D6889: sidedata: add a new module with basic documentation
marmoute (Pierre-Yves David)
phabricator at mercurial-scm.org
Fri Sep 27 16:16:52 UTC 2019
marmoute created this revision.
marmoute added a reviewer: durin42.
Herald added a subscriber: mercurial-devel.
Herald added a reviewer: hg-reviewers.
REVISION SUMMARY
For now the storage strategy is very simple. We can augment it in the future if
needed.
Code to actually support what is described will be introduced in later
changesets.
REPOSITORY
rHG Mercurial
REVISION DETAIL
https://phab.mercurial-scm.org/D6889
AFFECTED FILES
mercurial/revlogutils/sidedata.py
CHANGE DETAILS
diff --git a/mercurial/revlogutils/sidedata.py b/mercurial/revlogutils/sidedata.py
new file mode 100644
--- /dev/null
+++ b/mercurial/revlogutils/sidedata.py
@@ -0,0 +1,34 @@
+# sidedata.py - Logic around store extra data alongside revlog revisions
+#
+# Copyright 2019 Pierre-Yves David <pierre-yves.david at octobus.net)
+#
+# This software may be used and distributed according to the terms of the
+# GNU General Public License version 2 or any later version.
+"""core code for "sidedata" support
+
+The "sidedata" are stored alongside the revision without actually being part of
+its content and not affecting its hash. It's main use cases is to cache
+important information related to a changesets.
+
+The current implementation is experimental and subject to changes. Do not rely
+on it in production.
+
+Sidedata are stored in the revlog itself, withing the revision rawtext. They
+are inserted, removed from it using the flagprocessors mechanism. The following
+format is currently used::
+
+ initial header:
+ <number of sidedata; 2 bytes>
+ sidedata (repeated N times):
+ <sidedata-key; 2 bytes>
+ <sidedata-entry-length: 4 bytes>
+ <sidedata-content-sha1-digest: 20 bytes>
+ <sidedata-content; X bytes>
+ normal raw text:
+ <all bytes remaining in the rawtext>
+
+This is a simple and effective format. It should be enought to experiment with
+the concept.
+"""
+
+from __future__ import absolute_import
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