use checked_* methods

Author: Nate Catelli

src/structures/paging/frame.rs

@@ -146,10 +146,11 @@ impl<S: PageSize> core::iter::Step for PhysFrame<S> {
         use core::convert::TryFrom;
 
         match u64::try_from(count) {
-            Ok(n) => match start.start_address().as_u64().overflowing_add(n * S::SIZE) {
-                (_, true) => None,
-                (start_addr, false) => Self::from_start_address(PhysAddr::new(start_addr)).ok(),
-            },
+            Ok(n) => start
+                .start_address()
+                .as_u64()
+                .checked_add(n * S::SIZE)
+                .and_then(|start_addr| Self::from_start_address(PhysAddr::new(start_addr)).ok()),
             Err(_) => None, // if n is out of range, `unsigned_start + n`
         }
     }
@@ -158,10 +159,11 @@ impl<S: PageSize> core::iter::Step for PhysFrame<S> {
         use core::convert::TryFrom;
 
         match u64::try_from(count) {
-            Ok(n) => match start.start_address().as_u64().overflowing_sub(n * S::SIZE) {
-                (_, true) => None,
-                (start_addr, false) => Self::from_start_address(PhysAddr::new(start_addr)).ok(),
-            },
+            Ok(n) => start
+                .start_address()
+                .as_u64()
+                .checked_sub(n * S::SIZE)
+                .and_then(|start_addr| Self::from_start_address(PhysAddr::new(start_addr)).ok()),
             Err(_) => None, // if n is out of range, `unsigned_start + n`
         }
     }