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//! A macro for getting `&'static CStr` from literal or identifier.
//!
//! This macro checks whether the given literal is valid for `CStr`
//! at compile time, and returns a static reference of `CStr`.
//!
//! This macro can be used to to initialize constants on Rust 1.64 and above.
//!
//! ## Example
//!
//! ```
//! use cstr::cstr;
//! use std::ffi::CStr;
//!
//! let test = cstr!(b"hello\xff");
//! assert_eq!(test, CStr::from_bytes_with_nul(b"hello\xff\0").unwrap());
//! let test = cstr!("hello");
//! assert_eq!(test, CStr::from_bytes_with_nul(b"hello\0").unwrap());
//! let test = cstr!(hello);
//! assert_eq!(test, CStr::from_bytes_with_nul(b"hello\0").unwrap());
//! ```
// While this isn't necessary when using Cargo >= 1.42, omitting it actually requires path-less
// `--extern proc_macro` to be passed to `rustc` when building this crate. Some tools may not do
// this correctly. So it's added as a precaution.
extern crate proc_macro;
use crate::parse::parse_input;
use proc_macro::TokenStream as RawTokenStream;
use proc_macro2::{Literal, Span, TokenStream};
use quote::{quote, quote_spanned};
use std::ffi::CString;
mod parse;
struct Error(Span, &'static str);
#[proc_macro]
pub fn cstr(input: RawTokenStream) -> RawTokenStream {
let tokens = match build_byte_str(input.into()) {
Ok(s) => quote!(unsafe { ::core::ffi::CStr::from_bytes_with_nul_unchecked(#s) }),
Err(Error(span, msg)) => quote_spanned!(span => compile_error!(#msg)),
};
tokens.into()
}
fn build_byte_str(input: TokenStream) -> Result<Literal, Error> {
let (bytes, span) = parse_input(input)?;
match CString::new(bytes) {
Ok(s) => {
let mut lit = Literal::byte_string(s.as_bytes_with_nul());
lit.set_span(span);
Ok(lit)
}
Err(_) => Err(Error(span, "nul byte found in the literal")),
}
}