Mercurial > cpython-lru_cache-weakref

annotate Lib/statcache.py @ 19283:b865cd5c1925 legacy-trunk

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Added comments before recently added/assigned slots in the type object, so the backward compatibility issues will be easier to understand. I only added comments indicating additions and assignments back to Python 2.0.
author Fred Drake <fdrake@acm.org>
date Wed, 15 Aug 2001 18:32:33 +0000
parents f68dbffff927
children e2f2187c3d2c
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
rev   line source
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1 """Maintain a cache of stat() information on files.
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2
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3 There are functions to reset the cache or to selectively remove items.
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4 """
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6 import os as _os
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7 from stat import *
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8
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9 __all__ = ["stat","reset","forget","forget_prefix","forget_dir",
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10 "forget_except_prefix","isdir"]
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11
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12 # The cache. Keys are pathnames, values are os.stat outcomes.
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13 # Remember that multiple threads may be calling this! So, e.g., that
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14 # cache.has_key(path) returns 1 doesn't mean the cache will still contain
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15 # path on the next line. Code defensively.
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16
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17 cache = {}
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18
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19 def stat(path):
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20 """Stat a file, possibly out of the cache."""
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21 ret = cache.get(path, None)
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22 if ret is None:
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23 cache[path] = ret = _os.stat(path)
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24 return ret
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26 def reset():
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27 """Clear the cache."""
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28 cache.clear()
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29
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30 # For thread saftey, always use forget() internally too.
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31 def forget(path):
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32 """Remove a given item from the cache, if it exists."""
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33 try:
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34 del cache[path]
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35 except KeyError:
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36 pass
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37
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38 def forget_prefix(prefix):
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39 """Remove all pathnames with a given prefix."""
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40 for path in cache.keys():
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41 if path.startswith(prefix):
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42 forget(path)
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43
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44 def forget_dir(prefix):
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45 """Forget a directory and all entries except for entries in subdirs."""
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46
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47 # Remove trailing separator, if any. This is tricky to do in a
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48 # x-platform way. For example, Windows accepts both / and \ as
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49 # separators, and if there's nothing *but* a separator we want to
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50 # preserve that this is the root. Only os.path has the platform
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51 # knowledge we need.
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52 from os.path import split, join
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53 prefix = split(join(prefix, "xxx"))[0]
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54 forget(prefix)
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55 for path in cache.keys():
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56 # First check that the path at least starts with the prefix, so
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57 # that when it doesn't we can avoid paying for split().
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58 if path.startswith(prefix) and split(path)[0] == prefix:
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59 forget(path)
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61 def forget_except_prefix(prefix):
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62 """Remove all pathnames except with a given prefix.
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63
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64 Normally used with prefix = '/' after a chdir().
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65 """
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66
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67 for path in cache.keys():
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68 if not path.startswith(prefix):
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69 forget(path)
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71 def isdir(path):
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72 """Return 1 if directory, else 0."""
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73 try:
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74 st = stat(path)
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75 except _os.error:
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76 return 0
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77 return S_ISDIR(st[ST_MODE])