entity_data_macros/
lib.rs

1use proc_macro2::TokenStream;
2use quote::quote;
3use syn::{parse_macro_input, DeriveInput};
4
5/// Implements archetype capabilities for `struct`.
6#[proc_macro_derive(Archetype)]
7pub fn derive_archetype_fn(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
8    let main_crate = quote!(::entity_data);
9
10    let DeriveInput {
11        ident,
12        data,
13        generics,
14        ..
15    } = parse_macro_input!(input as DeriveInput);
16
17    let where_clause = &generics.where_clause;
18
19    let fields = if let syn::Data::Struct(data) = data {
20        data.fields
21    } else {
22        panic!("Not a structure!");
23    };
24
25    let types: Vec<_> = fields
26        .iter()
27        .map(|field| {
28            let field_ty = &field.ty;
29            quote! {
30                ::std::any::TypeId::of::<#field_ty>(),
31            }
32        })
33        .collect();
34
35    let field_impls: Vec<_> = fields
36        .into_iter()
37        .enumerate()
38        .map(|(i, field)| {
39            let field_ty = field.ty;
40
41            let offset = if let Some(field_ident) = &field.ident {
42                quote! {
43                    #main_crate::private::offset_of!(Self, #field_ident)
44                }
45            } else {
46                let i = syn::Index::from(i);
47                quote! {
48                    #main_crate::private::offset_of!(Self, #i)
49                }
50            };
51
52            quote! {
53                #main_crate::private::ComponentInfo {
54                    type_id: ::std::any::TypeId::of::<#field_ty>(),
55                    range: {
56                        let offset = #offset;
57                        let size = ::std::mem::size_of::<#field_ty>();
58                        offset..(offset + size)
59                    },
60                },
61            }
62        })
63        .collect();
64
65    let fields_len = field_impls.len();
66
67    // Check component uniqueness
68    {
69        let mut field_names: Vec<_> = types.iter().map(|v| v.to_string()).collect();
70        field_names.sort();
71        let initial_len = field_names.len();
72
73        field_names.dedup();
74        let deduped_len = field_names.len();
75
76        if initial_len != deduped_len {
77            panic!("Archetype contains multiple components of the same type.");
78        }
79    }
80
81    let mut field_types = TokenStream::new();
82    field_types.extend(types.into_iter());
83
84    let mut fields = TokenStream::new();
85    fields.extend(field_impls.into_iter());
86
87    quote! {
88        impl #generics #main_crate::StaticArchetype for #ident #generics #where_clause {
89            const N_COMPONENTS: usize = #fields_len;
90
91            fn metadata() -> #main_crate::private::ArchetypeMetadata {
92                #main_crate::private::ArchetypeMetadata {
93                    type_id: ::std::any::TypeId::of::<Self>(),
94                    component_type_ids: || #main_crate::private::smallvec![#field_types],
95                    component_infos: || #main_crate::private::smallvec![#fields],
96                    size: ::std::mem::size_of::<Self>(),
97                    needs_drop: ::std::mem::needs_drop::<Self>(),
98                    drop_fn: |p: *mut u8| unsafe { ::std::ptr::drop_in_place(p as *mut Self) },
99                }
100            }
101        }
102
103        impl #generics #main_crate::ArchetypeState for #ident #generics #where_clause {
104            fn ty(&self) -> ::std::any::TypeId {
105                ::std::any::TypeId::of::<Self>()
106            }
107
108            fn as_ptr(&self) -> *const u8 {
109                self as *const _ as *const u8
110            }
111
112            fn forget(self) {
113                ::std::mem::forget(self);
114            }
115
116            fn metadata(&self) -> #main_crate::private::ArchetypeMetadata {
117                <Self as #main_crate::StaticArchetype>::metadata()
118            }
119
120            fn num_components(&self) -> usize {
121                #fields_len
122            }
123
124            fn as_any(&self) -> &dyn ::std::any::Any {
125                self
126            }
127
128            fn as_any_mut(&mut self) -> &mut dyn ::std::any::Any {
129                self
130            }
131        }
132    }
133    .into()
134}
entity_data_macros/lib.rs

entity_data_macros/
lib.rs
