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 mut args = vec![];
24    for i in 0..variadic {
25        let ident = format_ident!("__{}_arg_{}", inner_fn_name, i);
26        args.push(ident);
27    }
28
29    let args = quote! {
30        ( #(args ,) )*
31    };
32
33    TokenStream::from(quote! {
34        #[no_mangle]
35        #inner_fn
36
37        #[no_mangle]
38        pub extern "C" fn #outer_fn_name(ptr: *const u8, len: usize) -> *const ::plugin::__Buffer {
39            // setup
40            let buffer = ::plugin::__Buffer { ptr, len };
41            let data = unsafe { buffer.to_vec() };
42
43            // operation
44            let #args = ::plugin::bincode::deserialize(&data).unwrap();
45            let result = #inner_fn_name #args;
46            let new_data: Result<Vec<u8>, _> = ::plugin::bincode::serialize(&result);
47            let new_data = new_data.unwrap();
48
49            // teardown
50            let new_buffer = unsafe { ::plugin::__Buffer::from_vec(new_data) };
51            return new_buffer.leak_to_heap();
52        }
53    })
54}