get rid of unnecessary mut

runtime/src/cache_hash_data.rs

@@ -50,6 +50,24 @@ impl CacheHashDataFile {
         }
     }
 
+    fn get<T: Sized>(&self, ix: u64) -> &T {
+        let start = (ix * self.cell_size) as usize + std::mem::size_of::<Header>();
+        let end = start + std::mem::size_of::<T>();
+        assert!(
+            end <= self.capacity as usize,
+            "end: {}, capacity: {}, ix: {}, cell size: {}",
+            end,
+            self.capacity,
+            ix,
+            self.cell_size
+        );
+        let item_slice: &[u8] = &self.mmap[start..end];
+        unsafe {
+            let item = item_slice.as_ptr() as *const T;
+            &*item
+        }
+    }
+
     fn get_header_mut(&mut self) -> &mut Header {
         let start = 0_usize;
         let end = start + std::mem::size_of::<Header>();
@@ -228,7 +246,7 @@ impl CacheHashData {
         stats.entries_loaded_from_cache += entries;
         let mut m2 = Measure::start("decode");
         for i in 0..entries {
-            let d = cache_file.get_mut::<EntryType>(i as u64);
+            let d = cache_file.get::<EntryType>(i as u64);
             let mut pubkey_to_bin_index = bin_calculator.bin_from_pubkey(&d.pubkey);
             assert!(
                 pubkey_to_bin_index >= start_bin_index,