From fc68829e1401acd7bd6dd433450834bff4324d46 Mon Sep 17 00:00:00 2001 From: Martin Geisler Date: Fri, 28 Apr 2023 01:00:07 -0700 Subject: [PATCH] Improve language around ownership of `OsString` (#602) Based on discussion in #598. --- src/exercises/day-3/safe-ffi-wrapper.md | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/src/exercises/day-3/safe-ffi-wrapper.md b/src/exercises/day-3/safe-ffi-wrapper.md index b7c51cc7..9ee5bd5e 100644 --- a/src/exercises/day-3/safe-ffi-wrapper.md +++ b/src/exercises/day-3/safe-ffi-wrapper.md @@ -24,11 +24,11 @@ You will convert between all these types: - `&str` to `CString`: you need to allocate space for a trailing `\0` character, - `CString` to `*const i8`: you need a pointer to call C functions, - `*const i8` to `&CStr`: you need something which can find the trailing `\0` character, -- `&CStr` to `&[u8]`: you will ultimately return a slice of bytes, -- `&[u8]` to `&OsStr`: you can create an `OsString` from `&[u8]`. Use +- `&CStr` to `&[u8]`: a slice of bytes is the universal interface for "some unknow data", +- `&[u8]` to `&OsStr`: `&OsStr` is a step towards `OsString`, use [`OsStrExt`](https://doc.rust-lang.org/std/os/unix/ffi/trait.OsStrExt.html) - for this. -- `&OsStr` to `OsString`: you need to take ownership of the data before you call + to create it, +- `&OsStr` to `OsString`: you need to clone the data in `&OsStr` to be able to return it and call `readdir` again. The [Nomicon] also has a very useful chapter about FFI.