91 lines
1.7 KiB
Python
91 lines
1.7 KiB
Python
# Module 'statcache'
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#
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# Maintain a cache of file stats.
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# There are functions to reset the cache or to selectively remove items.
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import posix
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# The cache.
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# Keys are pathnames, values are `posix.stat' outcomes.
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#
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cache = {}
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# Stat a file, possibly out of the cache.
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#
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def stat(path):
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try:
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return cache[path]
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except RuntimeError:
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pass
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cache[path] = ret = posix.stat(path)
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return ret
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# Reset the cache completely.
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# Hack: to reset a global variable, we import this module.
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#
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def reset():
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import statcache
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# Check that we really imported the same module
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if cache is not statcache.cache:
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raise 'sorry, statcache identity crisis'
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statcache.cache = {}
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# Remove a given item from the cache, if it exists.
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#
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def forget(path):
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try:
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del cache[path]
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except RuntimeError:
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pass
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# Remove all pathnames with a given prefix.
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#
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def forget_prefix(prefix):
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n = len(prefix)
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for path in cache.keys():
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if path[:n] = prefix:
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del cache[path]
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# Forget about a directory and all entries in it, but not about
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# entries in subdirectories.
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#
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def forget_dir(prefix):
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if prefix[-1:] = '/' and prefix <> '/':
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prefix = prefix[:-1]
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forget(prefix)
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if prefix[-1:] <> '/':
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prefix = prefix + '/'
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n = len(prefix)
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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:
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del cache[path]
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# Remove all pathnames except with a given prefix.
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# Normally used with prefix = '/' after a chdir().
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#
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def forget_except_prefix(prefix):
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n = len(prefix)
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for path in cache.keys():
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if path[:n] <> prefix:
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del cache[path]
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# Check for directory.
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#
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def isdir(path):
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try:
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# mode is st[0]; type is mode/4096; S_IFDIR is 4
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return stat(path)[0] / 4096 = 4
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except RuntimeError:
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return 0
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