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Do not clear usevalues when taking value out of userdata.

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It has big performance penalty.
Lua GC can collect uservalues when userdata is not referenced anymore.
This commit is contained in:
Alex Orlenko 2022-10-17 02:27:41 +01:00
parent a83ee546ba
commit cd0a1d1e7c
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GPG key ID: 4C150C250863B96D
2 changed files with 15 additions and 27 deletions
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27
src/userdata.rs
View file

@ -840,39 +840,21 @@ impl<'lua> AnyUserData<'lua> {
self.inspect(|cell| cell.try_borrow_mut())
}
/// Takes out the value of `UserData` and sets the special "destructed" metatable that prevents
/// any further operations with this userdata.
/// Takes the value out of this userdata.
/// Sets the special "destructed" metatable that prevents any further operations with this userdata.
///
/// All associated user values will be also cleared.
/// Keeps associated user values unchanged (they will be collected by Lua's GC).
pub fn take<T: 'static + UserData>(&self) -> Result<T> {
let lua = self.0.lua;
unsafe {
let _sg = StackGuard::new(lua.state);
check_stack(lua.state, 3)?;
check_stack(lua.state, 2)?;
let type_id = lua.push_userdata_ref(&self.0)?;
match type_id {
Some(type_id) if type_id == TypeId::of::<T>() => {
// Try to borrow userdata exclusively
let _ = (*get_userdata::<UserDataCell<T>>(lua.state, -1)).try_borrow_mut()?;
// Clear associated user values
#[cfg(feature = "lua54")]
for i in 1..=USER_VALUE_MAXSLOT {
ffi::lua_pushnil(lua.state);
ffi::lua_setiuservalue(lua.state, -2, i as c_int);
}
#[cfg(any(feature = "lua53", feature = "lua52", feature = "luau"))]
{
ffi::lua_pushnil(lua.state);
ffi::lua_setuservalue(lua.state, -2);
}
#[cfg(any(feature = "lua51", feature = "luajit"))]
protect_lua!(lua.state, 1, 1, fn(state) {
ffi::lua_newtable(state);
ffi::lua_setuservalue(state, -2);
})?;
Ok(take_userdata::<UserDataCell<T>>(lua.state).into_inner())
}
_ => Err(Error::UserDataTypeMismatch),
@ -1083,6 +1065,7 @@ impl<'lua> AnyUserData<'lua> {
/// For `T: UserData + 'static` returned metatable is shared among all instances of type `T`.
///
/// [`UserDataMetatable`]: crate::UserDataMetatable
#[inline]
pub fn get_metatable(&self) -> Result<UserDataMetatable<'lua>> {
self.get_raw_metatable().map(UserDataMetatable)
}

15
tests/userdata.rs
View file

@ -305,21 +305,19 @@ fn test_userdata_take() -> Result<()> {
fn check_userdata_take(lua: &Lua, userdata: AnyUserData, rc: Arc<i64>) -> Result<()> {
lua.globals().set("userdata", userdata.clone())?;
assert_eq!(Arc::strong_count(&rc), 3);
let userdata_copy = userdata.clone();
{
let _value = userdata.borrow::<MyUserdata>()?;
// We should not be able to take userdata if it's borrowed
match userdata_copy.take::<MyUserdata>() {
match userdata.take::<MyUserdata>() {
Err(Error::UserDataBorrowMutError) => {}
r => panic!("expected `UserDataBorrowMutError` error, got {:?}", r),
}
}
let value = userdata_copy.take::<MyUserdata>()?;
let value = userdata.take::<MyUserdata>()?;
assert_eq!(*value.0, 18);
drop(value);
lua.gc_collect()?;
assert_eq!(Arc::strong_count(&rc), 1);
assert_eq!(Arc::strong_count(&rc), 2);
match userdata.borrow::<MyUserdata>() {
Err(Error::UserDataDestructed) => {}
@ -332,6 +330,13 @@ fn test_userdata_take() -> Result<()> {
},
r => panic!("improper return for destructed userdata: {:?}", r),
}
drop(userdata);
lua.globals().raw_remove("userdata")?;
lua.gc_collect()?;
lua.gc_collect()?;
assert_eq!(Arc::strong_count(&rc), 1);
Ok(())
}