# HG changeset patch
# User Mads Kiilerich <madski@unity3d.com>
# Date 1468873358 -7200
# Node ID db0095c83344a03e1357da5486c054ad51d47afd
# Parent  b181a650a886b68a13d8364a5ed4ce1dd1032427
rbc: fix invalid rbc-revs entries caused by missing cache growth

It was in some cases possible to end up writing to the cache file without
growing it first. The range assignment in _setcachedata would append instead of
writing at the requested position and thus write the new record in the wrong
place.

To fix this, we avoid looking up in too small caches, and when growing the
cache, do it right before writing the new record to it so we know it has been
done correctly.

diff -r b181a650a886 -r db0095c83344 mercurial/branchmap.py
--- a/mercurial/branchmap.py	Mon Jul 18 22:21:42 2016 +0200
+++ b/mercurial/branchmap.py	Mon Jul 18 22:22:38 2016 +0200
@@ -402,10 +402,9 @@
         if rev == nullrev:
             return changelog.branchinfo(rev)
 
-        # if requested rev is missing, add and populate all missing revs
+        # if requested rev isn't allocated, grow and cache the rev info
         if len(self._rbcrevs) < rbcrevidx + _rbcrecsize:
-            self._rbcrevs.extend('\0' * (len(changelog) * _rbcrecsize -
-                                         len(self._rbcrevs)))
+            return self._branchinfo(rev)
 
         # fast path: extract data from cache, use it if node is matching
         reponode = changelog.node(rev)[:_rbcnodelen]
@@ -452,6 +451,10 @@
         rbcrevidx = rev * _rbcrecsize
         rec = array('c')
         rec.fromstring(pack(_rbcrecfmt, node, branchidx))
+        if len(self._rbcrevs) < rbcrevidx + _rbcrecsize:
+            self._rbcrevs.extend('\0' *
+                                 (len(self._repo.changelog) * _rbcrecsize -
+                                  len(self._rbcrevs)))
         self._rbcrevs[rbcrevidx:rbcrevidx + _rbcrecsize] = rec
         self._rbcrevslen = min(self._rbcrevslen, rev)
 
diff -r b181a650a886 -r db0095c83344 tests/test-branches.t
--- a/tests/test-branches.t	Mon Jul 18 22:21:42 2016 +0200
+++ b/tests/test-branches.t	Mon Jul 18 22:22:38 2016 +0200
@@ -655,12 +655,16 @@
   $ rm .hg/cache/rbc*
   $ hg log -r "5 & branch(5)" -T "{rev}\n"
   5
-BUG: rbc-revs should have an entry as 5th record but has it misplaced as the
-first:
   $ f --size --hexdump .hg/cache/rbc-*
   .hg/cache/rbc-names-v1: size=1
   0000: 61                                              |a|
-  .hg/cache/rbc-revs-v1: size=8
-  0000: d8 cb c6 1d 00 00 00 00                         |........|
+  .hg/cache/rbc-revs-v1: size=112
+  0000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
+  0010: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
+  0020: 00 00 00 00 00 00 00 00 d8 cb c6 1d 00 00 00 00 |................|
+  0030: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
+  0040: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
+  0050: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
+  0060: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
 
   $ cd ..