Mac/Lib/maccache.py

   1 # Module 'maccache'
   2 #
   3 # Maintain a cache of listdir(), isdir(), isfile() or exists() outcomes.
   4 # XXX Should merge with module statcache
   5
   6 import os
   7
   8
   9 # The cache.
  10 # Keys are absolute pathnames;
  11 # values are 0 (nothing), 1 (file) or [...] (dir).
  12 #
  13 cache = {}
  14
  15
  16 # Current working directory.
  17 #
  18 cwd = os.getcwd()
  19
  20
  21 # Constants.
  22 #
  23 NONE = 0
  24 FILE = 1
  25 LISTTYPE = type([])
  26
  27 def _stat(name):
  28         name = os.path.join(cwd, name)
  29         if cache.has_key(name):
  30                 return cache[name]
  31         if os.path.isfile(name):
  32                 cache[name] = FILE
  33                 return FILE
  34         try:
  35                 list = os.listdir(name)
  36         except:
  37                 cache[name] = NONE
  38                 return NONE
  39         cache[name] = list
  40         if name[-1:] == ':': cache[name[:-1]] = list
  41         else: cache[name+':'] = list
  42         return list
  43
  44 def isdir(name):
  45         st = _stat(name)
  46         return type(st) == LISTTYPE
  47
  48 def isfile(name):
  49         st = _stat(name)
  50         return st == FILE
  51
  52 def exists(name):
  53         st = _stat(name)
  54         return st <> NONE
  55
  56 def listdir(name):
  57         st = _stat(name)
  58         if type(st) == LISTTYPE:
  59                 return st
  60         else:
  61                 raise RuntimeError, 'list non-directory'