{-# LANGUAGE MagicHash     #-}
{-# LANGUAGE UnboxedTuples #-}
module Network.DNS.Internal.Prim
  ( BA(..)
  , MBA(..)
  , unsafeFreezeByteArray
  , newByteArray
  , writeWord8Array
  , writeWord8Array0
  )
where

import GHC.Exts (ByteArray#, Int#, MutableByteArray#, newByteArray#,
                 unsafeFreezeByteArray#, writeWord8Array#, (+#))
import GHC.Int (Int(..))
import GHC.ST (ST(..))
import GHC.Word (Word8(..))

data BA = BA# ByteArray#
data MBA s = MBA# (MutableByteArray# s)

unsafeFreezeByteArray :: MBA s -> ST s (BA)
unsafeFreezeByteArray (MBA# mab) = ST $ \s1 -> case unsafeFreezeByteArray# mab s1 of
  (# s2, ba #) -> (# s2, BA# ba #)

newByteArray :: Int -> ST s (MBA s)
newByteArray (I# l) = ST $ \s1 -> case newByteArray# l s1 of
  (# s2, mba #) -> (# s2, MBA# mba #)

writeWord8Array :: MBA s -> Int# -> Word8 -> ST s ()
writeWord8Array (MBA# mab) i (W8# w) = ST $ \s -> (# writeWord8Array# mab i w s, () #)

-- | Variant that appends every byte with a 0. This is for embedding ASCII into UTF16 code units.
writeWord8Array0 :: MBA s -> Int# -> Word8 -> ST s ()
writeWord8Array0 mba off w = writeWord8Array mba off w >> writeWord8Array mba (off +# 1#) 0