diff mercurial/pure/parsers.py @ 44313:6f9e8e142cea

nodemap: add a (python) index class for persistent nodemap testing

Using the persistent nodemap require a compeling performance boost and an
existing implementation. The benefit of the persistent nodemap for pure python
code is unclear and we don't have a C implementation for it. Yet we would like
to actually start testing it in more details and define an API for using that
persistent nodemap.

We introduce a new `devel` config option to use an index class dedicated to
Nodemap Testing. This feature is "pure" only because having using a pure-python
index with the `cext` policy proved more difficult than I would like.

There is nothing going on in that class for now, but the coming changeset will
change that.

Differential Revision: https://phab.mercurial-scm.org/D7840

--- a/mercurial/pure/parsers.py	Wed Jan 15 15:47:59 2020 +0100
+++ b/mercurial/pure/parsers.py	Wed Jan 15 15:48:09 2020 +0100
@@ -141,6 +141,15 @@
             self._extra = self._extra[: i - self._lgt]
 
 
+class PersistentNodeMapIndexObject(IndexObject):
+    """a Debug oriented class to test persistent nodemap
+
+    We need a simple python object to test API and higher level behavior. See
+    the Rust implementation for  more serious usage. This should be used only
+    through the dedicated `devel.persistent-nodemap` config.
+    """
+
+
 class InlinedIndexObject(BaseIndexObject):
     def __init__(self, data, inline=0):
         self._data = data
@@ -188,6 +197,12 @@
     return InlinedIndexObject(data, inline), (0, data)
 
 
+def parse_index_devel_nodemap(data, inline):
+    """like parse_index2, but alway return a PersistentNodeMapIndexObject
+    """
+    return PersistentNodeMapIndexObject(data), None
+
+
 def parse_dirstate(dmap, copymap, st):
     parents = [st[:20], st[20:40]]
     # dereference fields so they will be local in loop