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use proc_macro2::{Literal, Span, TokenTree};
use quote::quote;
use syn::{
parse_macro_input, parse_quote_spanned, Data, DeriveInput, Fields, Ident, WherePredicate,
};
#[proc_macro_derive(Encode)]
pub fn derive_encode(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
let DeriveInput {
ident,
data,
mut generics,
..
} = parse_macro_input!(input as DeriveInput);
match data {
Data::Struct(st) => {
generics
.make_where_clause()
.predicates
.extend(st.fields.iter().map(|field| -> WherePredicate {
let ty = &field.ty;
parse_quote_spanned! {
Span::call_site() => #ty: endecode::encode::Encode
}
}));
let (impl_generics, ty_generics, where_clause) = generics.split_for_impl();
let fields = match st.fields {
Fields::Named(fields) => fields
.named
.into_iter()
.map(|field| TokenTree::Ident(field.ident.clone().unwrap()))
.collect(),
Fields::Unnamed(fields) => (0..fields.unnamed.len())
.map(|field| TokenTree::Literal(Literal::usize_unsuffixed(field)))
.collect(),
Fields::Unit => vec![],
};
quote! {
#[automatically_derived]
impl #impl_generics endecode::encode::Encode for #ident #ty_generics #where_clause {
fn encode_internal(&self, vec: &mut Vec<u8>) {
#(
self.#fields.encode_internal(vec);
)*
}
}
}
.into()
}
Data::Enum(en) => {
let variants = en.variants.into_iter().enumerate().map(|(num, variant)| {
let num = Literal::usize_unsuffixed(num);
let ident = variant.ident;
match variant.fields {
Fields::Named(fields) => {
let fields: Vec<_> = fields
.named
.into_iter()
.map(|field| field.ident.unwrap())
.collect();
quote! {
#ident { #(#fields),* } => {
vec.push(#num);
#(
#fields.encode_internal(vec);
)*
}
}
}
Fields::Unnamed(fields) => {
let fields: Vec<_> = (0..fields.unnamed.len())
.map(|field| Ident::new(&format!("_{field}"), Span::call_site()))
.collect();
quote! {
#ident(#(#fields),*) => {
vec.push(#num);
#(
#fields.encode_internal(vec);
)*
}
}
}
Fields::Unit => {
quote! {
#ident => vec.push(#num),
}
}
}
});
quote! {
#[automatically_derived]
impl endecode::encode::Encode for #ident {
fn encode_internal(&self, vec: &mut Vec<u8>) {
match self {
#(Self::#variants)*
}
}
}
}
.into()
}
Data::Union(_) => {
panic!("Union... go implement it yourself");
}
}
}
#[proc_macro_derive(Decode)]
pub fn derive_decode(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
let DeriveInput {
ident,
data,
mut generics,
..
} = parse_macro_input!(input as DeriveInput);
match data {
Data::Struct(st) => {
generics
.make_where_clause()
.predicates
.extend(st.fields.iter().map(|field| -> WherePredicate {
let ty = &field.ty;
parse_quote_spanned! {
Span::call_site() => #ty: endecode::encode::Encode
}
}));
let (impl_generics, ty_generics, where_clause) = generics.split_for_impl();
let fields = match st.fields {
Fields::Named(fields) => {
let mut types = vec![];
let fields: Vec<_> = fields
.named
.into_iter()
.map(|field| {
types.push(field.ty);
field.ident.unwrap()
})
.collect();
quote! {
{
#(
#fields: <#types>::decode(iter)
),*
}
}
}
Fields::Unnamed(fields) => {
let mut types = vec![];
for field in fields.unnamed {
types.push(field.ty);
}
quote! {
(#(<#types>::decode(iter)),*)
}
}
Fields::Unit => quote! {},
};
quote! {
#[automatically_derived]
impl #impl_generics endecode::decode::Decode for #ident #ty_generics #where_clause {
fn decode(iter: &mut impl Iterator<Item = u8>) -> Self {
Self #fields
}
}
}
.into()
}
Data::Enum(en) => {
let nums = (0..en.variants.len()).map(|num| Literal::usize_unsuffixed(num));
let variants = en.variants.into_iter().map(|variant| {
let ident = variant.ident;
match variant.fields {
Fields::Named(fields) => {
let mut types = vec![];
let fields: Vec<_> = fields
.named
.into_iter()
.map(|field| {
types.push(field.ty);
field.ident.unwrap()
})
.collect();
quote! {
#ident { #(#fields: <#types>::decode(iter)),* }
}
}
Fields::Unnamed(fields) => {
let mut types = vec![];
for field in fields.unnamed {
types.push(field.ty);
}
quote! {
#ident(#(<#types>::decode(iter)),*)
}
}
Fields::Unit => quote! { #ident },
}
});
quote! {
#[automatically_derived]
impl endecode::decode::Decode for #ident {
fn decode(iter: &mut impl Iterator<Item = u8>) -> Self {
match iter.next().unwrap() {
#(#nums => Self::#variants,)*
i => panic!(concat!("index {} out of bounds for enum ", stringify!(#ident)), i)
}
}
}
}
.into()
}
Data::Union(_) => {
panic!("Now decoding?! You have to be kidding me");
}
}
}