add TransactionHandle::set

src/datastructures/string.rs

@@ -41,6 +41,7 @@ impl Str {
     }
 }
 
+// TODO: remove these impls for all datatypes
 impl FilePointer<Str> {
     pub fn set<R>(self, transaction: &mut TransactionHandle<R>, s: &str) -> FilePointer<Str> {
         let new_str = transaction.read::<Str>(self).set(transaction, s);

src/transaction.rs

@@ -136,6 +136,12 @@ impl<'t, R> TransactionHandle<'t, R> {
         (FilePointer::from_range(range), data)
     }
 
+    pub fn set<T: AsBytes + FromBytes>(&mut self, at: FilePointer<T>, value: T) -> FilePointer<T> {
+        let (ptr, data) = self.modify(at);
+        *data = value;
+        ptr
+    }
+
     pub fn allocate_range(&mut self, length: u64) -> (FileRange, &mut [u8]) {
         unsafe {
             let range = self.db.allocate(length);