81 lines
2.2 KiB
Rust
81 lines
2.2 KiB
Rust
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extern crate proc_macro;
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use proc_macro::TokenStream;
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use quote::quote;
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use syn::{parse_macro_input, DeriveInput};
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fn get_named_field_idents<'a>(struct_data: &'a syn::DataStruct) -> Vec<&'a syn::Ident> {
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struct_data.fields.iter().map(|f| {
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match &f.ident {
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Some(ref ident) => ident,
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_ => panic!("ssz_derive only supports named struct fields.")
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}
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}).collect()
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}
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#[proc_macro_derive(Encode)]
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pub fn ssz_encode_derive(input: TokenStream) -> TokenStream {
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let item = parse_macro_input!(input as DeriveInput);
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let name = &item.ident;
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let struct_data = match &item.data {
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syn::Data::Struct(s) => s,
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_ => panic!("ssz_derive only supports structs.")
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};
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let field_idents = get_named_field_idents(&struct_data);
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let output = quote! {
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impl Encodable for #name {
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fn ssz_append(&self, s: &mut SszStream) {
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#(
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s.append(&self.#field_idents);
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)*
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}
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}
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};
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output.into()
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}
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#[proc_macro_derive(Decode)]
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pub fn ssz_decode_derive(input: TokenStream) -> TokenStream {
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let item = parse_macro_input!(input as DeriveInput);
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let name = &item.ident;
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let struct_data = match &item.data {
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syn::Data::Struct(s) => s,
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_ => panic!("ssz_derive only supports structs.")
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};
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let field_idents = get_named_field_idents(&struct_data);
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// Using a var in an iteration always consumes the var, therefore we must make a `fields_a` and
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// a `fields_b` in order to perform two loops.
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//
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// https://github.com/dtolnay/quote/issues/8
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let field_idents_a = &field_idents;
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let field_idents_b = &field_idents;
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let output = quote! {
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impl Decodable for #name {
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fn ssz_decode(bytes: &[u8], i: usize) -> Result<(Self, usize), DecodeError> {
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#(
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let (#field_idents_a, i) = <_>::ssz_decode(bytes, i)?;
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)*
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Ok((
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Self {
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#(
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#field_idents_b,
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)*
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},
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i
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))
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}
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}
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};
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output.into()
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}
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