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