77 lines
2.3 KiB
Python
77 lines
2.3 KiB
Python
# Copyright (C) 2013 Nippon Telegraph and Telephone Corporation.
|
|
# Copyright (C) 2013 YAMAMOTO Takashi <yamamoto at valinux co jp>
|
|
#
|
|
# 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.
|
|
|
|
|
|
from abc import ABCMeta, abstractmethod
|
|
import six
|
|
|
|
|
|
@six.add_metaclass(ABCMeta)
|
|
class StreamParser(object):
|
|
"""Streaming parser base class.
|
|
|
|
An instance of a subclass of this class is used to extract messages
|
|
from a raw byte stream.
|
|
|
|
It's designed to be used for data read from a transport which doesn't
|
|
preserve message boundaries. A typical example of such a transport
|
|
is TCP.
|
|
|
|
"""
|
|
class TooSmallException(Exception):
|
|
pass
|
|
|
|
def __init__(self):
|
|
self._q = bytearray()
|
|
|
|
def parse(self, data):
|
|
"""Tries to extract messages from a raw byte stream.
|
|
|
|
The data argument would be python bytes newly read from the input
|
|
stream.
|
|
|
|
Returns an ordered list of extracted messages.
|
|
It can be an empty list.
|
|
|
|
The rest of data which doesn't produce a complete message is
|
|
kept internally and will be used when more data is come.
|
|
I.e. next time this method is called again.
|
|
"""
|
|
self._q.append(data)
|
|
msgs = []
|
|
while True:
|
|
try:
|
|
msg, self._q = self.try_parse(self._q)
|
|
except self.TooSmallException:
|
|
break
|
|
msgs.append(msg)
|
|
return msgs
|
|
|
|
@abstractmethod
|
|
def try_parse(self, q):
|
|
"""Try to extract a message from the given bytes.
|
|
|
|
This is an override point for subclasses.
|
|
|
|
This method tries to extract a message from bytes given by the
|
|
argument.
|
|
|
|
Raises TooSmallException if the given data is not enough to
|
|
extract a complete message but there's still a chance to extract
|
|
a message if more data is come later.
|
|
"""
|
|
pass
|