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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;
use proc_macro2::Ident;
use proc_macro2::TokenStream;
use quote::format_ident;
use quote::quote;
use quote::ToTokens;
use uuid::adapter::Simple;
use uuid::Uuid;
const CASTER_FN_NAME_PREFIX: &[u8] = b"__";
const FN_BUF_LEN: usize = CASTER_FN_NAME_PREFIX.len() + Simple::LENGTH;
pub fn generate_caster(ty: &impl ToTokens, dst_trait: &impl ToTokens) -> TokenStream
{
let fn_ident = create_caster_fn_ident();
let new_caster = quote! {
syrette::libs::intertrait::Caster::<dyn #dst_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))
}
}
}
fn create_caster_fn_ident() -> Ident
{
let buf = &mut [0u8; FN_BUF_LEN];
buf[..CASTER_FN_NAME_PREFIX.len()].copy_from_slice(CASTER_FN_NAME_PREFIX);
Uuid::new_v4()
.to_simple()
.encode_lower(&mut buf[CASTER_FN_NAME_PREFIX.len()..]);
let fn_name =
from_utf8(&buf[..FN_BUF_LEN]).expect("Created caster function name is not UTF-8");
format_ident!("{}", fn_name)
}
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