Casting a C pointer to a struct, in Rust

Question

I have bindings in Rust for a library in C and they aren't complete.

In C code I have a macros defined, simplified, like this:

  #define MY_MACROS1(PTR) (((my_struct1 *) (PTR))->field1.field2 >> 2)

I need to achieve the same thing in Rust.

I have a Rust binding definition for my_struct1 . And I have a pointer

  let my_ptr1: usize = unsafe { get_a_pointer_from_c(); }

How can I cast a pointer my_ptr1 to my_struct1 or rather to my_struct1 * ?

Rust binding to get_a_pointer_from_c() returns a pointer of type usize , note.

Answer 1

• Option 1 would be what Ôrel suggested: have the C side expose the proper accessor as a function, and call that from Rust.

• option 2 is to define the C struct on the Rust side and cast your pointer to a pointer / ref to that on the Rust side eg

  let mut p; let r = unsafe { p = ptr::NonNull::new( get_pointer_from_c() as *mut YourType ).unwrap(); p.as_mut() };