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
  13 def newer (source, target):
  14     """Return true if 'source' exists and is more recently modified than
  15     'target', or if 'source' exists and 'target' doesn't.  Return false if
  16     both exist and 'target' is the same age or younger than 'source'.
  17     Raise DistutilsFileError if 'source' does not exist.
  18     """
  19     if not os.path.exists(source):
  20         raise DistutilsFileError, ("file '%s' does not exist" %
  21                                    os.path.abspath(source))
  22     if not os.path.exists(target):
  23         return 1
  24
  25     from stat import ST_MTIME
  26     mtime1 = os.stat(source)[ST_MTIME]
  27     mtime2 = os.stat(target)[ST_MTIME]
  28
  29     return mtime1 > mtime2
  30
  31 # newer ()
  32
  33
  34 def newer_pairwise (sources, targets):
  35     """Walk two filename lists in parallel, testing if each source is newer
  36     than its corresponding target.  Return a pair of lists (sources,
  37     targets) where source is newer than target, according to the semantics
  38     of 'newer()'.
  39     """
  40     if len(sources) != len(targets):
  41         raise ValueError, "'sources' and 'targets' must be same length"
  42
  43     # build a pair of lists (sources, targets) where  source is newer
  44     n_sources = []
  45     n_targets = []
  46     for i in range(len(sources)):
  47         if newer(sources[i], targets[i]):
  48             n_sources.append(sources[i])
  49             n_targets.append(targets[i])
  50
  51     return (n_sources, n_targets)
  52
  53 # newer_pairwise ()
  54
  55
  56 def newer_group (sources, target, missing='error'):
  57     """Return true if 'target' is out-of-date with respect to any file
  58     listed in 'sources'.  In other words, if 'target' exists and is newer
  59     than every file in 'sources', return false; otherwise return true.
  60     'missing' controls what we do when a source file is missing; the
  61     default ("error") is to blow up with an OSError from inside 'stat()';
  62     if it is "ignore", we silently drop any missing source files; if it is
  63     "newer", any missing source files make us assume that 'target' is
  64     out-of-date (this is handy in "dry-run" mode: it'll make you pretend to
  65     carry out commands that wouldn't work because inputs are missing, but
  66     that doesn't matter because you're not actually going to run the
  67     commands).
  68     """
  69     # If the target doesn't even exist, then it's definitely out-of-date.
  70     if not os.path.exists(target):
  71         return 1
  72
  73     # Otherwise we have to find out the hard way: if *any* source file
  74     # is more recent than 'target', then 'target' is out-of-date and
  75     # we can immediately return true.  If we fall through to the end
  76     # of the loop, then 'target' is up-to-date and we return false.
  77     from stat import ST_MTIME
  78     target_mtime = os.stat(target)[ST_MTIME]
  79     for source in sources:
  80         if not os.path.exists(source):
  81             if missing == 'error':      # blow up when we stat() the file
  82                 pass
  83             elif missing == 'ignore':   # missing source dropped from
  84                 continue                #  target's dependency list
  85             elif missing == 'newer':    # missing source means target is
  86                 return 1                #  out-of-date
  87
  88         source_mtime = os.stat(source)[ST_MTIME]
  89         if source_mtime > target_mtime:
  90             return 1
  91     else:
  92         return 0
  93
  94 # newer_group ()