Skip to content

Instantly share code, notes, and snippets.

@rmmh
Created August 11, 2021 05:24
Show Gist options
  • Save rmmh/8ec90b5dd00d06212d3954f15e239ab9 to your computer and use it in GitHub Desktop.
Save rmmh/8ec90b5dd00d06212d3954f15e239ab9 to your computer and use it in GitHub Desktop.
#!/usr/bin/env python
# Copyright 2016 The Kubernetes Authors.
#
# 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.
"""
A tiny, minimal protobuf2 parser that's able to extract enough information
to be useful.
"""
import io
def parse_protobuf(data, schema=None, ingroup=False):
"""
Do a simple parse of a protobuf2 given minimal type information.
Args:
data: a string containing the encoded protocol buffer.
schema: a dict containing information about each field number.
The keys are field numbers, and the values represent:
- str: the name of the field
- dict: schema to recursively decode an embedded message.
May contain a 'name' key to name the field.
Returns:
dict: mapping from fields to values. The fields may be strings instead of
numbers if schema named them, and the value will *always* be
a list of values observed for that key.
"""
if schema is None:
schema = {}
buf = io.BytesIO(data)
def read_varint():
out = 0
shift = 0
c = 0x80
while c & 0x80:
c = ord(buf.read(1))
out = out | ((c & 0x7f) << shift)
shift += 7
return out
values = {}
while buf.tell() < len(data):
key = read_varint()
wire_type = key & 0b111
field_number = key >> 3
field_name = field_number
if wire_type == 0:
value = read_varint()
elif wire_type == 1: # 64-bit
value = buf.read(8)
elif wire_type == 2: # length-delim
length = read_varint()
value = buf.read(length)
if isinstance(schema.get(field_number), str):
field_name = schema[field_number]
value = value.decode('utf8')
elif field_number in schema:
# yes, I'm using dynamic features of a dynamic language.
# pylint: disable=redefined-variable-type
value = parse_protobuf(value, schema[field_number])
field_name = schema[field_number].get('name', field_name)
elif wire_type == 3: # start group
# https://stackoverflow.com/a/33821387/3694
value, length = parse_protobuf(data[buf.tell():], schema.get(field_number, {}), True)
buf.read(length)
field_name = schema.get(field_number, {}).get('name', field_name)
elif wire_type == 4: # end group
if not ingroup:
raise ValueError('unexpected end group tag')
return values, buf.tell()
elif wire_type == 5: # 32-bit
value = buf.read(4)
else:
raise ValueError('unhandled wire type %d' % wire_type)
values.setdefault(field_name, []).append(value)
return values
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment