[Commented On] D10643: revlog: improve documentation of the entry tuple
baymax (Baymax, Your Personal Patch-care Companion)
phabricator at mercurial-scm.org
Tue May 11 18:20:47 UTC 2021
baymax added a comment.
baymax updated this revision to Diff 27882.
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REPOSITORY
rHG Mercurial
CHANGES SINCE LAST UPDATE
https://phab.mercurial-scm.org/D10643?vs=27551&id=27882
BRANCH
default
CHANGES SINCE LAST ACTION
https://phab.mercurial-scm.org/D10643/new/
REVISION DETAIL
https://phab.mercurial-scm.org/D10643
AFFECTED FILES
mercurial/revlog.py
CHANGE DETAILS
diff --git a/mercurial/revlog.py b/mercurial/revlog.py
--- a/mercurial/revlog.py
+++ b/mercurial/revlog.py
@@ -284,6 +284,58 @@
file handle, a filename, and an expected position. It should check whether
the current position in the file handle is valid, and log/warn/fail (by
raising).
+
+
+ Internal details
+ ----------------
+
+ A large part of the revlog logic deal with revision "index entry" a tuple
+ object that constains the same "items" whatever the revlog version.
+ Different version will have different way to store these items (sometime
+ not having them at all), but the tuple will always be the same. New fields
+ are usually added at the end to avoid breaking existing, other, code
+ relying on the existing order. The field are defined as follow:
+
+ [0] offset:
+ The byte index of the start of revision data chunk.
+ That value is shifted up by 16 bits. use "offsett = field >> 16" to
+ retrieve it.
+
+ flags:
+ A flag fields that carry special information or change the behavior
+ of the revision. (see `REVIDX_*` constants for details)
+ The flag field only occupy the first 16 bits of this field,
+ use "flags = field && 0xFFFF" to retrive the value.
+
+ [1] compressed length:
+ The size, in bytes, of the chunk on disk
+
+ [2] uncompressed length:
+ The size, in bytes, of the full revision once reconstructed.
+
+ [3] base rev:
+ Either the base of the revision delta chain (without general
+ delta). Or the base of the delte (stored in the data chunk)
+ with general delta.
+
+ [4] link rev:
+ Changelog revision number of the changeset introducing this
+ revision.
+
+ [5] parent 1 rev:
+ Revision number of the first parent
+
+ [6] parent 2 rev:
+ Revision number of the second parent
+
+ [7] node id:
+ The node id of the current revision
+
+ [8] sidedata offset:
+ The byte index of the start of the revision side-data chunk.
+
+ [9] sidedata chunk length:
+ The size, in bytes, of the revision side-data chunk.
"""
_flagserrorclass = error.RevlogError
To: marmoute, indygreg, #hg-reviewers
Cc: mercurial-patches
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