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# Protocol Buffers - Google's data interchange format
# Copyright 2008 Google Inc. All rights reserved.
#
# Use of this source code is governed by a BSD-style
# license that can be found in the LICENSE file or at
# https://developers.google.com/open-source/licenses/bsd
"""Determine which implementation of the protobuf API is used in this process.
"""
import importlib
import os
import sys
import warnings
_GOOGLE3_PYTHON_UPB_DEFAULT = True
def _ApiVersionToImplementationType(api_version):
if api_version == 2:
return 'cpp'
if api_version == 1:
raise ValueError('api_version=1 is no longer supported.')
if api_version == 0:
return 'python'
return None
_implementation_type = None
try:
# pylint: disable=g-import-not-at-top
from google.protobuf.internal import _api_implementation
# The compile-time constants in the _api_implementation module can be used to
# switch to a certain implementation of the Python API at build time.
_implementation_type = _ApiVersionToImplementationType(
_api_implementation.api_version)
except ImportError:
pass # Unspecified by compiler flags.
def _CanImport(mod_name):
try:
mod = importlib.import_module(mod_name)
# Work around a known issue in the classic bootstrap .par import hook.
if not mod:
raise ImportError(mod_name + ' import succeeded but was None')
return True
except ImportError:
return False
if _implementation_type is None:
if _CanImport('google._upb._message'):
_implementation_type = 'upb'
elif _CanImport('google.protobuf.pyext._message'):
_implementation_type = 'cpp'
else:
_implementation_type = 'python'
# This environment variable can be used to switch to a certain implementation
# of the Python API, overriding the compile-time constants in the
# _api_implementation module. Right now only 'python', 'cpp' and 'upb' are
# valid values. Any other value will raise error.
_implementation_type = os.getenv('PROTOCOL_BUFFERS_PYTHON_IMPLEMENTATION',
_implementation_type)
if _implementation_type not in ('python', 'cpp', 'upb'):
raise ValueError('PROTOCOL_BUFFERS_PYTHON_IMPLEMENTATION {0} is not '
'supported. Please set to \'python\', \'cpp\' or '
'\'upb\'.'.format(_implementation_type))
if 'PyPy' in sys.version and _implementation_type == 'cpp':
warnings.warn('PyPy does not work yet with cpp protocol buffers. '
'Falling back to the python implementation.')
_implementation_type = 'python'
_c_module = None
if _implementation_type == 'cpp':
try:
# pylint: disable=g-import-not-at-top
from google.protobuf.pyext import _message
sys.modules['google3.net.proto2.python.internal.cpp._message'] = _message
_c_module = _message
del _message
except ImportError:
# TODO: fail back to python
warnings.warn(
'Selected implementation cpp is not available.')
pass
if _implementation_type == 'upb':
try:
# pylint: disable=g-import-not-at-top
from google._upb import _message
_c_module = _message
del _message
except ImportError:
warnings.warn('Selected implementation upb is not available. '
'Falling back to the python implementation.')
_implementation_type = 'python'
pass
# Detect if serialization should be deterministic by default
try:
# The presence of this module in a build allows the proto implementation to
# be upgraded merely via build deps.
#
# NOTE: Merely importing this automatically enables deterministic proto
# serialization for C++ code, but we still need to export it as a boolean so
# that we can do the same for `_implementation_type == 'python'`.
#
# NOTE2: It is possible for C++ code to enable deterministic serialization by
# default _without_ affecting Python code, if the C++ implementation is not in
# use by this module. That is intended behavior, so we don't actually expose
# this boolean outside of this module.
#
# pylint: disable=g-import-not-at-top,unused-import
from google.protobuf import enable_deterministic_proto_serialization
_python_deterministic_proto_serialization = True
except ImportError:
_python_deterministic_proto_serialization = False
# Usage of this function is discouraged. Clients shouldn't care which
# implementation of the API is in use. Note that there is no guarantee
# that differences between APIs will be maintained.
# Please don't use this function if possible.
def Type():
return _implementation_type
# See comment on 'Type' above.
# TODO: Remove the API, it returns a constant. b/228102101
def Version():
return 2
# For internal use only
def IsPythonDefaultSerializationDeterministic():
return _python_deterministic_proto_serialization
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