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bundled/Basement/Runtime.hs

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+{-# LANGUAGE BangPatterns #-}
+{-# LANGUAGE DeriveDataTypeable #-}
+{-# LANGUAGE TypeFamilies #-}
+{-# LANGUAGE RebindableSyntax #-}
+{-# LANGUAGE NoImplicitPrelude #-}
+-- |
+-- Module      : Basement.Runtime
+-- License     : BSD-style
+-- Maintainer  : foundation
+--
+-- Global configuration environment
+module Basement.Runtime
+    where
+
+import           Basement.Compat.Base
+import           Basement.Types.OffsetSize
+import           System.Environment
+import           System.IO.Unsafe (unsafePerformIO)
+import           Text.Read        (readMaybe)
+
+-- | Defines the maximum size in bytes of unpinned arrays.
+--
+-- You can change this value by setting the environment variable
+-- @HS_FOUNDATION_UARRAY_UNPINNED_MAX@ to an unsigned integer number.
+--
+-- Note: We use 'unsafePerformIO' here. If the environment variable
+-- changes during runtime and the runtime system decides to recompute
+-- this value, referential transparency is violated (like the First
+-- Order violated the Galactic Concordance!).
+--
+-- TODO The default value of 1024 bytes is arbitrarily chosen for now.
+unsafeUArrayUnpinnedMaxSize :: CountOf Word8
+unsafeUArrayUnpinnedMaxSize = unsafePerformIO $ do
+    maxSize <- (>>= readMaybe) <$> lookupEnv "HS_FOUNDATION_UARRAY_UNPINNED_MAX"
+    pure $ maybe (CountOf 1024) CountOf maxSize
+{-# NOINLINE unsafeUArrayUnpinnedMaxSize #-}