config/utils.py

   1 # ***** BEGIN LICENSE BLOCK *****
   2 # Version: MPL 1.1/GPL 2.0/LGPL 2.1
   3 #
   4 # The contents of this file are subject to the Mozilla Public License Version
   5 # 1.1 (the "License"); you may not use this file except in compliance with
   6 # the License. You may obtain a copy of the License at
   7 # http://www.mozilla.org/MPL/
   8 #
   9 # Software distributed under the License is distributed on an "AS IS" basis,
  10 # WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
  11 # for the specific language governing rights and limitations under the
  12 # License.
  13 #
  14 # The Original Code is Mozilla build system.
  15 #
  16 # The Initial Developer of the Original Code is
  17 # Mozilla Foundation.
  18 # Portions created by the Initial Developer are Copyright (C) 2008
  19 # the Initial Developer. All Rights Reserved.
  20 #
  21 # Contributor(s):
  22 #  Axel Hecht <axel@pike.org>
  23 #
  24 # Alternatively, the contents of this file may be used under the terms of
  25 # either the GNU General Public License Version 2 or later (the "GPL"), or
  26 # the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
  27 # in which case the provisions of the GPL or the LGPL are applicable instead
  28 # of those above. If you wish to allow use of your version of this file only
  29 # under the terms of either the GPL or the LGPL, and not to allow others to
  30 # use your version of this file under the terms of the MPL, indicate your
  31 # decision by deleting the provisions above and replace them with the notice
  32 # and other provisions required by the GPL or the LGPL. If you do not delete
  33 # the provisions above, a recipient may use your version of this file under
  34 # the terms of any one of the MPL, the GPL or the LGPL.
  35 #
  36 # ***** END LICENSE BLOCK *****
  37
  38 '''Utility methods to be used by python build infrastructure.
  39 '''
  40
  41 import os
  42 import errno
  43 import sys
  44 import time
  45 import stat
  46
  47 class LockFile(object):
  48   '''LockFile is used by the lockFile method to hold the lock.
  49
  50   This object should not be used directly, but only through
  51   the lockFile method below.
  52   '''
  53   def __init__(self, lockfile):
  54     self.lockfile = lockfile
  55   def __del__(self):
  56     os.remove(self.lockfile)
  57
  58
  59 def lockFile(lockfile, max_wait = 600):
  60   '''Create and hold a lockfile of the given name, with the given timeout.
  61
  62   To release the lock, delete the returned object.
  63   '''
  64   while True:
  65     try:
  66       fd = os.open(lockfile, os.O_EXCL | os.O_RDWR | os.O_CREAT)
  67       # we created the lockfile, so we're the owner
  68       break
  69     except OSError, e:
  70       if e.errno != errno.EEXIST:
  71         # should not occur
  72         raise
  73
  74     try:
  75       # the lock file exists, try to stat it to get its age
  76       # and read its contents to report the owner PID
  77       f = open(lockfile, "r")
  78       s = os.stat(lockfile)
  79     except OSError, e:
  80       if e.errno != errno.ENOENT:
  81         sys.exit("%s exists but stat() failed: %s" %
  82                  (lockfile, e.strerror))
  83       # we didn't create the lockfile, so it did exist, but it's
  84       # gone now. Just try again
  85       continue
  86
  87     # we didn't create the lockfile and it's still there, check
  88     # its age
  89     now = int(time.time())
  90     if now - s[stat.ST_MTIME] > max_wait:
  91       pid = f.readline()
  92       sys.exit("%s has been locked for more than " \
  93                "%d seconds (PID %s)" % (lockfile, max_wait,
  94                                         pid))
  95
  96     # it's not been locked too long, wait a while and retry
  97     f.close()
  98     time.sleep(1)
  99
 100   # if we get here. we have the lockfile. Convert the os.open file
 101   # descriptor into a Python file object and record our PID in it
 102
 103   f = os.fdopen(fd, "w")
 104   f.write("%d\n" % os.getpid())
 105   f.close()
 106   return LockFile(lockfile)
 107
 108 class pushback_iter(object):
 109   '''Utility iterator that can deal with pushed back elements.
 110
 111   This behaves like a regular iterable, just that you can call
 112     iter.pushback(item)
 113   to get the givem item as next item in the iteration.
 114   '''
 115   def __init__(self, iterable):
 116     self.it = iter(iterable)
 117     self.pushed_back = []
 118
 119   def __iter__(self):
 120     return self
 121
 122   def __nonzero__(self):
 123     if self.pushed_back:
 124       return True
 125
 126     try:
 127       self.pushed_back.insert(0, self.it.next())
 128     except StopIteration:
 129       return False
 130     else:
 131       return True
 132
 133   def next(self):
 134     if self.pushed_back:
 135       return self.pushed_back.pop()
 136     return self.it.next()
 137
 138   def pushback(self, item):
 139     self.pushed_back.append(item)