diff options
Diffstat (limited to 'Lib/test/test_struct.py')
| -rw-r--r-- | Lib/test/test_struct.py | 128 |
1 files changed, 108 insertions, 20 deletions
diff --git a/Lib/test/test_struct.py b/Lib/test/test_struct.py index efbdbfc..4d9d601 100644 --- a/Lib/test/test_struct.py +++ b/Lib/test/test_struct.py @@ -1,5 +1,6 @@ from collections import abc import array +import math import operator import unittest import struct @@ -15,22 +16,10 @@ byteorders = '', '@', '=', '<', '>', '!' def iter_integer_formats(byteorders=byteorders): for code in integer_codes: for byteorder in byteorders: - if (byteorder in ('', '@') and code in ('q', 'Q') and - not HAVE_LONG_LONG): - continue if (byteorder not in ('', '@') and code in ('n', 'N')): continue yield code, byteorder -# Native 'q' packing isn't available on systems that don't have the C -# long long type. -try: - struct.pack('q', 5) -except struct.error: - HAVE_LONG_LONG = False -else: - HAVE_LONG_LONG = True - def string_reverse(s): return s[::-1] @@ -158,9 +147,7 @@ class StructTest(unittest.TestCase): self.assertEqual(size, expected_size[code]) # native integer sizes - native_pairs = 'bB', 'hH', 'iI', 'lL', 'nN' - if HAVE_LONG_LONG: - native_pairs += 'qQ', + native_pairs = 'bB', 'hH', 'iI', 'lL', 'nN', 'qQ' for format_pair in native_pairs: for byteorder in '', '@': signed_size = struct.calcsize(byteorder + format_pair[0]) @@ -173,9 +160,8 @@ class StructTest(unittest.TestCase): self.assertLessEqual(4, struct.calcsize('l')) self.assertLessEqual(struct.calcsize('h'), struct.calcsize('i')) self.assertLessEqual(struct.calcsize('i'), struct.calcsize('l')) - if HAVE_LONG_LONG: - self.assertLessEqual(8, struct.calcsize('q')) - self.assertLessEqual(struct.calcsize('l'), struct.calcsize('q')) + self.assertLessEqual(8, struct.calcsize('q')) + self.assertLessEqual(struct.calcsize('l'), struct.calcsize('q')) self.assertGreaterEqual(struct.calcsize('n'), struct.calcsize('i')) self.assertGreaterEqual(struct.calcsize('n'), struct.calcsize('P')) @@ -366,8 +352,6 @@ class StructTest(unittest.TestCase): # SF bug 705836. "<f" and ">f" had a severe rounding bug, where a carry # from the low-order discarded bits could propagate into the exponent # field, causing the result to be wrong by a factor of 2. - import math - for base in range(1, 33): # smaller <- largest representable float less than base. delta = 0.5 @@ -659,6 +643,110 @@ class UnpackIteratorTest(unittest.TestCase): self.assertRaises(StopIteration, next, it) self.assertRaises(StopIteration, next, it) + def test_half_float(self): + # Little-endian examples from: + # http://en.wikipedia.org/wiki/Half_precision_floating-point_format + format_bits_float__cleanRoundtrip_list = [ + (b'\x00\x3c', 1.0), + (b'\x00\xc0', -2.0), + (b'\xff\x7b', 65504.0), # (max half precision) + (b'\x00\x04', 2**-14), # ~= 6.10352 * 10**-5 (min pos normal) + (b'\x01\x00', 2**-24), # ~= 5.96046 * 10**-8 (min pos subnormal) + (b'\x00\x00', 0.0), + (b'\x00\x80', -0.0), + (b'\x00\x7c', float('+inf')), + (b'\x00\xfc', float('-inf')), + (b'\x55\x35', 0.333251953125), # ~= 1/3 + ] + + for le_bits, f in format_bits_float__cleanRoundtrip_list: + be_bits = le_bits[::-1] + self.assertEqual(f, struct.unpack('<e', le_bits)[0]) + self.assertEqual(le_bits, struct.pack('<e', f)) + self.assertEqual(f, struct.unpack('>e', be_bits)[0]) + self.assertEqual(be_bits, struct.pack('>e', f)) + if sys.byteorder == 'little': + self.assertEqual(f, struct.unpack('e', le_bits)[0]) + self.assertEqual(le_bits, struct.pack('e', f)) + else: + self.assertEqual(f, struct.unpack('e', be_bits)[0]) + self.assertEqual(be_bits, struct.pack('e', f)) + + # Check for NaN handling: + format_bits__nan_list = [ + ('<e', b'\x01\xfc'), + ('<e', b'\x00\xfe'), + ('<e', b'\xff\xff'), + ('<e', b'\x01\x7c'), + ('<e', b'\x00\x7e'), + ('<e', b'\xff\x7f'), + ] + + for formatcode, bits in format_bits__nan_list: + self.assertTrue(math.isnan(struct.unpack('<e', bits)[0])) + self.assertTrue(math.isnan(struct.unpack('>e', bits[::-1])[0])) + + # Check that packing produces a bit pattern representing a quiet NaN: + # all exponent bits and the msb of the fraction should all be 1. + packed = struct.pack('<e', math.nan) + self.assertEqual(packed[1] & 0x7e, 0x7e) + packed = struct.pack('<e', -math.nan) + self.assertEqual(packed[1] & 0x7e, 0x7e) + + # Checks for round-to-even behavior + format_bits_float__rounding_list = [ + ('>e', b'\x00\x01', 2.0**-25 + 2.0**-35), # Rounds to minimum subnormal + ('>e', b'\x00\x00', 2.0**-25), # Underflows to zero (nearest even mode) + ('>e', b'\x00\x00', 2.0**-26), # Underflows to zero + ('>e', b'\x03\xff', 2.0**-14 - 2.0**-24), # Largest subnormal. + ('>e', b'\x03\xff', 2.0**-14 - 2.0**-25 - 2.0**-65), + ('>e', b'\x04\x00', 2.0**-14 - 2.0**-25), + ('>e', b'\x04\x00', 2.0**-14), # Smallest normal. + ('>e', b'\x3c\x01', 1.0+2.0**-11 + 2.0**-16), # rounds to 1.0+2**(-10) + ('>e', b'\x3c\x00', 1.0+2.0**-11), # rounds to 1.0 (nearest even mode) + ('>e', b'\x3c\x00', 1.0+2.0**-12), # rounds to 1.0 + ('>e', b'\x7b\xff', 65504), # largest normal + ('>e', b'\x7b\xff', 65519), # rounds to 65504 + ('>e', b'\x80\x01', -2.0**-25 - 2.0**-35), # Rounds to minimum subnormal + ('>e', b'\x80\x00', -2.0**-25), # Underflows to zero (nearest even mode) + ('>e', b'\x80\x00', -2.0**-26), # Underflows to zero + ('>e', b'\xbc\x01', -1.0-2.0**-11 - 2.0**-16), # rounds to 1.0+2**(-10) + ('>e', b'\xbc\x00', -1.0-2.0**-11), # rounds to 1.0 (nearest even mode) + ('>e', b'\xbc\x00', -1.0-2.0**-12), # rounds to 1.0 + ('>e', b'\xfb\xff', -65519), # rounds to 65504 + ] + + for formatcode, bits, f in format_bits_float__rounding_list: + self.assertEqual(bits, struct.pack(formatcode, f)) + + # This overflows, and so raises an error + format_bits_float__roundingError_list = [ + # Values that round to infinity. + ('>e', 65520.0), + ('>e', 65536.0), + ('>e', 1e300), + ('>e', -65520.0), + ('>e', -65536.0), + ('>e', -1e300), + ('<e', 65520.0), + ('<e', 65536.0), + ('<e', 1e300), + ('<e', -65520.0), + ('<e', -65536.0), + ('<e', -1e300), + ] + + for formatcode, f in format_bits_float__roundingError_list: + self.assertRaises(OverflowError, struct.pack, formatcode, f) + + # Double rounding + format_bits_float__doubleRoundingError_list = [ + ('>e', b'\x67\xff', 0x1ffdffffff * 2**-26), # should be 2047, if double-rounded 64>32>16, becomes 2048 + ] + + for formatcode, bits, f in format_bits_float__doubleRoundingError_list: + self.assertEqual(bits, struct.pack(formatcode, f)) + if __name__ == '__main__': unittest.main() |