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  53     """Return true if 'target' is out-of-date with respect to any file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  62     out-of-date (this is handy in "dry-run" mode: it'll make you pretend to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