buildbot/dnotify.py

   1 #! /usr/bin/python
   2
   3 # spiv wants this
   4
   5 import fcntl, signal
   6
   7 class DNotify_Handler:
   8     def __init__(self):
   9         self.watchers = {}
  10         self.installed = 0
  11     def install(self):
  12         if self.installed:
  13             return
  14         signal.signal(signal.SIGIO, self.fire)
  15         self.installed = 1
  16     def uninstall(self):
  17         if not self.installed:
  18             return
  19         signal.signal(signal.SIGIO, signal.SIG_DFL)
  20         self.installed = 0
  21     def add(self, watcher):
  22         self.watchers[watcher.fd.fileno()] = watcher
  23         self.install()
  24     def remove(self, watcher):
  25         if self.watchers.has_key(watcher.fd.fileno()):
  26             del(self.watchers[watcher.fd.fileno()])
  27             if not self.watchers:
  28                 self.uninstall()
  29     def fire(self, signum, frame):
  30         # this is the signal handler
  31         # without siginfo_t, we must fire them all
  32         for watcher in self.watchers.values():
  33             watcher.callback()
  34
  35 class DNotify:
  36     DN_ACCESS = fcntl.DN_ACCESS  # a file in the directory was read
  37     DN_MODIFY = fcntl.DN_MODIFY  # a file was modified (write,truncate)
  38     DN_CREATE = fcntl.DN_CREATE  # a file was created
  39     DN_DELETE = fcntl.DN_DELETE  # a file was unlinked
  40     DN_RENAME = fcntl.DN_RENAME  # a file was renamed
  41     DN_ATTRIB = fcntl.DN_ATTRIB  # a file had attributes changed (chmod,chown)
  42
  43     handler = [None]
  44
  45     def __init__(self, dirname, callback=None,
  46                  flags=[DN_MODIFY,DN_CREATE,DN_DELETE,DN_RENAME]):
  47
  48         """This object watches a directory for changes. The .callback
  49         attribute should be set to a function to be run every time something
  50         happens to it. Be aware that it will be called more times than you
  51         expect."""
  52
  53         if callback:
  54             self.callback = callback
  55         else:
  56             self.callback = self.fire
  57         self.dirname = dirname
  58         self.flags = reduce(lambda x, y: x | y, flags) | fcntl.DN_MULTISHOT
  59         self.fd = open(dirname, "r")
  60         # ideally we would move the notification to something like SIGRTMIN,
  61         # (to free up SIGIO) and use sigaction to have the signal handler
  62         # receive a structure with the fd number. But python doesn't offer
  63         # either.
  64         if not self.handler[0]:
  65             self.handler[0] = DNotify_Handler()
  66         self.handler[0].add(self)
  67         fcntl.fcntl(self.fd, fcntl.F_NOTIFY, self.flags)
  68     def remove(self):
  69         self.handler[0].remove(self)
  70         self.fd.close()
  71     def fire(self):
  72         print self.dirname, "changed!"
  73
  74 def test_dnotify1():
  75     d = DNotify(".")
  76     while 1:
  77         signal.pause()
  78
  79 def test_dnotify2():
  80     # create ./foo/, create/delete files in ./ and ./foo/ while this is
  81     # running. Notice how both notifiers are fired when anything changes;
  82     # this is an unfortunate side-effect of the lack of extended sigaction
  83     # support in Python.
  84     count = [0]
  85     d1 = DNotify(".")
  86     def fire1(count=count, d1=d1):
  87         print "./ changed!", count[0]
  88         count[0] += 1
  89         if count[0] > 5:
  90             d1.remove()
  91             del(d1)
  92     # change the callback, since we can't define it until after we have the
  93     # dnotify object. Hmm, unless we give the dnotify to the callback.
  94     d1.callback = fire1
  95     def fire2(): print "foo/ changed!"
  96     d2 = DNotify("foo", fire2)
  97     while 1:
  98         signal.pause()
  99
 100
 101 if __name__ == '__main__':
 102     test_dnotify2()
 103