test_memfunctions.py | Explore in Territory

import sys
import unittest
from test import support
from ctypes import (POINTER, sizeof, cast,
                    create_string_buffer, string_at,
                    create_unicode_buffer, wstring_at,
                    memmove, memset,
                    c_char_p, c_byte, c_ubyte, c_wchar)


class MemFunctionsTest(unittest.TestCase):
    def test_overflow(self):
        # string_at and wstring_at must use the Python calling
        # convention (which acquires the GIL and checks the Python
        # error flag).  Provoke an error and catch it; see also issue
        # gh-47804.
        self.assertRaises((OverflowError, MemoryError, SystemError),
                          lambda: wstring_at(u"foo", sys.maxsize - 1))
        self.assertRaises((OverflowError, MemoryError, SystemError),
                          lambda: string_at("foo", sys.maxsize - 1))

    def test_memmove(self):
        # large buffers apparently increase the chance that the memory
        # is allocated in high address space.
        a = create_string_buffer(1000000)
        p = b"Hello, World"
        result = memmove(a, p, len(p))
        self.assertEqual(a.value, b"Hello, World")

        self.assertEqual(string_at(result), b"Hello, World")
        self.assertEqual(string_at(result, 5), b"Hello")
        self.assertEqual(string_at(result, 16), b"Hello, World\0\0\0\0")
        self.assertEqual(string_at(result, 0), b"")

    def test_memset(self):
        a = create_string_buffer(1000000)
        result = memset(a, ord('x'), 16)
        self.assertEqual(a.value, b"xxxxxxxxxxxxxxxx")

        self.assertEqual(string_at(result), b"xxxxxxxxxxxxxxxx")
        self.assertEqual(string_at(a), b"xxxxxxxxxxxxxxxx")
        self.assertEqual(string_at(a, 20), b"xxxxxxxxxxxxxxxx\0\0\0\0")

    def test_cast(self):
        a = (c_ubyte * 32)(*map(ord, "abcdef"))
        self.assertEqual(cast(a, c_char_p).value, b"abcdef")
        self.assertEqual(cast(a, POINTER(c_byte))[:7],
                             [97, 98, 99, 100, 101, 102, 0])
        self.assertEqual(cast(a, POINTER(c_byte))[:7:],
                             [97, 98, 99, 100, 101, 102, 0])
        self.assertEqual(cast(a, POINTER(c_byte))[6:-1:-1],
                             [0, 102, 101, 100, 99, 98, 97])
        self.assertEqual(cast(a, POINTER(c_byte))[:7:2],
                             [97, 99, 101, 0])
        self.assertEqual(cast(a, POINTER(c_byte))[:7:7],
                             [97])

    @support.refcount_test
    def test_string_at(self):
        s = string_at(b"foo bar")
        # XXX The following may be wrong, depending on how Python
        # manages string instances
        self.assertEqual(2, sys.getrefcount(s))
        self.assertTrue(s, "foo bar")

        self.assertEqual(string_at(b"foo bar", 7), b"foo bar")
        self.assertEqual(string_at(b"foo bar", 3), b"foo")

    def test_wstring_at(self):
        p = create_unicode_buffer("Hello, World")
        a = create_unicode_buffer(1000000)
        result = memmove(a, p, len(p) * sizeof(c_wchar))
        self.assertEqual(a.value, "Hello, World")

        self.assertEqual(wstring_at(a), "Hello, World")
        self.assertEqual(wstring_at(a, 5), "Hello")
        self.assertEqual(wstring_at(a, 16), "Hello, World\0\0\0\0")
        self.assertEqual(wstring_at(a, 0), "")


if __name__ == "__main__":
    unittest.main()
cpython/Lib/test/test_ctypes/test_memfunctions.py
