buildbot/dnotify.py

   1
   2 # spiv wants this
   3
   4 import fcntl, signal
   5
   6 class DNotify_Handler:
   7     def __init__(self):
   8         self.watchers = {}
   9         self.installed = 0
  10     def install(self):
  11         if self.installed:
  12             return
  13         signal.signal(signal.SIGIO, self.fire)
  14         self.installed = 1
  15     def uninstall(self):
  16         if not self.installed:
  17             return
  18         signal.signal(signal.SIGIO, signal.SIG_DFL)
  19         self.installed = 0
  20     def add(self, watcher):
  21         self.watchers[watcher.fd.fileno()] = watcher
  22         self.install()
  23     def remove(self, watcher):
  24         if self.watchers.has_key(watcher.fd.fileno()):
  25             del(self.watchers[watcher.fd.fileno()])
  26             if not self.watchers:
  27                 self.uninstall()
  28     def fire(self, signum, frame):
  29         # this is the signal handler
  30         # without siginfo_t, we must fire them all
  31         for watcher in self.watchers.values():
  32             watcher.callback()
  33
  34 class DNotify:
  35     DN_ACCESS = fcntl.DN_ACCESS  # a file in the directory was read
  36     DN_MODIFY = fcntl.DN_MODIFY  # a file was modified (write,truncate)
  37     DN_CREATE = fcntl.DN_CREATE  # a file was created
  38     DN_DELETE = fcntl.DN_DELETE  # a file was unlinked
  39     DN_RENAME = fcntl.DN_RENAME  # a file was renamed
  40     DN_ATTRIB = fcntl.DN_ATTRIB  # a file had attributes changed (chmod,chown)
  41
  42     handler = [None]
  43
  44     def __init__(self, dirname, callback=None,
  45                  flags=[DN_MODIFY,DN_CREATE,DN_DELETE,DN_RENAME]):
  46
  47         """This object watches a directory for changes. The .callback
  48         attribute should be set to a function to be run every time something
  49         happens to it. Be aware that it will be called more times than you
  50         expect."""
  51
  52         if callback:
  53             self.callback = callback
  54         else:
  55             self.callback = self.fire
  56         self.dirname = dirname
  57         self.flags = reduce(lambda x, y: x | y, flags) | fcntl.DN_MULTISHOT
  58         self.fd = open(dirname, "r")
  59         # ideally we would move the notification to something like SIGRTMIN,
  60         # (to free up SIGIO) and use sigaction to have the signal handler
  61         # receive a structure with the fd number. But python doesn't offer
  62         # either.
  63         if not self.handler[0]:
  64             self.handler[0] = DNotify_Handler()
  65         self.handler[0].add(self)
  66         fcntl.fcntl(self.fd, fcntl.F_NOTIFY, self.flags)
  67     def remove(self):
  68         self.handler[0].remove(self)
  69         self.fd.close()
  70     def fire(self):
  71         print self.dirname, "changed!"
  72
  73 def test_dnotify1():
  74     d = DNotify(".")
  75     while 1:
  76         signal.pause()
  77
  78 def test_dnotify2():
  79     # create ./foo/, create/delete files in ./ and ./foo/ while this is
  80     # running. Notice how both notifiers are fired when anything changes;
  81     # this is an unfortunate side-effect of the lack of extended sigaction
  82     # support in Python.
  83     count = [0]
  84     d1 = DNotify(".")
  85     def fire1(count=count, d1=d1):
  86         print "./ changed!", count[0]
  87         count[0] += 1
  88         if count[0] > 5:
  89             d1.remove()
  90             del(d1)
  91     # change the callback, since we can't define it until after we have the
  92     # dnotify object. Hmm, unless we give the dnotify to the callback.
  93     d1.callback = fire1
  94     def fire2(): print "foo/ changed!"
  95     d2 = DNotify("foo", fire2)
  96     while 1:
  97         signal.pause()
  98
  99
 100 if __name__ == '__main__':
 101     test_dnotify2()
 102