ptrdiff (empty) → 0

raw patch · 5 files changed

+386/−0 lines, 5 filesdep +base

Dependencies added: base

Files

CHANGELOG.md +3/−0
LICENSE.md +230/−0
README.md +16/−0
ptrdiff.cabal +32/−0
src/Foreign/Ptr/Diff.hs +105/−0

+ CHANGELOG.md view

@@ -0,0 +1,3 @@+# 0++* Split off from `codex`

+ LICENSE.md view

@@ -0,0 +1,230 @@+# License++Licensed under either of+ * Apache License, Version 2.0 (http://www.apache.org/licenses/LICENSE-2.0)+ * BSD 2-Clause license (https://opensource.org/licenses/BSD-2-Clause)+at your option.++## BSD 2-Clause License++- Copyright 2019 Edward Kmett and Sean Chalmers++All rights reserved.++Redistribution and use in source and binary forms, with or without+modification, are permitted provided that the following conditions+are met:++1. Redistributions of source code must retain the above copyright+   notice, this list of conditions and the following disclaimer.++2. 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+ README.md view

@@ -0,0 +1,16 @@+ptrdiff+=======++[![Hackage](https://img.shields.io/hackage/v/ptrdiff.svg)](https://hackage.haskell.org/package/ptrdiff)++Type "safe" pointer differences. Mostly makes it easier to get things right when working with `plusPtr`.++Contact Information+-------------------++Contributions and bug reports are welcome!++Please feel free to contact me through github or on the #haskell IRC channel on irc.freenode.net.++-Edward Kmett+

+ ptrdiff.cabal view

@@ -0,0 +1,32 @@+cabal-version: 2.2+name: ptrdiff+version: 0+synopsis: Type-checked pointer diffs+homepage: https://github.com/ekmett/codex/tree/master/ptrdiff#readme+license: BSD-2-Clause OR Apache-2.0+license-file: LICENSE.md+author: Edward Kmett+maintainer: Edward Kmett <ekmett@gmail.com>+copyright: Copyright (c) 2019 Edward Kmett+stability: experimental+category: FFI+build-type: Simple+description: Type-checked pointer diffs.+extra-doc-files:+  README.md,+  CHANGELOG.md++source-repository head+  type: git+  location: https://github.com/ekmett/codex+  subdir: ptrdiff++library+  hs-source-dirs: src+  default-language: Haskell2010+  ghc-options:+    -Wall -Wincomplete-uni-patterns -Wincomplete-record-updates+    -Wredundant-constraints -Widentities -Wmissing-export-lists+  build-depends: base >= 4.11 && < 5+  exposed-modules:+    Foreign.Ptr.Diff

+ src/Foreign/Ptr/Diff.hs view

@@ -0,0 +1,105 @@+{-# language ScopedTypeVariables #-}+{-# language TypeApplications #-}+{-# language DeriveGeneric #-}+{-# language DeriveDataTypeable #-}+-- |+-- Copyright :  (c) 2019-2021 Edward Kmett+-- License   :  BSD-2-Clause OR Apache-2.0+-- Maintainer:  Edward Kmett <ekmett@gmail.com>+-- Stability :  experimental+-- Portability: non-portable+--+module Foreign.Ptr.Diff+( Diff(..)+, inv+, next, prev+, (.*)+, advance+, DiffTorsor(..)+, peekDiffOff+, pokeDiffOff+) where++import Control.Category+import Control.Monad.IO.Class+import Data.Coerce+import Data.Data (Data)+import Foreign.ForeignPtr+import Foreign.ForeignPtr.Unsafe+import Foreign.Ptr+import Foreign.Storable+import GHC.Generics+import Prelude hiding (id,(.))++-- | So long as 'minusPtr' returns an 'Int', we're stuck with size of 'Int' = size of 'ptrdiff_t'+newtype Diff a b = Diff { getDiff :: Int } +  deriving (Eq,Ord,Show,Read,Data,Generic)++instance Category Diff where+  id = Diff 0+  {-# inline id #-}+  Diff a . Diff b = Diff (a + b)+  {-# inline (.) #-}++-- | 'Diff' is a groupoid, so @Diff a a@ is a group, and as such it forms a module over the integers+(.*) :: Int -> Diff a a -> Diff a a+n .* Diff a = Diff (n*a)+{-# inline (.*) #-}++infixr 6 .*++-- | Invert a pointer 'Diff', e.g. convert a pointer to a field member to one that computes the location+-- of the parent, or one that computes the offset of the next item into one that computes the offset of+-- the previous element.+inv :: Diff a b -> Diff b a+inv (Diff a) = Diff (negate a)+{-# inline inv #-}++-- | Calculate the position of the next elment of a given type when they are packed in densely.+next :: forall a. Storable a => Diff a a+next = Diff (sizeOf @a undefined)+{-# inline next #-}++-- | Calculate the position of the previous element of a given type when they are packed in densely.+prev :: Storable a => Diff a a+prev = inv next+{-# inline prev #-}++-- | Advance @n@ (possibly negative) items in a dense packing.+advance :: Storable a => Int -> Diff a a+advance n = n .* next+{-# inline advance #-}++class DiffTorsor t where+  act :: Diff a b -> t a -> t b+  diff :: t b -> t a -> Diff a b++-- 'Ptr' is a torsor w/ structure category 'Diff'+instance DiffTorsor Ptr where+  act = coerce (flip plusPtr)+  diff = coerce minusPtr+  {-# inline act #-}+  {-# inline diff #-}++instance DiffTorsor FunPtr where+  act d p = castPtrToFunPtr $ act d (castFunPtrToPtr p)+  diff p q = diff (castFunPtrToPtr p) (castFunPtrToPtr q)+  {-# inline act #-}+  {-# inline diff #-}++-- | due to finalizers this doesn't _quite_ satisfy ForeignPtr a * Diff a b <-> ForeignPtr a * ForeignPtr b+instance DiffTorsor ForeignPtr where+  act = coerce (flip plusForeignPtr)+  diff p q = diff (unsafeForeignPtrToPtr p) (unsafeForeignPtrToPtr q)+  {-# inline act #-}+  {-# inline diff #-}++-- | 'peek' using a 'Diff' between pointers to calculate the offset.+peekDiffOff :: (MonadIO m, Storable b) => Ptr a -> Diff a b -> m b+peekDiffOff p (Diff d) = liftIO $ peekByteOff p d+{-# inline peekDiffOff #-}++-- | 'poke' using a 'Diff' between pointers to calculate the offset.+pokeDiffOff :: (MonadIO m, Storable b) => Ptr a -> Diff a b -> b -> m ()+pokeDiffOff p (Diff d) a = liftIO $ pokeByteOff p d a+{-# inline pokeDiffOff #-}