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""" Base module for BerkeleyStorage implementations """

__version__ ='$Revision: 1.5 $'[11:-2]

from ZODB.BaseStorage import BaseStorage
from ZODB import POSException
from bsddb3 import db
import os, tempfile
try:
    DB = db.DB
    DBEnv = db.DBEnv
    DBError = db.DBError
except:
    DB = db.Db
    DBEnv = db.DbEnv
    DBError = db.error
    
class BerkeleyDBError(POSException.POSError):
    """ A BerkeleyDB exception occurred.  This probably indicates that
    there is a low memory condition, a tempfile space shortage, or
    a space shortage in the directory which houses the BerkeleyDB log
    files.  Check available tempfile space, logfile space, and RAM and
    restart the server process.  This error could have additionally
    been caused by too few locks available to BerkeleyDB for the
    transaction size you were attempting to commit."""

class Base(BaseStorage):

    def __init__(self, name='', env=0, prefix="zodb_"):
        if type(env) is type(''):
            env=envFromString(env)
            if not name: name=env
        elif not name: name='bsddb3'

        BaseStorage.__init__(self, name)

        self._env=env
        self._prefix=prefix
        self._setupDbs()
        self._tmp=tempfile.TemporaryFile()
        self._tempdir = tempfile.tempdir
        self._init_oid()

    def _setupDB(self, name, flags=0):
        """Open an individual database and assign to an "_" attribute.
        """
        d=DB(self._env)
        if flags: d.set_flags(flags)
        d.open(self._prefix+name, db.DB_BTREE, db.DB_CREATE)
        setattr(self, '_'+name, d)
        return d

    def _setupDbs(self):
        """Set up the storages databases, typically using '_setupDB'.
        """

    def _init_oid(self):
        c=self._index.cursor()
        v=c.get(db.DB_LAST)
        if v: self._oid=v[0]
        else: self._oid='\0\0\0\0\0\0\0\0'

    _len=-1
    def __len__(self):
        l=self._len
        if l < 0:
            l=self._len=len(self._index)

        return l

    def new_oid(self, last=None):
        # increment the cached length:
        l=self._len
        if l >= 0: self._len=l+1
        return BaseStorage.new_oid(self, last)

    def getSize(self):
        # TBD
        return 0

    def _clear_temp(self):
        self._tmp.seek(0)

    def close(self):
        """Close the storage

        by closing the databases it uses and closing it's environment.
        """
        for name in self._dbnames():
            getattr(self, '_'+name).close()
            delattr(self, '_'+name)
        self._env.close()
        del self._env

    def _dbnames(self):
        """Return a list of the names of the databases used by the storage.
        """
        return ("index",)

def envFromString(name):
    try:
        if not os.path.exists(name): os.mkdir(name)
    except:
        raise "Error creating BerkeleyDB environment dir: %s" % name
    e=DBEnv()
    e.set_lk_max(10000)  # this can be overridden in the DB_CONFIG file
    try:
        e.open(name,
               db.DB_CREATE | db.DB_RECOVER
               | db.DB_INIT_MPOOL | db.DB_INIT_LOCK | db.DB_INIT_TXN
               )
    except DBError, msg:
        raise BerkeleyDBError, "%s (%s)" % (BerkeleyDBError.__doc__, msg)
    return e
