Synnefo

# 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.

class BaseBackend(object):

    """Abstract backend class that serves as a reference for actual implementations.

    The purpose of the backend is to provide the necessary functions for handling data

    and metadata. It is responsible for the actual storage and retrieval of information.

    Note that the account level is always valid as it is checked from another subsystem.

    The following variables should be available:

        'hash_algorithm': Suggested is 'sha256'

        'block_size': Suggested is 4MB

    """

    def delete_account(self, user, account):

        """Delete the account with the given name.

        Raises:

            IndexError: Account is not empty

        """

        return

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

        """Return a dictionary with the account metadata.

        The keys returned are all user-defined, except:

            'name': The account name

            'count': The number of containers (or 0)

            'bytes': The total data size (or 0)

            'modified': Last modification timestamp (overall)

            'until_timestamp': Last modification until the timestamp provided

        """

        return {}

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

        """Update the metadata associated with the account.

        Parameters:

            'meta': Dictionary with metadata to update

            'replace': Replace instead of update

        """

        return

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

        """Return a list of container (name, version_id) tuples existing under an account.

        Parameters:

            'marker': Start list from the next item after 'marker'

            'limit': Number of containers to return

        """

        return []

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

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

        Raises:

            NameError: Container already exists

        """

        return

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

        """Delete the container with the given name.

        Raises:

            NameError: Container does not exist

            IndexError: Container is not empty

        """

        return

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

        """Return a dictionary with the container metadata.

        The keys returned are all user-defined, except:

            'name': The container name

            'count': The number of objects

            'bytes': The total data size

            'modified': Last modification timestamp (overall)

            'until_timestamp': Last modification until the timestamp provided

        Raises:

            NameError: Container does not exist

        """

        return {}

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

        """Update the metadata associated with the container.

        Parameters:

            'meta': Dictionary with metadata to update

            'replace': Replace instead of update

        Raises:

            NameError: Container does not exist

        """

        return

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

        """Return a list of object (name, version_id) tuples existing under a container.

        Parameters:

            'prefix': List objects starting with 'prefix'

            'delimiter': Return unique names before 'delimiter' and after 'prefix'

            'marker': Start list from the next item after 'marker'

            'limit': Number of objects to return

            'virtual': If not set, the result will only include names starting\

                       with 'prefix' and ending without a 'delimiter' or with\

                       the first occurance of the 'delimiter' after 'prefix'.\

                       If set, the result will include all names after 'prefix',\

                       up to and including the 'delimiter' if it is found

            'keys': Include objects that have meta with the keys in the list

        Raises:

            NameError: Container does not exist

        """

        return []

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

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

        Raises:

            NameError: Container does not exist

        """

        return []

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

        """Return a dictionary with the object metadata.

        The keys returned are all user-defined, except:

            'name': The object name

            'bytes': The total data size

            'modified': Last modification timestamp (overall)

            'version': The version identifier

            'version_timestamp': The version's modification timestamp

        Raises:

            NameError: Container/object does not exist

            IndexError: Version does not exist

        """

        return {}

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

        """Update the metadata associated with the object.

        Parameters:

            'meta': Dictionary with metadata to update.

            'replace': Replace instead of update

        Raises:

            NameError: Container/object does not exist

        """

        return

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

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

        Raises:

            NameError: Container/object does not exist

            IndexError: Version does not exist

        """

        return 0, []

    def update_object_hashmap(self, user, account, container, name, size, hashmap, meta={}, replace_meta=False):

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

        Raises:

            NameError: Container does not exist

        """

        return

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

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

        Parameters:

            'dest_meta': Dictionary with metadata to changes from source to destination

            'replace_meta': Replace metadata instead of update

            'src_version': Copy from the version provided.

        Raises:

            NameError: Container/object does not exist

            IndexError: Version does not exist

        """

        return

    def move_object(self, user, account, src_container, src_name, dest_container, dest_name, dest_meta={}, replace_meta=False):

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

        Parameters:

            'dest_meta': Dictionary with metadata to changes from source to destination

            'replace_meta': Replace metadata instead of update

        Raises:

            NameError: Container/object does not exist

        """

        return

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

        """Delete an object.

        Raises:

            NameError: Container/object does not exist

        """

        return

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

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

        return []

    def get_block(self, hash):

        """Return a block's data.

        Raises:

            NameError: Block does not exist

        """

        return ''

    def put_block(self, data):

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

        return 0

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

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

        Raises:

            IndexError: Offset or data outside block limits

        """

        return 0