test(bitmap): Eliminate struct BytesHelper

This overly complex agglomeration of function pointers and closures was
used to... still write the same number of LoC in the end. So just
eliminate it and inline it into its one use site.

Signed-off-by: Patrick Roy <roypat@amazon.co.uk>

Author: roypat

src/bitmap/mod.rs

@@ -120,7 +120,6 @@ pub type MS<'a, M> = BS<'a, <<M as GuestMemory>::R as GuestMemoryRegion>::B>;
 pub(crate) mod tests {
     use super::*;
 
-    use std::marker::PhantomData;
     use std::mem::size_of_val;
     use std::sync::atomic::Ordering;
 
@@ -164,56 +163,6 @@ pub(crate) mod tests {
         assert!(range_is_dirty(&s, 0, dirty_len));
     }
 
-    // A helper object that implements auxiliary operations for testing `Bytes` implementations
-    // in the context of dirty bitmap tracking.
-    struct BytesHelper<F, G, M> {
-        check_range_fn: F,
-        address_fn: G,
-        phantom: PhantomData<*const M>,
-    }
-
-    // `F` represents a closure the checks whether a specified range associated with the `Bytes`
-    // object that's being tested is marked as dirty or not (depending on the value of the last
-    // parameter). It has the following parameters:
-    // - A reference to a `Bytes` implementations that's subject to testing.
-    // - The offset of the range.
-    // - The length of the range.
-    // - Whether we are checking if the range is clean (when `true`) or marked as dirty.
-    //
-    // `G` represents a closure that translates an offset into an address value that's
-    // relevant for the `Bytes` implementation being tested.
-    impl<F, G, M, A> BytesHelper<F, G, M>
-    where
-        F: Fn(&M, usize, usize, bool) -> bool,
-        G: Fn(usize) -> A,
-        M: Bytes<A>,
-    {
-        fn check_range(&self, m: &M, start: usize, len: usize, clean: bool) -> bool {
-            (self.check_range_fn)(m, start, len, clean)
-        }
-
-        fn address(&self, offset: usize) -> A {
-            (self.address_fn)(offset)
-        }
-
-        fn test_access<Op>(
-            &self,
-            bytes: &M,
-            dirty_offset: usize,
-            dirty_len: usize,
-            op: Op,
-        )
-        where
-            Op: Fn(&M, A),
-        {
-            assert!(self.check_range(bytes, dirty_offset, dirty_len, true));
-
-            op(bytes, self.address(dirty_offset));
-
-            assert!(self.check_range(bytes, dirty_offset, dirty_len, false));
-        }
-    }
-
     // `F` and `G` stand for the same closure types as described in the `BytesHelper` comment.
     // The `step` parameter represents the offset that's added the the current address after
     // performing each access. It provides finer grained control when testing tracking
@@ -223,45 +172,46 @@ pub(crate) mod tests {
     where
         F: Fn(&M, usize, usize, bool) -> bool,
         G: Fn(usize) -> A,
-        A: Copy,
         M: Bytes<A>,
         <M as Bytes<A>>::E: Debug,
     {
         const BUF_SIZE: usize = 1024;
         let buf = vec![1u8; 1024];
+        let mut dirty_offset = 0x1000;
 
         let val = 1u64;
 
-        let h = BytesHelper {
-            check_range_fn,
-            address_fn,
-            phantom: PhantomData,
-        };
-
-        let mut dirty_offset = 0x1000;
-
         // Test `write`.
-        h.test_access(bytes, dirty_offset, BUF_SIZE, |m, addr| {
-            assert_eq!(m.write(buf.as_slice(), addr).unwrap(), BUF_SIZE)
-        });
-        dirty_offset += step;
+        assert!(check_range_fn(bytes, dirty_offset, BUF_SIZE, true));
+        assert_eq!(
+            bytes
+                .write(buf.as_slice(), address_fn(dirty_offset))
+                .unwrap(),
+            BUF_SIZE
+        );
+        assert!(check_range_fn(bytes, dirty_offset, BUF_SIZE, false));
 
         // Test `write_slice`.
-        h.test_access(bytes, dirty_offset, BUF_SIZE, |m, addr| {
-            m.write_slice(buf.as_slice(), addr).unwrap()
-        });
         dirty_offset += step;
+        assert!(check_range_fn(bytes, dirty_offset, BUF_SIZE, true));
+        bytes
+            .write_slice(buf.as_slice(), address_fn(dirty_offset))
+            .unwrap();
+        assert!(check_range_fn(bytes, dirty_offset, BUF_SIZE, false));
 
         // Test `write_obj`.
-        h.test_access(bytes, dirty_offset, size_of_val(&val), |m, addr| {
-            m.write_obj(val, addr).unwrap()
-        });
         dirty_offset += step;
+        assert!(check_range_fn(bytes, dirty_offset, BUF_SIZE, true));
+        bytes.write_obj(val, address_fn(dirty_offset)).unwrap();
+        assert!(check_range_fn(bytes, dirty_offset, BUF_SIZE, false));
 
         // Test `store`.
-        h.test_access(bytes, dirty_offset, size_of_val(&val), |m, addr| {
-            m.store(val, addr, Ordering::Relaxed).unwrap()
-        });
+        dirty_offset += step;
+        assert!(check_range_fn(bytes, dirty_offset, BUF_SIZE, true));
+        bytes
+            .store(val, address_fn(dirty_offset), Ordering::Relaxed)
+            .unwrap();
+        assert!(check_range_fn(bytes, dirty_offset, BUF_SIZE, false));
     }
 
     // This function and the next are currently conditionally compiled because we only use