use proc_macro::TokenStream;
use quote::{format_ident, quote};
use syn::{Error, FnArg, ItemFn, PatType, Pat, PatIdent};
#[proc_macro_attribute]
pub fn cloud(_: TokenStream, input: TokenStream) -> TokenStream {
let ast = syn::parse::<ItemFn>(input).expect("Place this attribute above a function");
let name = ast.sig.ident;
let output = ast.sig.output;
let stub_name = format_ident!("{name}_stub");
let body = ast.block.stmts;
let stub = match ast.sig.inputs.first() {
Some(FnArg::Typed(PatType { pat, ty, .. })) => match &**pat {
Pat::Ident(PatIdent { mutability, ident, ..}) => quote! {
let #ident = ::cloud_lib::rmp_serde::from_slice::<#ty>(__input_bytes).unwrap();
fn #stub_name(#mutability #ident: #ty) #output {
#(#body);*
}
let output = #stub_name(#ident);
let __output_bytes = ::cloud_lib::rmp_serde::to_vec_named(&output).unwrap().leak();
::std::boxed::Box::new(::cloud_lib::CloudSlice {
len: __output_bytes.len(),
ptr: __output_bytes.as_mut_ptr(),
})
},
_ => Error::new(name.span(), "expected ident").to_compile_error(),
},
_ => Error::new(name.span(), "expected one argument").to_compile_error(),
};
quote! {
#[no_mangle]
fn #name(ptr: usize) -> ::std::boxed::Box<::cloud_lib::CloudSlice> {
let __input_bytes = unsafe {
let len = *(ptr as *const usize);
let data = (ptr + 4) as *mut u8;
::std::slice::from_raw_parts(data, len)
};
#stub
}
}
.into()
}