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{-# LANGUAGE BangPatterns #-}
{-# LANGUAGE MagicHash #-}
{-# LANGUAGE UnboxedTuples #-}
import GHC.Exts
import GHC.Word (Word8(..))
main :: IO ()
main = do
putStr "A: "
print $
I# (cstringLength# "hello_world"#)
==
naiveStrlen "hello_world"# 0
putStr "B: "
print $
I# (cstringLength# "aaaaaaaaaaaaa\x00b"#)
==
naiveStrlen "aaaaaaaaaaaaa\x00b"# 0
putStr "C: "
print $
I# (cstringLength# "cccccccccccccccccc\x00b"#)
==
naiveStrlen "cccccccccccccccccc\x00b"# 0
putStr "D: "
print $
I# (cstringLength# "araña\NULb"#)
==
naiveStrlen "araña\NULb"# 0
naiveStrlen :: Addr# -> Int -> Int
naiveStrlen addr !n =
-- TODO change back to pattern matching once we have negative literals.
if isTrue# (res `eqWord8#` zero)
then n
else naiveStrlen (plusAddr# addr 1#) (n + 1)
where
res = indexWord8OffAddr# addr 0#
W8# zero = 0
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