Current File : //lib/python3/dist-packages/zope/interface/_compat.py
##############################################################################
#
# Copyright (c) 2006 Zope Foundation and Contributors.
# All Rights Reserved.
#
# This software is subject to the provisions of the Zope Public License,
# Version 2.1 (ZPL). A copy of the ZPL should accompany this distribution.
# THIS SOFTWARE IS PROVIDED "AS IS" AND ANY AND ALL EXPRESS OR IMPLIED
# WARRANTIES ARE DISCLAIMED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
# WARRANTIES OF TITLE, MERCHANTABILITY, AGAINST INFRINGEMENT, AND FITNESS
# FOR A PARTICULAR PURPOSE.
#
##############################################################################
"""
Support functions for dealing with differences in platforms, including Python
versions and implementations.
This file should have no imports from the rest of zope.interface because it is
used during early bootstrapping.
"""
import os
import sys
def _normalize_name(name):
if isinstance(name, bytes):
name = str(name, 'ascii')
if isinstance(name, str):
return name
raise TypeError("name must be a string or ASCII-only bytes")
PYPY = hasattr(sys, 'pypy_version_info')
def _c_optimizations_required():
"""
Return a true value if the C optimizations are required.
This uses the ``PURE_PYTHON`` variable as documented in `_use_c_impl`.
"""
pure_env = os.environ.get('PURE_PYTHON')
require_c = pure_env == "0"
return require_c
def _c_optimizations_available():
"""
Return the C optimization module, if available, otherwise
a false value.
If the optimizations are required but not available, this
raises the ImportError.
This does not say whether they should be used or not.
"""
catch = () if _c_optimizations_required() else (ImportError,)
try:
from zope.interface import _zope_interface_coptimizations as c_opt
return c_opt
except catch: # pragma: no cover (only Jython doesn't build extensions)
return False
def _c_optimizations_ignored():
"""
The opposite of `_c_optimizations_required`.
"""
pure_env = os.environ.get('PURE_PYTHON')
return pure_env is not None and pure_env != "0"
def _should_attempt_c_optimizations():
"""
Return a true value if we should attempt to use the C optimizations.
This takes into account whether we're on PyPy and the value of the
``PURE_PYTHON`` environment variable, as defined in `_use_c_impl`.
"""
is_pypy = hasattr(sys, 'pypy_version_info')
if _c_optimizations_required():
return True
if is_pypy:
return False
return not _c_optimizations_ignored()
def _use_c_impl(py_impl, name=None, globs=None):
"""
Decorator. Given an object implemented in Python, with a name like
``Foo``, import the corresponding C implementation from
``zope.interface._zope_interface_coptimizations`` with the name
``Foo`` and use it instead.
If the ``PURE_PYTHON`` environment variable is set to any value
other than ``"0"``, or we're on PyPy, ignore the C implementation
and return the Python version. If the C implementation cannot be
imported, return the Python version. If ``PURE_PYTHON`` is set to
0, *require* the C implementation (let the ImportError propagate);
note that PyPy can import the C implementation in this case (and all
tests pass).
In all cases, the Python version is kept available. in the module
globals with the name ``FooPy`` and the name ``FooFallback`` (both
conventions have been used; the C implementation of some functions
looks for the ``Fallback`` version, as do some of the Sphinx
documents).
Example::
@_use_c_impl
class Foo(object):
...
"""
name = name or py_impl.__name__
globs = globs or sys._getframe(1).f_globals
def find_impl():
if not _should_attempt_c_optimizations():
return py_impl
c_opt = _c_optimizations_available()
if not c_opt: # pragma: no cover (only Jython doesn't build extensions)
return py_impl
__traceback_info__ = c_opt
return getattr(c_opt, name)
c_impl = find_impl()
# Always make available by the FooPy name and FooFallback
# name (for testing and documentation)
globs[name + 'Py'] = py_impl
globs[name + 'Fallback'] = py_impl
return c_impl
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