Adding darwin.py (MacOS) platform

#

#  Copyright (C) 2017 Codethink Limited

#  Copyright (C) 2018 Bloomberg Finance LP

#

#  This program is free software; you can redistribute it and/or

#  modify it under the terms of the GNU Lesser General Public

#  License as published by the Free Software Foundation; either

#  version 2 of the License, or (at your option) any later version.

#

#  This library is distributed in the hope that it will be useful,

#  but WITHOUT ANY WARRANTY; without even the implied warranty of

#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.	 See the GNU

#  Lesser General Public License for more details.

#

#  You should have received a copy of the GNU Lesser General Public

#  License along with this library. If not, see <http://www.gnu.org/licenses/>.

import os

import resource

from .._exceptions import PlatformError

from ..sandbox import SandboxChroot, SandboxDummy

from . import Platform

class Darwin(Platform):

    # This value comes from OPEN_MAX in syslimits.h

    OPEN_MAX = 10240

    def __init__(self, context):

        super().__init__(context)

    def create_sandbox(self, *args, **kwargs):

        return SandboxDummy(*args, **kwargs)

    def check_sandbox_config(self, config):

        # Accept all sandbox configs as it's irrelevant with the dummy sandbox (no Sandbox.run).

        return True

    def get_cpu_count(self, cap=None):

        if cap < os.cpu_count():

            return cap

        else:

            return os.cpu_count()

    def set_resource_limits(self, soft_limit=OPEN_MAX, hard_limit=None):

        super().set_resource_limits(soft_limit)

    @classmethod

    @classmethod

    def _create_instance(cls):

    def _create_instance(cls):

        if sys.platform.startswith('linux'):

            backend = 'linux'

        else:

            backend = 'unix'

        # Meant for testing purposes and therefore hidden in the

        # Meant for testing purposes and therefore hidden in the

        # deepest corners of the source code. Try not to abuse this,

        # deepest corners of the source code. Try not to abuse this,

        # please?

        # please?

        if os.getenv('BST_FORCE_BACKEND'):

        if os.getenv('BST_FORCE_BACKEND'):

            backend = os.getenv('BST_FORCE_BACKEND')

            backend = os.getenv('BST_FORCE_BACKEND')

        elif sys.platform.startswith('linux'):

            backend = 'linux'

        elif sys.platform.startswith('darwin'):

            backend = 'darwin'

        else:

            backend = 'unix'

        if backend == 'linux':

        if backend == 'linux':

            from .linux import Linux as PlatformImpl

            from .linux import Linux as PlatformImpl

        elif backend == 'darwin':

            from .darwin import Darwin as PlatformImpl

        elif backend == 'unix':

        elif backend == 'unix':

            from .unix import Unix as PlatformImpl

            from .unix import Unix as PlatformImpl

        else:

        else: