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/**
* Originally from Intertrait by CodeChain
*
* https://github.com/CodeChain-io/intertrait
* https://crates.io/crates/intertrait/0.2.2
*
* Licensed under either of
*
* Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
* MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)
* at your option.
*/
use std::str::from_utf8_unchecked;
use proc_macro2::TokenStream;
use quote::format_ident;
use quote::quote;
use quote::ToTokens;
use uuid::adapter::Simple;
use uuid::Uuid;
pub fn generate_caster(ty: &impl ToTokens, trait_: &impl ToTokens) -> TokenStream
{
let mut fn_buf = [0u8; FN_BUF_LEN];
let fn_ident = format_ident!("{}", new_fn_name(&mut fn_buf));
let new_caster = quote! {
syrette::libs::intertrait::Caster::<dyn #trait_>::new(
|from| from.downcast::<#ty>().unwrap(),
|from| from.downcast::<#ty>().unwrap(),
)
};
quote! {
#[syrette::libs::linkme::distributed_slice(syrette::libs::intertrait::CASTERS)]
#[linkme(crate = syrette::libs::linkme)]
fn #fn_ident() -> (::std::any::TypeId, syrette::libs::intertrait::BoxedCaster) {
(::std::any::TypeId::of::<#ty>(), Box::new(#new_caster))
}
}
}
const FN_PREFIX: &[u8] = b"__";
const FN_BUF_LEN: usize = FN_PREFIX.len() + Simple::LENGTH;
fn new_fn_name(buf: &mut [u8]) -> &str
{
buf[..FN_PREFIX.len()].copy_from_slice(FN_PREFIX);
Uuid::new_v4()
.to_simple()
.encode_lower(&mut buf[FN_PREFIX.len()..]);
unsafe { from_utf8_unchecked(&buf[..FN_BUF_LEN]) }
}
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