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Impl generic From/IntoFfi for Option

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This commit is contained in:
lumi 2025-06-25 21:24:24 +10:00
parent 530a1530ba
commit 30596d9331
Signed by: luaneko
GPG Key ID: 406809B8763FF07A
5 changed files with 157 additions and 57 deletions
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4
crates/luaffi/Cargo.toml
View File

@ -7,6 +7,10 @@ authors.workspace = true
homepage.workspace = true
repository.workspace = true
[features]
option_ref_abi = []
option_string_abi = []
[dependencies]
bstr = "1.12.0"
luaffi_impl = { path = "../luaffi_impl" }

8
crates/luaffi/src/lib.rs
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@ -11,13 +11,13 @@ use std::{
mem,
};
pub mod future;
pub mod string;
#[doc(hidden)]
#[path = "./internal.rs"]
pub mod __internal;
pub mod future;
pub mod option;
pub mod result;
pub mod string;
// Dummy function to ensure that strings passed to Rust via wrapper objects will not be
// garbage-collected until the end of the function (used in string.rs when string marshalling is
@ -857,7 +857,9 @@ macro_rules! impl_ptr_intoabi {
impl_ptr_intoabi!(*const T);
impl_ptr_intoabi!(*mut T);
#[cfg(feature = "option_ref_abi")] // disabled because it conflicts with the generic Option<T> impl
impl_ptr_intoabi!(Option<&'static T>);
#[cfg(feature = "option_ref_abi")]
impl_ptr_intoabi!(Option<&'static mut T>);
//

84
crates/luaffi/src/option.rs Normal file
View File

@ -0,0 +1,84 @@
use crate::{
__internal::{disp, display},
Cdef, CdefBuilder, IntoFfi, KEEP_FN, Type, TypeBuilder, TypeType,
};
use std::{ffi::c_int, fmt::Display};
#[repr(C)]
#[allow(non_camel_case_types)]
pub enum lua_option<T> {
None, // __tag = 0
Some(T), // __tag = 1
}
unsafe impl<T: Type> Type for lua_option<T> {
fn name() -> impl Display {
display!("option__{}", T::name())
}
fn ty() -> TypeType {
TypeType::Aggregate
}
fn cdecl(name: impl Display) -> impl Display {
display!("struct {} {name}", Self::name())
}
fn build(b: &mut TypeBuilder) {
b.cdef::<Self>();
}
}
unsafe impl<T: Type> Cdef for lua_option<T> {
fn build(b: &mut CdefBuilder) {
b.field::<c_int>("__tag");
(T::ty() != TypeType::Void).then(|| b.field::<T>("__value"));
}
}
unsafe impl<T: IntoFfi> IntoFfi for Option<T> {
type Into = lua_option<T::Into>;
fn convert(self) -> Self::Into {
match self {
Some(value) => lua_option::Some(T::convert(value)),
None => lua_option::None,
}
}
fn require_owned() -> bool {
// lua_option is only used to transmit information about whether we have a value or not and
// is forgotten immediately after use, so there is no need for an owned option
false
}
fn postlude(ret: &str) -> impl Display {
disp(move |f| {
write!(f, "if {ret}.__tag ~= 0 then ")?;
match T::Into::ty() {
TypeType::Void => write!(f, "{ret} = nil; ")?, // for void options, we don't have a __value
TypeType::Primitive => {
// can always copy primitives to stack
write!(f, "{ret} = {ret}.__value; {}", T::postlude(ret))?;
}
TypeType::Aggregate => {
let ct = T::Into::name();
if T::require_owned() {
// inner value requires ownership; copy it into its own cdata and forget
// option.
write!(f, "{ret} = __new(__ct.{ct}, {ret}.__value); ")?;
write!(f, "{}", T::postlude(ret))?;
} else {
// inner value is a "temporary" like an option itself and doesn't require
// full ownership of itself. we just need to keep the option object alive
// until its postlude completes.
write!(f, "local {ret}_keep = {ret}; {ret} = {ret}.__value; ")?;
write!(f, "do {}end; ", T::postlude(ret))?;
write!(f, "__C.{KEEP_FN}({ret}_keep); ")?; // keep original option alive
}
}
}
write!(f, "else {ret} = nil; end; ")
})
}
}

10
crates/luaffi/src/result.rs
View File

@ -72,12 +72,12 @@ unsafe impl<T: IntoFfi, E: Display> IntoFfi for Result<T, E> {
write!(f, "{ret} = __new(__ct.{ct}, {ret}.__value); ")?;
write!(f, "{}", T::postlude(ret))?;
} else {
// inner value is a "temporary" itself and doesn't require full ownership of
// itself. we just need to keep the result object alive until its postlude
// completes.
write!(f, "local __{ret} = {ret}; {ret} = {ret}.__value; ")?;
// inner value is a "temporary" like a result itself and doesn't require
// full ownership of itself. we just need to keep the result object alive
// until its postlude completes.
write!(f, "local {ret}_keep = {ret}; {ret} = {ret}.__value; ")?;
write!(f, "do {}end; ", T::postlude(ret))?;
write!(f, "__C.{KEEP_FN}(__{ret}); ")?; // keep original result alive
write!(f, "__C.{KEEP_FN}({ret}_keep); ")?; // keep original result alive
}
}
}

38
crates/luaffi/src/string.rs
View File

@ -4,7 +4,7 @@ use crate::{
};
use bstr::{BStr, BString};
use luaffi_impl::{cdef, metatype};
use std::{fmt::Display, mem::ManuallyDrop, ptr, slice};
use std::{fmt::Display, mem::ManuallyDrop, slice};
pub(crate) const IS_UTF8_FN: &str = "luaffi_is_utf8";
pub(crate) const DROP_BUFFER_FN: &str = "luaffi_drop_buffer";
@ -42,6 +42,7 @@ impl lua_buf {
}
}
#[cfg(feature = "option_string_ffi")]
pub(crate) fn null() -> Self {
Self {
__ptr: ptr::null(),
@ -71,6 +72,7 @@ impl lua_buffer {
}
}
#[cfg(feature = "option_string_ffi")]
pub(crate) fn null() -> Self {
Self {
__ptr: ptr::null_mut(),
@ -228,7 +230,14 @@ impl_into_via!(&'static str, &'static BStr);
impl_into_via!(BString, Vec<u8>);
impl_into_via!(String, BString);
macro_rules! impl_optional_from {
// `Option<String>: From/IntoFfi` isn't implemented because it conflicts with the generic
// `Option<T>: From/IntoFfi` impl and rust doesn't have specialisation yet (and probably not anytime
// soon). this is fine for now because we have specialisation for string-like parameters implemented
// in the #[metatype] macro already, and string returns wrapped in `Option<T>` isn't much additional
// overhead.
#[cfg(feature = "option_string_abi")]
mod impl_option_string {
macro_rules! impl_optional_from {
($ty:ty) => {
unsafe impl<'s> FromFfi for Option<$ty> {
type From = <$ty as FromFfi>::From;
@ -250,13 +259,13 @@ macro_rules! impl_optional_from {
}
}
};
}
}
impl_optional_from!(&'s [u8]);
impl_optional_from!(&'s BStr);
impl_optional_from!(&'s str);
impl_optional_from!(&'s [u8]);
impl_optional_from!(&'s BStr);
impl_optional_from!(&'s str);
macro_rules! impl_optional_into {
macro_rules! impl_optional_into {
($ty:ty, $null:expr) => {
unsafe impl IntoFfi for Option<$ty> {
type Into = <$ty as IntoFfi>::Into;
@ -273,11 +282,12 @@ macro_rules! impl_optional_into {
}
}
};
}
}
impl_optional_into!(&'static [u8], lua_buf::null());
impl_optional_into!(&'static BStr, lua_buf::null());
impl_optional_into!(&'static str, lua_buf::null());
impl_optional_into!(Vec<u8>, lua_buffer::null());
impl_optional_into!(BString, lua_buffer::null());
impl_optional_into!(String, lua_buffer::null());
impl_optional_into!(&'static [u8], lua_buf::null());
impl_optional_into!(&'static BStr, lua_buf::null());
impl_optional_into!(&'static str, lua_buf::null());
impl_optional_into!(Vec<u8>, lua_buffer::null());
impl_optional_into!(BString, lua_buffer::null());
impl_optional_into!(String, lua_buffer::null());
}