diff mercurial/changelog.py @ 47425:e0a314bcbc9d

revlog: Extract low-level random-access file read caching logic

The `revlog` class does many things, among which fulfilling requests for
arbitrary byte slices from the revlog "data file" by reading a larger chunk
and caching it in memory, in order to reduce the number of system calls.

This extracts that logic into a new class, so that it may later also be used
for the side-data file (with another instance of that class).

The copyright notice of the new file does not include a date or author name
since such information tend not to be kept up-to-date:

https://www.linuxfoundation.org/en/blog/copyright-notices-in-open-source-software-projects/

Differential Revision: https://phab.mercurial-scm.org/D10878

--- a/mercurial/changelog.py	Fri Jun 11 23:39:31 2021 -0400
+++ b/mercurial/changelog.py	Tue Jun 08 19:55:00 2021 +0200
@@ -454,6 +454,7 @@
                 self.opener = _delayopener(
                     self._realopener, self._indexfile, self._delaybuf
                 )
+            self._segmentfile.opener = self.opener
         self._delayed = True
         tr.addpending(b'cl-%i' % id(self), self._writepending)
         tr.addfinalize(b'cl-%i' % id(self), self._finalize)
@@ -462,6 +463,7 @@
         """finalize index updates"""
         self._delayed = False
         self.opener = self._realopener
+        self._segmentfile.opener = self.opener
         # move redirected index data back into place
         if self._docket is not None:
             self._write_docket(tr)
@@ -501,6 +503,7 @@
             self._delaybuf = None
             self._divert = True
             self.opener = _divertopener(self._realopener, self._indexfile)
+            self._segmentfile.opener = self.opener
 
         if self._divert:
             return True