128 lines
3.7 KiB
Python
128 lines
3.7 KiB
Python
#
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# Gramps - a GTK+/GNOME based genealogy program
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#
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# Copyright (C) 2000-2007 Donald N. Allingham
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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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# the Free Software Foundation; either version 2 of the License, or
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# (at your option) any later version.
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#
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# This program 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 this program; if not, write to the Free Software
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# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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#
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# gen/db/cursor.py
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# $Id$
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#
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#-------------------------------------------------------------------------
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#
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# Standard python modules
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#
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#-------------------------------------------------------------------------
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from cPickle import dumps, loads
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from gen.config import config
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if config.get('preferences.use-bsddb3'):
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from bsddb3 import db
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else:
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from bsddb import db
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#-------------------------------------------------------------------------
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#
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# BsddbBaseCursor class
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#
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#-------------------------------------------------------------------------
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class BsddbBaseCursor(object):
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"""
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Provide a basic iterator that allows the user to cycle through
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the elements in a particular map.
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A cursor should never be directly instantiated. Instead, in should be
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created by the database class.
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A cursor should only be used for a single pass through the
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database. If multiple passes are needed, multiple cursors
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should be used.
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"""
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def __init__(self, txn=None, update=False, commit=False):
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"""
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Instantiate the object. Note, this method should be overridden in
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derived classes that properly set self.cursor and self.source
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"""
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self.cursor = self.source = None
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self.txn = txn
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self._update = update
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self.commit = commit
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def __getattr__(self, name):
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"""
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Return a method from the underlying cursor object, if it exists
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"""
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return getattr(self.cursor, name)
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def __enter__(self):
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"""
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Context manager enter method
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"""
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return self
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def __exit__(self, exc_type, exc_val, exc_tb):
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"""
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Context manager exit method
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"""
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self.close()
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if self.txn and self.commit:
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self.txn.commit()
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return exc_type is None
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def __iter__(self):
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"""
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Iterator
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"""
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data = self.first()
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_n = self.next # Saved attribute lookup in the loop
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while data:
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yield data
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data = _n()
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def _get(_flags=0):
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""" Closure that returns a cursor get function """
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def get(self, flags=0, **kwargs):
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"""
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Issue DBCursor get call (with DB_RMW flag if update requested)
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Return results to caller
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"""
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data = self.cursor.get(
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_flags | flags | (db.DB_RMW if self._update else 0),
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**kwargs)
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return (data[0], loads(data[1])) if data else None
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return get
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# Use closure to define access methods
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current = _get(db.DB_CURRENT)
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first = _get(db.DB_FIRST)
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next = _get(db.DB_NEXT)
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last = _get(db.DB_LAST)
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prev = _get(db.DB_PREV)
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def update(self, key, data, flags=0, **kwargs):
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"""
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Write the current key, data pair to the database.
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"""
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self.cursor.put(key, dumps(data), flags=flags | db.DB_CURRENT,
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**kwargs)
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