Lib/statcache.py

   1 # Module 'statcache'
   2 #
   3 # Maintain a cache of file stats.
   4 # There are functions to reset the cache or to selectively remove items.
   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 # Stat a file, possibly out of the cache.
  16 #
  17 def stat(path):
  18         if cache.has_key(path):
  19                 return cache[path]
  20         cache[path] = ret = os.stat(path)
  21         return ret
  22
  23
  24 # Reset the cache completely.
  25 #
  26 def reset():
  27         global cache
  28         cache = {}
  29
  30
  31 # Remove a given item from the cache, if it exists.
  32 #
  33 def forget(path):
  34         if cache.has_key(path):
  35                 del cache[path]
  36
  37
  38 # Remove all pathnames with a given prefix.
  39 #
  40 def forget_prefix(prefix):
  41         n = len(prefix)
  42         for path in cache.keys():
  43                 if path[:n] == prefix:
  44                         del cache[path]
  45
  46
  47 # Forget about a directory and all entries in it, but not about
  48 # entries in subdirectories.
  49 #
  50 def forget_dir(prefix):
  51         if prefix[-1:] == '/' and prefix <> '/':
  52                 prefix = prefix[:-1]
  53         forget(prefix)
  54         if prefix[-1:] <> '/':
  55                 prefix = prefix + '/'
  56         n = len(prefix)
  57         for path in cache.keys():
  58                 if path[:n] == prefix:
  59                         rest = path[n:]
  60                         if rest[-1:] == '/': rest = rest[:-1]
  61                         if '/' not in rest:
  62                                 del cache[path]
  63
  64
  65 # Remove all pathnames except with a given prefix.
  66 # Normally used with prefix = '/' after a chdir().
  67 #
  68 def forget_except_prefix(prefix):
  69         n = len(prefix)
  70         for path in cache.keys():
  71                 if path[:n] <> prefix:
  72                         del cache[path]
  73
  74
  75 # Check for directory.
  76 #
  77 def isdir(path):
  78         try:
  79                 st = stat(path)
  80         except os.error:
  81                 return 0
  82         return S_ISDIR(st[ST_MODE])