diff mercurial/node.py @ 46780:6266d19556ad

node: introduce nodeconstants class

In preparing for moving from SHA1 hashes to a modern hash function,
place nullid and other constant magic vules in a class. Provide the
active set of constants in the repository and push it down. Provide
nullid directly in strategic places like the repository as it is
accessed very often. This changeset introduces the API change, but not
the mechanical replacement of the node.py attributes itself.

Differential Revision: https://phab.mercurial-scm.org/D9750

--- a/mercurial/node.py	Wed Mar 10 18:09:21 2021 +0100
+++ b/mercurial/node.py	Wed Jan 13 16:14:58 2021 +0100
@@ -21,29 +21,48 @@
         raise TypeError(e)
 
 
-nullrev = -1
-# In hex, this is '0000000000000000000000000000000000000000'
-nullid = b"\0" * 20
-nullhex = hex(nullid)
+def short(node):
+    return hex(node[:6])
+
 
-# Phony node value to stand-in for new files in some uses of
-# manifests.
-# In hex, this is '2121212121212121212121212121212121212121'
-newnodeid = b'!!!!!!!!!!!!!!!!!!!!'
-# In hex, this is '3030303030303030303030303030306164646564'
-addednodeid = b'000000000000000added'
-# In hex, this is '3030303030303030303030306d6f646966696564'
-modifiednodeid = b'000000000000modified'
+nullrev = -1
 
-wdirfilenodeids = {newnodeid, addednodeid, modifiednodeid}
-
-# pseudo identifiers for working directory
-# (they are experimental, so don't add too many dependencies on them)
+# pseudo identifier for working directory
+# (experimental, so don't add too many dependencies on it)
 wdirrev = 0x7FFFFFFF
-# In hex, this is 'ffffffffffffffffffffffffffffffffffffffff'
-wdirid = b"\xff" * 20
-wdirhex = hex(wdirid)
 
 
-def short(node):
-    return hex(node[:6])
+class sha1nodeconstants(object):
+    nodelen = 20
+
+    # In hex, this is '0000000000000000000000000000000000000000'
+    nullid = b"\0" * nodelen
+    nullhex = hex(nullid)
+
+    # Phony node value to stand-in for new files in some uses of
+    # manifests.
+    # In hex, this is '2121212121212121212121212121212121212121'
+    newnodeid = b'!!!!!!!!!!!!!!!!!!!!'
+    # In hex, this is '3030303030303030303030303030306164646564'
+    addednodeid = b'000000000000000added'
+    # In hex, this is '3030303030303030303030306d6f646966696564'
+    modifiednodeid = b'000000000000modified'
+
+    wdirfilenodeids = {newnodeid, addednodeid, modifiednodeid}
+
+    # pseudo identifier for working directory
+    # (experimental, so don't add too many dependencies on it)
+    # In hex, this is 'ffffffffffffffffffffffffffffffffffffffff'
+    wdirid = b"\xff" * nodelen
+    wdirhex = hex(wdirid)
+
+
+# legacy starting point for porting modules
+nullid = sha1nodeconstants.nullid
+nullhex = sha1nodeconstants.nullhex
+newnodeid = sha1nodeconstants.newnodeid
+addednodeid = sha1nodeconstants.addednodeid
+modifiednodeid = sha1nodeconstants.modifiednodeid
+wdirfilenodeids = sha1nodeconstants.wdirfilenodeids
+wdirid = sha1nodeconstants.wdirid
+wdirhex = sha1nodeconstants.wdirhex