45 lines
1.4 KiB
Rust
45 lines
1.4 KiB
Rust
use crate::modules::{get_modules, get_path};
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use proc_macro::TokenStream;
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use quote::quote;
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use syn::{parse_macro_input, Data, DataStruct, DeriveInput, Fields};
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pub fn derive_bytes(input: TokenStream) -> TokenStream {
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let ast = parse_macro_input!(input as DeriveInput);
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let fields = match &ast.data {
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Data::Struct(DataStruct {
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fields: Fields::Named(fields),
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..
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}) => &fields.named,
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_ => panic!("expected a struct with named fields"),
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};
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let modules = get_modules(&ast.attrs);
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let bevy_core_path = get_path(&modules.bevy_core);
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let fields = fields
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.iter()
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.map(|field| field.ident.as_ref().unwrap())
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.collect::<Vec<_>>();
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let generics = ast.generics;
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let (impl_generics, ty_generics, _where_clause) = generics.split_for_impl();
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let struct_name = &ast.ident;
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TokenStream::from(quote! {
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impl #impl_generics #bevy_core_path::Bytes for #struct_name#ty_generics {
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fn write_bytes(&self, buffer: &mut [u8]) {
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let mut offset: usize = 0;
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#(let byte_len = self.#fields.byte_len();
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self.#fields.write_bytes(&mut buffer[offset..(offset + byte_len)]);
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offset += byte_len;)*
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}
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fn byte_len(&self) -> usize {
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let mut byte_len: usize = 0;
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#(byte_len += self.#fields.byte_len();)*
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byte_len
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}
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}
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})
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}
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