Method test_long_fromnativebytes

Lib/test/test_capi/test_long.py:585–628

(self)

                raise AssertionError(f"Value: 0x{value_hex}") from ex

    def test_long_fromnativebytes(self):
        import math
        from _testcapi import (
            pylong_fromnativebytes as fromnativebytes,
            SIZE_MAX,
        )

        # Abbreviate sizeof(Py_ssize_t) to SZ because we use it a lot
        SZ = int(math.ceil(math.log(SIZE_MAX + 1) / math.log(2)) / 8)
        MAX_SSIZE = 2 ** (SZ * 8 - 1) - 1
        MAX_USIZE = 2 ** (SZ * 8) - 1

        for v_be, expect_s, expect_u in [
            (b'\x00', 0, 0),
            (b'\x01', 1, 1),
            (b'\xff', -1, 255),
            (b'\x00\xff', 255, 255),
            (b'\xff\xff', -1, 65535),
        ]:
            with self.subTest(f"{expect_s}-{expect_u:X}-{len(v_be)}bytes"):
                n = len(v_be)
                v_le = v_be[::-1]

                self.assertEqual(expect_s, fromnativebytes(v_be, n, 0, 1),
                    f"PyLong_FromNativeBytes(buffer, {n}, <big>)")
                self.assertEqual(expect_s, fromnativebytes(v_le, n, 1, 1),
                    f"PyLong_FromNativeBytes(buffer, {n}, <little>)")
                self.assertEqual(expect_u, fromnativebytes(v_be, n, 0, 0),
                    f"PyLong_FromUnsignedNativeBytes(buffer, {n}, <big>)")
                self.assertEqual(expect_u, fromnativebytes(v_le, n, 1, 0),
                    f"PyLong_FromUnsignedNativeBytes(buffer, {n}, <little>)")

                # Check native endian when the result would be the same either
                # way and we can test it.
                if v_be == v_le:
                    self.assertEqual(expect_s, fromnativebytes(v_be, n, -1, 1),
                        f"PyLong_FromNativeBytes(buffer, {n}, <native>)")
                    self.assertEqual(expect_u, fromnativebytes(v_be, n, -1, 0),
                        f"PyLong_FromUnsignedNativeBytes(buffer, {n}, <native>)")

                # Swap the unsigned request for tests and use the
                # Py_ASNATIVEBYTES_UNSIGNED_BUFFER flag instead
                self.assertEqual(expect_u, fromnativebytes(v_be, n, 4, 1),
                    f"PyLong_FromNativeBytes(buffer, {n}, <big|unsigned>)")

    def test_long_getsign(self):
        # Test PyLong_GetSign()