--- a/rust/hg-core/src/dirstate_tree/on_disk.rs	Thu Jul 08 12:18:21 2021 +0200
+++ b/rust/hg-core/src/dirstate_tree/on_disk.rs	Mon Jul 12 22:46:52 2021 +0200
@@ -21,7 +21,7 @@
 use bytes_cast::BytesCast;
 use format_bytes::format_bytes;
 use std::borrow::Cow;
-use std::convert::TryFrom;
+use std::convert::{TryFrom, TryInto};
 use std::time::{Duration, SystemTime, UNIX_EPOCH};
 
 /// Added at the start of `.hg/dirstate` when the "v2" format is used.
@@ -224,6 +224,11 @@
         DirstateParents { p1, p2 }
     }
 
+    pub fn data_size(&self) -> usize {
+        // This `unwrap` could only panic on a 16-bit CPU
+        self.header.data_size.get().try_into().unwrap()
+    }
+
     pub fn data_filename(&self) -> String {
         String::from_utf8(format_bytes!(b"dirstate.{}.d", self.uuid)).unwrap()
     }