Initial commit

bundled/Crypto/Internal/Compat.hs

@@ -0,0 +1,48 @@
+-- |
+-- Module      : Crypto.Internal.Compat
+-- License     : BSD-style
+-- Maintainer  : Vincent Hanquez <vincent@snarc.org>
+-- Stability   : stable
+-- Portability : Good
+--
+-- This module tries to keep all the difference between versions of base
+-- or other needed packages, so that modules don't need to use CPP.
+--
+{-# LANGUAGE CPP #-}
+module Crypto.Internal.Compat
+    ( unsafeDoIO
+    , popCount
+    , byteSwap64
+    ) where
+
+import System.IO.Unsafe
+import Data.Word
+import Data.Bits
+
+-- | Perform io for hashes that do allocation and FFI.
+-- 'unsafeDupablePerformIO' is used when possible as the
+-- computation is pure and the output is directly linked
+-- to the input. We also do not modify anything after it has
+-- been returned to the user.
+unsafeDoIO :: IO a -> a
+#if __GLASGOW_HASKELL__ > 704
+unsafeDoIO = unsafeDupablePerformIO
+#else
+unsafeDoIO = unsafePerformIO
+#endif
+
+#if !(MIN_VERSION_base(4,5,0))
+popCount :: Word64 -> Int
+popCount n = loop 0 n
+  where loop c 0 = c
+        loop c i = loop (c + if testBit c 0 then 1 else 0) (i `shiftR` 1)
+#endif
+
+#if !(MIN_VERSION_base(4,7,0))
+byteSwap64 :: Word64 -> Word64
+byteSwap64 w =
+        (w `shiftR` 56)                  .|. (w `shiftL` 56)
+    .|. ((w `shiftR` 40) .&. 0xff00)     .|. ((w .&. 0xff00) `shiftL` 40)
+    .|. ((w `shiftR` 24) .&. 0xff0000)   .|. ((w .&. 0xff0000) `shiftL` 24)
+    .|. ((w `shiftR` 8)  .&. 0xff000000) .|. ((w .&. 0xff000000) `shiftL` 8)
+#endif