rust/ffi: Convert str func to new "view" naming convention

More obvious one shouldn't leak the pointer.

Closes: #1688
Approved by: jlebon

rust/src/ffiutil.rs

@@ -37,12 +37,12 @@ use openat;
 /// Convert a C (UTF-8) string to a &str; will panic
 /// if it isn't valid UTF-8.  Note the lifetime of
 /// the return value must be <= the pointer.
-pub fn str_from_nullable<'a>(s: *const libc::c_char) -> Option<&'a str> {
+pub fn ffi_view_nullable_str<'a>(s: *const libc::c_char) -> Option<&'a str> {
     if s.is_null() {
         None
     } else {
         let s = unsafe { CStr::from_ptr(s) };
-        Some(s.to_str().unwrap())
+        Some(s.to_str().expect("ffi_view_nullable_str: valid utf-8"))
     }
 }
 

rust/src/progress.rs

@@ -212,7 +212,7 @@ mod ffi {
 
     #[no_mangle]
     pub extern "C" fn ror_progress_set_sub_message(msg: *const libc::c_char) {
-        let msg = str_from_nullable(msg);
+        let msg = ffi_view_nullable_str(msg);
         let mut lock = PROGRESS.lock().unwrap();
         let state = lock.as_mut().expect("progress to update");
         state.set_sub_message(msg);
@@ -227,7 +227,7 @@ mod ffi {
 
     #[no_mangle]
     pub extern "C" fn ror_progress_end(suffix: *const libc::c_char) {
-        let suffix = str_from_nullable(suffix);
+        let suffix = ffi_view_nullable_str(suffix);
         let mut lock = PROGRESS.lock().unwrap();
         let state = lock.take().expect("progress to end");
         state.end(suffix);

rust/src/treefile.rs

@@ -831,7 +831,7 @@ mod ffi {
     ) -> *mut Treefile {
         // Convert arguments
         let filename = OsStr::from_bytes(bytes_from_nonnull(filename));
-        let arch = str_from_nullable(arch);
+        let arch = ffi_view_nullable_str(arch);
         let workdir = ffi_view_openat_dir(workdir_dfd);
         // Run code, map error if any, otherwise extract raw pointer, passing
         // ownership back to C.

rust/src/utils.rs

@@ -128,7 +128,7 @@ mod ffi {
         url: *const libc::c_char,
         gerror: *mut *mut glib_sys::GError,
     ) -> libc::c_int {
-        let url = str_from_nullable(url).unwrap();
+        let url = ffi_view_nullable_str(url).unwrap();
         match download_url_to_tmpfile(url) {
             Ok(f) => f.into_raw_fd(),
             Err(e) => {
@@ -144,7 +144,7 @@ mod ffi {
         h: *mut glib_sys::GHashTable,
         gerror: *mut *mut glib_sys::GError,
     ) -> *mut libc::c_char {
-        let s = str_from_nullable(s).unwrap();
+        let s = ffi_view_nullable_str(s).unwrap();
         let h_rs: HashMap<String, String> =
             unsafe { glib::translate::FromGlibPtrContainer::from_glib_none(h) };
         match varsubst(s, &h_rs) {