231 lines
6.8 KiB
Python
231 lines
6.8 KiB
Python
# -*- Mode: Python; test-case-name: whipper.test.test_common_cache -*-
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# vi:si:et:sw=4:sts=4:ts=4
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# Copyright (C) 2009 Thomas Vander Stichele
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# This file is part of whipper.
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#
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# whipper 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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# the Free Software Foundation, either version 3 of the License, or
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# (at your option) any later version.
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#
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# whipper is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with whipper. If not, see <http://www.gnu.org/licenses/>.
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import os
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import os.path
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import glob
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import tempfile
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import shutil
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from whipper.result import result
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from whipper.common import directory
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import logging
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logger = logging.getLogger(__name__)
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class Persister:
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"""
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I wrap an optional pickle to persist an object to disk.
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Instantiate me with a path to automatically unpickle the object.
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Call persist to store the object to disk; it will get stored if it
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changed from the on-disk object.
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@ivar object: the persistent object
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"""
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def __init__(self, path=None, default=None):
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"""
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If path is not given, the object will not be persisted.
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This allows code to transparently deal with both persisted and
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non-persisted objects, since the persist method will just end up
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doing nothing.
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"""
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self._path = path
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self.object = None
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self._unpickle(default)
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def persist(self, obj=None):
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"""
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Persist the given object, if we have a persistence path and the
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object changed.
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If object is not given, re-persist our object, always.
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If object is given, only persist if it was changed.
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"""
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# don't pickle if it's already ok
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if obj and obj == self.object:
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return
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# store the object on ourselves if not None
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if obj is not None:
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self.object = obj
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# don't pickle if there is no path
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if not self._path:
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return
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# default to pickling our object again
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if obj is None:
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obj = self.object
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# pickle
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self.object = obj
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(fd, path) = tempfile.mkstemp(suffix='.whipper.pickle')
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handle = os.fdopen(fd, 'wb')
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import pickle
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pickle.dump(obj, handle, 2)
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handle.close()
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# do an atomic move
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shutil.move(path, self._path)
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logger.debug('saved persisted object to %r' % self._path)
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def _unpickle(self, default=None):
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self.object = default
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if not self._path:
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return None
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if not os.path.exists(self._path):
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return None
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handle = open(self._path)
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import pickle
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try:
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self.object = pickle.load(handle)
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logger.debug('loaded persisted object from %r' % self._path)
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except Exception as e:
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# TODO: restrict kind of caught exceptions?
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# can fail for various reasons; in that case, pretend we didn't
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# load it
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logger.debug(e)
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pass
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def delete(self):
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self.object = None
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os.unlink(self._path)
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class PersistedCache:
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"""
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I wrap a directory of persisted objects.
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"""
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path = None
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def __init__(self, path):
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self.path = path
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try:
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os.makedirs(self.path)
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except OSError, e:
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if e.errno != 17: # FIXME
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raise
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def _getPath(self, key):
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return os.path.join(self.path, '%s.pickle' % key)
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def get(self, key):
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"""
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Returns the persister for the given key.
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"""
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persister = Persister(self._getPath(key))
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if persister.object:
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if hasattr(persister.object, 'instanceVersion'):
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o = persister.object
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if o.instanceVersion < o.__class__.classVersion:
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logger.debug(
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'key %r persisted object version %d is outdated',
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key, o.instanceVersion)
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persister.object = None
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# FIXME: don't delete old objects atm
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# persister.delete()
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return persister
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class ResultCache:
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def __init__(self, path=None):
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self._path = path or directory.cache_path('result')
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self._pcache = PersistedCache(self._path)
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def getRipResult(self, cddbdiscid, create=True):
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"""
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Retrieve the persistable RipResult either from our cache (from a
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previous, possibly aborted rip), or return a new one.
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@rtype: L{Persistable} for L{result.RipResult}
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"""
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presult = self._pcache.get(cddbdiscid)
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if not presult.object:
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logger.debug('result for cddbdiscid %r not in cache', cddbdiscid)
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if not create:
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logger.debug('returning None')
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return None
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logger.debug('creating result')
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presult.object = result.RipResult()
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presult.persist(presult.object)
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else:
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logger.debug('result for cddbdiscid %r found in cache, reusing',
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cddbdiscid)
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return presult
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def getIds(self):
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paths = glob.glob(os.path.join(self._path, '*.pickle'))
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return [os.path.splitext(os.path.basename(path))[0] for path in paths]
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class TableCache:
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"""
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I read and write entries to and from the cache of tables.
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If no path is specified, the cache will write to the current cache
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directory and read from all possible cache directories (to allow for
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pre-0.2.1 cddbdiscid-keyed entries).
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"""
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def __init__(self, path=None):
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if not path:
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self._path = directory.cache_path('table')
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else:
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self._path = path
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self._pcache = PersistedCache(self._path)
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def get(self, cddbdiscid, mbdiscid):
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# Before 0.2.1, we only saved by cddbdiscid, and had collisions
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# mbdiscid collisions are a lot less likely
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ptable = self._pcache.get('mbdiscid.' + mbdiscid)
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if not ptable.object:
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ptable = self._pcache.get(cddbdiscid)
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if ptable.object:
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if ptable.object.getMusicBrainzDiscId() != mbdiscid:
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logger.debug('cached table is for different mb id %r' % (
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ptable.object.getMusicBrainzDiscId()))
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ptable.object = None
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else:
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logger.debug('no valid cached table found for %r' %
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cddbdiscid)
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if not ptable.object:
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# get an empty persistable from the writable location
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ptable = self._pcache.get('mbdiscid.' + mbdiscid)
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return ptable
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