Re: [Libguestfs] [libnbd PATCH 07/10] rust: Add a couple of integration tests

On 7/19/2023 4:50 PM, Richard W.M. Jones wrote: Yes, there is, but it would require cloning every string. The problem is that Libnbd uses null terminated strings and Rust uses "Vector like" strings with a stored length (as C++'s `String` type). So a rust string literal (`str`) like `"nbdkit"` is stored as an array of length 6 bytes without a NULL at the end, and the integer `6` to tell the length. (See here <https://doc.rust-lang.org/reference/type-layout.html> for more explonations.) The thing is that to convert an `&str` to a null terminated string (`&CStr`) it must be cloned to make room for the extra NULL character. One would need to use something like `impl Into<Vec<u8>>` instead of `&CStr` as type of the string arguments, and then convert it to a null terminated string with `CString::new()` <https://doc.rust-lang.org/std/ffi/struct.CString.html#method.new>;. Since these conversions would only take place when the user creates or configures the handle, the extra cost shouldn't be a problem in most cases, and I can definitely change this. But it doesn't become zero cost abstraction. Best regards, Tage So to summerize: I can change the type of strings that are sent to Libnbd so that the `c_str!(...)` macro wouldn't be needed, although that would require cloning every string. But I'd rather keep the type of strings going