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 # This module should be kept compatible with Python 2.1.
   8
   9 __revision__ = "$Id$"
  10
  11 import os
  12 from distutils.errors import DistutilsFileError
  13
  14
  15 def newer (source, target):
  16     """Return true if 'source' exists and is more recently modified than
  17     'target', or if 'source' exists and 'target' doesn't.  Return false if
  18     both exist and 'target' is the same age or younger than 'source'.
  19     Raise DistutilsFileError if 'source' does not exist.
  20     """
  21     if not os.path.exists(source):
  22         raise DistutilsFileError, ("file '%s' does not exist" %
  23                                    os.path.abspath(source))
  24     if not os.path.exists(target):
  25         return 1
  26
  27     from stat import ST_MTIME
  28     mtime1 = os.stat(source)[ST_MTIME]
  29     mtime2 = os.stat(target)[ST_MTIME]
  30
  31     return mtime1 > mtime2
  32
  33 # newer ()
  34
  35
  36 def newer_pairwise (sources, targets):
  37     """Walk two filename lists in parallel, testing if each source is newer
  38     than its corresponding target.  Return a pair of lists (sources,
  39     targets) where source is newer than target, according to the semantics
  40     of 'newer()'.
  41     """
  42     if len(sources) != len(targets):
  43         raise ValueError, "'sources' and 'targets' must be same length"
  44
  45     # build a pair of lists (sources, targets) where  source is newer
  46     n_sources = []
  47     n_targets = []
  48     for i in range(len(sources)):
  49         if newer(sources[i], targets[i]):
  50             n_sources.append(sources[i])
  51             n_targets.append(targets[i])
  52
  53     return (n_sources, n_targets)
  54
  55 # newer_pairwise ()
  56
  57
  58 def newer_group (sources, target, missing='error'):
  59     """Return true if 'target' is out-of-date with respect to any file
  60     listed in 'sources'.  In other words, if 'target' exists and is newer
  61     than every file in 'sources', return false; otherwise return true.
  62     'missing' controls what we do when a source file is missing; the
  63     default ("error") is to blow up with an OSError from inside 'stat()';
  64     if it is "ignore", we silently drop any missing source files; if it is
  65     "newer", any missing source files make us assume that 'target' is
  66     out-of-date (this is handy in "dry-run" mode: it'll make you pretend to
  67     carry out commands that wouldn't work because inputs are missing, but
  68     that doesn't matter because you're not actually going to run the
  69     commands).
  70     """
  71     # If the target doesn't even exist, then it's definitely out-of-date.
  72     if not os.path.exists(target):
  73         return 1
  74
  75     # Otherwise we have to find out the hard way: if *any* source file
  76     # is more recent than 'target', then 'target' is out-of-date and
  77     # we can immediately return true.  If we fall through to the end
  78     # of the loop, then 'target' is up-to-date and we return false.
  79     from stat import ST_MTIME
  80     target_mtime = os.stat(target)[ST_MTIME]
  81     for source in sources:
  82         if not os.path.exists(source):
  83             if missing == 'error':      # blow up when we stat() the file
  84                 pass
  85             elif missing == 'ignore':   # missing source dropped from
  86                 continue                #  target's dependency list
  87             elif missing == 'newer':    # missing source means target is
  88                 return 1                #  out-of-date
  89
  90         source_mtime = os.stat(source)[ST_MTIME]
  91         if source_mtime > target_mtime:
  92             return 1
  93     else:
  94         return 0
  95
  96 # newer_group ()