shiv_macro_impl/
bundle.rs

1use proc_macro2::Span;
2use quote::quote;
3use syn::{parse_quote, Data, DeriveInput, Fields, Generics, Index, Member, Path, Type};
4
5pub fn derive_bundle(mut input: DeriveInput, shiv: Path) -> proc_macro2::TokenStream {
6    let name = input.ident;
7
8    let types = types(&input.data);
9    let members = members(&input.data);
10
11    let count = types.len();
12
13    add_generics(&mut input.generics, &shiv);
14    let (impl_generics, ty_generics, where_clause) = input.generics.split_for_impl();
15
16    quote! {
17        #[automatically_derived]
18        unsafe impl #impl_generics #shiv::bundle::Bundle for #name #ty_generics #where_clause {
19            type Iter = std::array::IntoIter<*mut ::std::primitive::u8, #count>;
20
21            #[inline]
22            fn components(components: &mut #shiv::world::Components) -> ::std::vec::Vec<#shiv::world::ComponentId> {
23                ::std::vec![#(components.init_component::<#types>()),*]
24            }
25
26            #[inline]
27            unsafe fn get_components(bundle: *mut Self) -> Self::Iter {
28                std::array::IntoIter::new([#(unsafe { &mut (*bundle).#members as *mut _ as *mut ::std::primitive::u8 }),*])
29            }
30        }
31    }
32}
33
34fn add_generics(generics: &mut Generics, shiv: &Path) {
35    for param in generics.type_params_mut() {
36        param.bounds.push(parse_quote!(#shiv::world::Component));
37    }
38}
39
40fn types(data: &Data) -> Vec<Type> {
41    match data {
42        Data::Struct(data) => field_types(&data.fields),
43        _ => unimplemented!("Bundle can only be derived for structs"),
44    }
45}
46
47fn members(data: &Data) -> Vec<Member> {
48    match data {
49        Data::Struct(data) => field_members(&data.fields),
50        _ => unimplemented!("Bundle can only be derived for structs"),
51    }
52}
53
54fn field_types(fields: &Fields) -> Vec<Type> {
55    match fields {
56        Fields::Named(fields) => fields.named.iter().map(|field| field.ty.clone()).collect(),
57        Fields::Unnamed(fields) => fields
58            .unnamed
59            .iter()
60            .map(|field| field.ty.clone())
61            .collect(),
62        Fields::Unit => Vec::new(),
63    }
64}
65
66fn field_members(fields: &Fields) -> Vec<Member> {
67    match fields {
68        Fields::Named(fields) => fields
69            .named
70            .iter()
71            .map(|field| Member::Named(field.ident.clone().unwrap()))
72            .collect(),
73        Fields::Unnamed(fields) => fields
74            .unnamed
75            .iter()
76            .enumerate()
77            .map(|(i, _)| {
78                Member::Unnamed(Index {
79                    index: i as u32,
80                    span: Span::call_site(),
81                })
82            })
83            .collect(),
84        Fields::Unit => Vec::new(),
85    }
86}
shiv_macro_impl/bundle.rs

shiv_macro_impl/
bundle.rs
