module Octane.Type.CompressedWord
( CompressedWord(..)
, fromCompressedWord
) where
import Data.Aeson ((.=))
import Data.Function ((&))
import qualified Control.DeepSeq as DeepSeq
import qualified Data.Aeson as Aeson
import qualified Data.Binary.Bits as BinaryBit
import qualified Data.Binary.Bits.Get as BinaryBit
import qualified Data.Binary.Bits.Put as BinaryBit
import qualified Data.Bits as Bits
import qualified Data.Default.Class as Default
import qualified Data.OverloadedRecords.TH as OverloadedRecords
import qualified GHC.Generics as Generics
import qualified Octane.Type.Boolean as Boolean
data CompressedWord = CompressedWord
{ compressedWordLimit :: Word
, compressedWordValue :: Word
} deriving (Eq, Generics.Generic, Show)
$(OverloadedRecords.overloadedRecord Default.def ''CompressedWord)
instance BinaryBit.BinaryBit CompressedWord where
getBits n = do
let limit = fromIntegral n
value <- getStep limit (bitSize limit) 0 0
pure (CompressedWord limit value)
putBits _ compressedWord = do
let limit = fromIntegral (#limit compressedWord)
let value = fromIntegral (#value compressedWord)
let maxBits = bitSize limit
let upper = (2 ^ (maxBits 1)) 1
let lower = limit upper
let numBits = if lower > value || value > upper
then maxBits
else maxBits 1
BinaryBit.putWord64be numBits value
instance DeepSeq.NFData CompressedWord where
instance Aeson.ToJSON CompressedWord where
toJSON compressedWord = Aeson.object
[ "Limit" .= #limit compressedWord
, "Value" .= #value compressedWord
]
fromCompressedWord :: (Integral a) => CompressedWord -> a
fromCompressedWord compressedWord = compressedWord & #value & fromIntegral
bitSize :: (Integral a, Integral b) => a -> b
bitSize x = x & fromIntegral & logBase (2 :: Double) & ceiling
getStep :: Word -> Word -> Word -> Word -> BinaryBit.BitGet Word
getStep limit maxBits position value = do
let x = Bits.shiftL 1 (fromIntegral position)
if position < maxBits && value + x <= limit
then do
(bit :: Boolean.Boolean) <- BinaryBit.getBits 0
let newValue = if #unpack bit then value + x else value
getStep limit maxBits (position + 1) newValue
else pure value