Hi! I am using the ghc compiler for my final project and i am having
some problems. I need some amount of serialization for my project so i
decided to use drift to generate binary instances. I downloaded a port
of the binary class for ghc but i am afraid it is outdated and probably
not working correctly. My first question would be if someone has a
working version of binary for ghc 5.02.2.
In the meantime i have a temporary version of binary but its
performance is not what i would like. Let me paste some of it
class Binary a where
put :: WCarrier -> a -> IO ()
get :: RCarrier -> IO a
data RCarrier = RCarrier {handle::Handle
,byte::IORef Integer
,remb::IORef Int
,temp::IORef Integer}
getBits :: RCarrier -> Int -> IO Integer
getBits c w = if w == 0 then do
x <- readIORef . temp $ c
writeIORef (temp c) 0
return x
else do
r <- readIORef . remb $ c
n <- readIORef . byte $ c
t <- readIORef . temp $ c
if w <= r then do
let n' = n `shiftL` w .&. 255
r' = r - w
t' = t `shiftL` w + n `shiftR` (8 - w)
writeIORef (remb c) $! r'
writeIORef (byte c) $! n'
writeIORef (temp c) 0
return t'
else do
let w' = w - r
t' = t `shiftL` r + n `shiftR` (8 - r)
b <- hGetChar . handle $ c
writeIORef (byte c) $! (toInteger (ord b))
writeIORef (remb c) 8
writeIORef (temp c) $! t'
getBits c w'
data WCarrier = WCarrier {whandle::Handle
,wbyte::IORef Integer
,wremb::IORef Int}
ones n = (bit n) - 1
putBits :: WCarrier -> Int -> Integer -> IO ()
putBits (WCarrier ch cb cr) w n = f w n
where f w n = if w == 0 then return ()
else do b <- readIORef cb
r <- readIORef cr
if w < r then do
let b' = b `shiftL` w + n
r' = r - w
writeIORef cb $! b'
writeIORef cr $! r'
else do
let n' = ones w' .&. n
b' = b `shiftL` r + (n `shiftR` w' .&. ones r)
w' = w - r
hPutChar ch $! (chr (fromInteger b'))
writeIORef cb 0
writeIORef cr 8
n' `seq` b' `seq` f w' n'
My second question is how to optimize this piece of code. I suppose
that the main performance bottleneck is the use of hPutChar. I did some
profiling but some guidance will be really helpful.
Regards,
Alexey
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