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  • Committer: John Arbash Meinel
  • Date: 2009-07-08 14:28:04 UTC
  • mto: This revision was merged to the branch mainline in revision 4521.
  • Revision ID: john@arbash-meinel.com-20090708142804-i9rkpi9dmnu7v3x1
https://launchpad.net/bugs/396838
Fix bug #396838, Update LRUCache to maintain invariant even
if a cleanup function raises an exception.

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bzrlib/lru_cache.py
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# Copyright (C) 2006, 2008 Canonical Ltd
 
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# Copyright (C) 2006, 2008, 2009 Canonical Ltd
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#
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# This program is free software; you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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                                     self.next_key, prev_key)
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    def run_cleanup(self):
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        if self.cleanup is not None:
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            self.cleanup(self.key, self.value)
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        self.cleanup = None
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        # Just make sure to break any refcycles, etc
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        self.value = None
 
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        try:
 
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            if self.cleanup is not None:
 
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                self.cleanup(self.key, self.value)
 
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        finally:
 
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            self.cleanup = None
 
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            # Just make sure to break any refcycles, etc
 
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            self.value = None
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class LRUCache(object):
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            raise ValueError('cannot use _null_key as a key')
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        if key in self._cache:
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            node = self._cache[key]
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            node.run_cleanup()
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            node.value = value
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            node.cleanup = cleanup
 
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            try:
 
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                node.run_cleanup()
 
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            finally:
 
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                node.value = value
 
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                node.cleanup = cleanup
 
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                self._record_access(node)
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        else:
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            node = _LRUNode(key, value, cleanup=cleanup)
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            self._cache[key] = node
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        self._record_access(node)
 
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            self._record_access(node)
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        if len(self._cache) > self._max_cache:
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            # Trigger the cleanup
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        # If we have removed all entries, remove the head pointer as well
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        if self._least_recently_used is None:
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            self._most_recently_used = None
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        node.run_cleanup()
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        # Now remove this node from the linked list
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        if node.prev is not None:
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            node.prev.next_key = node.next_key
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        if node.next_key is not _null_key:
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            node_next = self._cache[node.next_key]
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            node_next.prev = node.prev
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        # And remove this node's pointers
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        node.prev = None
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        node.next_key = _null_key
 
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        try:
 
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            node.run_cleanup()
 
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        finally:
 
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            # Now remove this node from the linked list
 
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            if node.prev is not None:
 
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                node.prev.next_key = node.next_key
 
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            if node.next_key is not _null_key:
 
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                node_next = self._cache[node.next_key]
 
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                node_next.prev = node.prev
 
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            # And remove this node's pointers
 
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            node.prev = None
 
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            node.next_key = _null_key
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    def _remove_lru(self):
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        """Remove one entry from the lru, and handle consequences.