{-# language CPP #-}
module Graphics.Vulkan.Zero  (Zero(..)) where

import GHC.Ptr (nullFunPtr)
import Foreign.Ptr (nullPtr)
import qualified Data.Vector.Storable.Sized (replicate)
import Foreign.C.Types (CChar)
import Foreign.C.Types (CFloat)
import Foreign.C.Types (CInt)
import Foreign.C.Types (CSize)
import Foreign.Storable (Storable)
import Data.Int (Int16)
import Data.Int (Int32)
import Data.Int (Int64)
import Data.Int (Int8)
import Foreign.Ptr (FunPtr)
import Foreign.Ptr (Ptr)
import GHC.TypeNats (KnownNat)
import Data.Word (Word16)
import Data.Word (Word32)
import Data.Word (Word64)
import Data.Word (Word8)
import qualified Data.Vector.Storable.Sized (Vector)

-- | A class for initializing things with all zero data
--
-- Any instance should satisfy the following law:
--
-- @ new zero = calloc @ or @ with zero = withZeroCStruct @
--
-- i.e. Marshaling @zero@ to memory yeilds only zero-valued bytes, except
-- for structs which require a "type" tag
--
class Zero a where
  zero :: a

instance (KnownNat n, Storable a, Zero a) => Zero (Data.Vector.Storable.Sized.Vector n a) where
  zero = Data.Vector.Storable.Sized.replicate zero

instance Zero Bool where
  zero = False

instance Zero (FunPtr a) where
  zero = nullFunPtr

instance Zero (Ptr a) where
  zero = nullPtr

instance Zero Int8 where
  zero = 0

instance Zero Int16 where
  zero = 0

instance Zero Int32 where
  zero = 0

instance Zero Int64 where
  zero = 0

instance Zero Word8 where
  zero = 0

instance Zero Word16 where
  zero = 0

instance Zero Word32 where
  zero = 0

instance Zero Word64 where
  zero = 0

instance Zero Float where
  zero = 0

instance Zero CFloat where
  zero = 0

instance Zero CChar where
  zero = 0

instance Zero CSize where
  zero = 0

instance Zero CInt where
  zero = 0