cpython/Lib/statcache.py

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# Module 'statcache'
#
# Maintain a cache of file stats.
# There are functions to reset the cache or to selectively remove items.
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import os
from stat import *
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# The cache.
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# Keys are pathnames, values are `os.stat' outcomes.
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#
cache = {}
# Stat a file, possibly out of the cache.
#
def stat(path):
if cache.has_key(path):
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return cache[path]
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cache[path] = ret = os.stat(path)
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return ret
# Reset the cache completely.
# Hack: to reset a global variable, we import this module.
#
def reset():
import statcache
# Check that we really imported the same module
if cache is not statcache.cache:
raise 'sorry, statcache identity crisis'
statcache.cache = {}
# Remove a given item from the cache, if it exists.
#
def forget(path):
if cache.has_key(path):
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del cache[path]
# Remove all pathnames with a given prefix.
#
def forget_prefix(prefix):
n = len(prefix)
for path in cache.keys():
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if path[:n] == prefix:
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del cache[path]
# Forget about a directory and all entries in it, but not about
# entries in subdirectories.
#
def forget_dir(prefix):
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if prefix[-1:] == '/' and prefix <> '/':
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prefix = prefix[:-1]
forget(prefix)
if prefix[-1:] <> '/':
prefix = prefix + '/'
n = len(prefix)
for path in cache.keys():
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if path[:n] == prefix:
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rest = path[n:]
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if rest[-1:] == '/': rest = rest[:-1]
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if '/' not in rest:
del cache[path]
# Remove all pathnames except with a given prefix.
# Normally used with prefix = '/' after a chdir().
#
def forget_except_prefix(prefix):
n = len(prefix)
for path in cache.keys():
if path[:n] <> prefix:
del cache[path]
# Check for directory.
#
def isdir(path):
try:
st = stat(path)
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except os.error:
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return 0
return S_ISDIR(st[ST_MODE])