xref: /aosp_15_r20/external/cronet/third_party/protobuf/python/google/protobuf/internal/api_implementation.py (revision 6777b5387eb2ff775bb5750e3f5d96f37fb7352b) 
1# Protocol Buffers - Google's data interchange format
2# Copyright 2008 Google Inc.  All rights reserved.
3# https://developers.google.com/protocol-buffers/
4#
5# Redistribution and use in source and binary forms, with or without
6# modification, are permitted provided that the following conditions are
7# met:
8#
9#     * Redistributions of source code must retain the above copyright
10# notice, this list of conditions and the following disclaimer.
11#     * Redistributions in binary form must reproduce the above
12# copyright notice, this list of conditions and the following disclaimer
13# in the documentation and/or other materials provided with the
14# distribution.
15#     * Neither the name of Google Inc. nor the names of its
16# contributors may be used to endorse or promote products derived from
17# this software without specific prior written permission.
18#
19# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
20# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
21# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
22# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
23# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
24# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
25# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
26# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
27# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
28# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
29# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
30
31"""Determine which implementation of the protobuf API is used in this process.
32"""
33
34import importlib
35import os
36import sys
37import warnings
38
39
40def _ApiVersionToImplementationType(api_version):
41  if api_version == 2:
42    return 'cpp'
43  if api_version == 1:
44    raise ValueError('api_version=1 is no longer supported.')
45  if api_version == 0:
46    return 'python'
47  return None
48
49
50_implementation_type = None
51try:
52  # pylint: disable=g-import-not-at-top
53  from google.protobuf.internal import _api_implementation
54  # The compile-time constants in the _api_implementation module can be used to
55  # switch to a certain implementation of the Python API at build time.
56  _implementation_type = _ApiVersionToImplementationType(
57      _api_implementation.api_version)
58except ImportError:
59  pass  # Unspecified by compiler flags.
60
61
62def _CanImport(mod_name):
63  try:
64    mod = importlib.import_module(mod_name)
65    # Work around a known issue in the classic bootstrap .par import hook.
66    if not mod:
67      raise ImportError(mod_name + ' import succeeded but was None')
68    return True
69  except ImportError:
70    return False
71
72
73if _implementation_type is None:
74  if _CanImport('google._upb._message'):
75    _implementation_type = 'upb'
76  elif _CanImport('google.protobuf.pyext._message'):
77    _implementation_type = 'cpp'
78  else:
79    _implementation_type = 'python'
80
81
82# This environment variable can be used to switch to a certain implementation
83# of the Python API, overriding the compile-time constants in the
84# _api_implementation module. Right now only 'python', 'cpp' and 'upb' are
85# valid values. Any other value will raise error.
86_implementation_type = os.getenv('PROTOCOL_BUFFERS_PYTHON_IMPLEMENTATION',
87                                 _implementation_type)
88
89if _implementation_type not in ('python', 'cpp', 'upb'):
90  raise ValueError('PROTOCOL_BUFFERS_PYTHON_IMPLEMENTATION {0} is not '
91                   'supported. Please set to \'python\', \'cpp\' or '
92                   '\'upb\'.'.format(_implementation_type))
93
94if 'PyPy' in sys.version and _implementation_type == 'cpp':
95  warnings.warn('PyPy does not work yet with cpp protocol buffers. '
96                'Falling back to the python implementation.')
97  _implementation_type = 'python'
98
99_c_module = None
100
101if _implementation_type == 'cpp':
102  try:
103    # pylint: disable=g-import-not-at-top
104    from google.protobuf.pyext import _message
105    _c_module = _message
106    del _message
107  except ImportError:
108    # TODO(jieluo): fail back to python
109    warnings.warn(
110        'Selected implementation cpp is not available.')
111    pass
112
113if _implementation_type == 'upb':
114  try:
115    # pylint: disable=g-import-not-at-top
116    from google._upb import _message
117    _c_module = _message
118    del _message
119  except ImportError:
120    warnings.warn('Selected implementation upb is not available. '
121                  'Falling back to the python implementation.')
122    _implementation_type = 'python'
123    pass
124
125# Detect if serialization should be deterministic by default
126try:
127  # The presence of this module in a build allows the proto implementation to
128  # be upgraded merely via build deps.
129  #
130  # NOTE: Merely importing this automatically enables deterministic proto
131  # serialization for C++ code, but we still need to export it as a boolean so
132  # that we can do the same for `_implementation_type == 'python'`.
133  #
134  # NOTE2: It is possible for C++ code to enable deterministic serialization by
135  # default _without_ affecting Python code, if the C++ implementation is not in
136  # use by this module.  That is intended behavior, so we don't actually expose
137  # this boolean outside of this module.
138  #
139  # pylint: disable=g-import-not-at-top,unused-import
140  from google.protobuf import enable_deterministic_proto_serialization
141  _python_deterministic_proto_serialization = True
142except ImportError:
143  _python_deterministic_proto_serialization = False
144
145
146# Usage of this function is discouraged. Clients shouldn't care which
147# implementation of the API is in use. Note that there is no guarantee
148# that differences between APIs will be maintained.
149# Please don't use this function if possible.
150def Type():
151  return _implementation_type
152
153
154def _SetType(implementation_type):
155  """Never use! Only for protobuf benchmark."""
156  global _implementation_type
157  _implementation_type = implementation_type
158
159
160# See comment on 'Type' above.
161# TODO(jieluo): Remove the API, it returns a constant. b/228102101
162def Version():
163  return 2
164
165
166# For internal use only
167def IsPythonDefaultSerializationDeterministic():
168  return _python_deterministic_proto_serialization
169