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bundled/Crypto/Internal/ByteArray.hs

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+-- |
+-- Module      : Crypto.Internal.ByteArray
+-- License     : BSD-style
+-- Maintainer  : Vincent Hanquez <vincent@snarc.org>
+-- Stability   : stable
+-- Portability : Good
+--
+-- Simple and efficient byte array types
+--
+{-# LANGUAGE BangPatterns #-}
+{-# OPTIONS_HADDOCK hide #-}
+module Crypto.Internal.ByteArray
+    ( module Data.ByteArray
+    , module Data.ByteArray.Mapping
+    , module Data.ByteArray.Encoding
+    , constAllZero
+    ) where
+
+import Data.ByteArray
+import Data.ByteArray.Mapping
+import Data.ByteArray.Encoding
+
+import Data.Bits ((.|.))
+import Data.Word (Word8)
+import Foreign.Ptr (Ptr)
+import Foreign.Storable (peekByteOff)
+
+import Crypto.Internal.Compat (unsafeDoIO)
+
+constAllZero :: ByteArrayAccess ba => ba -> Bool
+constAllZero b = unsafeDoIO $ withByteArray b $ \p -> loop p 0 0
+  where
+    loop :: Ptr b -> Int -> Word8 -> IO Bool
+    loop p i !acc
+        | i == len  = return $! acc == 0
+        | otherwise = do
+            e <- peekByteOff p i
+            loop p (i+1) (acc .|. e)
+    len = Data.ByteArray.length b