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{-# LANGUAGE DataKinds #-}
{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE KindSignatures #-}
{-# LANGUAGE MagicHash #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE TypeOperators #-}
module Data.Primitive.ByteArray.Util where
import GHC.TypeLits
import Control.Monad.Primitive
import Data.Primitive.Types
import Data.Primitive.ByteArray
newtype Offset (n :: Nat) = Offset Int
offset :: KnownNat n => Offset n
offset = let k = Offset $ fromIntegral $ natVal k in k
(+.) :: Offset j -> Offset k -> Offset (j + k)
Offset j +. Offset k = Offset (j + k)
type family SizeOf a :: Nat
class IsMultipleOf (n::Nat) (k::Nat)
instance n ~ (q * k) => IsMultipleOf n k
writeAtByte :: ( Prim a
, PrimMonad m
, IsMultipleOf n (SizeOf a)
) => MutableByteArray (PrimState m) -> Offset n -> a -> m ()
writeAtByte buf (Offset offset) a = writeByteArray buf (div offset $ (sizeOf a)) a
{-# INLINE writeAtByte #-}
readAtByte :: forall a m n.
( Prim a
, PrimMonad m
, IsMultipleOf n (SizeOf a)
) => MutableByteArray (PrimState m) -> Offset n -> m a
readAtByte buf (Offset offset) = readByteArray buf (div offset $ (sizeOf (undefined :: a)))
{-# INLINE readAtByte #-}
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