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use crate::{
error, ffi, values::ToString, AsLua, LuaError, LuaRead, LuaState, Nil, Push, PushGuard,
PushInto, PushOne, PushOneInto, StaticLua, Void, WrongType,
};
use std::fmt::Display;
use std::marker::PhantomData;
use std::mem;
use std::ptr;
#[macro_export]
macro_rules! function {
(@ret) => { () };
(@ret $t:ty) => { $t };
(($($p:ty),*) $(-> $r:ty)?) => {
$crate::Function<
fn($($p),*) $(-> $r)?,
($($p,)*),
function!(@ret $($r)?)
>
}
}
macro_rules! impl_function {
($name:ident, $($p:ident),*) => (
/// Wraps a type that implements `FnMut` so that it can be used by tlua.
///
/// This is needed because of a limitation in Rust's inferrence system. Even though in
/// practice functions and closures always have a fixed number of parameters, the `FnMut`
/// trait of Rust was designed so that it allows calling the same closure with a varying
/// number of parameters. The consequence however is that there is no way of inferring
/// with the trait alone many parameters a function or closure expects.
#[inline]
pub fn $name<Z, R $(, $p)*>(f: Z) -> Function<Z, ($($p,)*), R>
where
Z: FnMut($($p),*) -> R,
{
Function {
function: f,
marker: PhantomData,
}
}
)
}
impl_function!(function0,);
impl_function!(function1, A);
impl_function!(function2, A, B);
impl_function!(function3, A, B, C);
impl_function!(function4, A, B, C, D);
impl_function!(function5, A, B, C, D, E);
impl_function!(function6, A, B, C, D, E, F);
impl_function!(function7, A, B, C, D, E, F, G);
impl_function!(function8, A, B, C, D, E, F, G, H);
impl_function!(function9, A, B, C, D, E, F, G, H, I);
impl_function!(function10, A, B, C, D, E, F, G, H, I, J);
/// Opaque type containing a Rust function or closure.
///
/// In order to build an instance of this struct, you need to use one of the `functionN` functions.
/// There is one function for each possible number of parameter. For example if you have a function
/// with two parameters, you must use [`function2`](fn.function2.html).
/// Example:
///
/// ```no_run
/// let f: tlua::Function<_, _, _> = tlua::function2(move |a: i32, b: i32| { });
/// ```
///
/// > **Note**: In practice you will never need to build an object of type `Function` as an
/// > intermediary step. Instead you will most likely always immediately push the function, like
/// > in the code below.
///
/// You can push a `Function` object like any other value:
///
/// ```no_run
/// use tlua::Lua;
/// let lua = Lua::new();
///
/// lua.set("foo", tlua::function1(move |a: i32| -> i32 {
/// a * 5
/// }));
/// ```
///
/// The function can then be called from Lua:
///
/// ```no_run
/// # use tlua::Lua;
/// # let lua = Lua::new();
/// # lua.set("foo", tlua::function1(move |a: i32| -> i32 { a * 5 }));
/// lua.exec("a = foo(12)").unwrap();
///
/// assert_eq!(lua.get::<i32, _>("a").unwrap(), 60);
/// ```
///
/// Remember that in Lua functions are regular variables, so you can do something like this
/// for example:
///
/// ```no_run
/// # use tlua::Lua;
/// # let lua = Lua::new();
/// # lua.set("foo", tlua::function1(move |a: i32| -> i32 { a * 5 }));
/// lua.exec("bar = foo; a = bar(12)").unwrap();
/// ```
///
/// # Multiple return values
///
/// The Lua language supports functions that return multiple values at once.
///
/// In order to return multiple values from a Rust function, you can return a tuple. The elements
/// of the tuple will be returned in order.
///
/// ```no_run
/// use tlua::Lua;
/// let lua = Lua::new();
///
/// lua.set("values", tlua::function0(move || -> (i32, i32, i32) {
/// (12, 24, 48)
/// }));
///
/// lua.exec("a, b, c = values()").unwrap();
///
/// assert_eq!(lua.get::<i32, _>("a").unwrap(), 12);
/// assert_eq!(lua.get::<i32, _>("b").unwrap(), 24);
/// assert_eq!(lua.get::<i32, _>("c").unwrap(), 48);
/// ```
///
/// # Using `Result`
///
/// If you want to return an error to the Lua script, you can use a `Result` that contains an
/// `Err`. The error will be returned to Lua as two values: A `nil` value and the error message.
///
/// The error type of the `Result` must implement the `Display` trait, and will be turned into a
/// Lua string.
///
/// ```no_run
/// use tlua::Lua;
/// let lua = Lua::new();
/// lua.openlibs();
///
/// lua.set("err", tlua::function0(move || -> Result<i32, &'static str> {
/// Err("something wrong happened")
/// }));
///
/// lua.exec(r#"
/// res, err = err();
/// assert(res == nil);
/// assert(err == "something wrong happened");
/// "#).unwrap();
/// ```
///
/// This also allows easy use of `assert` to act like `.unwrap()` in Rust:
///
/// ```no_run
/// use tlua::Lua;
/// let lua = Lua::new();
/// lua.openlibs();
///
/// lua.set("err", tlua::function0(move || -> Result<i32, &'static str> {
/// Err("something wrong happened")
/// }));
///
/// let ret = lua.exec("res = assert(err())");
/// assert!(ret.is_err());
/// ```
#[derive(Clone, Copy)]
pub struct Function<F, P, R> {
function: F,
marker: PhantomData<(P, R)>,
}
impl<F, P, R> std::fmt::Debug for Function<F, P, R> {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
write!(f, "Function({})", std::any::type_name::<F>())
}
}
impl<F, P, R> Function<F, P, R> {
pub fn new(function: F) -> Self {
Self {
function,
marker: PhantomData,
}
}
}
/// Trait implemented on `Function` to mimic `FnMut`.
///
/// We could in theory use the `FnMut` trait instead of this one, but it is still unstable.
pub trait FnMutExt<P> {
type Output;
fn call_mut(&mut self, params: P) -> Self::Output;
}
macro_rules! impl_function_ext {
(@recur) => {};
(@recur $_head:ident $($tail:ident)*) => {
impl_function_ext!{ $($tail)* }
};
($($p:ident)*) => {
impl<Z, R $(,$p)*> FnMutExt<($($p,)*)> for Function<Z, ($($p,)*), R>
where
Z: FnMut($($p),*) -> R,
{
type Output = R;
#[allow(non_snake_case)]
#[inline]
fn call_mut(&mut self, params: ($($p,)*)) -> Self::Output {
let ($($p,)*) = params;
(self.function)($($p),*)
}
}
impl<L, Z, R $(,$p: 'static)*> PushInto<L> for Function<Z, ($($p,)*), R>
where
L: AsLua,
Z: FnMut($($p),*) -> R,
Z: 'static,
($($p,)*): for<'p> LuaRead<&'p InsideCallback>,
R: PushInto<InsideCallback> + 'static,
{
type Err = Void; // TODO: use `!` instead (https://github.com/rust-lang/rust/issues/35121)
#[inline]
fn push_into_lua(self, lua: L) -> Result<PushGuard<L>, (Void, L)> {
unsafe {
// pushing the function pointer as a userdata
let ud = ffi::lua_newuserdata(lua.as_lua(), mem::size_of::<Self>() as _);
ptr::write(ud.cast(), self);
if std::mem::needs_drop::<Self>() {
// Creating a metatable.
ffi::lua_newtable(lua.as_lua());
// Index "__gc" in the metatable calls the object's destructor.
lua.as_lua().push("__gc").forget_internal();
ffi::lua_pushcfunction(lua.as_lua(), wrap_gc::<Self>);
ffi::lua_settable(lua.as_lua(), -3);
ffi::lua_setmetatable(lua.as_lua(), -2);
}
// pushing wrapper as a closure
ffi::lua_pushcclosure(lua.as_lua(), wrapper::<Self, _, R>, 1);
return Ok(PushGuard::new(lua, 1));
extern "C" fn wrap_gc<T>(lua: LuaState) -> i32 {
unsafe {
let obj = ffi::lua_touserdata(lua, -1);
ptr::drop_in_place(obj.cast::<T>());
0
}
}
}
}
}
impl<L, Z, R $(,$p: 'static)*> PushOneInto<L> for Function<Z, ($($p,)*), R>
where
L: AsLua,
Z: FnMut($($p),*) -> R,
Z: 'static,
($($p,)*): for<'p> LuaRead<&'p InsideCallback>,
R: PushInto<InsideCallback> + 'static,
{
}
impl<L, Z, R $(,$p: 'static)*> Push<L> for Function<Z, ($($p,)*), R>
where
L: AsLua,
Z: FnMut($($p),*) -> R,
Self: Copy + 'static,
($($p,)*): for<'p> LuaRead<&'p InsideCallback>,
R: PushInto<InsideCallback> + 'static,
{
type Err = Void; // TODO: use `!` instead (https://github.com/rust-lang/rust/issues/35121)
fn push_to_lua(&self, lua: L) -> Result<PushGuard<L>, (Void, L)> {
unsafe {
// pushing the function pointer as a userdata
let ud = ffi::lua_newuserdata(lua.as_lua(), mem::size_of::<Self>() as _);
ptr::write(ud.cast(), *self);
// pushing wrapper as a closure
ffi::lua_pushcclosure(lua.as_lua(), wrapper::<Self, _, R>, 1);
Ok(PushGuard::new(lua, 1))
}
}
}
impl<L, Z, R $(,$p: 'static)*> PushOne<L> for Function<Z, ($($p,)*), R>
where
L: AsLua,
Z: FnMut($($p),*) -> R,
Self: Copy + 'static,
($($p,)*): for<'p> LuaRead<&'p InsideCallback>,
R: PushInto<InsideCallback> + 'static,
{
}
impl_function_ext!{ @recur $($p)* }
}
}
impl_function_ext! {A B C D E F G H I J K M N}
/// A wrapper around [`ffi::lua_CFunction`] to push `C` functions
/// into lua as values.
///
/// # Example
/// ```no_run
/// use tlua::{Lua, CFunction, LuaState, ffi};
///
/// let lua = Lua::new();
/// unsafe extern "C" fn return_42(lua: LuaState) -> libc::c_int {
/// ffi::lua_pushinteger(lua, 42);
/// 1
/// }
/// assert_eq!(
/// lua.eval_with::<_, i32>("local fn = ...; return fn()", &CFunction::new(return_42))
/// .unwrap(),
/// 42
/// );
/// ```
#[derive(Debug, Copy, Clone, PartialEq, Eq)]
pub struct CFunction(ffi::lua_CFunction);
impl CFunction {
pub fn new(f: ffi::lua_CFunction) -> Self {
Self(f)
}
pub fn into_inner(self) -> ffi::lua_CFunction {
self.0
}
}
impl From<ffi::lua_CFunction> for CFunction {
fn from(f: ffi::lua_CFunction) -> Self {
Self::new(f)
}
}
impl<L: AsLua> PushInto<L> for CFunction {
type Err = Void;
fn push_into_lua(self, lua: L) -> Result<PushGuard<L>, (Self::Err, L)> {
unsafe {
ffi::lua_pushcfunction(lua.as_lua(), self.0);
Ok(PushGuard::new(lua, 1))
}
}
}
impl<L: AsLua> Push<L> for CFunction {
type Err = Void;
fn push_to_lua(&self, lua: L) -> Result<PushGuard<L>, (Self::Err, L)> {
unsafe {
ffi::lua_pushcfunction(lua.as_lua(), self.0);
Ok(PushGuard::new(lua, 1))
}
}
}
/// Opaque type that represents the Lua context when inside a callback.
///
/// Some types (like `Result`) can only be returned from a callback and not written inside a
/// Lua variable. This type is here to enforce this restriction.
#[derive(Debug)]
pub struct InsideCallback(LuaState);
impl AsLua for InsideCallback {
#[inline]
fn as_lua(&self) -> LuaState {
self.0
}
}
// This impl is the reason Push has a generic type parameter. But do we really
// need this impl at all?
impl<T, E> PushInto<InsideCallback> for Result<T, E>
where
T: PushInto<InsideCallback>,
E: Display,
{
type Err = T::Err;
#[inline]
fn push_into_lua(
self,
lua: InsideCallback,
) -> Result<PushGuard<InsideCallback>, (T::Err, InsideCallback)> {
match self {
Ok(val) => val.push_into_lua(lua),
Err(val) => Ok(lua.push(&(Nil, val.to_string()))),
}
}
}
/// A wrapper type for throwing lua errors from a rust callback's result.
///
/// # Example
/// ```no_run
/// use tlua::{Function, Lua, Throw};
///
/// fn may_fail() -> Result<String, String> {
/// Err("failed".into())
/// }
///
/// let lua = Lua::new();
/// lua.set("callback", Function::new(|| -> Result<String, Throw<String>> {
/// let foo = may_fail()?;
/// Ok(format!("bar{}", foo))
/// }));
/// assert!(lua.exec("callback()").is_err())
/// ```
#[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub struct Throw<E>(pub E);
impl<E> From<E> for Throw<E> {
fn from(err: E) -> Self {
Self(err)
}
}
impl<T, E> PushInto<InsideCallback> for Result<T, Throw<E>>
where
T: PushInto<InsideCallback>,
E: Display,
{
type Err = T::Err;
#[inline]
fn push_into_lua(
self,
lua: InsideCallback,
) -> Result<PushGuard<InsideCallback>, (T::Err, InsideCallback)> {
match self {
Ok(ok) => ok.push_into_lua(lua),
Err(Throw(err)) => crate::error!(lua, "{}", err),
}
}
}
impl<T, E> PushOneInto<InsideCallback> for Result<T, E>
where
T: PushOneInto<InsideCallback>,
E: Display,
{
}
// this function is called when Lua wants to call one of our functions
extern "C" fn wrapper<T, A, R>(lua: LuaState) -> libc::c_int
where
T: FnMutExt<A, Output = R>,
// TODO(gmoshkin): these bounds are too strict, how do we loosen them?
A: for<'p> LuaRead<&'p InsideCallback> + 'static,
R: PushInto<InsideCallback>,
{
// loading the object that we want to call from the Lua context
let data_raw = unsafe { ffi::lua_touserdata(lua, ffi::lua_upvalueindex(1)) };
let data = unsafe { data_raw.cast::<T>().as_mut() }.expect("lua_touserdata returned NULL");
// creating a temporary Lua context in order to pass it to push & read functions
let tmp_lua = InsideCallback(lua.as_lua());
// trying to read the arguments
let arguments_count = unsafe { ffi::lua_gettop(lua) } as i32;
// TODO: what if the user has the wrong params?
let args = A::lua_read_at_maybe_zero_position(&tmp_lua, -arguments_count);
let args = match args {
Err((lua, e)) => {
error!(
lua,
"{}",
WrongType::info("reading value(s) passed into rust callback")
.expected_type::<A>()
.actual_multiple_lua(&lua, arguments_count)
.subtype(e),
)
}
Ok(a) => a,
};
let ret_value = data.call_mut(args);
// pushing back the result of the function on the stack
let nb = match ret_value.push_into_lua(tmp_lua) {
Ok(p) => p.forget_internal(),
Err(_) => panic!(), // TODO: wrong
};
nb as _
}
/// See [`AsLua::pcall`].
#[track_caller]
pub fn protected_call<L, F, R>(lua: L, f: F) -> Result<R, LuaError>
where
L: AsLua,
F: FnOnce(StaticLua) -> R,
{
let mut ud = PCallCtx {
r#in: Some(f),
out: None,
};
let ud_ptr = &mut ud as *mut PCallCtx<_, _>;
let rc = unsafe { ffi::lua_cpcall(lua.as_lua(), trampoline::<F, R>, ud_ptr.cast()) };
match rc {
0 => {}
ffi::LUA_ERRMEM => panic!("lua_cpcall returned LUA_ERRMEM"),
ffi::LUA_ERRRUN => unsafe {
let error_msg = ToString::lua_read(PushGuard::new(lua, 1))
.ok()
.expect("can't find error message at the top of the Lua stack");
return Err(LuaError::ExecutionError(error_msg.into()));
},
rc => panic!("Unknown error code returned by lua_cpcall: {}", rc),
}
return Ok(ud.out.expect("if trampoline succeeded the value is set"));
struct PCallCtx<F, R> {
r#in: Option<F>,
out: Option<R>,
}
unsafe extern "C" fn trampoline<F, R>(l: LuaState) -> i32
where
F: FnOnce(StaticLua) -> R,
{
let ud_ptr = ffi::lua_touserdata(l, 1);
let PCallCtx { r#in, out } = ud_ptr
.cast::<PCallCtx<F, R>>()
.as_mut()
.unwrap_or_else(|| error!(l, "userdata is null"));
let f = r#in.take().expect("callback must be set by caller");
out.replace(f(StaticLua::from_static(l)));
0
}
}
#[cfg(feature = "internal_test")]
mod tests {
use super::*;
#[crate::test]
fn c_function() {
let lua = crate::Lua::new();
unsafe extern "C" fn return_42(lua: crate::LuaState) -> libc::c_int {
ffi::lua_pushinteger(lua, 42);
1
}
assert_eq!(
lua.eval_with::<_, i32>("local fn = ...; return fn()", &CFunction::new(return_42))
.unwrap(),
42
);
}
}