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     while True:
  57       try:
  58         os.remove(self.lockfile)
  59         break
  60       except OSError, e:
  61         if e.errno == errno.EACCES:
  62           # another process probably has the file open, we'll retry.
  63           # just a short sleep since we want to drop the lock ASAP
  64           # (but we need to let some other process close the file first)
  65           time.sleep(0.1)
  66         else:
  67           # re-raise unknown errors
  68           raise
  69
  70 def lockFile(lockfile, max_wait = 600):
  71   '''Create and hold a lockfile of the given name, with the given timeout.
  72
  73   To release the lock, delete the returned object.
  74   '''
  75   while True:
  76     try:
  77       fd = os.open(lockfile, os.O_EXCL | os.O_RDWR | os.O_CREAT)
  78       # we created the lockfile, so we're the owner
  79       break
  80     except OSError, e:
  81       if e.errno == errno.EEXIST or \
  82          (sys.platform == "win32" and e.errno == errno.EACCES):
  83         pass
  84       else:
  85         # should not occur
  86         raise
  87
  88     try:
  89       # the lock file exists, try to stat it to get its age
  90       # and read its contents to report the owner PID
  91       f = open(lockfile, "r")
  92       s = os.stat(lockfile)
  93     except EnvironmentError, e:
  94       if e.errno == errno.ENOENT or \
  95          (sys.platform == "win32" and e.errno == errno.EACCES):
  96         # we didn't create the lockfile, so it did exist, but it's
  97         # gone now. Just try again
  98         continue
  99       sys.exit("%s exists but stat() failed: %s" %
 100                (lockfile, e.strerror))
 101
 102     # we didn't create the lockfile and it's still there, check
 103     # its age
 104     now = int(time.time())
 105     if now - s[stat.ST_MTIME] > max_wait:
 106       pid = f.readline().rstrip()
 107       sys.exit("%s has been locked for more than " \
 108                "%d seconds (PID %s)" % (lockfile, max_wait,
 109                                         pid))
 110
 111     # it's not been locked too long, wait a while and retry
 112     f.close()
 113     time.sleep(1)
 114
 115   # if we get here. we have the lockfile. Convert the os.open file
 116   # descriptor into a Python file object and record our PID in it
 117
 118   f = os.fdopen(fd, "w")
 119   f.write("%d\n" % os.getpid())
 120   f.close()
 121   return LockFile(lockfile)
 122
 123 class pushback_iter(object):
 124   '''Utility iterator that can deal with pushed back elements.
 125
 126   This behaves like a regular iterable, just that you can call
 127     iter.pushback(item)
 128   to get the givem item as next item in the iteration.
 129   '''
 130   def __init__(self, iterable):
 131     self.it = iter(iterable)
 132     self.pushed_back = []
 133
 134   def __iter__(self):
 135     return self
 136
 137   def __nonzero__(self):
 138     if self.pushed_back:
 139       return True
 140
 141     try:
 142       self.pushed_back.insert(0, self.it.next())
 143     except StopIteration:
 144       return False
 145     else:
 146       return True
 147
 148   def next(self):
 149     if self.pushed_back:
 150       return self.pushed_back.pop()
 151     return self.it.next()
 152
 153   def pushback(self, item):
 154     self.pushed_back.append(item)