# HG changeset patch
# User Jun Wu <qu...@fb.com>
# Date 1488947963 28800
# Tue Mar 07 20:39:23 2017 -0800
# Node ID 60eb2c2b5196a62d635dbe0eb1e29fdd945d5058
# Parent c32f9eeec75445bfbbc55df4c1fcc584d3cf45cd
# Available At https://bitbucket.org/quark-zju/hg-draft
# hg pull https://bitbucket.org/quark-zju/hg-draft -r 60eb2c2b5196
chgcache: introduce a new global state
The new chgcache module will be used to store some cache state of chg, which
is useful to preload repo-related contents and speed up related operations.
Motivation:
Currently, chg only preloads extensions and one chg server is responsible
for multiple repos (to avoid unnecessary memory usage).
With the new module, eventually the master chg server will have a state
storing multiple components of multiple repos, like the changelog index
(with radix tree prebuilt), the dirstate, the phasecache, the bookmarks,
the obsstore, etc.
Why a new module:
The feature is low-level and relatively separate from chgserver (which is
focused on client/server stuff). So it's made a new module. It could be
used without chg in theory, although it depends on chg practically.
This patch only contains very basic "set" and "get" methods.
diff --git a/mercurial/chgcache.py b/mercurial/chgcache.py
new file mode 100644
--- /dev/null
+++ b/mercurial/chgcache.py
@@ -0,0 +1,22 @@
+# chgcache.py - caching state for chg
+#
+# Copyright 2017 Facebook, Inc.
+#
+# This software may be used and distributed according to the terms of the
+# GNU General Public License version 2 or any later version.
+
+from __future__ import absolute_import
+
+_cache = {}
+
+def get(key):
+ """look up an entry. returns None if key is not found"""
+ return _cache.get(key)
+
+def set(key, value):
+ """write to the cache. if value is None, remove the entry"""
+ if value is None:
+ if key in _cache:
+ del _cache[key]
+ else:
+ _cache[key] = value
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