class AppTestMemory:
    spaceconfig = dict(usemodules=('_multiprocessing', 'mmap',
                                   '_rawffi', 'itertools'))

    def test_address_of(self):
        import _multiprocessing
        raises(TypeError, _multiprocessing.address_of_buffer, None)
        raises(TypeError, _multiprocessing.address_of_buffer, "a")

    def test_mmap_address(self):
        import mmap
        import _multiprocessing

        # This is a bit faster than importing ctypes
        import _ctypes
        class c_double(_ctypes._SimpleCData):
            _type_ = "d"
        sizeof_double = _ctypes.sizeof(c_double)

        buf = mmap.mmap(-1, 300)
        buf[0:300] = '\0' * 300

        # Get the address of shared memory
        address, length = _multiprocessing.address_of_buffer(buf)
        assert length == 300

        # build a ctypes object from it
        var = c_double.from_address(address)
        assert buf[0:sizeof_double] == '\0' * sizeof_double
        assert var.value == 0

        # check that both objects share the same memory
        var.value = 123.456
        assert buf[0:sizeof_double] != '\0' * sizeof_double
        buf[0:sizeof_double] = '\0' * sizeof_double
        assert var.value == 0
