6 files changed, 503 insertions, 0 deletions

diff --git a/embassy-executor-macros/src/lib.rs b/embassy-executor-macros/src/lib.rs
new file mode 100644
index 000000000..c9d58746a
--- /dev/null
+++ b/embassy-executor-macros/src/lib.rs
@@ -0,0 +1,175 @@
+#![doc = include_str!("../README.md")]
+extern crate proc_macro;
+
+use darling::ast::NestedMeta;
+use proc_macro::TokenStream;
+
+mod macros;
+mod util;
+use macros::*;
+use syn::parse::{Parse, ParseBuffer};
+use syn::punctuated::Punctuated;
+use syn::Token;
+
+struct Args {
+    meta: Vec<NestedMeta>,
+}
+
+impl Parse for Args {
+    fn parse(input: &ParseBuffer) -> syn::Result<Self> {
+        let meta = Punctuated::<NestedMeta, Token![,]>::parse_terminated(input)?;
+        Ok(Args {
+            meta: meta.into_iter().collect(),
+        })
+    }
+}
+
+/// Declares an async task that can be run by `embassy-executor`. The optional `pool_size` parameter can be used to specify how
+/// many concurrent tasks can be spawned (default is 1) for the function.
+///
+///
+/// The following restrictions apply:
+///
+/// * The function must be declared `async`.
+/// * The function must not use generics.
+/// * The optional `pool_size` attribute must be 1 or greater.
+///
+///
+/// ## Examples
+///
+/// Declaring a task taking no arguments:
+///
+/// ``` rust
+/// #[embassy_executor::task]
+/// async fn mytask() {
+///     // Function body
+/// }
+/// ```
+///
+/// Declaring a task with a given pool size:
+///
+/// ``` rust
+/// #[embassy_executor::task(pool_size = 4)]
+/// async fn mytask() {
+///     // Function body
+/// }
+/// ```
+#[proc_macro_attribute]
+pub fn task(args: TokenStream, item: TokenStream) -> TokenStream {
+    let args = syn::parse_macro_input!(args as Args);
+    let f = syn::parse_macro_input!(item as syn::ItemFn);
+
+    task::run(&args.meta, f).unwrap_or_else(|x| x).into()
+}
+
+/// Creates a new `executor` instance and declares an application entry point for Cortex-M spawning the corresponding function body as an async task.
+///
+/// The following restrictions apply:
+///
+/// * The function must accept exactly 1 parameter, an `embassy_executor::Spawner` handle that it can use to spawn additional tasks.
+/// * The function must be declared `async`.
+/// * The function must not use generics.
+/// * Only a single `main` task may be declared.
+///
+/// ## Examples
+/// Spawning a task:
+///
+/// ``` rust
+/// #[embassy_executor::main]
+/// async fn main(_s: embassy_executor::Spawner) {
+///     // Function body
+/// }
+/// ```
+#[proc_macro_attribute]
+pub fn main_cortex_m(args: TokenStream, item: TokenStream) -> TokenStream {
+    let args = syn::parse_macro_input!(args as Args);
+    let f = syn::parse_macro_input!(item as syn::ItemFn);
+    main::run(&args.meta, f, main::cortex_m()).unwrap_or_else(|x| x).into()
+}
+
+/// Creates a new `executor` instance and declares an application entry point for RISC-V spawning the corresponding function body as an async task.
+///
+/// The following restrictions apply:
+///
+/// * The function must accept exactly 1 parameter, an `embassy_executor::Spawner` handle that it can use to spawn additional tasks.
+/// * The function must be declared `async`.
+/// * The function must not use generics.
+/// * Only a single `main` task may be declared.
+///
+/// A user-defined entry macro can be optionally provided via the `entry` argument to override the default of `riscv_rt::entry`.
+///
+/// ## Examples
+/// Spawning a task:
+///
+/// ``` rust
+/// #[embassy_executor::main]
+/// async fn main(_s: embassy_executor::Spawner) {
+///     // Function body
+/// }
+/// ```
+///
+/// Spawning a task using a custom entry macro:
+/// ``` rust
+/// #[embassy_executor::main(entry = "esp_riscv_rt::entry")]
+/// async fn main(_s: embassy_executor::Spawner) {
+///     // Function body
+/// }
+/// ```
+#[proc_macro_attribute]
+pub fn main_riscv(args: TokenStream, item: TokenStream) -> TokenStream {
+    let args = syn::parse_macro_input!(args as Args);
+    let f = syn::parse_macro_input!(item as syn::ItemFn);
+    main::run(&args.meta, f, main::riscv(&args.meta))
+        .unwrap_or_else(|x| x)
+        .into()
+}
+
+/// Creates a new `executor` instance and declares an application entry point for STD spawning the corresponding function body as an async task.
+///
+/// The following restrictions apply:
+///
+/// * The function must accept exactly 1 parameter, an `embassy_executor::Spawner` handle that it can use to spawn additional tasks.
+/// * The function must be declared `async`.
+/// * The function must not use generics.
+/// * Only a single `main` task may be declared.
+///
+/// ## Examples
+/// Spawning a task:
+///
+/// ``` rust
+/// #[embassy_executor::main]
+/// async fn main(_s: embassy_executor::Spawner) {
+///     // Function body
+/// }
+/// ```
+#[proc_macro_attribute]
+pub fn main_std(args: TokenStream, item: TokenStream) -> TokenStream {
+    let args = syn::parse_macro_input!(args as Args);
+    let f = syn::parse_macro_input!(item as syn::ItemFn);
+    main::run(&args.meta, f, main::std()).unwrap_or_else(|x| x).into()
+}
+
+/// Creates a new `executor` instance and declares an application entry point for WASM spawning the corresponding function body as an async task.
+///
+/// The following restrictions apply:
+///
+/// * The function must accept exactly 1 parameter, an `embassy_executor::Spawner` handle that it can use to spawn additional tasks.
+/// * The function must be declared `async`.
+/// * The function must not use generics.
+/// * Only a single `main` task may be declared.
+///
+/// ## Examples
+/// Spawning a task:
+///
+/// ``` rust
+/// #[embassy_executor::main]
+/// async fn main(_s: embassy_executor::Spawner) {
+///     // Function body
+/// }
+/// ```
+#[proc_macro_attribute]
+pub fn main_wasm(args: TokenStream, item: TokenStream) -> TokenStream {
+    let args = syn::parse_macro_input!(args as Args);
+    let f = syn::parse_macro_input!(item as syn::ItemFn);
+    main::run(&args.meta, f, main::wasm()).unwrap_or_else(|x| x).into()
+}
diff --git a/embassy-executor-macros/src/macros/main.rs b/embassy-executor-macros/src/macros/main.rs
new file mode 100644
index 000000000..3c0d58567
--- /dev/null
+++ b/embassy-executor-macros/src/macros/main.rs
@@ -0,0 +1,138 @@
+use darling::export::NestedMeta;
+use darling::FromMeta;
+use proc_macro2::TokenStream;
+use quote::quote;
+use syn::{Expr, ReturnType, Type};
+
+use crate::util::ctxt::Ctxt;
+
+#[derive(Debug, FromMeta)]
+struct Args {
+    #[darling(default)]
+    entry: Option<String>,
+}
+
+pub fn riscv(args: &[NestedMeta]) -> TokenStream {
+    let maybe_entry = match Args::from_list(args) {
+        Ok(args) => args.entry,
+        Err(e) => return e.write_errors(),
+    };
+
+    let entry = maybe_entry.unwrap_or("riscv_rt::entry".into());
+    let entry = match Expr::from_string(&entry) {
+        Ok(expr) => expr,
+        Err(e) => return e.write_errors(),
+    };
+
+    quote! {
+        #[#entry]
+        fn main() -> ! {
+            let mut executor = ::embassy_executor::Executor::new();
+            let executor = unsafe { __make_static(&mut executor) };
+            executor.run(|spawner| {
+                spawner.must_spawn(__embassy_main(spawner));
+            })
+        }
+    }
+}
+
+pub fn cortex_m() -> TokenStream {
+    quote! {
+        #[cortex_m_rt::entry]
+        fn main() -> ! {
+            let mut executor = ::embassy_executor::Executor::new();
+            let executor = unsafe { __make_static(&mut executor) };
+            executor.run(|spawner| {
+                spawner.must_spawn(__embassy_main(spawner));
+            })
+        }
+    }
+}
+
+pub fn wasm() -> TokenStream {
+    quote! {
+        #[wasm_bindgen::prelude::wasm_bindgen(start)]
+        pub fn main() -> Result<(), wasm_bindgen::JsValue> {
+            let executor = ::std::boxed::Box::leak(::std::boxed::Box::new(::embassy_executor::Executor::new()));
+
+            executor.start(|spawner| {
+                spawner.spawn(__embassy_main(spawner)).unwrap();
+            });
+
+            Ok(())
+        }
+    }
+}
+
+pub fn std() -> TokenStream {
+    quote! {
+        fn main() -> ! {
+            let mut executor = ::embassy_executor::Executor::new();
+            let executor = unsafe { __make_static(&mut executor) };
+
+            executor.run(|spawner| {
+                spawner.must_spawn(__embassy_main(spawner));
+            })
+        }
+    }
+}
+
+pub fn run(args: &[NestedMeta], f: syn::ItemFn, main: TokenStream) -> Result<TokenStream, TokenStream> {
+    #[allow(unused_variables)]
+    let args = Args::from_list(args).map_err(|e| e.write_errors())?;
+
+    let fargs = f.sig.inputs.clone();
+
+    let ctxt = Ctxt::new();
+
+    if f.sig.asyncness.is_none() {
+        ctxt.error_spanned_by(&f.sig, "main function must be async");
+    }
+    if !f.sig.generics.params.is_empty() {
+        ctxt.error_spanned_by(&f.sig, "main function must not be generic");
+    }
+    if !f.sig.generics.where_clause.is_none() {
+        ctxt.error_spanned_by(&f.sig, "main function must not have `where` clauses");
+    }
+    if !f.sig.abi.is_none() {
+        ctxt.error_spanned_by(&f.sig, "main function must not have an ABI qualifier");
+    }
+    if !f.sig.variadic.is_none() {
+        ctxt.error_spanned_by(&f.sig, "main function must not be variadic");
+    }
+    match &f.sig.output {
+        ReturnType::Default => {}
+        ReturnType::Type(_, ty) => match &**ty {
+            Type::Tuple(tuple) if tuple.elems.is_empty() => {}
+            Type::Never(_) => {}
+            _ => ctxt.error_spanned_by(
+                &f.sig,
+                "main function must either not return a value, return `()` or return `!`",
+            ),
+        },
+    }
+
+    if fargs.len() != 1 {
+        ctxt.error_spanned_by(&f.sig, "main function must have 1 argument: the spawner.");
+    }
+
+    ctxt.check()?;
+
+    let f_body = f.block;
+    let out = &f.sig.output;
+
+    let result = quote! {
+        #[::embassy_executor::task()]
+        async fn __embassy_main(#fargs) #out {
+            #f_body
+        }
+
+        unsafe fn __make_static<T>(t: &mut T) -> &'static mut T {
+            ::core::mem::transmute(t)
+        }
+
+        #main
+    };
+
+    Ok(result)
+}
diff --git a/embassy-executor-macros/src/macros/mod.rs b/embassy-executor-macros/src/macros/mod.rs
new file mode 100644
index 000000000..572094ca6
--- /dev/null
+++ b/embassy-executor-macros/src/macros/mod.rs
@@ -0,0 +1,2 @@
+pub mod main;
+pub mod task;
diff --git a/embassy-executor-macros/src/macros/task.rs b/embassy-executor-macros/src/macros/task.rs
new file mode 100644
index 000000000..5161e1020
--- /dev/null
+++ b/embassy-executor-macros/src/macros/task.rs
@@ -0,0 +1,114 @@
+use darling::export::NestedMeta;
+use darling::FromMeta;
+use proc_macro2::{Span, TokenStream};
+use quote::{format_ident, quote};
+use syn::{parse_quote, Expr, ExprLit, ItemFn, Lit, LitInt, ReturnType, Type};
+
+use crate::util::ctxt::Ctxt;
+
+#[derive(Debug, FromMeta)]
+struct Args {
+    #[darling(default)]
+    pool_size: Option<syn::Expr>,
+}
+
+pub fn run(args: &[NestedMeta], f: syn::ItemFn) -> Result<TokenStream, TokenStream> {
+    let args = Args::from_list(args).map_err(|e| e.write_errors())?;
+
+    let pool_size = args.pool_size.unwrap_or(Expr::Lit(ExprLit {
+        attrs: vec![],
+        lit: Lit::Int(LitInt::new("1", Span::call_site())),
+    }));
+
+    let ctxt = Ctxt::new();
+
+    if f.sig.asyncness.is_none() {
+        ctxt.error_spanned_by(&f.sig, "task functions must be async");
+    }
+    if !f.sig.generics.params.is_empty() {
+        ctxt.error_spanned_by(&f.sig, "task functions must not be generic");
+    }
+    if !f.sig.generics.where_clause.is_none() {
+        ctxt.error_spanned_by(&f.sig, "task functions must not have `where` clauses");
+    }
+    if !f.sig.abi.is_none() {
+        ctxt.error_spanned_by(&f.sig, "task functions must not have an ABI qualifier");
+    }
+    if !f.sig.variadic.is_none() {
+        ctxt.error_spanned_by(&f.sig, "task functions must not be variadic");
+    }
+    match &f.sig.output {
+        ReturnType::Default => {}
+        ReturnType::Type(_, ty) => match &**ty {
+            Type::Tuple(tuple) if tuple.elems.is_empty() => {}
+            Type::Never(_) => {}
+            _ => ctxt.error_spanned_by(
+                &f.sig,
+                "task functions must either not return a value, return `()` or return `!`",
+            ),
+        },
+    }
+
+    let mut arg_names = Vec::new();
+    let mut fargs = f.sig.inputs.clone();
+
+    for arg in fargs.iter_mut() {
+        match arg {
+            syn::FnArg::Receiver(_) => {
+                ctxt.error_spanned_by(arg, "task functions must not have receiver arguments");
+            }
+            syn::FnArg::Typed(t) => match t.pat.as_mut() {
+                syn::Pat::Ident(id) => {
+                    arg_names.push(id.ident.clone());
+                    id.mutability = None;
+                }
+                _ => {
+                    ctxt.error_spanned_by(arg, "pattern matching in task arguments is not yet supported");
+                }
+            },
+        }
+    }
+
+    ctxt.check()?;
+
+    let task_ident = f.sig.ident.clone();
+    let task_inner_ident = format_ident!("__{}_task", task_ident);
+
+    let mut task_inner = f;
+    let visibility = task_inner.vis.clone();
+    task_inner.vis = syn::Visibility::Inherited;
+    task_inner.sig.ident = task_inner_ident.clone();
+
+    #[cfg(feature = "nightly")]
+    let mut task_outer: ItemFn = parse_quote! {
+        #visibility fn #task_ident(#fargs) -> ::embassy_executor::SpawnToken<impl Sized> {
+            type Fut = impl ::core::future::Future + 'static;
+            const POOL_SIZE: usize = #pool_size;
+            static POOL: ::embassy_executor::raw::TaskPool<Fut, POOL_SIZE> = ::embassy_executor::raw::TaskPool::new();
+            unsafe { POOL._spawn_async_fn(move || #task_inner_ident(#(#arg_names,)*)) }
+        }
+    };
+    #[cfg(not(feature = "nightly"))]
+    let mut task_outer: ItemFn = parse_quote! {
+        #visibility fn #task_ident(#fargs) -> ::embassy_executor::SpawnToken<impl Sized> {
+            const POOL_SIZE: usize = #pool_size;
+            static POOL: ::embassy_executor::_export::TaskPoolRef = ::embassy_executor::_export::TaskPoolRef::new();
+            unsafe { POOL.get::<_, POOL_SIZE>()._spawn_async_fn(move || #task_inner_ident(#(#arg_names,)*)) }
+        }
+    };
+
+    task_outer.attrs.append(&mut task_inner.attrs.clone());
+
+    let result = quote! {
+        // This is the user's task function, renamed.
+        // We put it outside the #task_ident fn below, because otherwise
+        // the items defined there (such as POOL) would be in scope
+        // in the user's code.
+        #[doc(hidden)]
+        #task_inner
+
+        #task_outer
+    };
+
+    Ok(result)
+}
diff --git a/embassy-executor-macros/src/util/ctxt.rs b/embassy-executor-macros/src/util/ctxt.rs
new file mode 100644
index 000000000..74c872c3c
--- /dev/null
+++ b/embassy-executor-macros/src/util/ctxt.rs
@@ -0,0 +1,73 @@
+// nifty utility borrowed from serde :)
+// https://github.com/serde-rs/serde/blob/master/serde_derive/src/internals/ctxt.rs
+
+use std::cell::RefCell;
+use std::fmt::Display;
+use std::thread;
+
+use proc_macro2::TokenStream;
+use quote::{quote, ToTokens};
+use syn;
+
+/// A type to collect errors together and format them.
+///
+/// Dropping this object will cause a panic. It must be consumed using `check`.
+///
+/// References can be shared since this type uses run-time exclusive mut checking.
+#[derive(Default)]
+pub struct Ctxt {
+    // The contents will be set to `None` during checking. This is so that checking can be
+    // enforced.
+    errors: RefCell<Option<Vec<syn::Error>>>,
+}
+
+impl Ctxt {
+    /// Create a new context object.
+    ///
+    /// This object contains no errors, but will still trigger a panic if it is not `check`ed.
+    pub fn new() -> Self {
+        Ctxt {
+            errors: RefCell::new(Some(Vec::new())),
+        }
+    }
+
+    /// Add an error to the context object with a tokenenizable object.
+    ///
+    /// The object is used for spanning in error messages.
+    pub fn error_spanned_by<A: ToTokens, T: Display>(&self, obj: A, msg: T) {
+        self.errors
+            .borrow_mut()
+            .as_mut()
+            .unwrap()
+            // Curb monomorphization from generating too many identical methods.
+            .push(syn::Error::new_spanned(obj.into_token_stream(), msg));
+    }
+
+    /// Add one of Syn's parse errors.
+    #[allow(unused)]
+    pub fn syn_error(&self, err: syn::Error) {
+        self.errors.borrow_mut().as_mut().unwrap().push(err);
+    }
+
+    /// Consume this object, producing a formatted error string if there are errors.
+    pub fn check(self) -> Result<(), TokenStream> {
+        let errors = self.errors.borrow_mut().take().unwrap();
+        match errors.len() {
+            0 => Ok(()),
+            _ => Err(to_compile_errors(errors)),
+        }
+    }
+}
+
+fn to_compile_errors(errors: Vec<syn::Error>) -> proc_macro2::TokenStream {
+    let compile_errors = errors.iter().map(syn::Error::to_compile_error);
+    quote!(#(#compile_errors)*)
+}
+
+impl Drop for Ctxt {
+    fn drop(&mut self) {
+        if !thread::panicking() && self.errors.borrow().is_some() {
+            panic!("forgot to check for errors");
+        }
+    }
+}
diff --git a/embassy-executor-macros/src/util/mod.rs b/embassy-executor-macros/src/util/mod.rs
new file mode 100644
index 000000000..28702809e
--- /dev/null
+++ b/embassy-executor-macros/src/util/mod.rs
@@ -0,0 +1 @@
+pub mod ctxt;