made Header non generic, but everything is now broken :(

src/allocator.rs

@@ -43,7 +43,7 @@ pub struct GeneralPurposeAllocator {
 
 #[derive(Clone, Copy, FromBytes, FromZeroes, AsBytes, Unaligned)]
 #[repr(C)]
-struct FreeListBlock {
+pub struct FreeListBlock {
     next: FilePointer<FreeListBlock>,
     size: u8,
 }

src/lib.rs

@@ -26,13 +26,24 @@ type U64 = zerocopy::byteorder::U64<LE>;
 type U32 = zerocopy::byteorder::U32<LE>;
 type U16 = zerocopy::byteorder::U16<LE>;
 
-#[derive(Clone, Copy, FromBytes, FromZeroes, AsBytes, Unaligned, Hash)]
+#[derive(FromBytes, FromZeroes, AsBytes, Unaligned, Hash)]
 #[repr(transparent)]
 pub struct FilePointer<T> {
     inner: RawFilePointer,
     _phantom: PhantomData<*const T>,
 }
 
+impl<T> Clone for FilePointer<T> {
+    fn clone(&self) -> Self {
+        Self {
+            inner: self.inner,
+            _phantom: PhantomData,
+        }
+    }
+}
+
+impl<T> Copy for FilePointer<T> {}
+
 impl<T> Debug for FilePointer<T> {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         self.inner.fmt(f)
@@ -196,21 +207,21 @@ impl FileRange {
 
 #[derive(Clone, Copy, FromBytes, FromZeroes, AsBytes, Unaligned)]
 #[repr(C)]
-struct Header<R> {
+struct Header {
     magic: [u8; 16],
-    root: FilePointer<R>,
+    root: RawFilePointer, // if we make this FilePointer<R>, as it should be, AsBytes can not be derived
     allocator_state: AllocatorState,
 }
 
-impl<R> Default for Header<R> {
+impl Default for Header {
     fn default() -> Self {
         Self {
             magic: *b"cool db format 1",
-            root: FilePointer::null(),
+            root: RawFilePointer::null(),
             allocator_state: AllocatorState {
                 general: RawFilePointer::null(),
                 slabs: SlabListPointer(FilePointer::new(
-                    RawFilePointer::null() + size_of::<Header<R>>() as u64,
+                    RawFilePointer::null() + size_of::<Header>() as u64,
                 )),
             },
         }
@@ -257,11 +268,15 @@ struct SnapshotAndFreeList<R> {
 }
 
 impl<R> Db<R> {
-    fn header(&self) -> &Header<R> {
+    fn root(&self) -> FilePointer<R> {
+        FilePointer::new(self.header().root)
+    }
+
+    fn header(&self) -> &Header {
         unsafe { self.reference_range_unchecked(Self::header_ptr().range()) }
     }
 
-    fn header_mut(&mut self) -> &mut Header<R> {
+    fn header_mut(&mut self) -> &mut Header {
         unsafe { self.modify_range_unchecked(Self::header_ptr().range()) }
     }
 
@@ -315,16 +330,16 @@ impl<R> Db<R> {
         self.snapshots = snapshots;
     }
 
-    fn header_ptr() -> FilePointer<Header<R>> {
+    fn header_ptr() -> FilePointer<Header> {
         FilePointer::new(RawFilePointer(0.into()))
     }
 
     fn root_ptr() -> FilePointer<FilePointer<R>> {
-        FilePointer::new(RawFilePointer((size_of::<Header<R>>() as u64).into()))
+        FilePointer::new(RawFilePointer((size_of::<Header>() as u64).into()))
     }
 
     fn allocator_state_ptr() -> RawFilePointer {
-        RawFilePointer((size_of::<Header<R>>() as u64 + size_of::<RawFilePointer>() as u64).into())
+        RawFilePointer((size_of::<Header>() as u64 + size_of::<RawFilePointer>() as u64).into())
     }
 
     fn general_purpose_allocator() -> GeneralPurposeAllocator {
@@ -486,7 +501,7 @@ impl<R> Db<R> {
         }
 
         let _ = db.state.swap(Arc::new(Snapshot {
-            root: db.header().root,
+            root: db.root(),
             map: unsafe { Mmap::map(&db.file).unwrap() },
         }));
 
@@ -509,7 +524,7 @@ impl<R> Db<R> {
         };
 
         let _ = db.state.swap(Arc::new(Snapshot {
-            root: db.header().root,
+            root: db.root(),
             map: unsafe { Mmap::map(&db.file).unwrap() },
         }));
 
@@ -520,9 +535,7 @@ impl<R> Db<R> {
         let allocator_state = self.header().allocator_state;
         allocator_state.slabs.init(
             self,
-            (PAGE_SIZE - size_of::<Header<R>>() as u64)
-                .try_into()
-                .unwrap(),
+            (PAGE_SIZE - size_of::<Header>() as u64).try_into().unwrap(),
         );
 
         for &size in slabs {

src/transaction.rs

@@ -170,6 +170,6 @@ impl<'t, R> TransactionHandle<'t, R> {
     }
 
     pub fn root(&self) -> FilePointer<R> {
-        self.db.header().root
+        self.db.root()
     }
 }