python/invirt/common.py

   1 from __future__ import with_statement
   2
   3 import unittest
   4 from fcntl import flock, LOCK_EX, LOCK_SH, LOCK_UN
   5 import contextlib as clib
   6
   7 class struct(object):
   8     'A simple namespace object.'
   9     def __init__(self, d = {}, **kwargs):
  10         'd is the dictionary to update my __dict__ with.'
  11         self.__dict__.update(d)
  12         self.__dict__.update(kwargs)
  13
  14 def dicts2struct(x):
  15     """
  16     Given a tree of lists/dicts, perform a deep traversal to transform all the
  17     dicts to structs.
  18     """
  19     if type(x) == dict:
  20         return struct((k, dicts2struct(v)) for k,v in x.iteritems())
  21     elif type(x) == list:
  22         return [dicts2struct(v) for v in x]
  23     else:
  24         return x
  25
  26 @clib.contextmanager
  27 def lock_file(path, exclusive = True):
  28     with clib.closing(file(path, 'w')) as f:
  29         if exclusive:
  30             locktype = LOCK_EX
  31         else:
  32             locktype = LOCK_SH
  33         flock(f, locktype)
  34         try:
  35             yield
  36         finally:
  37             flock(f, LOCK_UN)
  38
  39 #
  40 # Exceptions.
  41 #
  42
  43 class InvalidInput(Exception):
  44     """Exception for user-provided input is invalid but maybe in good faith.
  45
  46     This would include setting memory to negative (which might be a
  47     typo) but not setting an invalid boot CD (which requires bypassing
  48     the select box).
  49     """
  50     def __init__(self, err_field, err_value, expl=None):
  51         MyException.__init__(self, expl)
  52         self.err_field = err_field
  53         self.err_value = err_value
  54
  55 class CodeError(Exception):
  56     """Exception for internal errors or bad faith input."""
  57     pass
  58
  59 #
  60 # Tests.
  61 #
  62
  63 class common_tests(unittest.TestCase):
  64     def test_dicts2structs(self):
  65         dicts = {
  66                 'atom': 0,
  67                 'dict': { 'atom': 'atom', 'list': [1,2,3] },
  68                 'list': [ 'atom', {'key': 'value'} ]
  69                 }
  70         structs = dicts2struct(dicts)
  71         self.assertEqual(structs.atom,        dicts['atom'])
  72         self.assertEqual(structs.dict.atom,   dicts['dict']['atom'])
  73         self.assertEqual(structs.dict.list,   dicts['dict']['list'])
  74         self.assertEqual(structs.list[0],     dicts['list'][0])
  75         self.assertEqual(structs.list[1].key, dicts['list'][1]['key'])
  76
  77 if __name__ == '__main__':
  78     unittest.main()