def test_middle_bits(self):
mid_4 = BitField(4, 7)
# A value that fits snugly in4 bits
self.assertEqual(mid_4.insert(13, 0), 13 << 4)
# A value that doesn't fit; some high bits lost
self.assertEqual(mid_4.insert(21, 0), 5 << 4)
# Extract unsigned
self.assertEqual(mid_4.extract(15 << 4), 15)
# Or convert negative numbers
self.assertEqual(mid_4.extract_signed(15 << 4), -1)
def test_low_order(self):
low_4 = BitField(0, 3)
# A value that fits snugly in the first 4 bits
self.assertEqual(low_4.insert(13, 0), 13)
# A value that doesn't fit; some high bits lost
self.assertEqual(low_4.insert(21, 0), 5)
# Extract unsigned
self.assertEqual(low_4.extract(15), 15)
# Or convert negative numbers
self.assertEqual(low_4.extract_signed(15), -1)
# Doesn't clobber other bits
higher = 15 << 4
self.assertEqual(low_4.insert(13, higher), 13 + higher)
# Extraction is masked
packed = low_4.insert(13, higher)
self.assertEqual(low_4.extract(packed), 13)
def test_insert_neg(self):
bitfield = BitField(3, 5)
packed = bitfield.insert(-1, 0)
self.assertEqual(packed, 0b000_111_000)
unpacked = bitfield.extract_signed(packed)
self.assertEqual(unpacked, -1)
def test_extract_pos(self):
bitfield = BitField(2, 4)
field_bits = 0b_101_011_10 # the 011 part is what we want to extract
self.assertEqual(bitfield.extract_signed(field_bits), 3)