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Ackermann is now encapsulated in a generator.

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Cédric Bonhomme 2019-06-01 00:58:00 +02:00
parent 1704aec690
commit 5694e5c806
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2 changed files with 21 additions and 2 deletions
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11
stegano/lsbset/generators.py
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@ -118,14 +118,14 @@ def ackermann_naive(m: int, n: int) -> int:
return ackermann(m - 1, ackermann(m, n - 1))
def ackermann(m: int, n: int) -> int:
def ackermann_fast(m: int, n: int) -> int:
"""Ackermann number.
"""
while m >= 4:
if n == 0:
n = 1
else:
n = ackermann(m, n - 1)
n = ackermann_fast(m, n - 1)
m -= 1
if m == 3:
return (1 << n + 3) - 3
@ -136,6 +136,13 @@ def ackermann(m: int, n: int) -> int:
else:
return n + 1
def ackermann(m: int) -> Iterator[int]:
"""Ackermann written as a generator.
"""
n = 0
while True:
yield ackermann_fast(m, n)
n += 1
def fibonacci() -> Iterator[int]:
"""Generate the sequence of Fibonacci.

12
tests/test_lsbset.py
View file

@ -54,6 +54,18 @@ class TestLSBSet(unittest.TestCase):
generators.eratosthenes())
self.assertEqual(message, clear_message)
def test_hide_and_reveal_with_ackermann(self):
messages_to_hide = ["foo"]
for message in messages_to_hide:
secret = lsbset.hide("./tests/sample-files/Lenna.png", message,
generators.ackermann(m=3))
secret.save("./image.png")
clear_message = lsbset.reveal("./image.png",
generators.ackermann(m=3))
self.assertEqual(message, clear_message)
def test_hide_and_reveal_with_shift(self):
messages_to_hide = ["a", "foo", "Hello World!", ":Python:"]