Create custom cxx binding to Utf8CStr

native/src/base/cstr.rs

@@ -6,10 +6,12 @@ use std::path::Path;
 use std::str::{Utf8Chunks, Utf8Error};
 use std::{fmt, mem, slice, str};
 
-use crate::slice_from_ptr_mut;
+use cxx::{type_id, ExternType};
 use libc::c_char;
 use thiserror::Error;
 
+use crate::slice_from_ptr_mut;
+
 // Utf8CStr types are UTF-8 validated and null terminated strings.
 //
 // Several Utf8CStr types:
@@ -380,6 +382,22 @@ impl DerefMut for Utf8CStr {
     }
 }
 
+// Notice that we only implement ExternType on Utf8CStr *reference*
+unsafe impl ExternType for &Utf8CStr {
+    type Id = type_id!("rust::Utf8CStr");
+    type Kind = cxx::kind::Trivial;
+}
+
+macro_rules! const_assert_eq {
+    ($left:expr, $right:expr $(,)?) => {
+        const _: [(); $left] = [(); $right];
+    };
+}
+
+// Assert ABI layout
+const_assert_eq!(mem::size_of::<&Utf8CStr>(), mem::size_of::<[usize; 2]>());
+const_assert_eq!(mem::align_of::<&Utf8CStr>(), mem::align_of::<[usize; 2]>());
+
 // File system path extensions types
 
 #[repr(transparent)]