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-rw-r--r--macros/src/caster.rs150
1 files changed, 150 insertions, 0 deletions
diff --git a/macros/src/caster.rs b/macros/src/caster.rs
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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, TokenStream};
+use quote::{format_ident, 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,
+ sync: bool,
+) -> TokenStream
+{
+ let fn_ident = create_caster_fn_ident(Uuid::new_v4());
+
+ let new_caster = if sync {
+ quote! {
+ syrette::private::cast::Caster::<#dst_trait>::new_sync(
+ |from| {
+ let concrete = from
+ .downcast::<#ty>()
+ .map_err(|_| syrette::private::cast::CasterError::CastBoxFailed)?;
+
+ Ok(concrete as Box<#dst_trait>)
+ },
+ |from| {
+ let concrete = from
+ .downcast::<#ty>()
+ .map_err(|_| syrette::private::cast::CasterError::CastRcFailed)?;
+
+ Ok(concrete as std::rc::Rc<#dst_trait>)
+ },
+ |from| {
+ let concrete = from
+ .downcast::<#ty>()
+ .map_err(|_| syrette::private::cast::CasterError::CastArcFailed)?;
+
+ Ok(concrete as std::sync::Arc<#dst_trait>)
+ },
+ )
+ }
+ } else {
+ quote! {
+ syrette::private::cast::Caster::<#dst_trait>::new(
+ |from| {
+ let concrete = from
+ .downcast::<#ty>()
+ .map_err(|_| syrette::private::cast::CasterError::CastBoxFailed)?;
+
+ Ok(concrete as Box<#dst_trait>)
+ },
+ |from| {
+ let concrete = from
+ .downcast::<#ty>()
+ .map_err(|_| syrette::private::cast::CasterError::CastRcFailed)?;
+
+ Ok(concrete as std::rc::Rc<#dst_trait>)
+ },
+ )
+ }
+ };
+
+ quote! {
+ #[syrette::private::linkme::distributed_slice(syrette::private::cast::CASTERS)]
+ #[linkme(crate = syrette::private::linkme)]
+ fn #fn_ident() -> (::std::any::TypeId, syrette::private::cast::BoxedCaster) {
+ (::std::any::TypeId::of::<#ty>(), Box::new(#new_caster))
+ }
+ }
+}
+
+fn create_caster_fn_ident(uuid: impl IUuid) -> Ident
+{
+ let buf = &mut [0u8; FN_BUF_LEN];
+
+ buf[..CASTER_FN_NAME_PREFIX.len()].copy_from_slice(CASTER_FN_NAME_PREFIX);
+
+ uuid.encode_simple_lower_into(&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)
+}
+
+/// Simple interface for `Uuid`.
+///
+/// Created for ease of testing the [`create_caster_fn_ident`] function.
+///
+/// [`Uuid`]: uuid::Uuid
+#[cfg_attr(test, mockall::automock)]
+trait IUuid
+{
+ /// Writes the Uuid as a simple lower-case string to `buf`.
+ fn encode_simple_lower_into(self, buf: &mut [u8]);
+}
+
+impl IUuid for Uuid
+{
+ fn encode_simple_lower_into(self, buf: &mut [u8])
+ {
+ self.to_simple().encode_lower(buf);
+ }
+}
+
+#[cfg(test)]
+mod tests
+{
+ use pretty_assertions::assert_eq;
+ use utility_macros::repeat_char;
+
+ use super::*;
+
+ #[test]
+ fn can_create_caster_fn_ident()
+ {
+ let mut uuid_mock = MockIUuid::new();
+
+ uuid_mock
+ .expect_encode_simple_lower_into()
+ .return_once(|buf| {
+ for index in 0..(FN_BUF_LEN - 2) {
+ buf[index] = b'f';
+ }
+ })
+ .once();
+
+ assert_eq!(
+ create_caster_fn_ident(uuid_mock),
+ format_ident!(concat!("__", repeat_char!('f', 32)))
+ );
+ }
+}