{-# LANGUAGE CPP, BangPatterns, MagicHash, CApiFFI, UnliftedFFITypes #-}
{-# LANGUAGE Trustworthy #-}
-- | A module containing low-level hash primitives.
module Data.Hashable.LowLevel (
    Salt,
    defaultSalt,
    hashInt,
    hashInt64,
    hashWord64,
    hashPtrWithSalt,
    hashByteArrayWithSalt,
) where

#include "MachDeps.h"

import Data.Array.Byte (ByteArray (..))
import Foreign.Ptr (Ptr, castPtr)
import GHC.Base (ByteArray#)

#ifdef HASHABLE_RANDOM_SEED
import System.IO.Unsafe (unsafePerformIO)
#endif

import Data.Hashable.Imports
import Data.Hashable.Mix
import Data.Hashable.XXH3

-------------------------------------------------------------------------------
-- Initial seed
-------------------------------------------------------------------------------

#ifdef HASHABLE_RANDOM_SEED
initialSeed :: Word64
initialSeed = unsafePerformIO initialSeedC
{-# NOINLINE initialSeed #-}

foreign import capi "HsHashable.h hs_hashable_init" initialSeedC :: IO Word64
#endif

-- | A default salt used in the implementation of 'hash'.
defaultSalt :: Salt
#ifdef HASHABLE_RANDOM_SEED
defaultSalt = hashInt defaultSalt' (fromIntegral initialSeed)
#else
defaultSalt :: Salt
defaultSalt = Salt
defaultSalt'
#endif
{-# INLINE defaultSalt #-}

defaultSalt' :: Salt
#if WORD_SIZE_IN_BITS == 64
defaultSalt' :: Salt
defaultSalt' = -Salt
3750763034362895579 -- 14695981039346656037 :: Int64
#else
defaultSalt' = -2128831035 -- 2166136261 :: Int32
#endif
{-# INLINE defaultSalt' #-}

-------------------------------------------------------------------------------
-- Hash primitives
-------------------------------------------------------------------------------

-- | Hash 'Int'. First argument is a salt, second argument is an 'Int'.
-- The result is new salt / hash value.
hashInt :: Salt -> Int -> Salt
hashInt :: Salt -> Salt -> Salt
hashInt !Salt
s !Salt
x = Word -> Salt
forall a b. (Integral a, Num b) => a -> b
fromIntegral (Word -> Word -> Word
mixHash (Salt -> Word
forall a b. (Integral a, Num b) => a -> b
fromIntegral Salt
s) (Salt -> Word
forall a b. (Integral a, Num b) => a -> b
fromIntegral Salt
x))

hashInt64  :: Salt -> Int64 -> Salt
hashWord64 :: Salt -> Word64 -> Salt

#if WORD_SIZE_IN_BITS == 64
hashInt64 :: Salt -> Int64 -> Salt
hashInt64  !Salt
s !Int64
x = Salt -> Salt -> Salt
hashInt Salt
s (Int64 -> Salt
forall a b. (Integral a, Num b) => a -> b
fromIntegral Int64
x)
hashWord64 :: Salt -> Word64 -> Salt
hashWord64 !Salt
s !Word64
x = Salt -> Salt -> Salt
hashInt Salt
s (Word64 -> Salt
forall a b. (Integral a, Num b) => a -> b
fromIntegral Word64
x)
#else
hashInt64  !s !x = hashInt (hashInt s (fromIntegral x)) (fromIntegral (x `unsafeShiftR` 32))
hashWord64 !s !x = hashInt (hashInt s (fromIntegral x)) (fromIntegral (x `unsafeShiftR` 32))
#endif

-- | Compute a hash value for the content of this pointer, using an
-- initial salt.
--
-- This function can for example be used to hash non-contiguous
-- segments of memory as if they were one contiguous segment, by using
-- the output of one hash as the salt for the next.
hashPtrWithSalt :: Ptr a   -- ^ pointer to the data to hash
                -> Int     -- ^ length, in bytes
                -> Salt    -- ^ salt
                -> IO Salt -- ^ hash value
hashPtrWithSalt :: forall a. Ptr a -> Salt -> Salt -> IO Salt
hashPtrWithSalt Ptr a
ptr Salt
len Salt
salt =
    Word64 -> Salt
forall a b. (Integral a, Num b) => a -> b
fromIntegral (Word64 -> Salt) -> IO Word64 -> IO Salt
forall a b. (a -> b) -> IO a -> IO b
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
`fmap` Ptr Word8 -> Salt -> Word64 -> IO Word64
xxh3_64bit_withSeed_ptr (Ptr a -> Ptr Word8
forall a b. Ptr a -> Ptr b
castPtr Ptr a
ptr) Salt
len (Salt -> Word64
forall a b. (Integral a, Num b) => a -> b
fromIntegral Salt
salt)

-- | Compute a hash value for the content of this 'ByteArray#', using
-- an initial salt.
--
-- This function can for example be used to hash non-contiguous
-- segments of memory as if they were one contiguous segment, by using
-- the output of one hash as the salt for the next.
hashByteArrayWithSalt
    :: ByteArray#  -- ^ data to hash
    -> Int         -- ^ offset, in bytes
    -> Int         -- ^ length, in bytes
    -> Salt        -- ^ salt
    -> Salt        -- ^ hash value
hashByteArrayWithSalt :: ByteArray# -> Salt -> Salt -> Salt -> Salt
hashByteArrayWithSalt ByteArray#
ba !Salt
off !Salt
len !Salt
salt =
    Word64 -> Salt
forall a b. (Integral a, Num b) => a -> b
fromIntegral (ByteArray -> Salt -> Salt -> Word64 -> Word64
xxh3_64bit_withSeed_ba (ByteArray# -> ByteArray
ByteArray ByteArray#
ba) Salt
off Salt
len (Salt -> Word64
forall a b. (Integral a, Num b) => a -> b
fromIntegral Salt
salt))