--- a/hgext/blackbox.py	Sun Nov 18 18:21:39 2018 +0900
+++ b/hgext/blackbox.py	Sun Nov 18 18:25:37 2018 +0900
@@ -42,7 +42,6 @@
 
 from __future__ import absolute_import
 
-import errno
 import re
 
 from mercurial.i18n import _
@@ -50,7 +49,7 @@
 
 from mercurial import (
     encoding,
-    pycompat,
+    loggingutil,
     registrar,
 )
 from mercurial.utils import (
@@ -89,51 +88,7 @@
     default='%Y/%m/%d %H:%M:%S',
 )
 
-def _openlogfile(ui, vfs, name, maxfiles=0, maxsize=0):
-    def rotate(oldpath, newpath):
-        try:
-            vfs.unlink(newpath)
-        except OSError as err:
-            if err.errno != errno.ENOENT:
-                ui.debug("warning: cannot remove '%s': %s\n" %
-                         (newpath, err.strerror))
-        try:
-            if newpath:
-                vfs.rename(oldpath, newpath)
-        except OSError as err:
-            if err.errno != errno.ENOENT:
-                ui.debug("warning: cannot rename '%s' to '%s': %s\n" %
-                         (newpath, oldpath, err.strerror))
-
-    if maxsize > 0:
-        try:
-            st = vfs.stat(name)
-        except OSError:
-            pass
-        else:
-            if st.st_size >= maxsize:
-                path = vfs.join(name)
-                for i in pycompat.xrange(maxfiles - 1, 1, -1):
-                    rotate(oldpath='%s.%d' % (path, i - 1),
-                           newpath='%s.%d' % (path, i))
-                rotate(oldpath=path,
-                       newpath=maxfiles > 0 and path + '.1')
-    return vfs(name, 'a', makeparentdirs=False)
-
-class proxylogger(object):
-    """Forward log events to another logger to be set later"""
-
-    def __init__(self):
-        self.logger = None
-
-    def tracked(self, event):
-        return self.logger is not None and self.logger.tracked(event)
-
-    def log(self, ui, event, msg, opts):
-        assert self.logger is not None
-        self.logger.log(ui, event, msg, opts)
-
-_lastlogger = proxylogger()
+_lastlogger = loggingutil.proxylogger()
 
 class blackboxlogger(object):
     def __init__(self, ui, repo):
@@ -165,9 +120,9 @@
         try:
             fmt = '%s %s @%s%s (%s)%s> %s'
             args = (date, user, rev, changed, pid, src, msg)
-            with _openlogfile(ui, self._repo.vfs, name='blackbox.log',
-                              maxfiles=self._maxfiles,
-                              maxsize=self._maxsize) as fp:
+            with loggingutil.openlogfile(
+                    ui, self._repo.vfs, name='blackbox.log',
+                    maxfiles=self._maxfiles, maxsize=self._maxsize) as fp:
                 fp.write(fmt % args)
         except (IOError, OSError) as err:
             # deactivate this to avoid failed logging again