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Lib/ctypes/test/test_cast.py
from ctypes import *
from ctypes.test import need_symbol
import unittest
import sys

class Test(unittest.TestCase):

    def test_array2pointer(self):
        array = (c_int * 3)(42, 17, 2)

        # casting an array to a pointer works.
        ptr = cast(array, POINTER(c_int))
        self.assertEqual([ptr[i] for i in range(3)], [42, 17, 2])

        if 2*sizeof(c_short) == sizeof(c_int):
            ptr = cast(array, POINTER(c_short))
            if sys.byteorder == "little":
                self.assertEqual([ptr[i] for i in range(6)],
                                     [42, 0, 17, 0, 2, 0])
            else:
                self.assertEqual([ptr[i] for i in range(6)],
                                     [0, 42, 0, 17, 0, 2])

    def test_address2pointer(self):
        array = (c_int * 3)(42, 17, 2)

        address = addressof(array)
        ptr = cast(c_void_p(address), POINTER(c_int))
        self.assertEqual([ptr[i] for i in range(3)], [42, 17, 2])

        ptr = cast(address, POINTER(c_int))
        self.assertEqual([ptr[i] for i in range(3)], [42, 17, 2])

    def test_p2a_objects(self):
        array = (c_char_p * 5)()
        self.assertEqual(array._objects, None)
        array[0] = "foo bar"
        self.assertEqual(array._objects, {'0': "foo bar"})

        p = cast(array, POINTER(c_char_p))
        # array and p share a common _objects attribute
        self.assertIs(p._objects, array._objects)
        self.assertEqual(array._objects, {'0': "foo bar", id(array): array})
        p[0] = "spam spam"
        self.assertEqual(p._objects, {'0': "spam spam", id(array): array})
        self.assertIs(array._objects, p._objects)
        p[1] = "foo bar"
        self.assertEqual(p._objects, {'1': 'foo bar', '0': "spam spam", id(array): array})
        self.assertIs(array._objects, p._objects)

    def test_other(self):
        p = cast((c_int * 4)(1, 2, 3, 4), POINTER(c_int))
        self.assertEqual(p[:4], [1,2, 3, 4])
        self.assertEqual(p[:4:], [1, 2, 3, 4])
        self.assertEqual(p[3:-1:-1], [4, 3, 2, 1])
        self.assertEqual(p[:4:3], [1, 4])
        c_int()
        self.assertEqual(p[:4], [1, 2, 3, 4])
        self.assertEqual(p[:4:], [1, 2, 3, 4])
        self.assertEqual(p[3:-1:-1], [4, 3, 2, 1])
        self.assertEqual(p[:4:3], [1, 4])
        p[2] = 96
        self.assertEqual(p[:4], [1, 2, 96, 4])
        self.assertEqual(p[:4:], [1, 2, 96, 4])
        self.assertEqual(p[3:-1:-1], [4, 96, 2, 1])
        self.assertEqual(p[:4:3], [1, 4])
        c_int()
        self.assertEqual(p[:4], [1, 2, 96, 4])
        self.assertEqual(p[:4:], [1, 2, 96, 4])
        self.assertEqual(p[3:-1:-1], [4, 96, 2, 1])
        self.assertEqual(p[:4:3], [1, 4])

    def test_char_p(self):
        # This didn't work: bad argument to internal function
        s = c_char_p("hiho")
        self.assertEqual(cast(cast(s, c_void_p), c_char_p).value,
                             "hiho")

    @need_symbol('c_wchar_p')
    def test_wchar_p(self):
        s = c_wchar_p("hiho")
        self.assertEqual(cast(cast(s, c_void_p), c_wchar_p).value,
                             "hiho")

if __name__ == "__main__":
    unittest.main()