how to let ReprC work with thrid party crate struct ? about safer_ffi HOT 3 CLOSED

#[derive_ReprC]
#[ReprC::opaque]
pub struct Hasher {
    h: ::blake3::Hasher,
}

// For convenience (you can use a helper crate to define newtype structs so as to have these impls autogenerated):
impl Hasher {
    pub fn new() -> Self { Self { h: ::blake3::Hasher::new() } }
}
impl ::core::ops::Deref for Hasher { … }
impl ::core::ops::DerefMut for Hasher { … }

#[ffi_export]
pub fn hasher_new() -> repr_c::Box<Hasher> {
    repr_c::Box::new(Hasher::new())
}

#[ffi_export]
pub fn hasher_free(hasher: Option<repr_c::Box<Hasher>>) {
    drop(hasher);
}