fix copy

src/lib.rs

@@ -232,6 +232,12 @@ impl RawFilePointer {
 }
 
 impl FileRange {
+    fn start(self) -> RawFilePointer {
+        self.start
+    }
+    fn end(self) -> RawFilePointer {
+        self.start + (self.len() - 1)
+    }
     fn len(&self) -> u64 {
         self.len.get()
     }
@@ -426,9 +432,24 @@ impl<R> Db<R> {
 
     // TODO: fix pls
     #[track_caller]
-    unsafe fn copy(&mut self, from: FileRange, to: FileRange) {
+    unsafe fn copy_nonoverlapping(&mut self, from: FileRange, to: FileRange) {
+        let len = from.len();
+        println!("copy from {from:?} to {to:?} ({len})",);
+
+        // intervals must be non-overlapping and of the same size
+        assert!(!from.as_range().contains(&(to.start().0.get() as usize)));
+        assert!(!from.as_range().contains(&(to.end().0.get() as usize)));
+        assert!(!to.as_range().contains(&(from.start().0.get() as usize)));
+        assert!(!to.as_range().contains(&(from.end().0.get() as usize)));
+        assert_eq!(from.len(), to.len());
+
+        if from.start > to.start {
+            let (head, tail) = self.map.split_at_mut(from.start.0.get() as usize);
+            head[to.as_range()].copy_from_slice(&tail[0..len as usize]);
+        } else {
             let (head, tail) = self.map.split_at_mut(to.start.0.get() as usize);
-        tail[0..to.len() as usize].copy_from_slice(&head[from.as_range()]);
+            tail[0..len as usize].copy_from_slice(&head[from.as_range()]);
+        }
     }
 
     #[track_caller]
@@ -841,7 +862,6 @@ mod tests {
         let mut snapshots = VecDeque::new();
 
         for i in 0..20 {
-            dbg!(i);
             db.transaction(|transaction| {
                 let root = transaction.root();
 
@@ -892,6 +912,12 @@ mod tests {
                 root
             });
 
+            snapshots.push_back(db.create_reader().state.get());
+            if snapshots.len() > 10 {
+                drop(snapshots.pop_front());
+                db.free_old_epochs()
+            }
+
             validate_db(&db, |snaphot, coverage| {
                 coverage.set_allocated(snaphot.root.range());
                 let data = snaphot.read(snaphot.root);
@@ -902,12 +928,6 @@ mod tests {
                     next = snaphot.read(next).next;
                 }
             });
-
-            snapshots.push_back(db.create_reader().state.get());
-            if snapshots.len() > 10 {
-                drop(snapshots.pop_front());
-                db.free_old_epochs()
-            }
         }
 
         // TODO: allocate some variably sized strings
@@ -1259,9 +1279,8 @@ mod tests {
 
         f(snapshot, &mut coverage);
 
-        print!("{}", coverage.print());
-
         if !coverage.all_covered() {
+            print!("{}", coverage.print());
             panic!("space in the file was lost...");
         }
     }

src/transaction.rs

@@ -77,7 +77,7 @@ impl<'t, R> TransactionHandle<'t, R> {
         } else {
             let (new, _) = self.allocate_range(range.len());
 
-            self.db.copy(range, new);
+            self.db.copy_nonoverlapping(range, new);
 
             let res = self.replaced.insert(
                 new.start,