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Code Issues Releases Wiki Activity

allow for simple math in size reference

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This commit is contained in:
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
View file

@ -107,10 +107,7 @@ extern crate proc_macro;
use proc_macro2::{Span, TokenStream}; use proc_macro2::{Span, TokenStream};
use quote::{quote, quote_spanned}; use quote::{quote, quote_spanned};
use syn::spanned::Spanned; use syn::spanned::Spanned;
use syn::{ use syn::{parse_macro_input, parse_quote, Attribute, Data, DeriveInput, Expr, Fields, GenericParam, Generics, Ident, Lit, LitStr, Meta, parse_str};
parse_macro_input, parse_quote, Attribute, Data, DeriveInput, Expr, Fields, GenericParam,
Generics, Ident, Lit, LitStr, Meta,
};
/// See the [crate documentation](index.html) for details /// See the [crate documentation](index.html) for details
#[proc_macro_derive(BitRead, attributes(size, size_bits, discriminant_bits, discriminant))] #[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) proc_macro::TokenStream::from(expanded)
} }
@ -203,8 +200,10 @@ fn parse(data: &Data, struct_name: &Ident, attrs: &Vec<Attribute>) -> TokenStrea
match size { match size {
Some(size) => { Some(size) => {
quote_spanned! {span=> quote_spanned! {span=>
let size: usize = #size; let #name:#field_type = {
let #name:#field_type = stream.read_sized(size)?; let _size: usize = #size;
stream.read_sized(_size)?
};
} }
} }
None => { None => {
@ -285,8 +284,8 @@ fn parse(data: &Data, struct_name: &Ident, attrs: &Vec<Attribute>) -> TokenStrea
Some(size) => { Some(size) => {
quote_spanned! {span=> quote_spanned! {span=>
#struct_name::#variant_name({ #struct_name::#variant_name({
let size:usize = #size; let _size:usize = #size;
stream.read_sized(size)? stream.read_sized(_size)?
}) })
} }
} }
@ -330,9 +329,9 @@ fn get_field_size(attrs: &Vec<Attribute>, span: Span) -> Option<TokenStream> {
} }
} }
Lit::Str(size_field) => { Lit::Str(size_field) => {
let size = Ident::new(&size_field.value(), span); let size = parse_str::<Expr>(&size_field.value()).unwrap();
quote_spanned! {span=> quote_spanned! {span=>
#size as usize (#size) as usize
} }
} }
_ => panic!("Unsupported value for size attribute"), _ => panic!("Unsupported value for size attribute"),

34
bitstream_reader_derive/tests/test.rs
View file

@ -178,3 +178,37 @@ fn test_read_unnamed_field_enum_sized() {
); );
assert_eq!(8, stream.pos()); assert_eq!(8, stream.pos());
} }
#[derive(BitRead, PartialEq, Debug)]
struct TestStruct2 {
size: u8,
#[size = "size * 2"]
str: String,
}
#[test]
fn test_read_struct2() {
let bytes = vec![
0b0000_0101,
'h' as u8,
'e' as u8,
'l' as u8,
'l' as u8,
'o' as u8,
' ' as u8,
'w' as u8,
'o' as u8,
'r' as u8,
'l' as u8,
'e' as u8,
];
let buffer = BitBuffer::new(bytes, BigEndian);
let mut stream = BitStream::from(buffer);
assert_eq!(
TestStruct2 {
size: 5,
str: "hello worl".to_owned(),
},
stream.read().unwrap()
);
}