openethereum/util/rlp-derive/src/de.rs

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// Copyright 2015-2019 Parity Technologies (UK) Ltd.
// This file is part of Parity Ethereum.
// Parity Ethereum is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
// Parity Ethereum is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
// You should have received a copy of the GNU General Public License
// along with Parity Ethereum. If not, see <http://www.gnu.org/licenses/>.
use syn;
use proc_macro2::{TokenStream, Span};
struct ParseQuotes {
single: TokenStream,
list: TokenStream,
takes_index: bool,
}
fn decodable_parse_quotes() -> ParseQuotes {
ParseQuotes {
single: quote! { rlp.val_at },
list: quote! { rlp.list_at },
takes_index: true,
}
}
fn decodable_wrapper_parse_quotes() -> ParseQuotes {
ParseQuotes {
single: quote! { rlp.as_val },
list: quote! { rlp.as_list },
takes_index: false,
}
}
pub fn impl_decodable(ast: &syn::DeriveInput) -> TokenStream {
let body = match ast.data {
syn::Data::Struct(ref s) => s,
_ => panic!("#[derive(RlpDecodable)] is only defined for structs."),
};
let stmts: Vec<_> = body.fields.iter().enumerate().map(decodable_field_map).collect();
let name = &ast.ident;
let dummy_const = syn::Ident::new(&format!("_IMPL_RLP_DECODABLE_FOR_{}", name), Span::call_site());
let impl_block = quote! {
impl rlp::Decodable for #name {
fn decode(rlp: &rlp::Rlp) -> Result<Self, rlp::DecoderError> {
let result = #name {
#(#stmts)*
};
Ok(result)
}
}
};
quote! {
#[allow(non_upper_case_globals, unused_attributes, unused_qualifications)]
const #dummy_const: () = {
extern crate rlp;
#impl_block
};
}
}
pub fn impl_decodable_wrapper(ast: &syn::DeriveInput) -> TokenStream {
let body = match ast.data {
syn::Data::Struct(ref s) => s,
_ => panic!("#[derive(RlpDecodableWrapper)] is only defined for structs."),
};
let stmt = {
let fields: Vec<_> = body.fields.iter().collect();
if fields.len() == 1 {
let field = fields.first().expect("fields.len() == 1; qed");
decodable_field(0, field, decodable_wrapper_parse_quotes())
} else {
panic!("#[derive(RlpEncodableWrapper)] is only defined for structs with one field.")
}
};
let name = &ast.ident;
let dummy_const = syn::Ident::new(&format!("_IMPL_RLP_DECODABLE_FOR_{}", name), Span::call_site());
let impl_block = quote! {
impl rlp::Decodable for #name {
fn decode(rlp: &rlp::Rlp) -> Result<Self, rlp::DecoderError> {
let result = #name {
#stmt
};
Ok(result)
}
}
};
quote! {
#[allow(non_upper_case_globals, unused_attributes, unused_qualifications)]
const #dummy_const: () = {
extern crate rlp;
#impl_block
};
}
}
fn decodable_field_map(tuple: (usize, &syn::Field)) -> TokenStream {
decodable_field(tuple.0, tuple.1, decodable_parse_quotes())
}
fn decodable_field(index: usize, field: &syn::Field, quotes: ParseQuotes) -> TokenStream {
let id = match field.ident {
Some(ref ident) => quote! { #ident },
None => {
let index: syn::Index = index.into();
quote! { #index }
}
};
let index = quote! { #index };
let single = quotes.single;
let list = quotes.list;
match field.ty {
syn::Type::Path(ref path) => {
let ident = &path.path.segments.first().expect("there must be at least 1 segment").value().ident;
if &ident.to_string() == "Vec" {
if quotes.takes_index {
quote! { #id: #list(#index)?, }
} else {
quote! { #id: #list()?, }
}
} else {
if quotes.takes_index {
quote! { #id: #single(#index)?, }
} else {
quote! { #id: #single()?, }
}
}
},
_ => panic!("rlp_derive not supported"),
}
}