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# Module 'statcache'
#
# Maintain a cache of file stats.
# There are functions to reset the cache or to selectively remove items.
import posix
# The cache.
# Keys are pathnames, values are `posix.stat' outcomes.
#
cache = {}
# Stat a file, possibly out of the cache.
#
def stat(path):
try:
return cache[path]
except RuntimeError:
pass
cache[path] = ret = posix.stat(path)
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):
try:
del cache[path]
except RuntimeError:
pass
# Remove all pathnames with a given prefix.
#
def forget_prefix(prefix):
n = len(prefix)
for path in cache.keys():
if path[:n] = prefix:
del cache[path]
# Forget about a directory and all entries in it, but not about
# entries in subdirectories.
#
def forget_dir(prefix):
if prefix[-1:] = '/' and prefix <> '/':
prefix = prefix[:-1]
forget(prefix)
if prefix[-1:] <> '/':
prefix = prefix + '/'
n = len(prefix)
for path in cache.keys():
if path[:n] = prefix:
rest = path[n:]
if rest[-1:] = '/': rest = rest[:-1]
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:
# mode is st[0]; type is mode/4096; S_IFDIR is 4
return stat(path)[0] / 4096 = 4
except RuntimeError:
return 0
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