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 e.errno == errno.EACCES:
  95         # we didn't create the lockfile, so it did exist, but it's
  96         # gone now. Just try again
  97         continue
  98       sys.exit("%s exists but stat() failed: %s" %
  99                (lockfile, e.strerror))
 100
 101     # we didn't create the lockfile and it's still there, check
 102     # its age
 103     now = int(time.time())
 104     if now - s[stat.ST_MTIME] > max_wait:
 105       pid = f.readline().rstrip()
 106       sys.exit("%s has been locked for more than " \
 107                "%d seconds (PID %s)" % (lockfile, max_wait,
 108                                         pid))
 109
 110     # it's not been locked too long, wait a while and retry
 111     f.close()
 112     time.sleep(1)
 113
 114   # if we get here. we have the lockfile. Convert the os.open file
 115   # descriptor into a Python file object and record our PID in it
 116
 117   f = os.fdopen(fd, "w")
 118   f.write("%d\n" % os.getpid())
 119   f.close()
 120   return LockFile(lockfile)
 121
 122 class pushback_iter(object):
 123   '''Utility iterator that can deal with pushed back elements.
 124
 125   This behaves like a regular iterable, just that you can call
 126     iter.pushback(item)
 127   to get the givem item as next item in the iteration.
 128   '''
 129   def __init__(self, iterable):
 130     self.it = iter(iterable)
 131     self.pushed_back = []
 132
 133   def __iter__(self):
 134     return self
 135
 136   def __nonzero__(self):
 137     if self.pushed_back:
 138       return True
 139
 140     try:
 141       self.pushed_back.insert(0, self.it.next())
 142     except StopIteration:
 143       return False
 144     else:
 145       return True
 146
 147   def next(self):
 148     if self.pushed_back:
 149       return self.pushed_back.pop()
 150     return self.it.next()
 151
 152   def pushback(self, item):
 153     self.pushed_back.append(item)