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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
use proc_macro::TokenStream;
use quote::quote;
use syn::parse::{Parse, ParseStream, Result};
use syn::{parse_macro_input, Attribute, LitStr, Signature};
/* Proc macro equivalent to the following rust macro:
* ```
* macro_rules! link {
* ($library:literal $abi:literal $($link_name:literal)? $(#[$($doc:tt)*])* fn $name:ident($($arg:ident: $argty:ty),*)->$ret:ty) => (
* extern $abi {
* #[link(name = $library)]
* $(#[link_name=$link_name])?
* pub fn $name($($arg: $argty),*) -> $ret;
* }
* )
* }
* ```
* with the additional feature of removing ".dll" from the $library literal.
*
* The macro is derived from the equivalent macro in the real windows-targets crate,
* with the difference that it uses #[link] with the name of the library rather than
* a single "windows.$version" library, so as to avoid having to vendor all the fake
* "windows.$version" import libraries. We can do that because we also require MSVC
* to build, so we do have the real import libraries available.
*
* As the library name is there in the original for raw-dylib support, it contains
* a suffixed name, but plain #[link] expects a non-suffixed name, which is why we
* remove the suffix (and why this had to be a proc-macro).
*
* Once raw-dylib is more widely available and tested, we'll be able to use the
* raw-dylib variants directly.
*/
struct LinkMacroInput {
library: LitStr,
abi: LitStr,
link_name: Option<LitStr>,
function: Signature,
}
impl Parse for LinkMacroInput {
fn parse(input: ParseStream) -> Result<Self> {
let library: LitStr = input.parse()?;
let abi: LitStr = input.parse()?;
let link_name: Option<LitStr> = input.parse().ok();
let _doc_comments = Attribute::parse_outer(input)?;
let function: Signature = input.parse()?;
Ok(LinkMacroInput {
library,
abi,
link_name,
function,
})
}
}
#[proc_macro]
pub fn link(input: TokenStream) -> TokenStream {
let LinkMacroInput {
library,
abi,
link_name,
function,
} = parse_macro_input!(input as LinkMacroInput);
let link_name_attr = link_name.map(|lit| quote! { #[link_name = #lit] });
let library = library.value();
let library = library.strip_suffix(".dll").unwrap_or(&library);
let generated = quote! {
extern #abi {
#[link(name = #library)]
#link_name_attr
pub #function;
}
};
TokenStream::from(generated)
}
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