mirror of
https://github.com/TheAlgorithms/Python.git
synced 2024-11-30 16:31:08 +00:00
37 lines
1.0 KiB
Python
37 lines
1.0 KiB
Python
|
"""
|
|||
|
|
The Fletcher checksum is an algorithm for computing a position-dependent
|
|||
|
|
checksum devised by John G. Fletcher (1934–2012) at Lawrence Livermore Labs
|
|||
|
|
in the late 1970s.[1] The objective of the Fletcher checksum was to
|
|||
|
|
provide error-detection properties approaching those of a cyclic
|
|||
|
|
redundancy check but with the lower computational effort associated
|
|||
|
|
with summation techniques.
|
|||
|
|
|
|||
|
|
Source: https://en.wikipedia.org/wiki/Fletcher%27s_checksum
|
|||
|
|
"""
|
|||
|
|
|
|||
|
|
|
|||
|
|
def fletcher16(text: str) -> int:
|
|||
|
|
"""
|
|||
|
|
Loop through every character in the data and add to two sums.
|
|||
|
|
|
|||
|
|
>>> fletcher16('hello world')
|
|||
|
|
6752
|
|||
|
|
>>> fletcher16('onethousandfourhundredthirtyfour')
|
|||
|
|
28347
|
|||
|
|
>>> fletcher16('The quick brown fox jumps over the lazy dog.')
|
|||
|
|
5655
|
|||
|
|
"""
|
|||
|
|
data = bytes(text, "ascii")
|
|||
|
|
sum1 = 0
|
|||
|
|
sum2 = 0
|
|||
|
|
for character in data:
|
|||
|
|
sum1 = (sum1 + character) % 255
|
|||
|
|
sum2 = (sum1 + sum2) % 255
|
|||
|
|
return (sum2 << 8) | sum1
|
|||
|
|
|
|||
|
|
|
|||
|
|
if __name__ == "__main__":
|
|||
|
|
import doctest
|
|||
|
|
|
|||
|
|
doctest.testmod()
|