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extern crate proc_macro;
use proc_macro as pm;
use proc_macro2::TokenStream;
use quote::quote;
use syn::{self, parse_macro_input, parse_quote, Data, DeriveInput, Fields};
#[proc_macro_derive(IntoWaker)]
pub fn into_waker_derive(stream: pm::TokenStream) -> pm::TokenStream {
let input = parse_macro_input!(stream as DeriveInput);
if !input.generics.params.is_empty() {
panic!("IntoWaker can only be derived for concrete types");
}
#[allow(non_snake_case)]
let WakerStruct = input.ident;
let implementation = quote! {
impl cooked_waker::IntoWaker for #WakerStruct {
#[must_use]
fn into_waker(self) -> core::task::Waker {
use core::task::{Waker, RawWaker, RawWakerVTable};
use core::clone::Clone;
use cooked_waker::{Wake, WakeRef};
use cooked_waker::stowaway::{self, Stowaway};
#[inline]
fn make_raw_waker(waker: #WakerStruct) -> RawWaker {
let stowed = Stowaway::new(waker);
RawWaker::new(Stowaway::into_raw(stowed), &VTABLE)
}
static VTABLE: RawWakerVTable = RawWakerVTable::new(
|raw| {
let raw = raw as *mut ();
let waker: & #WakerStruct = unsafe { stowaway::ref_from_stowed(&raw) };
make_raw_waker(Clone::clone(waker))
},
|raw| {
let waker: #WakerStruct = unsafe { stowaway::unstow(raw as *mut ()) };
Wake::wake(waker);
},
|raw| {
let raw = raw as *mut ();
let waker: & #WakerStruct = unsafe { stowaway::ref_from_stowed(&raw) };
WakeRef::wake_by_ref(waker)
},
|raw| {
let _waker: Stowaway<#WakerStruct> = unsafe {
Stowaway::from_raw(raw as *mut ())
};
},
);
let raw_waker = make_raw_waker(self);
unsafe { Waker::from_raw(raw_waker) }
}
}
};
implementation.into()
}
#[derive(Debug, Copy, Clone, PartialEq, Eq)]
enum WakeTrait {
Wake,
WakeRef,
}
impl WakeTrait {
#[inline]
fn trait_path(self) -> syn::Path {
match self {
WakeTrait::Wake => parse_quote! {::cooked_waker::Wake},
WakeTrait::WakeRef => parse_quote! {::cooked_waker::WakeRef},
}
}
#[inline]
fn method(self) -> syn::Ident {
match self {
WakeTrait::Wake => parse_quote! {wake},
WakeTrait::WakeRef => parse_quote! {wake_by_ref},
}
}
#[inline]
fn name(self) -> &'static str {
match self {
WakeTrait::Wake => "Wake",
WakeTrait::WakeRef => "WakeRef",
}
}
#[inline]
fn apply_reference(self, input: TokenStream) -> TokenStream {
match self {
WakeTrait::Wake => input,
WakeTrait::WakeRef => quote! {& #input},
}
}
}
fn derive_wake_like(spec: WakeTrait, stream: pm::TokenStream) -> pm::TokenStream {
let input = parse_macro_input!(stream as DeriveInput);
let trait_path = spec.trait_path();
let method = spec.method();
let type_name = input.ident;
let mut generics = input.generics;
let where_clause = generics.make_where_clause();
match input.data {
Data::Struct(s) => {
let fields = match s.fields {
Fields::Named(fields) => fields.named,
Fields::Unnamed(fields) => fields.unnamed,
Fields::Unit => panic!(
"`{name}` can only be derived on structs with a single `{name}` field",
name = spec.name()
),
};
if fields.len() != 1 {
panic!(
"Can only derive `{name}` on structs with exactly 1 field",
name = spec.name()
);
}
let field = fields.first().unwrap();
let field_type = &field.ty;
let field_name: syn::Member = field
.ident
.clone()
.map(syn::Member::Named)
.unwrap_or_else(|| parse_quote!(0));
where_clause
.predicates
.push(parse_quote! {#field_type: #trait_path});
let (impl_generics, ty_generics, where_clause) = generics.split_for_impl();
let self_param = spec.apply_reference(quote! {self});
let field_invocation = spec.apply_reference(quote! {self.#field_name});
let implementation = quote! {
impl #impl_generics #trait_path for #type_name #ty_generics #where_clause {
#[inline]
fn #method(#self_param) {
#trait_path::#method(#field_invocation)
}
}
};
implementation.into()
}
Data::Enum(..) => unimplemented!("derive(Wake) for enums is still WIP"),
Data::Union(..) => panic!("`Wake` can only be derived for struct or enum types"),
}
}
#[proc_macro_derive(Wake)]
pub fn wake_derive(stream: pm::TokenStream) -> pm::TokenStream {
derive_wake_like(WakeTrait::Wake, stream)
}
#[proc_macro_derive(WakeRef)]
pub fn wake_ref_derive(stream: pm::TokenStream) -> pm::TokenStream {
derive_wake_like(WakeTrait::WakeRef, stream)
}