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extern crate proc_macro; extern crate quote; extern crate syn; use proc_macro::TokenStream; use proc_macro_hack::proc_macro_hack; use quote::quote; use syn::{parse_macro_input, LitStr}; #[inline] fn is_normalized(value: u32) -> bool { value & 0xFF != 0 } #[inline] fn normalize(value: u32) -> u32 { if is_normalized(value) { value } else { let mut res = value | 0x20; for i in 1..4 { if res & (0xFF << i) != 0 { res |= 0x20 << (i * 8); } } res } } #[inline] fn str_to_u32(value: &str) -> u32 { if value.len() != 4 { panic!("{} is not a valid four char code", value); } let mut res: u32 = 0; unsafe { std::ptr::copy( value.as_ptr(), &mut res as *mut _ as *mut u8, std::mem::size_of::<u8>() * 4, ); } normalize(u32::from_be(res)) } #[proc_macro_hack] pub fn four_char_code(input: TokenStream) -> TokenStream { let value = str_to_u32(&parse_macro_input!(input as LitStr).value()); let expanded = quote! { ::four_char_code::FourCharCode(#value) }; TokenStream::from(expanded) }