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().enumerate()
37        .map(|(i, field)| {
38            let field_ty = field.ty;
39
40            let offset = if let Some(field_ident) = &field.ident {
41                quote! {
42                    #main_crate::private::offset_of!(Self, #field_ident)
43                }
44            } else {
45                let i = syn::Index::from(i);
46                quote! {
47                    #main_crate::private::offset_of!(Self, #i)
48                }
49            };
50
51            quote! {
52                #main_crate::private::ComponentInfo {
53                    type_id: ::std::any::TypeId::of::<#field_ty>(),
54                    range: {
55                        let offset = #offset;
56                        let size = ::std::mem::size_of::<#field_ty>();
57                        offset..(offset + size)
58                    },
59                },
60            }
61        })
62        .collect();
63
64    let fields_len = field_impls.len();
65
66    // Check component uniqueness
67    {
68        let mut field_names: Vec<_> = types.iter().map(|v| v.to_string()).collect();
69        field_names.sort();
70        let initial_len = field_names.len();
71
72        field_names.dedup();
73        let deduped_len = field_names.len();
74
75        if initial_len != deduped_len {
76            panic!("Archetype contains multiple components of the same type.");
77        }
78    }
79
80    let mut field_types = TokenStream::new();
81    field_types.extend(types.into_iter());
82
83    let mut fields = TokenStream::new();
84    fields.extend(field_impls.into_iter());
85
86    quote! {
87        impl #generics #main_crate::StaticArchetype for #ident #generics #where_clause {
88            const N_COMPONENTS: usize = #fields_len;
89
90            fn metadata() -> #main_crate::private::ArchetypeMetadata {
91                #main_crate::private::ArchetypeMetadata {
92                    type_id: ::std::any::TypeId::of::<Self>(),
93                    component_type_ids: || #main_crate::private::smallvec![#field_types],
94                    component_infos: || #main_crate::private::smallvec![#fields],
95                    size: ::std::mem::size_of::<Self>(),
96                    needs_drop: ::std::mem::needs_drop::<Self>(),
97                    drop_fn: |p: *mut u8| unsafe { ::std::ptr::drop_in_place(p as *mut Self) },
98                }
99            }
100        }
101
102        impl #generics #main_crate::ArchetypeState for #ident #generics #where_clause {
103            fn ty(&self) -> ::std::any::TypeId {
104                ::std::any::TypeId::of::<Self>()
105            }
106
107            fn as_ptr(&self) -> *const u8 {
108                self as *const _ as *const u8
109            }
110
111            fn forget(self) {
112                ::std::mem::forget(self);
113            }
114
115            fn metadata(&self) -> #main_crate::private::ArchetypeMetadata {
116                <Self as #main_crate::StaticArchetype>::metadata()
117            }
118
119            fn num_components(&self) -> usize {
120                #fields_len
121            }
122
123            fn as_any(&self) -> &dyn ::std::any::Any {
124                self
125            }
126
127            fn as_any_mut(&mut self) -> &mut dyn ::std::any::Any {
128                self
129            }
130        }
131    }
132    .into()
133}
entity_data_macros/lib.rs

entity_data_macros/
lib.rs
