712 

   713 class filecacheentry(object):

   714     def __init__(self, path):

   715         self.path = path

   716         self.cachestat = filecacheentry.stat(self.path)

   717 

   718         if self.cachestat:

   719             self._cacheable = self.cachestat.cacheable()

   720         else:

   721             # None means we don't know yet

   722             self._cacheable = None

   723 

   724     def refresh(self):

   725         if self.cacheable():

   726             self.cachestat = filecacheentry.stat(self.path)

   727 

   728     def cacheable(self):

   729         if self._cacheable is not None:

   730             return self._cacheable

   731 

   732         # we don't know yet, assume it is for now

   733         return True

   734 

   735     def changed(self):

   736         # no point in going further if we can't cache it

   737         if not self.cacheable():

   738             return True

   739 

   740         newstat = filecacheentry.stat(self.path)

   741 

   742         # we may not know if it's cacheable yet, check again now

   743         if newstat and self._cacheable is None:

   744             self._cacheable = newstat.cacheable()

   745 

   746             # check again

   747             if not self._cacheable:

   748                 return True

   749 

   750         if self.cachestat != newstat:

   751             self.cachestat = newstat

   752             return True

   753         else:

   754             return False

   755 

   756     @staticmethod

   757     def stat(path):

   758         try:

   759             return util.cachestat(path)

   760         except OSError, e:

   761             if e.errno != errno.ENOENT:

   762                 raise

   763 

   764 class filecache(object):

   765     '''A property like decorator that tracks a file under .hg/ for updates.

   766 

   767     Records stat info when called in _filecache.

   768 

   769     On subsequent calls, compares old stat info with new info, and recreates

   770     the object when needed, updating the new stat info in _filecache.

   771 

   772     Mercurial either atomic renames or appends for files under .hg,

   773     so to ensure the cache is reliable we need the filesystem to be able

   774     to tell us if a file has been replaced. If it can't, we fallback to

   775     recreating the object on every call (essentially the same behaviour as

   776     propertycache).'''

   777     def __init__(self, path, instore=False):

   778         self.path = path

   779         self.instore = instore

   780 

   781     def __call__(self, func):

   782         self.func = func

   783         self.name = func.__name__

   784         return self

   785 

   786     def __get__(self, obj, type=None):

   787         entry = obj._filecache.get(self.name)

   788 

   789         if entry:

   790             if entry.changed():

   791                 entry.obj = self.func(obj)

   792         else:

   793             path = self.instore and obj.sjoin(self.path) or obj.join(self.path)

   794 

   795             # We stat -before- creating the object so our cache doesn't lie if

   796             # a writer modified between the time we read and stat

   797             entry = filecacheentry(path)

   798             entry.obj = self.func(obj)

   799 

   800             obj._filecache[self.name] = entry

   801 

   802         setattr(obj, self.name, entry.obj)

   803         return entry.obj