[PATCH 2 of 5 V2] manifest: make manifest derive from manifestrevlog

[Durham Goode]

# HG changeset patch
# User Durham Goode <durham at fb.com>
# Date 1471465513 25200
#      Wed Aug 17 13:25:13 2016 -0700
# Node ID 8ddbe86953023c40beb7be9dcb8025d1055813c5
# Parent  b5eca5d531599261641e1d2d3f9f2e60b6538da7
manifest: make manifest derive from manifestrevlog

As part of our refactoring to split the manifest concept from its storage, we
need to start moving the revlog specific parts of the manifest implementation to
a new class. This patch creates manifestrevlog and moves the fulltextcache onto
the base class.

diff --git a/mercurial/manifest.py b/mercurial/manifest.py
--- a/mercurial/manifest.py
+++ b/mercurial/manifest.py
@@ -890,7 +890,31 @@ class treemanifest(object):
                 subp1, subp2 = subp2, subp1
             writesubtree(subm, subp1, subp2)
 
-class manifest(revlog.revlog):
+class manifestrevlog(revlog.revlog):
+    '''A revlog that stores manifest texts. This is responsible for caching the
+    full-text manifest contents.
+    '''
+    def __init__(self, opener, indexfile):
+        super(manifestrevlog, self).__init__(opener, indexfile)
+
+        # During normal operations, we expect to deal with not more than four
+        # revs at a time (such as during commit --amend). When rebasing large
+        # stacks of commits, the number can go up, hence the config knob below.
+        cachesize = 4
+        opts = getattr(opener, 'options', None)
+        if opts is not None:
+            cachesize = opts.get('manifestcachesize', cachesize)
+        self._fulltextcache = util.lrucachedict(cachesize)
+
+    @property
+    def fulltextcache(self):
+        return self._fulltextcache
+
+    def clearcaches(self):
+        super(manifestrevlog, self).clearcaches()
+        self._fulltextcache.clear()
+
+class manifest(manifestrevlog):
     def __init__(self, opener, dir='', dirlogcache=None):
         '''The 'dir' and 'dirlogcache' arguments are for internal use by
         manifest.manifest only. External users should create a root manifest
@@ -908,7 +932,6 @@ class manifest(revlog.revlog):
             usetreemanifest = opts.get('treemanifest', usetreemanifest)
             usemanifestv2 = opts.get('manifestv2', usemanifestv2)
         self._mancache = util.lrucachedict(cachesize)
-        self._fulltextcache = util.lrucachedict(cachesize)
         self._treeinmem = usetreemanifest
         self._treeondisk = usetreemanifest
         self._usemanifestv2 = usemanifestv2
@@ -918,7 +941,7 @@ class manifest(revlog.revlog):
             if not dir.endswith('/'):
                 dir = dir + '/'
             indexfile = "meta/" + dir + "00manifest.i"
-        revlog.revlog.__init__(self, opener, indexfile)
+        super(manifest, self).__init__(opener, indexfile)
         self._dir = dir
         # The dirlogcache is kept on the root manifest log
         if dir:
@@ -1016,7 +1039,7 @@ class manifest(revlog.revlog):
             m = self._newmanifest(text)
             arraytext = array.array('c', text)
         self._mancache[node] = m
-        self._fulltextcache[node] = arraytext
+        self.fulltextcache[node] = arraytext
         return m
 
     def readshallow(self, node):
@@ -1036,7 +1059,7 @@ class manifest(revlog.revlog):
             return None, None
 
     def add(self, m, transaction, link, p1, p2, added, removed):
-        if (p1 in self._fulltextcache and not self._treeinmem
+        if (p1 in self.fulltextcache and not self._treeinmem
             and not self._usemanifestv2):
             # If our first parent is in the manifest cache, we can
             # compute a delta here using properties we know about the
@@ -1048,7 +1071,7 @@ class manifest(revlog.revlog):
             work = heapq.merge([(x, False) for x in added],
                                [(x, True) for x in removed])
 
-            arraytext, deltatext = m.fastdelta(self._fulltextcache[p1], work)
+            arraytext, deltatext = m.fastdelta(self.fulltextcache[p1], work)
             cachedelta = self.rev(p1), deltatext
             text = util.buffer(arraytext)
             n = self.addrevision(text, transaction, link, p1, p2, cachedelta)
@@ -1068,7 +1091,7 @@ class manifest(revlog.revlog):
                 arraytext = array.array('c', text)
 
         self._mancache[n] = m
-        self._fulltextcache[n] = arraytext
+        self.fulltextcache[n] = arraytext
 
         return n
 
@@ -1095,6 +1118,5 @@ class manifest(revlog.revlog):
 
     def clearcaches(self):
         super(manifest, self).clearcaches()
-        self._fulltextcache.clear()
         self._mancache.clear()
         self._dirlogcache = {'': self}