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# Copyright (c) 2018-2024 Open Text.
# Copyright (c) 2018 Uber Technologies, Inc.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
# Copyright (c) 2013-2017 Uber Technologies, Inc.
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.
"""
Vertica Frontend/Backend Protocol
All communication between frontend (client) and backend (server) is through a
stream of messages.
Message Format: The first byte of a message identifies the message type, and
the next four bytes specify the length of the rest of the message (this length
count includes itself, but not the message-type byte). The remaining contents
of the message are determined by the message type. An exception is the Startup
message sent by frontend, which has no message-type byte.
All data in Vertica is represented as UTF-8, so the frontend has to convert data
going to the backend from Python text string into UTF-8, and to convert data
coming from the backend from UTF-8 into Python text string.
"""
from __future__ import print_function, division, absolute_import, annotations
from abc import ABCMeta
from struct import pack
from ..messages import *
class Message(object):
__metaclass__ = ABCMeta
def __init__(self):
pass
@property
def message_id(self):
raise NotImplementedError("no default message_id")
def _bytes_to_message(self, msg):
if isinstance(msg, list):
msg = ''.join(msg)
if hasattr(msg, 'bytesize'):
bytesize = msg.bytesize + 4
else:
bytesize = len(msg) + 4
message_size = pack('!I', bytesize)
if self.message_id is not None:
msg_with_size = self.message_id + message_size + msg
else:
msg_with_size = message_size + msg
return msg_with_size
def __str__(self):
return self.__class__.__name__
# noinspection PyAbstractClass
class BackendMessage(Message):
__metaclass__ = ABCMeta
_message_id_map = {}
@classmethod
def from_type(cls, type_, data, **kwargs) -> BackendMessage:
klass = cls._message_id_map.get(type_)
if klass is not None:
return klass(data, **kwargs)
else:
from .backend_messages import Unknown
return Unknown(type_, data)
@staticmethod
def register(cls):
# TODO replace _message_id() with that
assert issubclass(cls, BackendMessage), \
"{0} is not subclass of BackendMessage".format(cls.__name__)
assert cls.message_id not in BackendMessage._message_id_map, \
"can't write the same key twice: {0}".format(cls.message_id)
BackendMessage._message_id_map[cls.message_id] = cls
# noinspection PyAbstractClass
class FrontendMessage(Message):
__metaclass__ = ABCMeta
def fetch_message(self):
"""Generator for getting the message's content"""
raise NotImplementedError("fetch_bytes has no default implementation")
# noinspection PyAbstractClass
class BulkFrontendMessage(FrontendMessage):
__metaclass__ = ABCMeta
def read_bytes(self):
return b''
def get_message(self):
bytes_ = self.read_bytes()
return self._bytes_to_message(bytes_)
def fetch_message(self):
yield self.get_message()
# noinspection PyAbstractClass
class StreamFrontendMessage(FrontendMessage):
__metaclass__ = ABCMeta
def stream_bytes(self):
raise NotImplementedError("stream_bytes has no default implementation")
def stream_message(self):
for bytes_ in self.stream_bytes():
yield self._bytes_to_message(bytes_)
def fetch_message(self):
for message in self.stream_message():
yield message
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