from collections import abc import array import math import operator import unittest import struct import sys from test import support ISBIGENDIAN = sys.byteorder == "big" integer_codes = 'b', 'B', 'h', 'H', 'i', 'I', 'l', 'L', 'q', 'Q', 'n', 'N' byteorders = '', '@', '=', '<', '>', '!' def iter_integer_formats(byteorders=byteorders): for code in integer_codes: for byteorder in byteorders: if (byteorder not in ('', '@') and code in ('n', 'N')): continue yield code, byteorder def string_reverse(s): return s[::-1] def bigendian_to_native(value): if ISBIGENDIAN: return value else: return string_reverse(value) class StructTest(unittest.TestCase): def test_isbigendian(self): self.assertEqual((struct.pack('=i', 1)[0] == 0), ISBIGENDIAN) def test_consistence(self): self.assertRaises(struct.error, struct.calcsize, 'Z') sz = struct.calcsize('i') self.assertEqual(sz * 3, struct.calcsize('iii')) fmt = 'cbxxxxxxhhhhiillffd?' fmt3 = '3c3b18x12h6i6l6f3d3?' sz = struct.calcsize(fmt) sz3 = struct.calcsize(fmt3) self.assertEqual(sz * 3, sz3) self.assertRaises(struct.error, struct.pack, 'iii', 3) self.assertRaises(struct.error, struct.pack, 'i', 3, 3, 3) self.assertRaises((TypeError, struct.error), struct.pack, 'i', 'foo') self.assertRaises((TypeError, struct.error), struct.pack, 'P', 'foo') self.assertRaises(struct.error, struct.unpack, 'd', b'flap') s = struct.pack('ii', 1, 2) self.assertRaises(struct.error, struct.unpack, 'iii', s) self.assertRaises(struct.error, struct.unpack, 'i', s) def test_transitiveness(self): c = b'a' b = 1 h = 255 i = 65535 l = 65536 f = 3.1415 d = 3.1415 t = True for prefix in ('', '@', '<', '>', '=', '!'): for format in ('xcbhilfd?', 'xcBHILfd?'): format = prefix + format s = struct.pack(format, c, b, h, i, l, f, d, t) cp, bp, hp, ip, lp, fp, dp, tp = struct.unpack(format, s) self.assertEqual(cp, c) self.assertEqual(bp, b) self.assertEqual(hp, h) self.assertEqual(ip, i) self.assertEqual(lp, l) self.assertEqual(int(100 * fp), int(100 * f)) self.assertEqual(int(100 * dp), int(100 * d)) self.assertEqual(tp, t) def test_new_features(self): # Test some of the new features in detail # (format, argument, big-endian result, little-endian result, asymmetric) tests = [ ('c', b'a', b'a', b'a', 0), ('xc', b'a', b'\0a', b'\0a', 0), ('cx', b'a', b'a\0', b'a\0', 0), ('s', b'a', b'a', b'a', 0), ('0s', b'helloworld', b'', b'', 1), ('1s', b'helloworld', b'h', b'h', 1), ('9s', b'helloworld', b'helloworl', b'helloworl', 1), ('10s', b'helloworld', b'helloworld', b'helloworld', 0), ('11s', b'helloworld', b'helloworld\0', b'helloworld\0', 1), ('20s', b'helloworld', b'helloworld'+10*b'\0', b'helloworld'+10*b'\0', 1), ('b', 7, b'\7', b'\7', 0), ('b', -7, b'\371', b'\371', 0), ('B', 7, b'\7', b'\7', 0), ('B', 249, b'\371', b'\371', 0), ('h', 700, b'\002\274', b'\274\002', 0), ('h', -700, b'\375D', b'D\375', 0), ('H', 700, b'\002\274', b'\274\002', 0), ('H', 0x10000-700, b'\375D', b'D\375', 0), ('i', 70000000, b'\004,\035\200', b'\200\035,\004', 0), ('i', -70000000, b'\373\323\342\200', b'\200\342\323\373', 0), ('I', 70000000, b'\004,\035\200', b'\200\035,\004', 0), ('I', 0x100000000-70000000, b'\373\323\342\200', b'\200\342\323\373', 0), ('l', 70000000, b'\004,\035\200', b'\200\035,\004', 0), ('l', -70000000, b'\373\323\342\200', b'\200\342\323\373', 0), ('L', 70000000, b'\004,\035\200', b'\200\035,\004', 0), ('L', 0x100000000-70000000, b'\373\323\342\200', b'\200\342\323\373', 0), ('f', 2.0, b'@\000\000\000', b'\000\000\000@', 0), ('d', 2.0, b'@\000\000\000\000\000\000\000', b'\000\000\000\000\000\000\000@', 0), ('f', -2.0, b'\300\000\000\000', b'\000\000\000\300', 0), ('d', -2.0, b'\300\000\000\000\000\000\000\000', b'\000\000\000\000\000\000\000\300', 0), ('?', 0, b'\0', b'\0', 0), ('?', 3, b'\1', b'\1', 1), ('?', True, b'\1', b'\1', 0), ('?', [], b'\0', b'\0', 1), ('?', (1,), b'\1', b'\1', 1), ] for fmt, arg, big, lil, asy in tests: for (xfmt, exp) in [('>'+fmt, big), ('!'+fmt, big), ('<'+fmt, lil), ('='+fmt, ISBIGENDIAN and big or lil)]: res = struct.pack(xfmt, arg) self.assertEqual(res, exp) self.assertEqual(struct.calcsize(xfmt), len(res)) rev = struct.unpack(xfmt, res)[0] if rev != arg: self.assertTrue(asy) def test_calcsize(self): expected_size = { 'b': 1, 'B': 1, 'h': 2, 'H': 2, 'i': 4, 'I': 4, 'l': 4, 'L': 4, 'q': 8, 'Q': 8, } # standard integer sizes for code, byteorder in iter_integer_formats(('=', '<', '>', '!')): format = byteorder+code size = struct.calcsize(format) self.assertEqual(size, expected_size[code]) # native integer sizes 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]) unsigned_size = struct.calcsize(byteorder + format_pair[1]) self.assertEqual(signed_size, unsigned_size) # bounds for native integer sizes self.assertEqual(struct.calcsize('b'), 1) self.assertLessEqual(2, struct.calcsize('h')) self.assertLessEqual(4, struct.calcsize('l')) self.assertLessEqual(struct.calcsize('h'), struct.calcsize('i')) self.assertLessEqual(struct.calcsize('i'), struct.calcsize('l')) 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')) def test_integers(self): # Integer tests (bBhHiIlLqQnN). import binascii class IntTester(unittest.TestCase): def __init__(self, format): super(IntTester, self).__init__(methodName='test_one') self.format = format self.code = format[-1] self.byteorder = format[:-1] if not self.byteorder in byteorders: raise ValueError("unrecognized packing byteorder: %s" % self.byteorder) self.bytesize = struct.calcsize(format) self.bitsize = self.bytesize * 8 if self.code in tuple('bhilqn'): self.signed = True self.min_value = -(2**(self.bitsize-1)) self.max_value = 2**(self.bitsize-1) - 1 elif self.code in tuple('BHILQN'): self.signed = False self.min_value = 0 self.max_value = 2**self.bitsize - 1 else: raise ValueError("unrecognized format code: %s" % self.code) def test_one(self, x, pack=struct.pack, unpack=struct.unpack, unhexlify=binascii.unhexlify): format = self.format if self.min_value <= x <= self.max_value: expected = x if self.signed and x < 0: expected += 1 << self.bitsize self.assertGreaterEqual(expected, 0) expected = '%x' % expected if len(expected) & 1: expected = "0" + expected expected = expected.encode('ascii') expected = unhexlify(expected) expected = (b"\x00" * (self.bytesize - len(expected)) + expected) if (self.byteorder == '<' or self.byteorder in ('', '@', '=') and not ISBIGENDIAN): expected = string_reverse(expected) self.assertEqual(len(expected), self.bytesize) # Pack work? got = pack(format, x) self.assertEqual(got, expected) # Unpack work? retrieved = unpack(format, got)[0] self.assertEqual(x, retrieved) # Adding any byte should cause a "too big" error. self.assertRaises((struct.error, TypeError), unpack, format, b'\x01' + got) else: # x is out of range -- verify pack realizes that. self.assertRaises((OverflowError, ValueError, struct.error), pack, format, x) def run(self): from random import randrange # Create all interesting powers of 2. values = [] for exp in range(self.bitsize + 3): values.append(1 << exp) # Add some random values. for i in range(self.bitsize): val = 0 for j in range(self.bytesize): val = (val << 8) | randrange(256) values.append(val) # Values absorbed from other tests values.extend([300, 700000, sys.maxsize*4]) # Try all those, and their negations, and +-1 from # them. Note that this tests all power-of-2 # boundaries in range, and a few out of range, plus # +-(2**n +- 1). for base in values: for val in -base, base: for incr in -1, 0, 1: x = val + incr self.test_one(x) # Some error cases. class NotAnInt: def __int__(self): return 42 # Objects with an '__index__' method should be allowed # to pack as integers. That is assuming the implemented # '__index__' method returns an 'int'. class Indexable(object): def __init__(self, value): self._value = value def __index__(self): return self._value # If the '__index__' method raises a type error, then # '__int__' should be used with a deprecation warning. class BadIndex(object): def __index__(self): raise TypeError def __int__(self): return 42 self.assertRaises((TypeError, struct.error), struct.pack, self.format, "a string") self.assertRaises((TypeError, struct.error), struct.pack, self.format, randrange) self.assertRaises((TypeError, struct.error), struct.pack, self.format, 3+42j) self.assertRaises((TypeError, struct.error), struct.pack, self.format, NotAnInt()) self.assertRaises((TypeError, struct.error), struct.pack, self.format, BadIndex()) # Check for legitimate values from '__index__'. for obj in (Indexable(0), Indexable(10), Indexable(17), Indexable(42), Indexable(100), Indexable(127)): try: struct.pack(format, obj) except: self.fail("integer code pack failed on object " "with '__index__' method") # Check for bogus values from '__index__'. for obj in (Indexable(b'a'), Indexable('b'), Indexable(None), Indexable({'a': 1}), Indexable([1, 2, 3])): self.assertRaises((TypeError, struct.error), struct.pack, self.format, obj) for code, byteorder in iter_integer_formats(): format = byteorder+code t = IntTester(format) t.run() def test_nN_code(self): # n and N don't exist in standard sizes def assertStructError(func, *args, **kwargs): with self.assertRaises(struct.error) as cm: func(*args, **kwargs) self.assertIn("bad char in struct format", str(cm.exception)) for code in 'nN': for byteorder in ('=', '<', '>', '!'): format = byteorder+code assertStructError(struct.calcsize, format) assertStructError(struct.pack, format, 0) assertStructError(struct.unpack, format, b"") def test_p_code(self): # Test p ("Pascal string") code. for code, input, expected, expectedback in [ ('p', b'abc', b'\x00', b''), ('1p', b'abc', b'\x00', b''), ('2p', b'abc', b'\x01a', b'a'), ('3p', b'abc', b'\x02ab', b'ab'), ('4p', b'abc', b'\x03abc', b'abc'), ('5p', b'abc', b'\x03abc\x00', b'abc'), ('6p', b'abc', b'\x03abc\x00\x00', b'abc'), ('1000p', b'x'*1000, b'\xff' + b'x'*999, b'x'*255)]: got = struct.pack(code, input) self.assertEqual(got, expected) (got,) = struct.unpack(code, got) self.assertEqual(got, expectedback) def test_705836(self): # SF bug 705836. "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. for base in range(1, 33): # smaller <- largest representable float less than base. delta = 0.5 while base - delta / 2.0 != base: delta /= 2.0 smaller = base - delta # Packing this rounds away a solid string of trailing 1 bits. packed = struct.pack("f", smaller) self.assertEqual(bigpacked, string_reverse(packed)) unpacked = struct.unpack(">f", bigpacked)[0] self.assertEqual(base, unpacked) # Largest finite IEEE single. big = (1 << 24) - 1 big = math.ldexp(big, 127 - 23) packed = struct.pack(">f", big) unpacked = struct.unpack(">f", packed)[0] self.assertEqual(big, unpacked) # The same, but tack on a 1 bit so it rounds up to infinity. big = (1 << 25) - 1 big = math.ldexp(big, 127 - 24) self.assertRaises(OverflowError, struct.pack, ">f", big) def test_1530559(self): for code, byteorder in iter_integer_formats(): format = byteorder + code self.assertRaises(struct.error, struct.pack, format, 1.0) self.assertRaises(struct.error, struct.pack, format, 1.5) self.assertRaises(struct.error, struct.pack, 'P', 1.0) self.assertRaises(struct.error, struct.pack, 'P', 1.5) def test_unpack_from(self): test_string = b'abcd01234' fmt = '4s' s = struct.Struct(fmt) for cls in (bytes, bytearray): data = cls(test_string) self.assertEqual(s.unpack_from(data), (b'abcd',)) self.assertEqual(s.unpack_from(data, 2), (b'cd01',)) self.assertEqual(s.unpack_from(data, 4), (b'0123',)) for i in range(6): self.assertEqual(s.unpack_from(data, i), (data[i:i+4],)) for i in range(6, len(test_string) + 1): self.assertRaises(struct.error, s.unpack_from, data, i) for cls in (bytes, bytearray): data = cls(test_string) self.assertEqual(struct.unpack_from(fmt, data), (b'abcd',)) self.assertEqual(struct.unpack_from(fmt, data, 2), (b'cd01',)) self.assertEqual(struct.unpack_from(fmt, data, 4), (b'0123',)) for i in range(6): self.assertEqual(struct.unpack_from(fmt, data, i), (data[i:i+4],)) for i in range(6, len(test_string) + 1): self.assertRaises(struct.error, struct.unpack_from, fmt, data, i) # keyword arguments self.assertEqual(s.unpack_from(buffer=test_string, offset=2), (b'cd01',)) def test_pack_into(self): test_string = b'Reykjavik rocks, eow!' writable_buf = array.array('b', b' '*100) fmt = '21s' s = struct.Struct(fmt) # Test without offset s.pack_into(writable_buf, 0, test_string) from_buf = writable_buf.tobytes()[:len(test_string)] self.assertEqual(from_buf, test_string) # Test with offset. s.pack_into(writable_buf, 10, test_string) from_buf = writable_buf.tobytes()[:len(test_string)+10] self.assertEqual(from_buf, test_string[:10] + test_string) # Go beyond boundaries. small_buf = array.array('b', b' '*10) self.assertRaises((ValueError, struct.error), s.pack_into, small_buf, 0, test_string) self.assertRaises((ValueError, struct.error), s.pack_into, small_buf, 2, test_string) # Test bogus offset (issue 3694) sb = small_buf self.assertRaises((TypeError, struct.error), struct.pack_into, b'', sb, None) def test_pack_into_fn(self): test_string = b'Reykjavik rocks, eow!' writable_buf = array.array('b', b' '*100) fmt = '21s' pack_into = lambda *args: struct.pack_into(fmt, *args) # Test without offset. pack_into(writable_buf, 0, test_string) from_buf = writable_buf.tobytes()[:len(test_string)] self.assertEqual(from_buf, test_string) # Test with offset. pack_into(writable_buf, 10, test_string) from_buf = writable_buf.tobytes()[:len(test_string)+10] self.assertEqual(from_buf, test_string[:10] + test_string) # Go beyond boundaries. small_buf = array.array('b', b' '*10) self.assertRaises((ValueError, struct.error), pack_into, small_buf, 0, test_string) self.assertRaises((ValueError, struct.error), pack_into, small_buf, 2, test_string) def test_unpack_with_buffer(self): # SF bug 1563759: struct.unpack doesn't support buffer protocol objects data1 = array.array('B', b'\x12\x34\x56\x78') data2 = memoryview(b'\x12\x34\x56\x78') # XXX b'......XXXX......', 6, 4 for data in [data1, data2]: value, = struct.unpack('>I', data) self.assertEqual(value, 0x12345678) def test_bool(self): class ExplodingBool(object): def __bool__(self): raise OSError for prefix in tuple("<>!=")+('',): false = (), [], [], '', 0 true = [1], 'test', 5, -1, 0xffffffff+1, 0xffffffff/2 falseFormat = prefix + '?' * len(false) packedFalse = struct.pack(falseFormat, *false) unpackedFalse = struct.unpack(falseFormat, packedFalse) trueFormat = prefix + '?' * len(true) packedTrue = struct.pack(trueFormat, *true) unpackedTrue = struct.unpack(trueFormat, packedTrue) self.assertEqual(len(true), len(unpackedTrue)) self.assertEqual(len(false), len(unpackedFalse)) for t in unpackedFalse: self.assertFalse(t) for t in unpackedTrue: self.assertTrue(t) packed = struct.pack(prefix+'?', 1) self.assertEqual(len(packed), struct.calcsize(prefix+'?')) if len(packed) != 1: self.assertFalse(prefix, msg='encoded bool is not one byte: %r' %packed) try: struct.pack(prefix + '?', ExplodingBool()) except OSError: pass else: self.fail("Expected OSError: struct.pack(%r, " "ExplodingBool())" % (prefix + '?')) for c in [b'\x01', b'\x7f', b'\xff', b'\x0f', b'\xf0']: self.assertTrue(struct.unpack('>?', c)[0]) def test_count_overflow(self): hugecount = '{}b'.format(sys.maxsize+1) self.assertRaises(struct.error, struct.calcsize, hugecount) hugecount2 = '{}b{}H'.format(sys.maxsize//2, sys.maxsize//2) self.assertRaises(struct.error, struct.calcsize, hugecount2) def test_trailing_counter(self): store = array.array('b', b' '*100) # format lists containing only count spec should result in an error self.assertRaises(struct.error, struct.pack, '12345') self.assertRaises(struct.error, struct.unpack, '12345', '') self.assertRaises(struct.error, struct.pack_into, '12345', store, 0) self.assertRaises(struct.error, struct.unpack_from, '12345', store, 0) # Format lists with trailing count spec should result in an error self.assertRaises(struct.error, struct.pack, 'c12345', 'x') self.assertRaises(struct.error, struct.unpack, 'c12345', 'x') self.assertRaises(struct.error, struct.pack_into, 'c12345', store, 0, 'x') self.assertRaises(struct.error, struct.unpack_from, 'c12345', store, 0) # Mixed format tests self.assertRaises(struct.error, struct.pack, '14s42', 'spam and eggs') self.assertRaises(struct.error, struct.unpack, '14s42', 'spam and eggs') self.assertRaises(struct.error, struct.pack_into, '14s42', store, 0, 'spam and eggs') self.assertRaises(struct.error, struct.unpack_from, '14s42', store, 0) def test_Struct_reinitialization(self): # Issue 9422: there was a memory leak when reinitializing a # Struct instance. This test can be used to detect the leak # when running with regrtest -L. s = struct.Struct('i') s.__init__('ii') def check_sizeof(self, format_str, number_of_codes): # The size of 'PyStructObject' totalsize = support.calcobjsize('2n3P') # The size taken up by the 'formatcode' dynamic array totalsize += struct.calcsize('P3n0P') * (number_of_codes + 1) support.check_sizeof(self, struct.Struct(format_str), totalsize) @support.cpython_only def test__sizeof__(self): for code in integer_codes: self.check_sizeof(code, 1) self.check_sizeof('BHILfdspP', 9) self.check_sizeof('B' * 1234, 1234) self.check_sizeof('fd', 2) self.check_sizeof('xxxxxxxxxxxxxx', 0) self.check_sizeof('100H', 1) self.check_sizeof('187s', 1) self.check_sizeof('20p', 1) self.check_sizeof('0s', 1) self.check_sizeof('0c', 0) class UnpackIteratorTest(unittest.TestCase): """ Tests for iterative unpacking (struct.Struct.iter_unpack). """ def test_construct(self): def _check_iterator(it): self.assertIsInstance(it, abc.Iterator) self.assertIsInstance(it, abc.Iterable) s = struct.Struct('>ibcp') it = s.iter_unpack(b"") _check_iterator(it) it = s.iter_unpack(b"1234567") _check_iterator(it) # Wrong bytes length with self.assertRaises(struct.error): s.iter_unpack(b"123456") with self.assertRaises(struct.error): s.iter_unpack(b"12345678") # Zero-length struct s = struct.Struct('>') with self.assertRaises(struct.error): s.iter_unpack(b"") with self.assertRaises(struct.error): s.iter_unpack(b"12") def test_iterate(self): s = struct.Struct('>IB') b = bytes(range(1, 16)) it = s.iter_unpack(b) self.assertEqual(next(it), (0x01020304, 5)) self.assertEqual(next(it), (0x06070809, 10)) self.assertEqual(next(it), (0x0b0c0d0e, 15)) self.assertRaises(StopIteration, next, it) self.assertRaises(StopIteration, next, it) def test_arbitrary_buffer(self): s = struct.Struct('>IB') b = bytes(range(1, 11)) it = s.iter_unpack(memoryview(b)) self.assertEqual(next(it), (0x01020304, 5)) self.assertEqual(next(it), (0x06070809, 10)) self.assertRaises(StopIteration, next, it) self.assertRaises(StopIteration, next, it) def test_length_hint(self): lh = operator.length_hint s = struct.Struct('>IB') b = bytes(range(1, 16)) it = s.iter_unpack(b) self.assertEqual(lh(it), 3) next(it) self.assertEqual(lh(it), 2) next(it) self.assertEqual(lh(it), 1) next(it) self.assertEqual(lh(it), 0) self.assertRaises(StopIteration, next, it) self.assertEqual(lh(it), 0) def test_module_func(self): # Sanity check for the global struct.iter_unpack() it = struct.iter_unpack('>IB', bytes(range(1, 11))) self.assertEqual(next(it), (0x01020304, 5)) self.assertEqual(next(it), (0x06070809, 10)) 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', 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', 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', 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', 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()