AppPkg/Applications/Python/Python-2.7.2/Lib/distutils/dep_util.py

   1 """distutils.dep_util
   2
   3 Utility functions for simple, timestamp-based dependency of files
   4 and groups of files; also, function based entirely on such
   5 timestamp dependency analysis."""
   6
   7 __revision__ = "$Id$"
   8
   9 import os
  10 from distutils.errors import DistutilsFileError
  11
  12 def newer(source, target):
  13     """Tells if the target is newer than the source.
  14
  15     Return true if 'source' exists and is more recently modified than
  16     'target', or if 'source' exists and 'target' doesn't.
  17
  18     Return false if both exist and 'target' is the same age or younger
  19     than 'source'. Raise DistutilsFileError if 'source' does not exist.
  20
  21     Note that this test is not very accurate: files created in the same second
  22     will have the same "age".
  23     """
  24     if not os.path.exists(source):
  25         raise DistutilsFileError("file '%s' does not exist" %
  26                                  os.path.abspath(source))
  27     if not os.path.exists(target):
  28         return True
  29
  30     return os.stat(source).st_mtime > os.stat(target).st_mtime
  31
  32 def newer_pairwise(sources, targets):
  33     """Walk two filename lists in parallel, testing if each source is newer
  34     than its corresponding target.  Return a pair of lists (sources,
  35     targets) where source is newer than target, according to the semantics
  36     of 'newer()'.
  37     """
  38     if len(sources) != len(targets):
  39         raise ValueError, "'sources' and 'targets' must be same length"
  40
  41     # build a pair of lists (sources, targets) where  source is newer
  42     n_sources = []
  43     n_targets = []
  44     for source, target in zip(sources, targets):
  45         if newer(source, target):
  46             n_sources.append(source)
  47             n_targets.append(target)
  48
  49     return n_sources, n_targets
  50
  51 def newer_group(sources, target, missing='error'):
  52     """Return true if 'target' is out-of-date with respect to any file
  53     listed in 'sources'.
  54
  55     In other words, if 'target' exists and is newer
  56     than every file in 'sources', return false; otherwise return true.
  57     'missing' controls what we do when a source file is missing; the
  58     default ("error") is to blow up with an OSError from inside 'stat()';
  59     if it is "ignore", we silently drop any missing source files; if it is
  60     "newer", any missing source files make us assume that 'target' is
  61     out-of-date (this is handy in "dry-run" mode: it'll make you pretend to
  62     carry out commands that wouldn't work because inputs are missing, but
  63     that doesn't matter because you're not actually going to run the
  64     commands).
  65     """
  66     # If the target doesn't even exist, then it's definitely out-of-date.
  67     if not os.path.exists(target):
  68         return True
  69
  70     # Otherwise we have to find out the hard way: if *any* source file
  71     # is more recent than 'target', then 'target' is out-of-date and
  72     # we can immediately return true.  If we fall through to the end
  73     # of the loop, then 'target' is up-to-date and we return false.
  74     target_mtime = os.stat(target).st_mtime
  75
  76     for source in sources:
  77         if not os.path.exists(source):
  78             if missing == 'error':      # blow up when we stat() the file
  79                 pass
  80             elif missing == 'ignore':   # missing source dropped from
  81                 continue                #  target's dependency list
  82             elif missing == 'newer':    # missing source means target is
  83                 return True             #  out-of-date
  84
  85         if os.stat(source).st_mtime > target_mtime:
  86             return True
  87
  88     return False