def test_case_one(self):
x = 0b111000111
bitfield_low = BitField(0, 3)
bitfield_mid = BitField(4, 5)
bitfield_low.insert(x, 1)
self.assertEqual(bitfield_low.extract(x), 0b111) # 7
self.assertEqual(bitfield_mid.extract(x),
0) # middle should still == 0 after insertion
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_invert(self):
lowpart = BitField(0, 3)
midpart = BitField(4, 6)
highpart = BitField(7, 9)
for v in range(8):
packed = 0
packed = lowpart.insert(v, packed)
packed = midpart.insert(v, packed)
packed = highpart.insert(v, packed)
self.assertEqual(lowpart.extract(packed), v)
self.assertEqual(midpart.extract(packed), v)
self.assertEqual(highpart.extract(packed), v)
def test_replace(self):
"""Test replacing an existing field of bits."""
packed = 0x0f0 # 11110000 --- we want to clobber those ones
newval = 0x005 # 00000101 --- and replaced them with 0101
field = BitField(4, 7) # ____xxxx --- in positions 4..7
packed = field.insert(newval, packed)
self.assertEqual(packed, 0x50) # 01010000 --- some zeros replaced 1s
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_width(self):
"""Make sure we are masking out any bits that don't fit in
the field.
"""
second_nibble = BitField(4, 7)
value = 0xff # A full byte; two nibbles
packed = second_nibble.insert(value, 0)
self.assertEqual(packed, 0xf0)
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_insert_low(self):
"""Inserting a few bits in the lowest part of the word. """
low_bits = BitField(0, 4)
self.assertEqual(low_bits.insert(15, 0), 15) # All the bits to 1
# Slip it in without disturbing higher bits
self.assertEqual(low_bits.insert(0b1010, 0b1111_0000), 0b1111_1010)
def test_insert_case(self):
insert_bits = BitField(0,5)
self.assertEqual(insert_bits.insert(0b00000, 31), 0b11111)