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  import os
       8  from distutils.errors import DistutilsFileError
       9  
      10  
      11  def newer (source, target):
      12      """Return true if 'source' exists and is more recently modified than
      13      'target', or if 'source' exists and 'target' doesn't.  Return false if
      14      both exist and 'target' is the same age or younger than 'source'.
      15      Raise DistutilsFileError if 'source' does not exist.
      16      """
      17      if not os.path.exists(source):
      18          raise DistutilsFileError("file '%s' does not exist" %
      19                                   os.path.abspath(source))
      20      if not os.path.exists(target):
      21          return 1
      22  
      23      from stat import ST_MTIME
      24      mtime1 = os.stat(source)[ST_MTIME]
      25      mtime2 = os.stat(target)[ST_MTIME]
      26  
      27      return mtime1 > mtime2
      28  
      29  # newer ()
      30  
      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 i in range(len(sources)):
      45          if newer(sources[i], targets[i]):
      46              n_sources.append(sources[i])
      47              n_targets.append(targets[i])
      48  
      49      return (n_sources, n_targets)
      50  
      51  # newer_pairwise ()
      52  
      53  
      54  def newer_group (sources, target, missing='error'):
      55      """Return true if 'target' is out-of-date with respect to any file
      56      listed in 'sources'.  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 1
      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      from stat import ST_MTIME
      76      target_mtime = os.stat(target)[ST_MTIME]
      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 1                #  out-of-date
      85  
      86          source_mtime = os.stat(source)[ST_MTIME]
      87          if source_mtime > target_mtime:
      88              return 1
      89      else:
      90          return 0
      91  
      92  # newer_group ()