1use core::panic;
 2
 3use proc_macro::TokenStream;
 4use quote::{format_ident, quote};
 5use syn::{parse_macro_input, ItemFn, Visibility};
 6
 7#[proc_macro_attribute]
 8pub fn bind(args: TokenStream, function: TokenStream) -> TokenStream {
 9    if !args.is_empty() {
10        panic!("The bind attribute does not take any arguments");
11    }
12
13    let inner_fn = parse_macro_input!(function as ItemFn);
14    if let Visibility::Public(_) = inner_fn.vis {
15    } else {
16        panic!("The bind attribute only works for public functions");
17    }
18
19    let inner_fn_name = format_ident!("{}", inner_fn.sig.ident);
20    let outer_fn_name = format_ident!("__{}", inner_fn_name);
21
22    let variadic = inner_fn.sig.inputs.len();
23    let i = (0..variadic).map(syn::Index::from);
24    let t = (0..variadic).map(|_| quote! { _ });
25
26    // this is cursed...
27    let (args, ty) = if variadic != 1 {
28        (
29            quote! {
30                #( data.#i ),*
31            },
32            quote! {
33                ( #( #t ),* )
34            },
35        )
36    } else {
37        (quote! { data }, quote! { _ })
38    };
39
40    TokenStream::from(quote! {
41        #[no_mangle]
42        #inner_fn
43
44        #[no_mangle]
45        pub extern "C" fn #outer_fn_name(ptr: *const u8, len: usize) -> *const ::plugin::__Buffer {
46            // setup
47            let buffer = ::plugin::__Buffer { ptr, len };
48            let data = unsafe { buffer.to_vec() };
49
50            // operation
51            let data: #ty = ::plugin::bincode::deserialize(&data).unwrap();
52            let result = #inner_fn_name(#args);
53            let new_data: Result<Vec<u8>, _> = ::plugin::bincode::serialize(&result);
54            let new_data = new_data.unwrap();
55
56            // teardown
57            let new_buffer = unsafe { ::plugin::__Buffer::from_vec(new_data) };
58            return new_buffer.leak_to_heap();
59        }
60    })
61}