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cpython/Lib/bsddb/__init__.py

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#----------------------------------------------------------------------
# Copyright (c) 1999-2001, Digital Creations, Fredericksburg, VA, USA
# and Andrew Kuchling. All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are
# met:
#
# o Redistributions of source code must retain the above copyright
# notice, this list of conditions, and the disclaimer that follows.
#
# o Redistributions in binary form must reproduce the above copyright
# notice, this list of conditions, and the following disclaimer in
# the documentation and/or other materials provided with the
# distribution.
#
# o Neither the name of Digital Creations nor the names of its
# contributors may be used to endorse or promote products derived
# from this software without specific prior written permission.
#
# THIS SOFTWARE IS PROVIDED BY DIGITAL CREATIONS AND CONTRIBUTORS *AS
# IS* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
# TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
# PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL DIGITAL
# CREATIONS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
# INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
# BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
# OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
# ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR
# TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
# USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
# DAMAGE.
#----------------------------------------------------------------------
"""Support for BerkeleyDB 3.3 through 4.4 with a simple interface.
For the full featured object oriented interface use the bsddb.db module
instead. It mirrors the Sleepycat BerkeleyDB C API.
"""
try:
if __name__ == 'bsddb3':
# import _pybsddb binary as it should be the more recent version from
# a standalone pybsddb addon package than the version included with
# python as bsddb._bsddb.
import _pybsddb
_bsddb = _pybsddb
from bsddb3.dbutils import DeadlockWrap as _DeadlockWrap
else:
import _bsddb
from bsddb.dbutils import DeadlockWrap as _DeadlockWrap
except ImportError:
# Remove ourselves from sys.modules
import sys
del sys.modules[__name__]
raise
# bsddb3 calls it db, but provide _db for backwards compatibility
db = _db = _bsddb
__version__ = db.__version__
error = db.DBError # So bsddb.error will mean something...
#----------------------------------------------------------------------
import sys, os
# for backwards compatibility with python versions older than 2.3, the
# iterator interface is dynamically defined and added using a mixin
# class. old python can't tokenize it due to the yield keyword.
if sys.version >= '2.3':
import UserDict
from weakref import ref
exec """
class _iter_mixin(UserDict.DictMixin):
def _make_iter_cursor(self):
cur = _DeadlockWrap(self.db.cursor)
key = id(cur)
self._cursor_refs[key] = ref(cur, self._gen_cref_cleaner(key))
return cur
def _gen_cref_cleaner(self, key):
# use generate the function for the weakref callback here
# to ensure that we do not hold a strict reference to cur
# in the callback.
return lambda ref: self._cursor_refs.pop(key, None)
def __iter__(self):
try:
cur = self._make_iter_cursor()
# FIXME-20031102-greg: race condition. cursor could
# be closed by another thread before this call.
# since we're only returning keys, we call the cursor
# methods with flags=0, dlen=0, dofs=0
key = _DeadlockWrap(cur.first, 0,0,0)[0]
yield key
next = cur.next
while 1:
try:
key = _DeadlockWrap(next, 0,0,0)[0]
yield key
except _bsddb.DBCursorClosedError:
cur = self._make_iter_cursor()
# FIXME-20031101-greg: race condition. cursor could
# be closed by another thread before this call.
_DeadlockWrap(cur.set, key,0,0,0)
next = cur.next
except _bsddb.DBNotFoundError:
return
except _bsddb.DBCursorClosedError:
# the database was modified during iteration. abort.
return
def iteritems(self):
if not self.db:
return
try:
cur = self._make_iter_cursor()
# FIXME-20031102-greg: race condition. cursor could
# be closed by another thread before this call.
kv = _DeadlockWrap(cur.first)
key = kv[0]
yield kv
next = cur.next
while 1:
try:
kv = _DeadlockWrap(next)
key = kv[0]
yield kv
except _bsddb.DBCursorClosedError:
cur = self._make_iter_cursor()
# FIXME-20031101-greg: race condition. cursor could
# be closed by another thread before this call.
_DeadlockWrap(cur.set, key,0,0,0)
next = cur.next
except _bsddb.DBNotFoundError:
return
except _bsddb.DBCursorClosedError:
# the database was modified during iteration. abort.
return
"""
else:
class _iter_mixin: pass
class _DBWithCursor(_iter_mixin):
"""
A simple wrapper around DB that makes it look like the bsddbobject in
the old module. It uses a cursor as needed to provide DB traversal.
"""
def __init__(self, db):
self.db = db
self.db.set_get_returns_none(0)
# FIXME-20031101-greg: I believe there is still the potential
# for deadlocks in a multithreaded environment if someone
# attempts to use the any of the cursor interfaces in one
# thread while doing a put or delete in another thread. The
# reason is that _checkCursor and _closeCursors are not atomic
# operations. Doing our own locking around self.dbc,
# self.saved_dbc_key and self._cursor_refs could prevent this.
# TODO: A test case demonstrating the problem needs to be written.
# self.dbc is a DBCursor object used to implement the
# first/next/previous/last/set_location methods.
self.dbc = None
self.saved_dbc_key = None
# a collection of all DBCursor objects currently allocated
# by the _iter_mixin interface.
self._cursor_refs = {}
def __del__(self):
self.close()
def _checkCursor(self):
if self.dbc is None:
self.dbc = _DeadlockWrap(self.db.cursor)
if self.saved_dbc_key is not None:
_DeadlockWrap(self.dbc.set, self.saved_dbc_key)
self.saved_dbc_key = None
# This method is needed for all non-cursor DB calls to avoid
# BerkeleyDB deadlocks (due to being opened with DB_INIT_LOCK
# and DB_THREAD to be thread safe) when intermixing database
# operations that use the cursor internally with those that don't.
def _closeCursors(self, save=1):
if self.dbc:
c = self.dbc
self.dbc = None
if save:
try:
self.saved_dbc_key = _DeadlockWrap(c.current, 0,0,0)[0]
except db.DBError:
pass
_DeadlockWrap(c.close)
del c
for cref in self._cursor_refs.values():
c = cref()
if c is not None:
_DeadlockWrap(c.close)
def _checkOpen(self):
if self.db is None:
raise error, "BSDDB object has already been closed"
def isOpen(self):
return self.db is not None
def __len__(self):
self._checkOpen()
return _DeadlockWrap(lambda: len(self.db)) # len(self.db)
def __getitem__(self, key):
self._checkOpen()
return _DeadlockWrap(lambda: self.db[key]) # self.db[key]
def __setitem__(self, key, value):
self._checkOpen()
self._closeCursors()
def wrapF():
self.db[key] = value
_DeadlockWrap(wrapF) # self.db[key] = value
def __delitem__(self, key):
self._checkOpen()
self._closeCursors()
def wrapF():
del self.db[key]
_DeadlockWrap(wrapF) # del self.db[key]
def close(self):
self._closeCursors(save=0)
if self.dbc is not None:
_DeadlockWrap(self.dbc.close)
v = 0
if self.db is not None:
v = _DeadlockWrap(self.db.close)
self.dbc = None
self.db = None
return v
def keys(self):
self._checkOpen()
return _DeadlockWrap(self.db.keys)
def has_key(self, key):
self._checkOpen()
return _DeadlockWrap(self.db.has_key, key)
__contains__ = has_key
def set_location(self, key):
self._checkOpen()
self._checkCursor()
return _DeadlockWrap(self.dbc.set_range, key)
def next(self):
self._checkOpen()
self._checkCursor()
rv = _DeadlockWrap(self.dbc.next)
return rv
def previous(self):
self._checkOpen()
self._checkCursor()
rv = _DeadlockWrap(self.dbc.prev)
return rv
def first(self):
self._checkOpen()
self._checkCursor()
rv = _DeadlockWrap(self.dbc.first)
return rv
def last(self):
self._checkOpen()
self._checkCursor()
rv = _DeadlockWrap(self.dbc.last)
return rv
def sync(self):
self._checkOpen()
return _DeadlockWrap(self.db.sync)
#----------------------------------------------------------------------
# Compatibility object factory functions
def hashopen(file, flag='c', mode=0666, pgsize=None, ffactor=None, nelem=None,
cachesize=None, lorder=None, hflags=0):
flags = _checkflag(flag, file)
e = _openDBEnv(cachesize)
d = db.DB(e)
d.set_flags(hflags)
if pgsize is not None: d.set_pagesize(pgsize)
if lorder is not None: d.set_lorder(lorder)
if ffactor is not None: d.set_h_ffactor(ffactor)
if nelem is not None: d.set_h_nelem(nelem)
d.open(file, db.DB_HASH, flags, mode)
return _DBWithCursor(d)
#----------------------------------------------------------------------
def btopen(file, flag='c', mode=0666,
btflags=0, cachesize=None, maxkeypage=None, minkeypage=None,
pgsize=None, lorder=None):
flags = _checkflag(flag, file)
e = _openDBEnv(cachesize)
d = db.DB(e)
if pgsize is not None: d.set_pagesize(pgsize)
if lorder is not None: d.set_lorder(lorder)
d.set_flags(btflags)
if minkeypage is not None: d.set_bt_minkey(minkeypage)
if maxkeypage is not None: d.set_bt_maxkey(maxkeypage)
d.open(file, db.DB_BTREE, flags, mode)
return _DBWithCursor(d)
#----------------------------------------------------------------------
def rnopen(file, flag='c', mode=0666,
rnflags=0, cachesize=None, pgsize=None, lorder=None,
rlen=None, delim=None, source=None, pad=None):
flags = _checkflag(flag, file)
e = _openDBEnv(cachesize)
d = db.DB(e)
if pgsize is not None: d.set_pagesize(pgsize)
if lorder is not None: d.set_lorder(lorder)
d.set_flags(rnflags)
if delim is not None: d.set_re_delim(delim)
if rlen is not None: d.set_re_len(rlen)
if source is not None: d.set_re_source(source)
if pad is not None: d.set_re_pad(pad)
d.open(file, db.DB_RECNO, flags, mode)
return _DBWithCursor(d)
#----------------------------------------------------------------------
def _openDBEnv(cachesize):
e = db.DBEnv()
if cachesize is not None:
if cachesize >= 20480:
e.set_cachesize(0, cachesize)
else:
raise error, "cachesize must be >= 20480"
e.set_lk_detect(db.DB_LOCK_DEFAULT)
e.open('.', db.DB_PRIVATE | db.DB_CREATE | db.DB_THREAD | db.DB_INIT_LOCK | db.DB_INIT_MPOOL)
return e
def _checkflag(flag, file):
if flag == 'r':
flags = db.DB_RDONLY
elif flag == 'rw':
flags = 0
elif flag == 'w':
flags = db.DB_CREATE
elif flag == 'c':
flags = db.DB_CREATE
elif flag == 'n':
flags = db.DB_CREATE
#flags = db.DB_CREATE | db.DB_TRUNCATE
# we used db.DB_TRUNCATE flag for this before but BerkeleyDB
# 4.2.52 changed to disallowed truncate with txn environments.
if file is not None and os.path.isfile(file):
os.unlink(file)
else:
raise error, "flags should be one of 'r', 'w', 'c' or 'n'"
return flags | db.DB_THREAD
#----------------------------------------------------------------------
# This is a silly little hack that allows apps to continue to use the
# DB_THREAD flag even on systems without threads without freaking out
# BerkeleyDB.
#
# This assumes that if Python was built with thread support then
# BerkeleyDB was too.
try:
import thread
del thread
if db.version() < (3, 3, 0):
db.DB_THREAD = 0
except ImportError:
db.DB_THREAD = 0
#----------------------------------------------------------------------
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