+
−"""custom storages for the system source"""
+
−from os import unlink, path as osp
+
−
+
−from cubicweb.server.hook import Operation
+
−
+
−
+
−ETYPE_ATTR_STORAGE = {}
+
−def set_attribute_storage(repo, etype, attr, storage):
+
−    ETYPE_ATTR_STORAGE.setdefault(etype, {})[attr] = storage
+
−    repo.system_source.map_attribute(etype, attr, storage.sqlgen_callback)
+
−
+
−
+
−class Storage(object):
+
−    """abstract storage"""
+
−    def sqlgen_callback(self, generator, relation, linkedvar):
+
−        """sql generator callback when some attribute with a custom storage is
+
−        accessed
+
−        """
+
−        raise NotImplementedError()
+
−
+
−    def entity_added(self, entity, attr):
+
−        """an entity using this storage for attr has been added"""
+
−        raise NotImplementedError()
+
−    def entity_updated(self, entity, attr):
+
−        """an entity using this storage for attr has been updatded"""
+
−        raise NotImplementedError()
+
−    def entity_deleted(self, entity, attr):
+
−        """an entity using this storage for attr has been deleted"""
+
−        raise NotImplementedError()
+
−
+
−# TODO
+
−# * make it configurable without code
+
−# * better file path attribution
+
−# * handle backup/restore
+
−
+
−class BytesFileSystemStorage(Storage):
+
−    """store Bytes attribute value on the file system"""
+
−    def __init__(self, defaultdir):
+
−        self.default_directory = defaultdir
+
−
+
−    def sqlgen_callback(self, generator, linkedvar, relation):
+
−        """sql generator callback when some attribute with a custom storage is
+
−        accessed
+
−        """
+
−        linkedvar.accept(generator)
+
−        return '_fsopen(%s.cw_%s)' % (
+
−            linkedvar._q_sql.split('.', 1)[0], # table name
+
−            relation.r_type) # attribute name
+
−
+
−    def entity_added(self, entity, attr):
+
−        """an entity using this storage for attr has been added"""
+
−        if not entity._cw.transaction_data.get('fs_importing'):
+
−            try:
+
−                value = entity.pop(attr)
+
−            except KeyError:
+
−                pass
+
−            else:
+
−                fpath = self.new_fs_path(entity, attr)
+
−                # bytes storage used to store file's path
+
−                entity[attr]= Binary(fpath)
+
−                file(fpath, 'w').write(value.getvalue())
+
−                AddFileOp(entity._cw, filepath=fpath)
+
−        # else entity[attr] is expected to be an already existant file path
+
−
+
−    def entity_updated(self, entity, attr):
+
−        """an entity using this storage for attr has been updatded"""
+
−        try:
+
−            value = entity.pop(attr)
+
−        except KeyError:
+
−            pass
+
−        else:
+
−            fpath = self.current_fs_path(entity, attr)
+
−            UpdateFileOp(entity._cw, filepath=fpath, filedata=value.getvalue())
+
−
+
−    def entity_deleted(self, entity, attr):
+
−        """an entity using this storage for attr has been deleted"""
+
−        DeleteFileOp(entity._cw, filepath=self.current_fs_path(entity, attr))
+
−
+
−    def new_fs_path(self, entity, attr):
+
−        fpath = osp.join(self.default_directory, '%s_%s_%s' % (
+
−            self.default_directory, entity.eid, attr))
+
−        while osp.exists(fspath):
+
−            fspath = '_' + fspath
+
−        return fspath
+
−
+
−    def current_fs_path(self, entity, attr):
+
−        cu = entity._cw.system_sql('SELECT cw_%s.%s WHERE cw_eid=%s' %
+
−                                   (entity.__regid__, attr, entity.eid))
+
−        return cu.fetchone()[0]
+
−
+
−
+
−class AddFileOp(Operation):
+
−    def rollback_event(self):
+
−        try:
+
−            unlink(self.filepath)
+
−        except:
+
−            pass
+
−
+
−class DeleteFileOp(Operation):
+
−    def commit_event(self):
+
−        try:
+
−            unlink(self.filepath)
+
−        except:
+
−            pass
+
−
+
−class UpdateFileOp(Operation):
+
−    def precommit_event(self):
+
−        try:
+
−            file(self.filepath, 'w').write(self.filedata)
+
−        except:
+
−            pass