Synnefo » Pithos

# Copyright 2011 GRNET S.A. All rights reserved.

# 

# Redistribution and use in source and binary forms, with or

# without modification, are permitted provided that the following

# conditions are met:

# 

#   1. Redistributions of source code must retain the above

#      copyright notice, this list of conditions and the following

#      disclaimer.

# 

#   2. 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.

# 

# THIS SOFTWARE IS PROVIDED BY GRNET S.A. ``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 GRNET S.A 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.

# 

# The views and conclusions contained in the software and

# documentation are those of the authors and should not be

# interpreted as representing official policies, either expressed

# or implied, of GRNET S.A.

import sys

import os

import time

import sqlite3

import logging

import hashlib

import binascii

from base import NotAllowedError, BaseBackend

from lib.hashfiler import Mapper, Blocker

( CLUSTER_NORMAL, CLUSTER_HISTORY, CLUSTER_DELETED ) = range(3)

inf = float('inf')

logger = logging.getLogger(__name__)

def backend_method(func=None, autocommit=1):

    if func is None:

        def fn(func):

            return backend_method(func, autocommit)

        return fn

    if not autocommit:

        return func

    def fn(self, *args, **kw):

        self.wrapper.execute()

        try:

            ret = func(self, *args, **kw)

            self.wrapper.commit()

            return ret

        except:

            self.wrapper.rollback()

            raise

    return fn

class ModularBackend(BaseBackend):

    """A modular backend.

    Uses modules for SQL functions and hashfiler for storage.

    """

    def __init__(self, mod, path, db):

        self.hash_algorithm = 'sha256'

        self.block_size = 4 * 1024 * 1024 # 4MB

        self.default_policy = {'quota': 0, 'versioning': 'auto'}

        if path and not os.path.exists(path):

            os.makedirs(path)

        if not os.path.isdir(path):

            raise RuntimeError("Cannot open path '%s'" % (path,))

        __import__(mod)

        self.mod = sys.modules[mod]

        self.wrapper = self.mod.dbwrapper.DBWrapper(db)

        params = {'blocksize': self.block_size,

                  'blockpath': os.path.join(path + '/blocks'),

                  'hashtype': self.hash_algorithm}

        self.blocker = Blocker(**params)

        params = {'mappath': os.path.join(path + '/maps'),

                  'namelen': self.blocker.hashlen}

        self.mapper = Mapper(**params)

        params = {'wrapper': self.wrapper}

        self.permissions = self.mod.permissions.Permissions(**params)

        for x in ['READ', 'WRITE']:

            setattr(self, x, getattr(self.mod.permissions, x))

        self.policy = self.mod.policy.Policy(**params)

        self.node = self.mod.node.Node(**params)

        for x in ['ROOTNODE', 'SERIAL', 'SIZE', 'MTIME', 'MUSER', 'CLUSTER']:

            setattr(self, x, getattr(self.mod.node, x))

    @backend_method

    def list_accounts(self, user, marker=None, limit=10000):

        """Return a list of accounts the user can access."""

        logger.debug("list_accounts: %s %s %s", user, marker, limit)

        allowed = self._allowed_accounts(user)

        start, limit = self._list_limits(allowed, marker, limit)

        return allowed[start:start + limit]

    @backend_method

    def get_account_meta(self, user, account, until=None):

        """Return a dictionary with the account metadata."""

        logger.debug("get_account_meta: %s %s", account, until)

        path, node = self._lookup_account(account, user == account)

        if user != account:

            if until or node is None or account not in self._allowed_accounts(user):

                raise NotAllowedError

        try:

            props = self._get_properties(node, until)

            mtime = props[self.MTIME]

        except NameError:

            props = None

            mtime = until

        count, bytes, tstamp = self._get_statistics(node, until)

        tstamp = max(tstamp, mtime)

        if until is None:

            modified = tstamp

        else:

            modified = self._get_statistics(node)[2] # Overall last modification.

            modified = max(modified, mtime)

        if user != account:

            meta = {'name': account}

        else:

            meta = {}

            if props is not None:

                meta.update(dict(self.node.attribute_get(props[self.SERIAL])))

            if until is not None:

                meta.update({'until_timestamp': tstamp})

            meta.update({'name': account, 'count': count, 'bytes': bytes})

        meta.update({'modified': modified})

        return meta

    @backend_method

    def update_account_meta(self, user, account, meta, replace=False):

        """Update the metadata associated with the account."""

        logger.debug("update_account_meta: %s %s %s", account, meta, replace)

        if user != account:

            raise NotAllowedError

        path, node = self._lookup_account(account, True)

        self._put_metadata(user, node, meta, replace, False)

    @backend_method

    def get_account_groups(self, user, account):

        """Return a dictionary with the user groups defined for this account."""

        logger.debug("get_account_groups: %s", account)

        if user != account:

            if account not in self._allowed_accounts(user):

                raise NotAllowedError

            return {}

        self._lookup_account(account, True)

        return self.permissions.group_dict(account)

    @backend_method

    def update_account_groups(self, user, account, groups, replace=False):

        """Update the groups associated with the account."""

        logger.debug("update_account_groups: %s %s %s", account, groups, replace)

        if user != account:

            raise NotAllowedError

        self._lookup_account(account, True)

        self._check_groups(groups)

        if replace:

            self.permissions.group_destroy(account)

        for k, v in groups.iteritems():

            if not replace: # If not already deleted.

                self.permissions.group_delete(account, k)

            if v:

                self.permissions.group_addmany(account, k, v)

    @backend_method

    def put_account(self, user, account):

        """Create a new account with the given name."""

        logger.debug("put_account: %s", account)

        if user != account:

            raise NotAllowedError

        node = self.node.node_lookup(account)

        if node is not None:

            raise NameError('Account already exists')

        self._put_path(user, self.ROOTNODE, account)

    @backend_method

    def delete_account(self, user, account):

        """Delete the account with the given name."""

        logger.debug("delete_account: %s", account)

        if user != account:

            raise NotAllowedError

        node = self.node.node_lookup(account)

        if node is None:

            return

        if not self.node.node_remove(node):

            raise IndexError('Account is not empty')

        self.permissions.group_destroy(account)

    @backend_method

    def list_containers(self, user, account, marker=None, limit=10000, shared=False, until=None):

        """Return a list of containers existing under an account."""

        logger.debug("list_containers: %s %s %s %s %s", account, marker, limit, shared, until)

        if user != account:

            if until or account not in self._allowed_accounts(user):

                raise NotAllowedError

            allowed = self._allowed_containers(user, account)

            start, limit = self._list_limits(allowed, marker, limit)

            return allowed[start:start + limit]

        if shared:

            allowed = [x.split('/', 2)[1] for x in self.permissions.access_list_shared(account)]

            allowed = list(set(allowed))

            start, limit = self._list_limits(allowed, marker, limit)

            return allowed[start:start + limit]

        node = self.node.node_lookup(account)

        return [x[0] for x in self._list_objects(node, account, '', '/', marker, limit, False, [], until)]

    @backend_method

    def get_container_meta(self, user, account, container, until=None):

        """Return a dictionary with the container metadata."""

        logger.debug("get_container_meta: %s %s %s", account, container, until)

        if user != account:

            if until or container not in self._allowed_containers(user, account):

                raise NotAllowedError

        path, node = self._lookup_container(account, container)

        props = self._get_properties(node, until)

        mtime = props[self.MTIME]

        count, bytes, tstamp = self._get_statistics(node, until)

        tstamp = max(tstamp, mtime)

        if until is None:

            modified = tstamp

        else:

            modified = self._get_statistics(node)[2] # Overall last modification.

            modified = max(modified, mtime)

        if user != account:

            meta = {'name': container}

        else:

            meta = dict(self.node.attribute_get(props[self.SERIAL]))

            if until is not None:

                meta.update({'until_timestamp': tstamp})

            meta.update({'name': container, 'count': count, 'bytes': bytes})

        meta.update({'modified': modified})

        return meta

    @backend_method

    def update_container_meta(self, user, account, container, meta, replace=False):

        """Update the metadata associated with the container."""

        logger.debug("update_container_meta: %s %s %s %s", account, container, meta, replace)

        if user != account:

            raise NotAllowedError

        path, node = self._lookup_container(account, container)

        self._put_metadata(user, node, meta, replace, False)

    @backend_method

    def get_container_policy(self, user, account, container):

        """Return a dictionary with the container policy."""

        logger.debug("get_container_policy: %s %s", account, container)

        if user != account:

            if container not in self._allowed_containers(user, account):

                raise NotAllowedError

            return {}

        path = self._lookup_container(account, container)[0]

        return self.policy.policy_get(path)

    @backend_method

    def update_container_policy(self, user, account, container, policy, replace=False):

        """Update the policy associated with the account."""

        logger.debug("update_container_policy: %s %s %s %s", account, container, policy, replace)

        if user != account:

            raise NotAllowedError

        path = self._lookup_container(account, container)[0]

        self._check_policy(policy)

        if replace:

            for k, v in self.default_policy.iteritems():

                if k not in policy:

                    policy[k] = v

        self.policy.policy_set(path, policy)

    @backend_method

    def put_container(self, user, account, container, policy=None):

        """Create a new container with the given name."""

        logger.debug("put_container: %s %s %s", account, container, policy)

        if user != account:

            raise NotAllowedError

        try:

            path, node = self._lookup_container(account, container)

        except NameError:

            pass

        else:

            raise NameError('Container already exists')

        if policy:

            self._check_policy(policy)

        path = '/'.join((account, container))

        self._put_path(user, self._lookup_account(account, True)[1], path)

        for k, v in self.default_policy.iteritems():

            if k not in policy:

                policy[k] = v

        self.policy.policy_set(path, policy)

    @backend_method

    def delete_container(self, user, account, container, until=None):

        """Delete/purge the container with the given name."""

        logger.debug("delete_container: %s %s %s", account, container, until)

        if user != account:

            raise NotAllowedError

        path, node = self._lookup_container(account, container)

        if until is not None:

            versions = self.node.node_purge_children(node, until, CLUSTER_HISTORY)

            for v in versions:

                self.mapper.map_remv(v)

            self.node.node_purge_children(node, until, CLUSTER_DELETED)

            return

        if self._get_statistics(node)[0] > 0:

            raise IndexError('Container is not empty')

        versions = self.node.node_purge_children(node, inf, CLUSTER_HISTORY)

        for v in versions:

            self.mapper.map_remv(v)

        self.node.node_purge_children(node, inf, CLUSTER_DELETED)

        self.node.node_remove(node)

        self.policy.policy_unset(path)

    @backend_method

    def list_objects(self, user, account, container, prefix='', delimiter=None, marker=None, limit=10000, virtual=True, keys=[], shared=False, until=None):

        """Return a list of objects existing under a container."""

        logger.debug("list_objects: %s %s %s %s %s %s %s %s %s %s", account, container, prefix, delimiter, marker, limit, virtual, keys, shared, until)

        allowed = []

        if user != account:

            if until:

                raise NotAllowedError

            allowed = self.permissions.access_list_paths(user, '/'.join((account, container)))

            if not allowed:

                raise NotAllowedError

        else:

            if shared:

                allowed = self.permissions.access_list_shared('/'.join((account, container)))

                if not allowed:

                    return []

        path, node = self._lookup_container(account, container)

        return self._list_objects(node, path, prefix, delimiter, marker, limit, virtual, keys, until, allowed)

    @backend_method

    def list_object_meta(self, user, account, container, until=None):

        """Return a list with all the container's object meta keys."""

        logger.debug("list_object_meta: %s %s %s", account, container, until)

        allowed = []

        if user != account:

            if until:

                raise NotAllowedError

            allowed = self.permissions.access_list_paths(user, '/'.join((account, container)))

            if not allowed:

                raise NotAllowedError

        path, node = self._lookup_container(account, container)

        before = until if until is not None else inf

        return self.node.latest_attribute_keys(node, before, CLUSTER_DELETED, allowed)

    @backend_method

    def get_object_meta(self, user, account, container, name, version=None):

        """Return a dictionary with the object metadata."""

        logger.debug("get_object_meta: %s %s %s %s", account, container, name, version)

        self._can_read(user, account, container, name)

        path, node = self._lookup_object(account, container, name)

        props = self._get_version(node, version)

        if version is None:

            modified = props[self.MTIME]

        else:

            try:

                modified = self._get_version(node)[self.MTIME] # Overall last modification.

            except NameError: # Object may be deleted.

                del_props = self.node.version_lookup(node, inf, CLUSTER_DELETED)

                if del_props is None:

                    raise NameError('Object does not exist')

                modified = del_props[self.MTIME]

        meta = dict(self.node.attribute_get(props[self.SERIAL]))

        meta.update({'name': name, 'bytes': props[self.SIZE]})

        meta.update({'version': props[self.SERIAL], 'version_timestamp': props[self.MTIME]})

        meta.update({'modified': modified, 'modified_by': props[self.MUSER]})

        return meta

    @backend_method

    def update_object_meta(self, user, account, container, name, meta, replace=False):

        """Update the metadata associated with the object."""

        logger.debug("update_object_meta: %s %s %s %s %s", account, container, name, meta, replace)

        self._can_write(user, account, container, name)

        path, node = self._lookup_object(account, container, name)

        return self._put_metadata(user, node, meta, replace)

    @backend_method

    def get_object_permissions(self, user, account, container, name):

        """Return the action allowed on the object, the path

        from which the object gets its permissions from,

        along with a dictionary containing the permissions."""

        logger.debug("get_object_permissions: %s %s %s", account, container, name)

        allowed = 'write'

        if user != account:

            path = '/'.join((account, container, name))

            if self.permissions.access_check(path, self.WRITE, user):

                allowed = 'write'

            elif self.permissions.access_check(path, self.READ, user):

                allowed = 'read'

            else:

                raise NotAllowedError

        path = self._lookup_object(account, container, name)[0]

        return (allowed,) + self.permissions.access_inherit(path)

    @backend_method

    def update_object_permissions(self, user, account, container, name, permissions):

        """Update the permissions associated with the object."""

        logger.debug("update_object_permissions: %s %s %s %s", account, container, name, permissions)

        if user != account:

            raise NotAllowedError

        path = self._lookup_object(account, container, name)[0]

        self._check_permissions(path, permissions)

        self.permissions.access_set(path, permissions)

    @backend_method

    def get_object_public(self, user, account, container, name):

        """Return the public URL of the object if applicable."""

        logger.debug("get_object_public: %s %s %s", account, container, name)

        self._can_read(user, account, container, name)

        path = self._lookup_object(account, container, name)[0]

        if self.permissions.public_check(path):

            return '/public/' + path

        return None

    @backend_method

    def update_object_public(self, user, account, container, name, public):

        """Update the public status of the object."""

        logger.debug("update_object_public: %s %s %s %s", account, container, name, public)

        self._can_write(user, account, container, name)

        path = self._lookup_object(account, container, name)[0]

        if not public:

            self.permissions.public_unset(path)

        else:

            self.permissions.public_set(path)

    @backend_method

    def get_object_hashmap(self, user, account, container, name, version=None):

        """Return the object's size and a list with partial hashes."""

        logger.debug("get_object_hashmap: %s %s %s %s", account, container, name, version)

        self._can_read(user, account, container, name)

        path, node = self._lookup_object(account, container, name)

        props = self._get_version(node, version)

        hashmap = self.mapper.map_retr(props[self.SERIAL])

        return props[self.SIZE], [binascii.hexlify(x) for x in hashmap]

    @backend_method

    def update_object_hashmap(self, user, account, container, name, size, hashmap, meta={}, replace_meta=False, permissions=None):

        """Create/update an object with the specified size and partial hashes."""

        logger.debug("update_object_hashmap: %s %s %s %s %s", account, container, name, size, hashmap)

        if permissions is not None and user != account:

            raise NotAllowedError

        self._can_write(user, account, container, name)

        missing = self.blocker.block_ping([binascii.unhexlify(x) for x in hashmap])

        if missing:

            ie = IndexError()

            ie.data = [binascii.hexlify(x) for x in missing]

            raise ie

        if permissions is not None:

            path = '/'.join((account, container, name))

            self._check_permissions(path, permissions)

        path, node = self._put_object_node(account, container, name)

        src_version_id, dest_version_id = self._copy_version(user, node, None, node, size)

        self.mapper.map_stor(dest_version_id, [binascii.unhexlify(x) for x in hashmap])

        if not replace_meta and src_version_id is not None:

            self.node.attribute_copy(src_version_id, dest_version_id)

        self.node.attribute_set(dest_version_id, ((k, v) for k, v in meta.iteritems()))

        if permissions is not None:

            self.permissions.access_set(path, permissions)

        return dest_version_id

    def _copy_object(self, user, src_account, src_container, src_name, dest_account, dest_container, dest_name, dest_meta={}, replace_meta=False, permissions=None, src_version=None):

        if permissions is not None and user != dest_account:

            raise NotAllowedError

        self._can_read(user, src_account, src_container, src_name)

        self._can_write(user, dest_account, dest_container, dest_name)

        src_path, src_node = self._lookup_object(src_account, src_container, src_name)

        self._get_version(src_node, src_version)

        if permissions is not None:

            dest_path = '/'.join((dest_account, dest_container, dest_name))

            self._check_permissions(dest_path, permissions)

        dest_path, dest_node = self._put_object_node(dest_account, dest_container, dest_name)

        src_version_id, dest_version_id = self._copy_version(user, src_node, src_version, dest_node)

        if src_version_id is not None:

            self._copy_data(src_version_id, dest_version_id)

        if not replace_meta and src_version_id is not None:

            self.node.attribute_copy(src_version_id, dest_version_id)

        self.node.attribute_set(dest_version_id, ((k, v) for k, v in dest_meta.iteritems()))

        if permissions is not None:

            self.permissions.access_set(dest_path, permissions)

        return dest_version_id

    @backend_method

    def copy_object(self, user, src_account, src_container, src_name, dest_account, dest_container, dest_name, dest_meta={}, replace_meta=False, permissions=None, src_version=None):

        """Copy an object's data and metadata."""

        logger.debug("copy_object: %s %s %s %s %s %s %s %s %s %s", src_account, src_container, src_name, dest_account, dest_container, dest_name, dest_meta, replace_meta, permissions, src_version)

        return self._copy_object(user, src_account, src_container, src_name, dest_account, dest_container, dest_name, dest_meta, replace_meta, permissions, src_version)

    @backend_method

    def move_object(self, user, src_account, src_container, src_name, dest_account, dest_container, dest_name, dest_meta={}, replace_meta=False, permissions=None):

        """Move an object's data and metadata."""

        logger.debug("move_object: %s %s %s %s %s %s %s %s %s", src_account, src_container, src_name, dest_account, dest_container, dest_name, dest_meta, replace_meta, permissions)

        if user != src_account:

            raise NotAllowedError

        dest_version_id = self._copy_object(user, src_account, src_container, src_name, dest_account, dest_container, dest_name, dest_meta, replace_meta, permissions, None)

        self._delete_object(user, src_account, src_container, src_name)

        return dest_version_id

    def _delete_object(self, user, account, container, name, until=None):

        if user != account:

            raise NotAllowedError

        if until is not None:

            path = '/'.join((account, container, name))

            node = self.node.node_lookup(path)

            if node is None:

                return

            versions = self.node.node_purge(node, until, CLUSTER_NORMAL)

            versions += self.node.node_purge(node, until, CLUSTER_HISTORY)

            for v in versions:

                self.mapper.map_remv(v)

            self.node.node_purge_children(node, until, CLUSTER_DELETED)

            try:

                props = self._get_version(node)

            except NameError:

                pass

            else:

                self.permissions.access_clear(path)

            return

        path, node = self._lookup_object(account, container, name)

        self._copy_version(user, node, None, node, 0, CLUSTER_DELETED)

        self.permissions.access_clear(path)

    @backend_method

    def delete_object(self, user, account, container, name, until=None):

        """Delete/purge an object."""

        logger.debug("delete_object: %s %s %s %s", account, container, name, until)

        self._delete_object(user, account, container, name, until)

    @backend_method

    def list_versions(self, user, account, container, name):

        """Return a list of all (version, version_timestamp) tuples for an object."""

        logger.debug("list_versions: %s %s %s", account, container, name)

        self._can_read(user, account, container, name)

        path, node = self._lookup_object(account, container, name)

        versions = self.node.node_get_versions(node)

        return [[x[self.SERIAL], x[self.MTIME]] for x in versions if x[self.CLUSTER] != CLUSTER_DELETED]

    @backend_method(autocommit=0)

    def get_block(self, hash):

        """Return a block's data."""

        logger.debug("get_block: %s", hash)

        blocks = self.blocker.block_retr((binascii.unhexlify(hash),))

        if not blocks:

            raise NameError('Block does not exist')

        return blocks[0]

    @backend_method(autocommit=0)

    def put_block(self, data):

        """Store a block and return the hash."""

        logger.debug("put_block: %s", len(data))

        hashes, absent = self.blocker.block_stor((data,))

        return binascii.hexlify(hashes[0])

    @backend_method(autocommit=0)

    def update_block(self, hash, data, offset=0):

        """Update a known block and return the hash."""

        logger.debug("update_block: %s %s %s", hash, len(data), offset)

        if offset == 0 and len(data) == self.block_size:

            return self.put_block(data)

        h, e = self.blocker.block_delta(binascii.unhexlify(hash), ((offset, data),))

        return binascii.hexlify(h)

    # Path functions.

    def _put_object_node(self, account, container, name):

        path, parent = self._lookup_container(account, container)

        path = '/'.join((path, name))

        node = self.node.node_lookup(path)

        if node is None:

            node = self.node.node_create(parent, path)

        return path, node

    def _put_path(self, user, parent, path):

        node = self.node.node_create(parent, path)

        self.node.version_create(node, 0, None, user, CLUSTER_NORMAL)

        return node

    def _lookup_account(self, account, create=True):

        node = self.node.node_lookup(account)

        if node is None and create:

            node = self._put_path(account, self.ROOTNODE, account) # User is account.

        return account, node

    def _lookup_container(self, account, container):

        path = '/'.join((account, container))

        node = self.node.node_lookup(path)

        if node is None:

            raise NameError('Container does not exist')

        return path, node

    def _lookup_object(self, account, container, name):

        path = '/'.join((account, container, name))

        node = self.node.node_lookup(path)

        if node is None:

            raise NameError('Object does not exist')

        return path, node

    def _get_properties(self, node, until=None):

        """Return properties until the timestamp given."""

        before = until if until is not None else inf

        props = self.node.version_lookup(node, before, CLUSTER_NORMAL)

        if props is None and until is not None:

            props = self.node.version_lookup(node, before, CLUSTER_HISTORY)

        if props is None:

            raise NameError('Path does not exist')

        return props

    def _get_statistics(self, node, until=None):

        """Return count, sum of size and latest timestamp of everything under node."""

        if until is None:

            stats = self.node.statistics_get(node, CLUSTER_NORMAL)

        else:

            stats = self.node.statistics_latest(node, until, CLUSTER_DELETED)

        if stats is None:

            stats = (0, 0, 0)

        return stats

    def _get_version(self, node, version=None):

        if version is None:

            props = self.node.version_lookup(node, inf, CLUSTER_NORMAL)

            if props is None:

                raise NameError('Object does not exist')

        else:

            props = self.node.version_get_properties(version)

            if props is None or props[self.CLUSTER] == CLUSTER_DELETED:

                raise IndexError('Version does not exist')

        return props

    def _copy_version(self, user, src_node, src_version, dest_node, dest_size=None, dest_cluster=CLUSTER_NORMAL):

        # Get source serial and size.

        if src_version is not None:

            src_props = self._get_version(src_node, src_version)

            src_version_id = src_props[self.SERIAL]

            size = src_props[self.SIZE]

        else:

            # Latest or create from scratch.

            try:

                src_props = self._get_version(src_node)

                src_version_id = src_props[self.SERIAL]

                size = src_props[self.SIZE]

            except NameError:

                src_version_id = None

                size = 0

        if dest_size is not None:

            size = dest_size

        # Move the latest version at destination to CLUSTER_HISTORY and create new.

        if src_node == dest_node and src_version is None and src_version_id is not None:

            self.node.version_recluster(src_version_id, CLUSTER_HISTORY)

        else:

            dest_props = self.node.version_lookup(dest_node, inf, CLUSTER_NORMAL)

            if dest_props is not None:

                self.node.version_recluster(dest_props[self.SERIAL], CLUSTER_HISTORY)

        dest_version_id, mtime = self.node.version_create(dest_node, size, src_version_id, user, dest_cluster)

        return src_version_id, dest_version_id

    def _copy_data(self, src_version, dest_version):

        hashmap = self.mapper.map_retr(src_version)

        self.mapper.map_stor(dest_version, hashmap)

    def _get_metadata(self, version):

        if version is None:

            return {}

        return dict(self.node.attribute_get(version))

    def _put_metadata(self, user, node, meta, replace=False, copy_data=True):

        """Create a new version and store metadata."""

        src_version_id, dest_version_id = self._copy_version(user, node, None, node)

        if not replace:

            if src_version_id is not None:

                self.node.attribute_copy(src_version_id, dest_version_id)

            self.node.attribute_del(dest_version_id, (k for k, v in meta.iteritems() if v == ''))

            self.node.attribute_set(dest_version_id, ((k, v) for k, v in meta.iteritems() if v != ''))

        else:

            self.node.attribute_set(dest_version_id, ((k, v) for k, v in meta.iteritems()))

        if copy_data and src_version_id is not None:

            self._copy_data(src_version_id, dest_version_id)

        return dest_version_id

    def _list_limits(self, listing, marker, limit):

        start = 0

        if marker:

            try:

                start = listing.index(marker) + 1

            except ValueError:

                pass

        if not limit or limit > 10000:

            limit = 10000

        return start, limit

    def _list_objects(self, parent, path, prefix='', delimiter=None, marker=None, limit=10000, virtual=True, keys=[], until=None, allowed=[]):

        cont_prefix = path + '/'

        prefix = cont_prefix + prefix

        start = cont_prefix + marker if marker else None

        before = until if until is not None else inf

        filterq = ','.join(keys) if keys else None

        objects, prefixes = self.node.latest_version_list(parent, prefix, delimiter, start, limit, before, CLUSTER_DELETED, allowed, filterq)

        objects.extend([(p, None) for p in prefixes] if virtual else [])

        objects.sort(key=lambda x: x[0])

        objects = [(x[0][len(cont_prefix):], x[1]) for x in objects]

        start, limit = self._list_limits([x[0] for x in objects], marker, limit)

        return objects[start:start + limit]

    # Policy functions.

    def _check_policy(self, policy):

        for k in policy.keys():

            if policy[k] == '':

                policy[k] = self.default_policy.get(k)

        for k, v in policy.iteritems():

            if k == 'quota':

                q = int(v) # May raise ValueError.

                if q < 0:

                    raise ValueError

            elif k == 'versioning':

                if v not in ['auto', 'manual', 'none']:

                    raise ValueError

            else:

                raise ValueError

    # Access control functions.

    def _check_groups(self, groups):

        # raise ValueError('Bad characters in groups')

        pass

    def _check_permissions(self, path, permissions):

        # raise ValueError('Bad characters in permissions')

        # Check for existing permissions.

        paths = self.permissions.access_list(path)

        if paths:

            ae = AttributeError()

            ae.data = paths

            raise ae

    def _can_read(self, user, account, container, name):

        if user == account:

            return True

        path = '/'.join((account, container, name))

        if not self.permissions.access_check(path, self.READ, user) and not self.permissions.access_check(path, self.WRITE, user):

            raise NotAllowedError

    def _can_write(self, user, account, container, name):

        if user == account:

            return True

        path = '/'.join((account, container, name))

        if not self.permissions.access_check(path, self.WRITE, user):

            raise NotAllowedError

    def _allowed_accounts(self, user):

        allow = set()

        for path in self.permissions.access_list_paths(user):

            allow.add(path.split('/', 1)[0])

        return sorted(allow)

    def _allowed_containers(self, user, account):

        allow = set()

        for path in self.permissions.access_list_paths(user, account):

            allow.add(path.split('/', 2)[1])

        return sorted(allow)