73 lines
2.1 KiB
Rust
73 lines
2.1 KiB
Rust
use proc_macro::TokenStream;
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use proc_macro2 as pm2;
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use crate::common::add_trait_bounds;
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pub fn derive(input: TokenStream) -> TokenStream {
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// Parse the input tokens into a syntax tree
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let input = parse_macro_input!(input as syn::DeriveInput);
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let generics = add_trait_bounds(input.generics, parse_quote!(orchid_api_traits::Decode));
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let (impl_generics, ty_generics, where_clause) = generics.split_for_impl();
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let name = input.ident;
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let decode = decode_body(&input.data);
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let expanded = quote! {
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impl #impl_generics orchid_api_traits::Decode for #name #ty_generics #where_clause {
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async fn decode<R: orchid_api_traits::async_std::io::Read + ?Sized>(
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mut read: std::pin::Pin<&mut R>
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) -> Self {
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#decode
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}
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}
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};
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TokenStream::from(expanded)
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}
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fn decode_fields(fields: &syn::Fields) -> pm2::TokenStream {
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match fields {
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syn::Fields::Unit => quote! {},
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syn::Fields::Named(_) => {
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let exprs = fields.iter().map(|f| {
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let syn::Field { ty, ident, .. } = &f;
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quote! {
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#ident : (Box::pin(< #ty as orchid_api_traits::Decode>::decode(read.as_mut()))
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as std::pin::Pin<Box<dyn std::future::Future<Output = _>>>).await
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}
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});
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quote! { { #( #exprs, )* } }
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},
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syn::Fields::Unnamed(_) => {
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let exprs = fields.iter().map(|field| {
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let ty = &field.ty;
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quote! {
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(Box::pin(< #ty as orchid_api_traits::Decode>::decode(read.as_mut()))
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as std::pin::Pin<Box<dyn std::future::Future<Output = _>>>).await,
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}
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});
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quote! { ( #( #exprs )* ) }
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},
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}
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}
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fn decode_body(data: &syn::Data) -> proc_macro2::TokenStream {
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match data {
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syn::Data::Union(_) => panic!("Unions can't be deserialized"),
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syn::Data::Struct(str) => {
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let fields = decode_fields(&str.fields);
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quote! { Self #fields }
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},
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syn::Data::Enum(en) => {
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let opts = en.variants.iter().enumerate().map(|(i, v @ syn::Variant { ident, .. })| {
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let fields = decode_fields(&v.fields);
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let id = i as u8;
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quote! { #id => Self::#ident #fields, }
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});
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quote! {
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match <u8 as orchid_api_traits::Decode>::decode(read.as_mut()).await {
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#(#opts)*
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x => panic!("Unrecognized enum kind {x}")
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}
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}
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},
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}
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}
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