self);
-        let cstr = s.as_ptr() as *const i8;
-        lua::lua_pushstring(state.state_ptr(), cstr);
-
-        Ok(())
-    }
-}
-
-impl<'a> FromLua<'a> for String {
-    fn from_lua(_lua: &State, val: Value) -> crate::Result<Self> {
-        val.as_string().cloned()
-    }
-}
-
-impl<'a> PushToLuaStack<'a> for &str {
-    unsafe fn push_to_lua_stack(&self, state: &State) -> Result<()> {
-        state.ensure_stack(1)?;
-
-        let s = format!("{}\0", self);
-        let cstr = s.as_ptr() as *const i8;
-        lua::lua_pushstring(state.state_ptr(), cstr);
-
-        Ok(())
-    }
-}
-
-#[allow(dead_code)]
-pub struct Vec3 {
-    x: f32,
-    y: f32,
-    z: f32,
-}
-
-impl Userdata for Vec3 {
-    fn build<'a>(_state: &State, _builder: &mut UserdataBuilder<'a, Self>) -> crate::Result<()> {
-        todo!()
-    }
-
-    fn name() -> String {
-        todo!()
-    }
-}
-
-pub struct Vec2 {
-    x: f32,
-    y: f32,
-}
-
-impl Userdata for Vec2 {
-    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))
-            .field_setter("x", |_, this, x: f32| this.x = x)
-            .field_setter("y", |_, this, y: f32| this.y = y)
-            .function("new", |lua, (x, y)| lua.create_userdata(Vec2 { x, y }))
-            // method test
-            .method("add", |lua, lhs: &Vec2, (rhs,): (Ref<Vec3>,)| {
-                let lx = lhs.x;
-                let ly = lhs.y;
-
-                let rx = rhs.x;
-                let ry = rhs.y;
-
-                lua.create_userdata(Vec2 {
-                    x: lx + rx,
-                    y: ly + ry,
-                })
-            })
-            .meta_method(MetaMethod::Add, |lua, lhs: &Vec2, (rhs,): (Ref<Vec2>,)| {
-                let lx = lhs.x;
-                let ly = lhs.y;
-
-                let rx = rhs.x;
-                let ry = rhs.y;
-
-                lua.create_userdata(Vec2 {
-                    x: lx + rx,
-                    y: ly + ry,
-                })
-            });
-
-        Ok(())
-    }
-
-    fn name() -> String {
-        "Vec2".to_string()
-    }
-}
-
-pub struct UserdataProxy<T: Userdata>(PhantomData<T>);
-
-impl<T: Userdata> UserdataProxy<T> {
-    pub fn new() -> Self {
-        Self(PhantomData)
-    }
-}
-
-impl<'a, T: Userdata> AsLua<'a> for UserdataProxy<T> {
-    fn as_lua(&self, _lua: &'a State) -> crate::Result<Value<'a>> {
-        todo!()
-    }
-}
-
-impl<T: Userdata> Userdata for UserdataProxy<T> {
-    fn build<'a>(state: &State, builder: &mut UserdataBuilder<'a, Self>) -> crate::Result<()> {
-        let mut other = UserdataBuilder::<T>::new();
-        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;
-
-        Ok(())
-    }
-
-    fn name() -> String {
-        let name = format!("{}Proxy", T::name());
-        name
-    }
-}
-
-pub enum Borrow<'a, T> {
-    Wrapped(Ref<'a, T>),
-    Raw(&'a T),
-}
-
-impl<'a, T> Deref for Borrow<'a, T> {
-    type Target = T;
-
-    fn deref(&self) -> &Self::Target {
-        match self {
-            Borrow::Wrapped(w) => w,
-            Borrow::Raw(w) => w,
-        }
-    }
-}
-
-pub struct UserdataRef<'a, T: Userdata> {
-    ud_ptr: Borrow<'a, T>,
-}
-
-impl<'a, T: Userdata> From<&'a T> for UserdataRef<'static, T> {
-    fn from(value: &'a T) -> Self {
-        let ud = Borrow::Raw(value);
-
-        Self {
-            ud_ptr: unsafe {
-                mem::transmute(ud)
-            }
-        }
-    }
-}
-
-impl<'a, T: Userdata> From<Ref<'a, T>> for UserdataRef<'static, T> {
-    fn from(value: Ref<'a, T>) -> Self {
-        let ud = Borrow::Wrapped(value);
-
-        Self {
-            ud_ptr: unsafe {
-                mem::transmute(ud)
-            },
-        }
-    }
-}
-
-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
-    }
-}

src/tests.rs

@@ -0,0 +1,50 @@
+use std::cell::Ref;
+
+use crate::{MetaMethod, State, Userdata, UserdataBuilder};
+
+pub struct Vec2 {
+    x: f32,
+    y: f32,
+}
+
+impl Userdata for Vec2 {
+    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))
+            .field_setter("x", |_, this, x: f32| this.x = x)
+            .field_setter("y", |_, this, y: f32| this.y = y)
+            .function("new", |lua, (x, y)| lua.create_userdata(Vec2 { x, y }))
+            // method test
+            .method("add", |lua, lhs: &Vec2, (rhs,): (Ref<Vec2>,)| {
+                let lx = lhs.x;
+                let ly = lhs.y;
+
+                let rx = rhs.x;
+                let ry = rhs.y;
+
+                lua.create_userdata(Vec2 {
+                    x: lx + rx,
+                    y: ly + ry,
+                })
+            })
+            .meta_method(MetaMethod::Add, |lua, lhs: &Vec2, (rhs,): (Ref<Vec2>,)| {
+                let lx = lhs.x;
+                let ly = lhs.y;
+
+                let rx = rhs.x;
+                let ry = rhs.y;
+
+                lua.create_userdata(Vec2 {
+                    x: lx + rx,
+                    y: ly + ry,
+                })
+            });
+
+        Ok(())
+    }
+
+    fn name() -> String {
+        "Vec2".to_string()
+    }
+}

src/userdata/borrow.rs

@@ -0,0 +1,78 @@
+use std::{cell::Ref, mem, ops::Deref};
+
+use crate::{AnyUserdata, Result, State, Userdata, UserdataBuilder};
+
+enum Borrow<'a, T> {
+    Wrapped(Ref<'a, T>),
+    Raw(&'a T),
+}
+
+impl<'a, T> Deref for Borrow<'a, T> {
+    type Target = T;
+
+    fn deref(&self) -> &Self::Target {
+        match self {
+            Borrow::Wrapped(w) => w,
+            Borrow::Raw(w) => w,
+        }
+    }
+}
+
+pub struct UserdataRef<'a, T: Userdata> {
+    borrow: Borrow<'a, T>,
+}
+
+impl<'a, T: Userdata> From<&'a T> for UserdataRef<'static, T> {
+    fn from(value: &'a T) -> Self {
+        let ud = Borrow::Raw(value);
+
+        Self {
+            borrow: unsafe {
+                mem::transmute(ud)
+            }
+        }
+    }
+}
+
+impl<'a, T: Userdata> From<Ref<'a, T>> for UserdataRef<'static, T> {
+    fn from(value: Ref<'a, T>) -> Self {
+        let ud = Borrow::Wrapped(value);
+
+        Self {
+            borrow: unsafe {
+                mem::transmute(ud)
+            },
+        }
+    }
+}
+
+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.borrow;
+                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
+    }
+}

src/userdata/mod.rs

@@ -7,6 +7,14 @@ use mlua_sys as lua;
 pub mod unsafe_ud;
 pub use unsafe_ud::*;
 
+pub mod proxy;
+#[allow(unused_imports)]
+use proxy::*;
+
+pub mod borrow;
+#[allow(unused_imports)]
+use borrow::*;
+
 /// An enum representing all Lua MetaMethods
 /// https://gist.github.com/oatmealine/655c9e64599d0f0dd47687c1186de99f
 pub enum MetaMethod {

src/userdata/proxy.rs

@@ -0,0 +1,34 @@
+use std::marker::PhantomData;
+
+use crate::{AsLua, State, Userdata, UserdataBuilder, Value};
+
+pub struct UserdataProxy<T: Userdata>(PhantomData<T>);
+
+impl<T: Userdata> UserdataProxy<T> {
+    pub fn new() -> Self {
+        Self(PhantomData)
+    }
+}
+
+impl<'a, T: Userdata> AsLua<'a> for UserdataProxy<T> {
+    fn as_lua(&self, _lua: &'a State) -> crate::Result<Value<'a>> {
+        todo!()
+    }
+}
+
+impl<T: Userdata> Userdata for UserdataProxy<T> {
+    fn build<'a>(state: &State, builder: &mut UserdataBuilder<'a, Self>) -> crate::Result<()> {
+        let mut other = UserdataBuilder::<T>::new();
+        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;
+
+        Ok(())
+    }
+
+    fn name() -> String {
+        let name = format!("{}Proxy", T::name());
+        name
+    }
+}

src/util.rs

@@ -1,10 +1,10 @@
 use std::ffi::CStr;
 
-use crate::State;
+use crate::{FromLuaStack, PushToLuaStack, StackGuard, State, Value};
 
 use mlua_sys as lua;
 
-pub unsafe fn ensure_type(state: &State, typ: i32, idx: i32) -> crate::Result<()> {
+pub(crate) unsafe fn ensure_type(state: &State, typ: i32, idx: i32) -> crate::Result<()> {
     let s = state.state_ptr();
 
     let lua_type = lua::lua_type(s, idx);
@@ -25,3 +25,39 @@ pub unsafe fn ensure_type(state: &State, typ: i32, idx: i32) -> crate::Result<()
         Err(crate::Error::UnexpectedType(exp_s.to_string(), s.to_string()))
     }
 }
+
+/// Iterates through all entries in the registry and prints the types of each entry.
+#[allow(dead_code)]
+pub(crate) fn print_registry(lua: &State) -> crate::Result<()> {
+    unsafe {
+        let _g = StackGuard::new(&lua);
+        let s = lua.state_ptr();
+
+        Value::String(String::from("Hello World")).push_to_lua_stack(&lua)?;
+        let r = lua::luaL_ref(s, lua::LUA_REGISTRYINDEX);
+        lua::luaL_unref(s, lua::LUA_REGISTRYINDEX, r);
+        
+        for i in 0..r {
+            let ty = lua::lua_rawgeti(s, lua::LUA_REGISTRYINDEX, i as i64);
+            
+            match ty {
+                lua::LUA_TUSERDATA => {
+                    lua::lua_getmetatable(s, -1);
+                    lua::lua_pushliteral(s, "__name");
+                    lua::lua_rawget(s, -2);
+                    
+                    let v = Value::from_lua_stack(&lua)?;
+                    println!("{}: {}", i, v.as_string().unwrap());
+                },
+                _ => {
+                    let tyname = CStr::from_ptr(lua::lua_typename(s, ty));
+                    let tyname = tyname.to_str().unwrap();
+                    println!("{}: {}", i, tyname);
+                }
+            }
+            
+            lua::lua_pop(s, 1);
+        }
+    }
+    Ok(())
+}