Lib/statcache.py

   1 """Maintain a cache of stat() information on files.
   2
   3 There are functions to reset the cache or to selectively remove items.
   4 """
   5
   6 import os
   7 from stat import *
   8
   9 # The cache.
  10 # Keys are pathnames, values are `os.stat' outcomes.
  11 #
  12 cache = {}
  13
  14
  15 def stat(path):
  16         """Stat a file, possibly out of the cache."""
  17         if cache.has_key(path):
  18                 return cache[path]
  19         cache[path] = ret = os.stat(path)
  20         return ret
  21
  22
  23 def reset():
  24         """Reset the cache completely."""
  25         global cache
  26         cache = {}
  27
  28
  29 def forget(path):
  30         """Remove a given item from the cache, if it exists."""
  31         if cache.has_key(path):
  32                 del cache[path]
  33
  34
  35 def forget_prefix(prefix):
  36         """Remove all pathnames with a given prefix."""
  37         n = len(prefix)
  38         for path in cache.keys():
  39                 if path[:n] == prefix:
  40                         del cache[path]
  41
  42
  43 def forget_dir(prefix):
  44         """Forget about a directory and all entries in it, but not about
  45         entries in subdirectories."""
  46         if prefix[-1:] == '/' and prefix <> '/':
  47                 prefix = prefix[:-1]
  48         forget(prefix)
  49         if prefix[-1:] <> '/':
  50                 prefix = prefix + '/'
  51         n = len(prefix)
  52         for path in cache.keys():
  53                 if path[:n] == prefix:
  54                         rest = path[n:]
  55                         if rest[-1:] == '/': rest = rest[:-1]
  56                         if '/' not in rest:
  57                                 del cache[path]
  58
  59
  60 def forget_except_prefix(prefix):
  61         """Remove all pathnames except with a given prefix.
  62         Normally used with prefix = '/' after a chdir()."""
  63         n = len(prefix)
  64         for path in cache.keys():
  65                 if path[:n] <> prefix:
  66                         del cache[path]
  67
  68
  69 def isdir(path):
  70         """Check for directory."""
  71         try:
  72                 st = stat(path)
  73         except os.error:
  74                 return 0
  75         return S_ISDIR(st[ST_MODE])