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extern crate proc_macro;
extern crate proc_macro_hack;
use proc_macro_hack::proc_macro_hack;
#[macro_use]
extern crate quote;
use std::iter::FromIterator;
struct StaticStr {
len: usize,
value: syn::LitStr,
}
impl syn::parse::Parse for StaticStr {
fn parse(input: syn::parse::ParseStream) -> syn::parse::Result<Self> {
let mut len: Option<(usize, syn::export::Span)> = None;
if input.peek(syn::LitInt) {
let parsed: syn::LitInt = input.parse()?;
len = Some((parsed.base10_parse()?, parsed.span()));
let _: syn::token::Comma = input.parse()?;
}
let val: syn::LitStr = input.parse()?;
match len {
None => {
len = Some((val.value().as_bytes().len() + 1, val.span()));
}
Some((ref l, sp)) => {
if *l <= val.value().as_bytes().len() {
return Err(syn::parse::Error::new(
sp,
format!("defined string length {} is shorter than given string ({} + null-byte)",
l, val.value().as_bytes().len())
));
}
}
}
Ok(StaticStr{
len: len.unwrap().0,
value: val,
})
}
}
fn byte_to_expr(b: u8, span: syn::export::Span) -> syn::Expr {
syn::Expr::Lit(syn::ExprLit{
attrs: vec!(),
lit: syn::Lit::Byte(syn::LitByte::new(b, span)),
})
}
#[proc_macro_hack]
pub fn bystr(item: proc_macro::TokenStream) -> proc_macro::TokenStream {
let input = syn::parse_macro_input!(item as StaticStr);
let strval = input.value.value();
let strbytes = strval.as_bytes();
let strlen = strbytes.len();
let mut elems = strbytes.iter()
.map(|b| byte_to_expr(*b, input.value.span()))
.collect::<Vec<syn::Expr>>();
for _ in 0..(input.len - strlen) {
elems.push(byte_to_expr(0, input.value.span()));
}
let expr = syn::ExprArray{
attrs: vec!(),
bracket_token: syn::token::Bracket::default(),
elems: syn::punctuated::Punctuated::from_iter(elems.into_iter()),
};
let result = quote! {
#expr
};
result.into()
}