forked from YovM/Algorithms
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()
|