--
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-- Copyright (c) 2007-2010, Johan Tibell
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module Network.WireGuard.Foreign.In6Addr
 ( In6Addr(..)
 ) where

import Foreign
import Network.Socket.Internal

#include "uapi.h"

-- Extracted from network:Network/Socket/Types.hsc, with some modification.

-- The peek32 and poke32 functions work around the fact that the RFCs
-- don't require 32-bit-wide address fields to be present.  We can
-- only portably rely on an 8-bit field, s6_addr.

s6_addr_offset :: Int
s6_addr_offset = (#offset struct in6_addr, s6_addr)

peek32 :: Ptr a -> Int -> IO Word32
peek32 p i0 = do
    let i' = i0 * 4
        peekByte n = peekByteOff p (s6_addr_offset + i' + n) :: IO Word8
        a `sl` i = fromIntegral a `shiftL` i
    a0 <- peekByte 0
    a1 <- peekByte 1
    a2 <- peekByte 2
    a3 <- peekByte 3
    return ((a0 `sl` 24) .|. (a1 `sl` 16) .|. (a2 `sl` 8) .|. (a3 `sl` 0))

poke32 :: Ptr a -> Int -> Word32 -> IO ()
poke32 p i0 a = do
    let i' = i0 * 4
        pokeByte n = pokeByteOff p (s6_addr_offset + i' + n)
        x `sr` i = fromIntegral (x `shiftR` i) :: Word8
    pokeByte 0 (a `sr` 24)
    pokeByte 1 (a `sr` 16)
    pokeByte 2 (a `sr`  8)
    pokeByte 3 (a `sr`  0)

-- | Private newtype proxy for the Storable instance. To avoid orphan instances.
newtype In6Addr = In6Addr { fromIn6Addr :: HostAddress6 }

instance Storable In6Addr where
    sizeOf _    = #const sizeof(struct in6_addr)
    alignment _ = #alignment struct in6_addr

    peek p = do
        a <- peek32 p 0
        b <- peek32 p 1
        c <- peek32 p 2
        d <- peek32 p 3
        return $ In6Addr (a, b, c, d)

    poke p (In6Addr (a, b, c, d)) = do
        poke32 p 0 a
        poke32 p 1 b
        poke32 p 2 c
        poke32 p 3 d