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use proc_macro2::Span; use proc_macro2::TokenStream; use quote::quote; enum Subset { Both, Reader, Writer, } pub fn impl_trait(ast: &syn::DeriveInput) -> TokenStream { use syn::Data::*; match &ast.data { Struct(ref s) => impl_trait_struct(&ast.ident, &ast.attrs, s, &ast.generics, Subset::Both), _ => unimplemented!(), } } pub fn impl_writer(ast: &syn::DeriveInput) -> TokenStream { use syn::Data::*; match &ast.data { Struct(ref s) => { impl_trait_struct(&ast.ident, &ast.attrs, s, &ast.generics, Subset::Writer) } _ => unimplemented!(), } } pub fn impl_reader(ast: &syn::DeriveInput) -> TokenStream { use syn::Data::*; match &ast.data { Struct(ref s) => { impl_trait_struct(&ast.ident, &ast.attrs, s, &ast.generics, Subset::Reader) } _ => unimplemented!(), } } fn def_decode( name: &syn::Ident, field: &[syn::Member], tlv_type: &[Option<syn::Lit>], ) -> proc_macro2::TokenStream { let wire_item_read_expr = tlv_type.iter().map(|t| { if let Some(t) = t { quote! { lightning_wire_msgs::TLVWireItemReader::decode_tlv(&mut peek_reader, #t)? } } else { quote! { lightning_wire_msgs::WireItemReader::decode(&mut peek_reader)? } } }); quote! { fn decode<R: std::io::Read>(reader: &mut R, check_type: bool) -> std::io::Result<Self> { if check_type { let mut msg_type = [0_u8; 2]; reader.read_exact(&mut msg_type)?; let msg_type = u16::from_be_bytes(msg_type); if msg_type != Self::MSG_TYPE { return Err(std::io::Error::from(std::io::ErrorKind::InvalidData)); } } let mut peek_reader = lightning_wire_msgs::PeekReader::from(reader); Ok(#name { #( #field: #wire_item_read_expr, )* }) } } } fn def_encode(field: &[syn::Member], tlv_type: &[Option<syn::Lit>]) -> proc_macro2::TokenStream { let wire_item_write_expr = field.iter().enumerate().map(|(i, field)| { if let Some(ref t) = &tlv_type[i] { quote! { if let Some(ref field) = &self.#field { count += lightning_wire_msgs::TLVWireItemWriter::encode_tlv(field, w, #t)?; } } } else { quote! { count += lightning_wire_msgs::WireItemWriter::encode(&self.#field, w)?; } } }); quote! { fn encode<W: std::io::Write>(&self, w: &mut W) -> std::io::Result<usize> { let mut count = 0; count += w.write(&u16::to_be_bytes(Self::MSG_TYPE))?; #( #wire_item_write_expr )* w.flush()?; Ok(count) } } } fn impl_trait_struct( name: &syn::Ident, attrs: &Vec<syn::Attribute>, struct_data: &syn::DataStruct, generics: &syn::Generics, subset: Subset, ) -> TokenStream { let num = attrs .iter() .filter_map(|a| match a.parse_meta() { Ok(m) => match m { syn::Meta::NameValue(nv) => { if nv.path.is_ident("msg_type") { Some(nv.lit) } else { None } } _ => None, }, Err(_) => None, }) .next() .expect("missing attribute \"msg_type\"\n\nhelp: add #[msg_type = ...]"); let mut tlv = None; let field_mapper = |(i, f): (usize, &syn::Field)| -> (syn::Member, Option<syn::Lit>) { let mut new_tlv = None; let res = ( f.ident .as_ref() .map(|id| syn::Member::Named(id.clone())) .unwrap_or_else(|| { syn::Member::Unnamed(syn::Index { index: i as u32, span: Span::call_site(), }) }), f.attrs .iter() .filter_map(|a| match a.parse_meta() { Ok(m) => match m { syn::Meta::NameValue(nv) => { if nv.path.is_ident("tlv_type") { if let syn::Lit::Int(ref lit) = nv.lit { new_tlv = Some( lit.base10_parse::<u64>().expect("tlv_type must be a u64"), ); Some(nv.lit) } else { panic!("tlv_type must be a u64") } } else { None } } _ => None, }, Err(_) => None, }) .next(), ); match (tlv, new_tlv) { (Some(_), None) => panic!("tlv stream must occur after expected fields"), (Some(old), Some(new)) if old > new => { panic!("tlv stream must be monotonically increasing by type") } (_, Some(_)) => match &f.ty { syn::Type::Path(ref p) if p.path.segments.last().expect("missing type").ident == "Option" => { match &p.path.segments.last().unwrap().arguments { syn::PathArguments::AngleBracketed(a) => { (match a.args.first().expect("tlv value must be Option") { syn::GenericArgument::Type(t) => t.clone(), _ => panic!("tlv value must be Option"), }) } _ => panic!("tlv value must be Option"), }; } _ => panic!("tlv value must be Option"), }, _ => (), }; tlv = new_tlv; res }; let punc = syn::punctuated::Punctuated::<syn::Field, ()>::new(); let (field, tlv_type): (Vec<syn::Member>, Vec<Option<syn::Lit>>) = match &struct_data.fields { syn::Fields::Named(n) => n.named.iter(), syn::Fields::Unnamed(n) => n.unnamed.iter(), syn::Fields::Unit => punc.iter(), } .enumerate() .map(field_mapper) .unzip(); let type_params: Vec<syn::GenericParam> = generics .params .iter() .map(|gparam| match gparam { syn::GenericParam::Type(tp) => { let mut tp = tp.clone(); tp.bounds = syn::punctuated::Punctuated::new(); syn::GenericParam::Type(tp) } syn::GenericParam::Lifetime(ltp) => { let mut ltp = ltp.clone(); ltp.bounds = syn::punctuated::Punctuated::new(); syn::GenericParam::Lifetime(ltp) } a => a.clone(), }) .collect(); let generics_stripped = { let mut generics = generics.clone(); generics.params = syn::punctuated::Punctuated::new(); for param in type_params.iter() { generics.params.push(param.clone()); } generics.where_clause = None; generics }; let generics_params = &generics.params; let generics_where_clause = &generics.where_clause; let decode = def_decode(name, &field, &tlv_type); let encode = def_encode(&field, &tlv_type); let gen = match subset { Subset::Both => quote! { impl<#generics_params> lightning_wire_msgs::WireMessage for #name#generics_stripped #generics_where_clause { const MSG_TYPE: u16 = #num; #encode #decode } }, Subset::Writer => quote! { impl<#generics_params> lightning_wire_msgs::WireMessageWriter for #name#generics_stripped #generics_where_clause { const MSG_TYPE: u16 = #num; #encode } }, Subset::Reader => quote! { impl<#generics_params> lightning_wire_msgs::WireMessageReader for #name#generics_stripped #generics_where_clause { const MSG_TYPE: u16 = #num; #decode } }, }; gen.into() }