openethereum/util/rlp_derive/src/de.rs

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use {syn, quote};
struct ParseQuotes {
single: quote::Tokens,
list: quote::Tokens,
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) -> quote::Tokens {
let body = match ast.body {
syn::Body::Struct(ref s) => s,
_ => panic!("#[derive(RlpDecodable)] is only defined for structs."),
};
let stmts: Vec<_> = match *body {
syn::VariantData::Struct(ref fields) | syn::VariantData::Tuple(ref fields) =>
fields.iter().enumerate().map(decodable_field_map).collect(),
syn::VariantData::Unit => panic!("#[derive(RlpDecodable)] is not defined for Unit structs."),
};
let name = &ast.ident;
let dummy_const = syn::Ident::new(format!("_IMPL_RLP_DECODABLE_FOR_{}", name));
let impl_block = quote! {
impl rlp::Decodable for #name {
fn decode(rlp: &rlp::UntrustedRlp) -> 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) -> quote::Tokens {
let body = match ast.body {
syn::Body::Struct(ref s) => s,
_ => panic!("#[derive(RlpDecodableWrapper)] is only defined for structs."),
};
let stmt = match *body {
syn::VariantData::Struct(ref fields) | syn::VariantData::Tuple(ref fields) => {
if fields.len() == 1 {
let field = fields.first().expect("fields.len() == 1; qed");
decodable_field(0, field, decodable_wrapper_parse_quotes())
} else {
panic!("#[derive(RlpDecodableWrapper)] is only defined for structs with one field.")
}
},
syn::VariantData::Unit => panic!("#[derive(RlpDecodableWrapper)] is not defined for Unit structs."),
};
let name = &ast.ident;
let dummy_const = syn::Ident::new(format!("_IMPL_RLP_DECODABLE_FOR_{}", name));
let impl_block = quote! {
impl rlp::Decodable for #name {
fn decode(rlp: &rlp::UntrustedRlp) -> 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)) -> quote::Tokens {
decodable_field(tuple.0, tuple.1, decodable_parse_quotes())
}
fn decodable_field(index: usize, field: &syn::Field, quotes: ParseQuotes) -> quote::Tokens {
let ident = match field.ident {
Some(ref ident) => ident.to_string(),
None => index.to_string(),
};
let id = syn::Ident::new(ident);
let index = syn::Ident::new(index.to_string());
let single = quotes.single;
let list = quotes.list;
match field.ty {
syn::Ty::Path(_, ref path) => {
let ident = &path.segments.first().expect("there must be at least 1 segment").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"),
}
}