MLPY/Lib/site-packages/google/protobuf/internal/api_implementation.py

# Protocol Buffers - Google's data interchange format
# Copyright 2008 Google Inc.  All rights reserved.
# https://developers.google.com/protocol-buffers/
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are
# met:
#
#     * Redistributions of source code must retain the above copyright
# notice, this list of conditions and the following disclaimer.
#     * Redistributions in binary form must reproduce the above
# copyright notice, this list of conditions and the following disclaimer
# in the documentation and/or other materials provided with the
# distribution.
#     * Neither the name of Google Inc. nor the names of its
# contributors may be used to endorse or promote products derived from
# this software without specific prior written permission.
#
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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"""Determine which implementation of the protobuf API is used in this process.
"""

import os
import sys
import warnings

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.
  _api_version = _api_implementation.api_version
except ImportError:
  _api_version = -1  # Unspecified by compiler flags.

if _api_version == 1:
  raise ValueError('api_version=1 is no longer supported.')


_default_implementation_type = ('cpp' if _api_version > 0 else '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' and 'cpp' are valid
# values. Any other value will be ignored.
_implementation_type = os.getenv('PROTOCOL_BUFFERS_PYTHON_IMPLEMENTATION',
                                 _default_implementation_type)

if _implementation_type != 'python':
  _implementation_type = 'cpp'

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'


# 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


def _SetType(implementation_type):
  """Never use! Only for protobuf benchmark."""
  global _implementation_type
  _implementation_type = implementation_type


# See comment on 'Type' above.
def Version():
  return 2


# For internal use only
def IsPythonDefaultSerializationDeterministic():
  return _python_deterministic_proto_serialization