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+Creative Commons Legal Code
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diff --git a/CHANGELOG.md b/CHANGELOG.md
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--- /dev/null
+++ b/CHANGELOG.md
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+# Revision history for primitive-primvar
+
+## 0.0.0.0 -- 2022-09-15
+
+* First version. Released on an unsuspecting world.
diff --git a/README.md b/README.md
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--- /dev/null
+++ b/README.md
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+# `primitive-primvar`
+
+Version 0.0.0.0
+
+## Description
+
+This package provides the type `PrimVar`, which is internally a
+`PrimArray` of one element, but with a convenient `MutVar`-like API.
+
+This project follows the [Haskell Package Versioning Policy][PVP].
+
+[PVP]: https://pvp.haskell.org/
+
+## Copyright
+
+Each contributor waives their Copyright and Related Rights to
+this work according to [CC0-1.0].
+
+[CC0-1.0]: https://creativecommons.org/publicdomain/zero/1.0/
+
+## Patent
+
+Each contributor licenses you to do everything with this work that
+would otherwise infringe any patent claims they can license or become
+able to license.
diff --git a/primitive-primvar.cabal b/primitive-primvar.cabal
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--- /dev/null
+++ b/primitive-primvar.cabal
@@ -0,0 +1,46 @@
+cabal-version:      2.4
+name:               primitive-primvar
+version:            0.0.0.0
+license:            CC0-1.0
+license-file:       CC0-1.0.txt
+author:             Russell Hernandez Ruiz
+maintainer:         qrpnxz@hyperlife.xyz
+stability:          stable
+homepage:           https://sr.ht/~qrpnxz/primitive-primvar/
+bug-reports:        https://todo.sr.ht/~qrpnxz/primitive-primvar
+synopsis:           Unboxed variables for `Prim` values.
+description:
+  This package provides the type `PrimVar`, which is internally a
+  `PrimArray` of one element, but with a convenient `MutVar`-like API.
+category:           primitive
+extra-source-files: README.md
+extra-source-files: CHANGELOG.md
+
+source-repository head
+  type:     git
+  location: https://git.sr.ht/~qrpnxz/primitive-primvar
+
+source-repository this
+  type:     git
+  location: https://git.sr.ht/~qrpnxz/primitive-primvar
+  tag:      0.0.0.0
+
+library
+  hs-source-dirs:   src
+  exposed-modules:
+      Data.Primitive.PrimVar
+  build-depends:
+      base >=4.13 && <4.18
+    , primitive >=0.7.1 && <0.8
+  default-language: Haskell2010
+  ghc-options:
+    -Wall
+    -Wcompat
+    -Widentities
+    -Wincomplete-record-updates
+    -Wincomplete-uni-patterns
+    -Wpartial-fields
+    -Wredundant-constraints
+  ghc-options:
+    -Wno-redundant-constraints
+    -Wno-unticked-promoted-constructors
diff --git a/src/Data/Primitive/PrimVar.hs b/src/Data/Primitive/PrimVar.hs
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--- /dev/null
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+-- SPDX-License-Identifier: CC0-1.0
+{-
+Each contributor licenses you to do everything with this work that
+would otherwise infringe any patent claims they can license or become
+able to license.
+-}
+{-|
+`PrimVar` is internally a `PrimArray` of one element,
+but with a convenient `MutVar`-like API.
+-}
+module Data.Primitive.PrimVar
+  ( -- * Types
+    PrimVar(..)
+    -- * Allocation
+  , newPrimVar
+  , newPinnedPrimVar
+  , newAlignedPinnedPrimVar
+    -- * Access
+  , readPrimVar
+  , writePrimVar
+  , modifyPrimVar
+    -- * Information
+  , samePrimVar
+  , primVarContents
+  , isPrimVarPinned
+  ) where
+
+import Data.Functor ( ($>) )
+import Foreign (Ptr)
+
+import Control.Monad.Primitive ( PrimMonad(PrimState) )
+import Data.Primitive
+  ( MutablePrimArray
+  , Prim
+  , newPrimArray
+  , newPinnedPrimArray
+  , newAlignedPinnedPrimArray
+  , readPrimArray
+  , writePrimArray
+  , sameMutablePrimArray
+  , mutablePrimArrayContents
+  , isMutablePrimArrayPinned
+  )
+
+newtype PrimVar s a = PrimVar (MutablePrimArray s a)
+
+newPrimVar
+  :: (Prim a, PrimMonad m)
+  => a -> m (PrimVar (PrimState m) a)
+-- ^ Create a new `PrimVar` with the specified initial value.
+newPrimVar a =
+  newPrimArray 1 >>= \arr ->
+    writePrimArray arr 0 a $> PrimVar arr
+
+newPinnedPrimVar
+  :: (Prim a, PrimMonad m)
+  => a -> m (PrimVar (PrimState m) a)
+-- ^ Create a new /pinned/ `PrimVar` with the specified initial value.
+-- The garbage collector is guaranteed not to move it.
+newPinnedPrimVar a =
+  newPinnedPrimArray 1 >>= \arr ->
+    writePrimArray arr 0 a $> PrimVar arr
+
+newAlignedPinnedPrimVar
+  :: (Prim a, PrimMonad m)
+  => a -> m (PrimVar (PrimState m) a)
+-- ^ Create a new /pinned/ `PrimVar` with the specified initial value
+-- and with the alignment given by its Prim instance.
+-- The garbage collector is guaranteed not to move it.
+newAlignedPinnedPrimVar a =
+  newAlignedPinnedPrimArray 1 >>= \arr ->
+    writePrimArray arr 0 a $> PrimVar arr
+
+readPrimVar
+  :: (Prim a, PrimMonad m)
+  => PrimVar (PrimState m) a -> m a
+-- ^ Read the value of a `PrimVar`.
+readPrimVar (PrimVar v) = readPrimArray v 0
+
+writePrimVar
+  :: (Prim a, PrimMonad m)
+  => PrimVar (PrimState m) a -> a -> m ()
+-- ^ Write a new value into a `PrimVar`.
+writePrimVar (PrimVar v) = writePrimArray v 0
+
+modifyPrimVar
+  :: (Prim a, PrimMonad m)
+  => PrimVar (PrimState m) a -> (a -> a) -> m ()
+-- ^ Mutate the contents of a `PrimVar`.
+modifyPrimVar v f =
+  readPrimVar v >>= \a ->
+    writePrimVar v (f a)
+
+samePrimVar :: PrimVar s a -> PrimVar s a -> Bool
+-- ^ Check if two `PrimVar`s refer to the same memory block.
+samePrimVar (PrimVar v0) (PrimVar v1) =
+  sameMutablePrimArray v0 v1
+
+primVarContents :: PrimVar s a -> Ptr a
+-- ^ Yield a pointer to a `PrimVar`'s data.
+-- This operation is only safe on pinned `PrimVar`s
+-- allocated by `newPinnedPrimVar` or `newAlignedPinnedPrimVar`.
+primVarContents (PrimVar v) =
+  mutablePrimArrayContents v
+
+isPrimVarPinned :: PrimVar s a -> Bool
+-- ^ Check whether or not a `PrimVar` is pinned.
+isPrimVarPinned (PrimVar v) =
+  isMutablePrimArrayPinned v