Add a few changes for #996

Add a few fixes on top of pull request #996. Among others, remove an
'as' cast which potentially could be the source of unsoundness, remove
some other unnecessary ones, and don't repeat code needlessly.

Signed-off-by: Daniel Müller <deso@posteo.net>

libbpf-rs/CHANGELOG.md

@@ -1,8 +1,12 @@
+Unreleased
+----------
+- Added `Map::lookup_batch` and `Map::lookup_and_delete_batch` method
+
+
 0.24.8
 ------
 - Added `Program::attach_netfilter_with_opts` for attaching to netfilter
   hooks
-- Added `Map::lookup_batch` and `Map::lookup_and_delete_batch` method
 
 
 0.24.5

libbpf-rs/src/map.rs

@@ -1397,31 +1397,27 @@ impl<'map> BatchedMapIter<'map> {
     }
 
     fn lookup_next_batch(&mut self) {
-        let prev = self.prev.as_ref().map_or(ptr::null(), |p| p.as_ptr());
+        let prev = self
+            .prev
+            .as_mut()
+            .map_or(ptr::null_mut(), |p| p.as_mut_ptr());
         let mut count = self.count as u32;
 
         let ret = unsafe {
-            if self.delete {
-                libbpf_sys::bpf_map_lookup_and_delete_batch(
-                    self.map_fd.as_raw_fd(),
-                    prev as _,
-                    self.next.as_mut_ptr().cast(),
-                    self.keys.as_mut_ptr().cast(),
-                    self.values.as_mut_ptr().cast(),
-                    (&mut count) as *mut u32,
-                    &self.batch_opts as *const libbpf_sys::bpf_map_batch_opts,
-                )
+            let lookup_fn = if self.delete {
+                libbpf_sys::bpf_map_lookup_and_delete_batch
             } else {
-                libbpf_sys::bpf_map_lookup_batch(
-                    self.map_fd.as_raw_fd(),
-                    prev as _,
-                    self.next.as_mut_ptr().cast(),
-                    self.keys.as_mut_ptr().cast(),
-                    self.values.as_mut_ptr().cast(),
-                    (&mut count) as *mut u32,
-                    &self.batch_opts as *const libbpf_sys::bpf_map_batch_opts,
-                )
-            }
+                libbpf_sys::bpf_map_lookup_batch
+            };
+            lookup_fn(
+                self.map_fd.as_raw_fd(),
+                prev.cast(),
+                self.next.as_mut_ptr().cast(),
+                self.keys.as_mut_ptr().cast(),
+                self.values.as_mut_ptr().cast(),
+                &mut count,
+                &self.batch_opts,
+            )
         };
 
         if let Err(e) = util::parse_ret(ret) {