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Copy pathuserdata.rs
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1276 lines (1168 loc) · 46 KB
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//! Lua userdata handling.
//!
//! This module provides types for creating and working with Lua userdata from Rust.
use std::any::TypeId;
use std::ffi::CStr;
use std::fmt;
use std::hash::Hash;
use std::os::raw::{c_char, c_void};
use crate::Either;
use crate::error::{Error, Result};
use crate::function::Function;
use crate::state::{Lua, WeakLua};
use crate::string::LuaString;
use crate::table::{Table, TablePairs};
use crate::traits::{FromLua, FromLuaMulti, IntoLua, IntoLuaMulti};
use crate::types::{MaybeSend, MaybeSync, ValueRef};
use crate::util::{StackGuard, check_stack, get_userdata, push_string, short_type_name, take_userdata};
use crate::value::Value;
#[cfg(feature = "async")]
use std::future::Future;
#[cfg(feature = "serde")]
use {
serde::ser::{self, Serialize, Serializer},
std::result::Result as StdResult,
};
// Re-export for convenience
pub(crate) use cell::UserDataStorage;
pub use r#ref::{UserDataOwned, UserDataRef, UserDataRefMut};
pub use registry::UserDataRegistry;
pub(crate) use registry::{RawUserDataRegistry, UserDataProxy};
pub(crate) use util::{
TypeIdHints, borrow_userdata_scoped, borrow_userdata_scoped_mut, collect_userdata,
init_userdata_metatable,
};
/// Kinds of metamethods that can be overridden.
///
/// Currently, this mechanism does not allow overriding the `__gc` metamethod, since there is
/// generally no need to do so: [`UserData`] implementors can instead just implement `Drop`.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
#[non_exhaustive]
pub enum MetaMethod {
/// The `+` operator.
Add,
/// The `-` operator.
Sub,
/// The `*` operator.
Mul,
/// The `/` operator.
Div,
/// The `%` operator.
Mod,
/// The `^` operator.
Pow,
/// The unary minus (`-`) operator.
Unm,
/// The floor division (//) operator.
#[cfg(any(feature = "lua55", feature = "lua54", feature = "lua53", feature = "luau"))]
#[cfg_attr(
docsrs,
doc(cfg(any(feature = "lua55", feature = "lua54", feature = "lua53", feature = "luau")))
)]
IDiv,
/// The bitwise AND (&) operator.
#[cfg(any(feature = "lua55", feature = "lua54", feature = "lua53"))]
#[cfg_attr(
docsrs,
doc(cfg(any(feature = "lua55", feature = "lua54", feature = "lua53")))
)]
BAnd,
/// The bitwise OR (|) operator.
#[cfg(any(feature = "lua55", feature = "lua54", feature = "lua53"))]
#[cfg_attr(
docsrs,
doc(cfg(any(feature = "lua55", feature = "lua54", feature = "lua53")))
)]
BOr,
/// The bitwise XOR (binary ~) operator.
#[cfg(any(feature = "lua55", feature = "lua54", feature = "lua53"))]
#[cfg_attr(
docsrs,
doc(cfg(any(feature = "lua55", feature = "lua54", feature = "lua53")))
)]
BXor,
/// The bitwise NOT (unary ~) operator.
#[cfg(any(feature = "lua55", feature = "lua54", feature = "lua53"))]
#[cfg_attr(
docsrs,
doc(cfg(any(feature = "lua55", feature = "lua54", feature = "lua53")))
)]
BNot,
/// The bitwise left shift (<<) operator.
#[cfg(any(feature = "lua55", feature = "lua54", feature = "lua53"))]
#[cfg_attr(
docsrs,
doc(cfg(any(feature = "lua55", feature = "lua54", feature = "lua53")))
)]
Shl,
/// The bitwise right shift (>>) operator.
#[cfg(any(feature = "lua55", feature = "lua54", feature = "lua53"))]
#[cfg_attr(
docsrs,
doc(cfg(any(feature = "lua55", feature = "lua54", feature = "lua53")))
)]
Shr,
/// The string concatenation operator `..`.
Concat,
/// The length operator `#`.
Len,
/// The `==` operator.
Eq,
/// The `<` operator.
Lt,
/// The `<=` operator.
Le,
/// Index access `obj[key]`.
Index,
/// Index write access `obj[key] = value`.
NewIndex,
/// The call "operator" `obj(arg1, args2, ...)`.
Call,
/// The `__tostring` metamethod.
///
/// This is not an operator, but will be called by methods such as `tostring` and `print`.
ToString,
/// The `__todebugstring` metamethod for debug purposes.
///
/// This is an mlua-specific metamethod that can be used to provide debug representation for
/// userdata.
ToDebugString,
/// The `__pairs` metamethod.
///
/// This is not an operator, but it will be called by the built-in `pairs` function.
#[cfg(any(
feature = "lua55",
feature = "lua54",
feature = "lua53",
feature = "lua52",
feature = "luajit52"
))]
#[cfg_attr(
docsrs,
doc(cfg(any(
feature = "lua55",
feature = "lua54",
feature = "lua53",
feature = "lua52",
feature = "luajit52"
)))
)]
Pairs,
/// The `__ipairs` metamethod.
///
/// This is not an operator, but it will be called by the built-in [`ipairs`] function.
///
/// [`ipairs`]: https://www.lua.org/manual/5.2/manual.html#pdf-ipairs
#[cfg(any(feature = "lua52", feature = "luajit52", doc))]
#[cfg_attr(docsrs, doc(cfg(any(feature = "lua52", feature = "luajit52"))))]
IPairs,
/// The `__iter` metamethod.
///
/// Executed before the iteration begins, and should return an iterator function like `next`
/// (or a custom one).
#[cfg(any(feature = "luau", doc))]
#[cfg_attr(docsrs, doc(cfg(feature = "luau")))]
Iter,
/// The `__close` metamethod.
///
/// Executed when a variable, that marked as to-be-closed, goes out of scope.
///
/// More information about to-be-closed variables can be found in the Lua 5.4
/// [documentation][lua_doc].
///
/// [lua_doc]: https://www.lua.org/manual/5.4/manual.html#3.3.8
#[cfg(any(feature = "lua55", feature = "lua54"))]
#[cfg_attr(docsrs, doc(cfg(any(feature = "lua55", feature = "lua54"))))]
Close,
/// The `__name`/`__type` metafield.
///
/// This is not a function, but it's value can be used by `tostring` and `typeof` built-in
/// functions.
#[doc(hidden)]
Type,
}
impl PartialEq<MetaMethod> for &str {
fn eq(&self, other: &MetaMethod) -> bool {
*self == other.name()
}
}
impl PartialEq<MetaMethod> for String {
fn eq(&self, other: &MetaMethod) -> bool {
self == other.name()
}
}
impl fmt::Display for MetaMethod {
fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
write!(fmt, "{}", self.name())
}
}
impl MetaMethod {
/// Returns Lua metamethod name, usually prefixed by two underscores.
pub const fn name(self) -> &'static str {
match self {
MetaMethod::Add => "__add",
MetaMethod::Sub => "__sub",
MetaMethod::Mul => "__mul",
MetaMethod::Div => "__div",
MetaMethod::Mod => "__mod",
MetaMethod::Pow => "__pow",
MetaMethod::Unm => "__unm",
#[cfg(any(feature = "lua55", feature = "lua54", feature = "lua53", feature = "luau"))]
MetaMethod::IDiv => "__idiv",
#[cfg(any(feature = "lua55", feature = "lua54", feature = "lua53"))]
MetaMethod::BAnd => "__band",
#[cfg(any(feature = "lua55", feature = "lua54", feature = "lua53"))]
MetaMethod::BOr => "__bor",
#[cfg(any(feature = "lua55", feature = "lua54", feature = "lua53"))]
MetaMethod::BXor => "__bxor",
#[cfg(any(feature = "lua55", feature = "lua54", feature = "lua53"))]
MetaMethod::BNot => "__bnot",
#[cfg(any(feature = "lua55", feature = "lua54", feature = "lua53"))]
MetaMethod::Shl => "__shl",
#[cfg(any(feature = "lua55", feature = "lua54", feature = "lua53"))]
MetaMethod::Shr => "__shr",
MetaMethod::Concat => "__concat",
MetaMethod::Len => "__len",
MetaMethod::Eq => "__eq",
MetaMethod::Lt => "__lt",
MetaMethod::Le => "__le",
MetaMethod::Index => "__index",
MetaMethod::NewIndex => "__newindex",
MetaMethod::Call => "__call",
MetaMethod::ToString => "__tostring",
MetaMethod::ToDebugString => "__todebugstring",
#[cfg(any(
feature = "lua55",
feature = "lua54",
feature = "lua53",
feature = "lua52",
feature = "luajit52"
))]
MetaMethod::Pairs => "__pairs",
#[cfg(any(feature = "lua52", feature = "luajit52"))]
MetaMethod::IPairs => "__ipairs",
#[cfg(feature = "luau")]
MetaMethod::Iter => "__iter",
#[cfg(any(feature = "lua55", feature = "lua54"))]
MetaMethod::Close => "__close",
#[rustfmt::skip]
MetaMethod::Type => if cfg!(feature = "luau") { "__type" } else { "__name" },
}
}
pub(crate) const fn as_cstr(self) -> &'static CStr {
match self {
#[rustfmt::skip]
MetaMethod::Type => if cfg!(feature = "luau") { c"__type" } else { c"__name" },
_ => unreachable!(),
}
}
pub(crate) fn validate(name: &str) -> Result<&str> {
match name {
"__gc" | "__metatable" => Err(Error::MetaMethodRestricted(name.to_string())),
_ if name.starts_with("__mlua") => Err(Error::MetaMethodRestricted(name.to_string())),
name => Ok(name),
}
}
}
impl AsRef<str> for MetaMethod {
fn as_ref(&self) -> &str {
self.name()
}
}
impl From<MetaMethod> for String {
#[inline]
fn from(method: MetaMethod) -> Self {
method.name().to_owned()
}
}
/// Method registry for [`UserData`] implementors.
pub trait UserDataMethods<T> {
/// Add a regular method which accepts a `&T` as the first parameter.
///
/// Regular methods are implemented by overriding the `__index` metamethod and returning the
/// accessed method. This allows them to be used with the expected `userdata:method()` syntax.
///
/// If `add_meta_method` is used to set the `__index` metamethod, the `__index` metamethod will
/// be used as a fall-back if no regular method is found.
fn add_method<M, A, R>(&mut self, name: impl Into<String>, method: M)
where
M: Fn(&Lua, &T, A) -> Result<R> + MaybeSend + 'static,
A: FromLuaMulti,
R: IntoLuaMulti;
/// Add a regular method which accepts a `&mut T` as the first parameter.
///
/// Refer to [`add_method`] for more information about the implementation.
///
/// [`add_method`]: UserDataMethods::add_method
fn add_method_mut<M, A, R>(&mut self, name: impl Into<String>, method: M)
where
M: FnMut(&Lua, &mut T, A) -> Result<R> + MaybeSend + 'static,
A: FromLuaMulti,
R: IntoLuaMulti;
/// Add a method which accepts `T` as the first parameter.
///
/// The userdata `T` will be moved out of the userdata container. This is useful for
/// methods that need to consume the userdata.
///
/// The method can be called only once per userdata instance. A subsequent call returns an
/// [`Error::BadArgument`] for `self` whose cause is [`Error::UserDataDestructed`].
fn add_method_once<M, A, R>(&mut self, name: impl Into<String>, method: M)
where
T: 'static,
M: Fn(&Lua, T, A) -> Result<R> + MaybeSend + 'static,
A: FromLuaMulti,
R: IntoLuaMulti,
{
let name = name.into();
let method_name = format!("{}.{name}", short_type_name::<T>());
self.add_function(name, move |lua, (ud, args): (AnyUserData, A)| {
let this = (ud.take()).map_err(|err| Error::bad_self_argument(&method_name, err))?;
method(lua, this, args)
});
}
/// Add an async method which accepts a `&T` as the first parameter and returns [`Future`].
///
/// Refer to [`add_method`] for more information about the implementation.
///
/// [`add_method`]: UserDataMethods::add_method
#[cfg(feature = "async")]
#[cfg_attr(docsrs, doc(cfg(feature = "async")))]
fn add_async_method<M, A, MR, R>(&mut self, name: impl Into<String>, method: M)
where
T: 'static,
M: Fn(Lua, UserDataRef<T>, A) -> MR + MaybeSend + 'static,
A: FromLuaMulti,
MR: Future<Output = Result<R>> + MaybeSend + 'static,
R: IntoLuaMulti;
/// Add an async method which accepts a `&mut T` as the first parameter and returns [`Future`].
///
/// Refer to [`add_method`] for more information about the implementation.
///
/// [`add_method`]: UserDataMethods::add_method
#[cfg(feature = "async")]
#[cfg_attr(docsrs, doc(cfg(feature = "async")))]
fn add_async_method_mut<M, A, MR, R>(&mut self, name: impl Into<String>, method: M)
where
T: 'static,
M: Fn(Lua, UserDataRefMut<T>, A) -> MR + MaybeSend + 'static,
A: FromLuaMulti,
MR: Future<Output = Result<R>> + MaybeSend + 'static,
R: IntoLuaMulti;
/// Add an async method which accepts a `T` as the first parameter and returns [`Future`].
///
/// The userdata `T` will be moved out of the userdata container. This is useful for
/// methods that need to consume the userdata.
///
/// The method can be called only once per userdata instance. A subsequent call returns an
/// [`Error::BadArgument`] for `self` whose cause is [`Error::UserDataDestructed`].
#[cfg(feature = "async")]
#[cfg_attr(docsrs, doc(cfg(feature = "async")))]
fn add_async_method_once<M, A, MR, R>(&mut self, name: impl Into<String>, method: M)
where
T: 'static,
M: Fn(Lua, T, A) -> MR + MaybeSend + 'static,
A: FromLuaMulti,
MR: Future<Output = Result<R>> + MaybeSend + 'static,
R: IntoLuaMulti,
{
let name = name.into();
let method_name = format!("{}.{name}", short_type_name::<T>());
self.add_async_function(name, move |lua, (ud, args): (AnyUserData, A)| {
match (ud.take()).map_err(|err| Error::bad_self_argument(&method_name, err)) {
Ok(this) => either::Either::Left(method(lua, this, args)),
Err(err) => either::Either::Right(async move { Err(err) }),
}
});
}
/// Add a regular method as a function which accepts generic arguments.
///
/// The first argument will be a [`AnyUserData`] of type `T` if the method is called with Lua
/// method syntax: `my_userdata:my_method(arg1, arg2)`, or it is passed in as the first
/// argument: `my_userdata.my_method(my_userdata, arg1, arg2)`.
fn add_function<F, A, R>(&mut self, name: impl Into<String>, function: F)
where
F: Fn(&Lua, A) -> Result<R> + MaybeSend + 'static,
A: FromLuaMulti,
R: IntoLuaMulti;
/// Add a regular method as a mutable function which accepts generic arguments.
///
/// This is a version of [`add_function`] that accepts a `FnMut` argument.
///
/// [`add_function`]: UserDataMethods::add_function
fn add_function_mut<F, A, R>(&mut self, name: impl Into<String>, function: F)
where
F: FnMut(&Lua, A) -> Result<R> + MaybeSend + 'static,
A: FromLuaMulti,
R: IntoLuaMulti;
/// Add a regular method as an async function which accepts generic arguments and returns
/// [`Future`].
///
/// This is an async version of [`add_function`].
///
/// [`add_function`]: UserDataMethods::add_function
#[cfg(feature = "async")]
#[cfg_attr(docsrs, doc(cfg(feature = "async")))]
fn add_async_function<F, A, FR, R>(&mut self, name: impl Into<String>, function: F)
where
F: Fn(Lua, A) -> FR + MaybeSend + 'static,
A: FromLuaMulti,
FR: Future<Output = Result<R>> + MaybeSend + 'static,
R: IntoLuaMulti;
/// Add a metamethod which accepts a `&T` as the first parameter.
///
/// # Note
///
/// This can cause an error with certain binary metamethods that can trigger if only the right
/// side has a metatable. To prevent this, use [`add_meta_function`].
///
/// [`add_meta_function`]: UserDataMethods::add_meta_function
fn add_meta_method<M, A, R>(&mut self, name: impl Into<String>, method: M)
where
M: Fn(&Lua, &T, A) -> Result<R> + MaybeSend + 'static,
A: FromLuaMulti,
R: IntoLuaMulti;
/// Add a metamethod as a function which accepts a `&mut T` as the first parameter.
///
/// # Note
///
/// This can cause an error with certain binary metamethods that can trigger if only the right
/// side has a metatable. To prevent this, use [`add_meta_function`].
///
/// [`add_meta_function`]: UserDataMethods::add_meta_function
fn add_meta_method_mut<M, A, R>(&mut self, name: impl Into<String>, method: M)
where
M: FnMut(&Lua, &mut T, A) -> Result<R> + MaybeSend + 'static,
A: FromLuaMulti,
R: IntoLuaMulti;
/// Add an async metamethod which accepts a `&T` as the first parameter and returns [`Future`].
///
/// This is an async version of [`add_meta_method`].
///
/// [`add_meta_method`]: UserDataMethods::add_meta_method
#[cfg(all(feature = "async", not(any(feature = "lua51", feature = "luau"))))]
#[cfg_attr(
docsrs,
doc(cfg(all(feature = "async", not(any(feature = "lua51", feature = "luau")))))
)]
fn add_async_meta_method<M, A, MR, R>(&mut self, name: impl Into<String>, method: M)
where
T: 'static,
M: Fn(Lua, UserDataRef<T>, A) -> MR + MaybeSend + 'static,
A: FromLuaMulti,
MR: Future<Output = Result<R>> + MaybeSend + 'static,
R: IntoLuaMulti;
/// Add an async metamethod which accepts a `&mut T` as the first parameter and returns
/// [`Future`].
///
/// This is an async version of [`add_meta_method_mut`].
///
/// [`add_meta_method_mut`]: UserDataMethods::add_meta_method_mut
#[cfg(all(feature = "async", not(any(feature = "lua51", feature = "luau"))))]
#[cfg_attr(
docsrs,
doc(cfg(all(feature = "async", not(any(feature = "lua51", feature = "luau")))))
)]
fn add_async_meta_method_mut<M, A, MR, R>(&mut self, name: impl Into<String>, method: M)
where
T: 'static,
M: Fn(Lua, UserDataRefMut<T>, A) -> MR + MaybeSend + 'static,
A: FromLuaMulti,
MR: Future<Output = Result<R>> + MaybeSend + 'static,
R: IntoLuaMulti;
/// Add a metamethod which accepts generic arguments.
///
/// Metamethods for binary operators can be triggered if either the left or right argument to
/// the binary operator has a metatable, so the first argument here is not necessarily a
/// userdata of type `T`.
fn add_meta_function<F, A, R>(&mut self, name: impl Into<String>, function: F)
where
F: Fn(&Lua, A) -> Result<R> + MaybeSend + 'static,
A: FromLuaMulti,
R: IntoLuaMulti;
/// Add a metamethod as a mutable function which accepts generic arguments.
///
/// This is a version of [`add_meta_function`] that accepts a `FnMut` argument.
///
/// [`add_meta_function`]: UserDataMethods::add_meta_function
fn add_meta_function_mut<F, A, R>(&mut self, name: impl Into<String>, function: F)
where
F: FnMut(&Lua, A) -> Result<R> + MaybeSend + 'static,
A: FromLuaMulti,
R: IntoLuaMulti;
/// Add a metamethod which accepts generic arguments and returns [`Future`].
///
/// This is an async version of [`add_meta_function`].
///
/// [`add_meta_function`]: UserDataMethods::add_meta_function
#[cfg(all(feature = "async", not(any(feature = "lua51", feature = "luau"))))]
#[cfg_attr(
docsrs,
doc(cfg(all(feature = "async", not(any(feature = "lua51", feature = "luau")))))
)]
fn add_async_meta_function<F, A, FR, R>(&mut self, name: impl Into<String>, function: F)
where
F: Fn(Lua, A) -> FR + MaybeSend + 'static,
A: FromLuaMulti,
FR: Future<Output = Result<R>> + MaybeSend + 'static,
R: IntoLuaMulti;
}
/// Field registry for [`UserData`] implementors.
pub trait UserDataFields<T> {
/// Add a static field to the [`UserData`].
///
/// Static fields are implemented by updating the `__index` metamethod and returning the
/// accessed field. This allows them to be used with the expected `userdata.field` syntax.
///
/// Static fields are usually shared between all instances of the [`UserData`] of the same type.
///
/// If `add_meta_method` is used to set the `__index` metamethod, it will
/// be used as a fall-back if no regular field or method are found.
fn add_field<V>(&mut self, name: impl Into<String>, value: V)
where
V: IntoLua + 'static;
/// Add a regular field getter as a method which accepts a `&T` as the parameter.
///
/// Regular field getters are implemented by overriding the `__index` metamethod and returning
/// the accessed field. This allows them to be used with the expected `userdata.field` syntax.
///
/// If `add_meta_method` is used to set the `__index` metamethod, the `__index` metamethod will
/// be used as a fall-back if no regular field or method are found.
fn add_field_method_get<M, R>(&mut self, name: impl Into<String>, method: M)
where
M: Fn(&Lua, &T) -> Result<R> + MaybeSend + 'static,
R: IntoLua;
/// Add a regular field setter as a method which accepts a `&mut T` as the first parameter.
///
/// Regular field setters are implemented by overriding the `__newindex` metamethod and setting
/// the accessed field. This allows them to be used with the expected `userdata.field = value`
/// syntax.
///
/// If `add_meta_method` is used to set the `__newindex` metamethod, the `__newindex` metamethod
/// will be used as a fall-back if no regular field is found.
fn add_field_method_set<M, A>(&mut self, name: impl Into<String>, method: M)
where
M: FnMut(&Lua, &mut T, A) -> Result<()> + MaybeSend + 'static,
A: FromLua;
/// Add a regular field getter as a function which accepts a generic [`AnyUserData`] of type `T`
/// argument.
fn add_field_function_get<F, R>(&mut self, name: impl Into<String>, function: F)
where
F: Fn(&Lua, AnyUserData) -> Result<R> + MaybeSend + 'static,
R: IntoLua;
/// Add a regular field setter as a function which accepts a generic [`AnyUserData`] of type `T`
/// first argument.
fn add_field_function_set<F, A>(&mut self, name: impl Into<String>, function: F)
where
F: FnMut(&Lua, AnyUserData, A) -> Result<()> + MaybeSend + 'static,
A: FromLua;
/// Add a metatable field.
///
/// This will initialize the metatable field with `value` on [`UserData`] creation.
///
/// # Note
///
/// `mlua` will trigger an error on an attempt to define a protected metamethod,
/// like `__gc` or `__metatable`.
fn add_meta_field<V>(&mut self, name: impl Into<String>, value: V)
where
V: IntoLua + 'static;
/// Add a metatable field computed from `f`.
///
/// This will initialize the metatable field from `f` on [`UserData`] creation.
///
/// # Note
///
/// `mlua` will trigger an error on an attempt to define a protected metamethod,
/// like `__gc` or `__metatable`.
fn add_meta_field_with<F, R>(&mut self, name: impl Into<String>, f: F)
where
F: FnOnce(&Lua) -> Result<R> + 'static,
R: IntoLua;
}
/// Trait for custom userdata types.
///
/// By implementing this trait, a struct becomes eligible for use inside Lua code.
///
/// Implementation of [`IntoLua`] is automatically provided, [`FromLua`] needs to be implemented
/// manually.
///
///
/// # Examples
///
/// ```
/// # use mlua::{Lua, Result, UserData};
/// # fn main() -> Result<()> {
/// # let lua = Lua::new();
/// struct MyUserData;
///
/// impl UserData for MyUserData {}
///
/// // `MyUserData` now implements `IntoLua`:
/// lua.globals().set("myobject", MyUserData)?;
///
/// lua.load("assert(type(myobject) == 'userdata')").exec()?;
/// # Ok(())
/// # }
/// ```
///
/// Custom fields, methods and operators can be provided by implementing `add_fields` or
/// `add_methods` (refer to [`UserDataFields`] and [`UserDataMethods`] for more information):
///
/// ```
/// # use mlua::{Lua, MetaMethod, Result, UserData, UserDataFields, UserDataMethods};
/// # fn main() -> Result<()> {
/// # let lua = Lua::new();
/// struct MyUserData(i32);
///
/// impl UserData for MyUserData {
/// fn add_fields<F: UserDataFields<Self>>(fields: &mut F) {
/// fields.add_field_method_get("val", |_, this| Ok(this.0));
/// }
///
/// fn add_methods<M: UserDataMethods<Self>>(methods: &mut M) {
/// methods.add_method_mut("add", |_, mut this, value: i32| {
/// this.0 += value;
/// Ok(())
/// });
///
/// methods.add_meta_method(MetaMethod::Add, |_, this, value: i32| {
/// Ok(this.0 + value)
/// });
/// }
/// }
///
/// lua.globals().set("myobject", MyUserData(123))?;
///
/// lua.load(r#"
/// assert(myobject.val == 123)
/// myobject:add(7)
/// assert(myobject.val == 130)
/// assert(myobject + 10 == 140)
/// "#).exec()?;
/// # Ok(())
/// # }
/// ```
pub trait UserData: Sized {
/// Adds custom fields specific to this userdata.
#[allow(unused_variables)]
fn add_fields<F: UserDataFields<Self>>(fields: &mut F) {}
/// Adds custom methods and operators specific to this userdata.
#[allow(unused_variables)]
fn add_methods<M: UserDataMethods<Self>>(methods: &mut M) {}
/// Registers this type for use in Lua.
///
/// This method is responsible for calling `add_fields` and `add_methods` on the provided
/// [`UserDataRegistry`].
fn register(registry: &mut UserDataRegistry<Self>) {
Self::add_fields(registry);
Self::add_methods(registry);
}
}
/// Handle to an internal Lua userdata for any type that implements [`UserData`].
///
/// Similar to [`std::any::Any`], this provides an interface for dynamic type checking via the
/// [`is`] and [`borrow`] methods.
///
/// # Note
///
/// This API should only be used when necessary. Implementing [`UserData`] already allows defining
/// methods which check the type and acquire a borrow behind the scenes.
///
/// [`is`]: crate::AnyUserData::is
/// [`borrow`]: crate::AnyUserData::borrow
#[derive(Clone, PartialEq)]
pub struct AnyUserData(pub(crate) ValueRef);
impl AnyUserData {
/// Checks whether the type of this userdata is `T`.
#[inline]
pub fn is<T: 'static>(&self) -> bool {
let type_id = self.type_id();
// We do not use wrapped types here, rather prefer to check the "real" type of the userdata
matches!(type_id, Some(type_id) if type_id == TypeId::of::<T>())
}
/// Checks whether the type of this userdata is a [proxy object] for `T`.
///
/// [proxy object]: crate::Lua::create_proxy
#[inline]
pub fn is_proxy<T: 'static>(&self) -> bool {
self.is::<UserDataProxy<T>>()
}
/// Borrow this userdata immutably if it is of type `T`.
///
/// # Errors
///
/// Returns a [`UserDataBorrowError`] if the userdata is already mutably borrowed.
/// Returns a [`DataTypeMismatch`] if the userdata is not of type `T` or if it's
/// scoped.
///
/// [`UserDataBorrowError`]: crate::Error::UserDataBorrowError
/// [`DataTypeMismatch`]: crate::Error::UserDataTypeMismatch
#[inline]
pub fn borrow<T: 'static>(&self) -> Result<UserDataRef<T>> {
let lua = self.0.lua.lock();
unsafe { UserDataRef::borrow_from_stack(&lua, lua.ref_thread(), self.0.index) }
}
/// Borrow this userdata immutably if it is of type `T`, passing the borrowed value
/// to the closure.
///
/// This method is the only way to borrow scoped userdata (created inside [`Lua::scope`]).
pub fn borrow_scoped<T: 'static, R>(&self, f: impl FnOnce(&T) -> R) -> Result<R> {
let lua = self.0.lua.lock();
let type_id = lua.get_userdata_ref_type_id(&self.0)?;
let type_hints = TypeIdHints::new::<T>();
unsafe { borrow_userdata_scoped(lua.ref_thread(), self.0.index, type_id, type_hints, f) }
}
/// Borrow this userdata mutably if it is of type `T`.
///
/// # Errors
///
/// Returns a [`UserDataBorrowMutError`] if the userdata cannot be mutably borrowed.
/// Returns a [`UserDataTypeMismatch`] if the userdata is not of type `T` or if it's
/// scoped.
///
/// [`UserDataBorrowMutError`]: crate::Error::UserDataBorrowMutError
/// [`UserDataTypeMismatch`]: crate::Error::UserDataTypeMismatch
#[inline]
pub fn borrow_mut<T: 'static>(&self) -> Result<UserDataRefMut<T>> {
let lua = self.0.lua.lock();
unsafe { UserDataRefMut::borrow_from_stack(&lua, lua.ref_thread(), self.0.index) }
}
/// Borrow this userdata mutably if it is of type `T`, passing the borrowed value
/// to the closure.
///
/// This method is the only way to borrow scoped userdata (created inside [`Lua::scope`]).
pub fn borrow_mut_scoped<T: 'static, R>(&self, f: impl FnOnce(&mut T) -> R) -> Result<R> {
let lua = self.0.lua.lock();
let type_id = lua.get_userdata_ref_type_id(&self.0)?;
let type_hints = TypeIdHints::new::<T>();
unsafe { borrow_userdata_scoped_mut(lua.ref_thread(), self.0.index, type_id, type_hints, f) }
}
/// Takes the value out of this userdata.
///
/// Sets the special "destructed" metatable that prevents any further operations with this
/// userdata.
///
/// Keeps associated user values unchanged (they will be collected by Lua's GC).
pub fn take<T: 'static>(&self) -> Result<T> {
let lua = self.0.lua.lock();
match lua.get_userdata_ref_type_id(&self.0)? {
Some(type_id) if type_id == TypeId::of::<T>() => unsafe {
let ref_thread = lua.ref_thread();
if (*get_userdata::<UserDataStorage<T>>(ref_thread, self.0.index)).has_exclusive_access() {
take_userdata::<UserDataStorage<T>>(ref_thread, self.0.index).into_inner()
} else {
Err(Error::UserDataBorrowMutError)
}
},
_ => Err(Error::UserDataTypeMismatch),
}
}
/// Destroys this userdata.
///
/// This is similar to [`AnyUserData::take`], but it doesn't require a type.
///
/// This method works for non-scoped userdata only.
///
/// Panics from the value's destructor propagate to the caller. During garbage collection,
/// destructor panics abort the process instead.
pub fn destroy(&self) -> Result<()> {
let lua = self.0.lua.lock();
let state = lua.state();
unsafe {
let _sg = StackGuard::new(state);
check_stack(state, 3)?;
lua.push_userdata_ref(&self.0)?;
protect_lua!(state, 1, 1, fn(state) {
if ffi::luaL_getmetafield(state, 1, cstr!("__gc")) != ffi::LUA_TNIL {
ffi::lua_pushvalue(state, 1);
// Only explicit destruction may propagate panics
ffi::lua_pushboolean(state, 1);
ffi::lua_call(state, 2, 1);
} else {
ffi::lua_pushboolean(state, 0);
}
})?;
if ffi::lua_isboolean(state, -1) != 0 && ffi::lua_toboolean(state, -1) != 0 {
return Ok(());
}
Err(Error::UserDataBorrowMutError)
}
}
/// Sets an associated value to this [`AnyUserData`].
///
/// The value may be any Lua value whatsoever, and can be retrieved with [`user_value`].
///
/// This is the same as calling [`set_nth_user_value`] with `n` set to 1.
///
/// [`user_value`]: AnyUserData::user_value
/// [`set_nth_user_value`]: AnyUserData::set_nth_user_value
#[inline]
pub fn set_user_value(&self, v: impl IntoLua) -> Result<()> {
self.set_nth_user_value(1, v)
}
/// Returns an associated value set by [`set_user_value`].
///
/// This is the same as calling [`nth_user_value`] with `n` set to 1.
///
/// [`set_user_value`]: AnyUserData::set_user_value
/// [`nth_user_value`]: AnyUserData::nth_user_value
#[inline]
pub fn user_value<V: FromLua>(&self) -> Result<V> {
self.nth_user_value(1)
}
/// Sets an associated `n`th value to this [`AnyUserData`].
///
/// The value may be any Lua value whatsoever, and can be retrieved with [`nth_user_value`].
/// `n` starts from 1 and can be up to 65535.
///
/// This is supported for all Lua versions using a wrapping table.
///
/// [`nth_user_value`]: AnyUserData::nth_user_value
pub fn set_nth_user_value(&self, n: usize, v: impl IntoLua) -> Result<()> {
if n < 1 || n > u16::MAX as usize {
return Err(Error::runtime("user value index out of bounds"));
}
let lua = self.0.lua.lock();
let state = lua.state();
unsafe {
let _sg = StackGuard::new(state);
check_stack(state, 5)?;
lua.push_userdata_ref(&self.0)?;
lua.push(v)?;
// Multiple (extra) user values are emulated by storing them in a table
protect_lua!(state, 2, 0, |state| {
if ffi::lua_getuservalue(state, -2) != ffi::LUA_TTABLE {
// Create a new table to use as uservalue
ffi::lua_pop(state, 1);
ffi::lua_newtable(state);
ffi::lua_pushvalue(state, -1);
ffi::lua_setuservalue(state, -4);
}
ffi::lua_pushvalue(state, -2);
ffi::lua_rawseti(state, -2, n as ffi::lua_Integer);
})?;
Ok(())
}
}
/// Returns an associated `n`th value set by [`set_nth_user_value`].
///
/// `n` starts from 1 and can be up to 65535.
///
/// This is supported for all Lua versions using a wrapping table.
///
/// [`set_nth_user_value`]: AnyUserData::set_nth_user_value
pub fn nth_user_value<V: FromLua>(&self, n: usize) -> Result<V> {
if n < 1 || n > u16::MAX as usize {
return Err(Error::runtime("user value index out of bounds"));
}
let lua = self.0.lua.lock();
let state = lua.state();
unsafe {
let _sg = StackGuard::new(state);
check_stack(state, 4)?;
lua.push_userdata_ref(&self.0)?;
// Multiple (extra) user values are emulated by storing them in a table
if ffi::lua_getuservalue(state, -1) != ffi::LUA_TTABLE {
return V::from_lua(Value::Nil, lua.lua());
}
ffi::lua_rawgeti(state, -1, n as ffi::lua_Integer);
V::from_stack(-1, &lua)
}
}
/// Sets an associated value to this [`AnyUserData`] by name.
///
/// The value can be retrieved with [`named_user_value`].
///
/// [`named_user_value`]: AnyUserData::named_user_value
pub fn set_named_user_value(&self, name: &str, v: impl IntoLua) -> Result<()> {
let lua = self.0.lua.lock();
let state = lua.state();
unsafe {
let _sg = StackGuard::new(state);
check_stack(state, 5)?;
lua.push_userdata_ref(&self.0)?;
lua.push(v)?;
// Multiple (extra) user values are emulated by storing them in a table
protect_lua!(state, 2, 0, |state| {
if ffi::lua_getuservalue(state, -2) != ffi::LUA_TTABLE {
// Create a new table to use as uservalue
ffi::lua_pop(state, 1);
ffi::lua_newtable(state);
ffi::lua_pushvalue(state, -1);
ffi::lua_setuservalue(state, -4);
}
ffi::lua_pushlstring(state, name.as_ptr() as *const c_char, name.len());
ffi::lua_pushvalue(state, -3);
ffi::lua_rawset(state, -3);
})?;
Ok(())
}
}
/// Returns an associated value by name set by [`set_named_user_value`].
///
/// [`set_named_user_value`]: AnyUserData::set_named_user_value
pub fn named_user_value<V: FromLua>(&self, name: &str) -> Result<V> {
let lua = self.0.lua.lock();
let state = lua.state();
unsafe {
let _sg = StackGuard::new(state);
check_stack(state, 4)?;
lua.push_userdata_ref(&self.0)?;
// Multiple (extra) user values are emulated by storing them in a table
if ffi::lua_getuservalue(state, -1) != ffi::LUA_TTABLE {
return V::from_lua(Value::Nil, lua.lua());
}
push_string(state, name.as_bytes(), !lua.unlikely_memory_error())?;
ffi::lua_rawget(state, -2);
V::from_stack(-1, &lua)
}
}
/// Returns a metatable of this [`AnyUserData`].
///
/// Returned [`UserDataMetatable`] object wraps the original metatable and
/// provides safe access to its methods.
///