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bundled/Data/ByteArray/MemView.hs

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+-- |
+-- Module      : Data.ByteArray.MemView
+-- License     : BSD-style
+-- Maintainer  : Vincent Hanquez <vincent@snarc.org>
+-- Stability   : stable
+-- Portability : Good
+--
+module Data.ByteArray.MemView
+    ( MemView(..)
+    , memViewPlus
+    ) where
+
+import           Foreign.Ptr
+import           Data.ByteArray.Types
+import           Data.Memory.Internal.Imports
+
+-- | A simple abstraction to a piece of memory.
+--
+-- Do beware that garbage collection related to
+-- piece of memory could be triggered before this
+-- is used.
+--
+-- Only use with the appropriate handler has been
+-- used (e.g. withForeignPtr on ForeignPtr)
+--
+data MemView = MemView {-# UNPACK #-} !(Ptr Word8) {-# UNPACK #-} !Int
+    deriving (Show,Eq)
+
+instance ByteArrayAccess MemView where
+    length (MemView _ l) = l
+    withByteArray (MemView p _) f = f (castPtr p)
+
+-- | Increase the memory view while reducing the size of the window
+--
+-- this is useful as an abstraction to represent the current offset
+-- in a buffer, and the remaining bytes left.
+memViewPlus :: MemView -> Int -> MemView
+memViewPlus (MemView p len) n = MemView (p `plusPtr` n) (len - n)