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Code Issues Releases Wiki Activity

allow for simple math in size reference

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Robin Appelman 2019-02-28 22:19:04 +01:00
commit 92b5763aea
2 changed files with 44 additions and 11 deletions
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21
bitstream_reader_derive/src/lib.rs
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@ -107,10 +107,7 @@ extern crate proc_macro;
use proc_macro2::{Span, TokenStream};
use quote::{quote, quote_spanned};
use syn::spanned::Spanned;
use syn::{
parse_macro_input, parse_quote, Attribute, Data, DeriveInput, Expr, Fields, GenericParam,
Generics, Ident, Lit, LitStr, Meta,
};
use syn::{parse_macro_input, parse_quote, Attribute, Data, DeriveInput, Expr, Fields, GenericParam, Generics, Ident, Lit, LitStr, Meta, parse_str};
/// See the [crate documentation](index.html) for details
#[proc_macro_derive(BitRead, attributes(size, size_bits, discriminant_bits, discriminant))]
@ -138,7 +135,7 @@ pub fn derive_bitread(input: proc_macro::TokenStream) -> proc_macro::TokenStream
}
};
//panic!("{}", TokenStream::to_string(&expanded));
// panic!("{}", TokenStream::to_string(&expanded));
proc_macro::TokenStream::from(expanded)
}
@ -203,8 +200,10 @@ fn parse(data: &Data, struct_name: &Ident, attrs: &Vec<Attribute>) -> TokenStrea
match size {
Some(size) => {
quote_spanned! {span=>
let size: usize = #size;
let #name:#field_type = stream.read_sized(size)?;
let #name:#field_type = {
let _size: usize = #size;
stream.read_sized(_size)?
};
}
}
None => {
@ -285,8 +284,8 @@ fn parse(data: &Data, struct_name: &Ident, attrs: &Vec<Attribute>) -> TokenStrea
Some(size) => {
quote_spanned! {span=>
#struct_name::#variant_name({
let size:usize = #size;
stream.read_sized(size)?
let _size:usize = #size;
stream.read_sized(_size)?
})
}
}
@ -330,9 +329,9 @@ fn get_field_size(attrs: &Vec<Attribute>, span: Span) -> Option<TokenStream> {
}
}
Lit::Str(size_field) => {
let size = Ident::new(&size_field.value(), span);
let size = parse_str::<Expr>(&size_field.value()).unwrap();
quote_spanned! {span=>
#size as usize
(#size) as usize
}
}
_ => panic!("Unsupported value for size attribute"),