# HG changeset patch
# User Pierre-Yves David <pierre-yves.david@octobus.net>
# Date 2020-01-15 14:50:43
# Node ID 2ea6a67ff5029f7c64d06331cdb7034404d44d43
# Parent  1d2b37def017bb806653b04c1e735c26e261df3a

nodemap: write new data from the expected current data length

If the amount of data in the file exceed the expect amount, we will overwrite
the extra data. This is a simple way to be safer.

Differential Revision: https://phab.mercurial-scm.org/D7891

diff --git a/mercurial/revlogutils/nodemap.py b/mercurial/revlogutils/nodemap.py
--- a/mercurial/revlogutils/nodemap.py
+++ b/mercurial/revlogutils/nodemap.py
@@ -92,7 +92,8 @@ def _persist_nodemap(tr, revlog):
             datafile = _rawdata_filepath(revlog, target_docket)
             # EXP-TODO: if this is a cache, this should use a cache vfs, not a
             # store vfs
-            with revlog.opener(datafile, b'a') as fd:
+            with revlog.opener(datafile, b'r+') as fd:
+                fd.seek(target_docket.data_length)
                 fd.write(data)
             target_docket.data_length += len(data)
             target_docket.data_unused += data_changed_count