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jackhftang/fletcher.nim

Created October 25, 2019 13:35
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fletcher
Raw
fletcher.nim
proc fletcher16*(arr: openArray[uint8]): uint16 =
var
c1: int = 0
c2: int = 0
for d in arr:
c1 += d.int
c2 += c1
result = (((c2 mod 255) shl 8) + (c1 mod 255)).uint16
Raw
fletcher_test.nim
import unittest
import fletcher
suite "fletcher":
test "fletcher16":
# https://en.wikipedia.org/wiki/Fletcher%27s_checksum#Test_vectors
check: fletcher([97.byte,98,99,100,101]) == 51440.uint16
check: fletcher([97.byte,98,99,100,101,102]) == 8279.uint16
check: fletcher([97.byte,98,99,100,101,102,103,104]) == 1575.uint16
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