From e005881fd7b99211bbbd16988b2a29d2ed1910ec Mon Sep 17 00:00:00 2001
From: Adithya Kumar <adithya@composewell.com>
Date: Fri, 11 Oct 2024 12:52:22 +0530
Subject: [PATCH] Use fromPtrN in unsafeFromForeignPtr and make it monadic in
 nature

---
 core/src/Streamly/Internal/Data/Array/Type.hs | 14 +++++---------
 test/Streamly/Test/Data/Array.hs              |  8 ++------
 2 files changed, 7 insertions(+), 15 deletions(-)

diff --git a/core/src/Streamly/Internal/Data/Array/Type.hs b/core/src/Streamly/Internal/Data/Array/Type.hs
index d64394c6b6..46e11f6a40 100644
--- a/core/src/Streamly/Internal/Data/Array/Type.hs
+++ b/core/src/Streamly/Internal/Data/Array/Type.hs
@@ -183,10 +183,9 @@ import GHC.Base (build)
 import GHC.Exts (IsList, IsString(..), Addr#, minusAddr#)
 import GHC.Int (Int(..))
 import GHC.ForeignPtr (ForeignPtr(..), ForeignPtrContents(..))
-import Foreign.Storable (peek)
 
 import GHC.IO (unsafePerformIO)
-import GHC.Ptr (Ptr(..), plusPtr, nullPtr)
+import GHC.Ptr (Ptr(..), nullPtr)
 import Streamly.Internal.Data.Producer.Type (Producer(..))
 import Streamly.Internal.Data.MutArray.Type (MutArray(..))
 import Streamly.Internal.Data.MutByteArray.Type (MutByteArray)
@@ -308,17 +307,14 @@ mutableByteArrayContents# x = Exts.byteArrayContents# (Exts.unsafeCoerce# x)
 -- | @unsafeFromForeignPtr fptr len@ converts the "ForeignPtr" to an "Array".
 --
 unsafeFromForeignPtr
-    :: ForeignPtr Word8 -> Int -> Array Word8
+    :: MonadIO m => ForeignPtr Word8 -> Int -> m (Array Word8)
 unsafeFromForeignPtr (ForeignPtr addr# _) i
-    | Ptr addr# == nullPtr || i == 0 = empty
+    | Ptr addr# == nullPtr || i == 0 = pure empty
 unsafeFromForeignPtr (ForeignPtr addr# (PlainPtr marr#)) len =
     let off = I# (addr# `minusAddr#` mutableByteArrayContents# marr#)
-     in Array (Unboxed.MutByteArray marr#) off (off + len)
+     in pure (Array (Unboxed.MutByteArray marr#) off (off + len))
 unsafeFromForeignPtr (ForeignPtr addr# _) len =
-    unsafeInlineIO
-        $ fromStreamN len
-        $ D.mapM (peek . plusPtr (Ptr addr#))
-        $ D.fromList [0,1..(len - 1)]
+    fromPtrN len (Ptr addr#)
 
 {-# DEPRECATED asPtrUnsafe "Please use unsafePinnedAsPtr instead." #-}
 {-# INLINE asPtrUnsafe #-}
diff --git a/test/Streamly/Test/Data/Array.hs b/test/Streamly/Test/Data/Array.hs
index c2957885c7..a690efd42b 100644
--- a/test/Streamly/Test/Data/Array.hs
+++ b/test/Streamly/Test/Data/Array.hs
@@ -226,10 +226,7 @@ testForeignPtrConversionId :: IO ()
 testForeignPtrConversionId = do
     arr0 <- MA.unsafeGetSlice 10 50 <$> MA.fromList ([0 .. 99] :: [Word8])
     let arr = A.unsafeFreeze arr0
-    arr1 <-
-        A.unsafeAsForeignPtr
-             arr
-             (\fptr len -> pure $ A.unsafeFromForeignPtr fptr len)
+    arr1 <- A.unsafeAsForeignPtr arr A.unsafeFromForeignPtr
     arr1 `shouldBe` arr
 
 testUnsafeFromForeignPtr :: IO ()
@@ -239,8 +236,7 @@ testUnsafeFromForeignPtr = do
     A.unsafePinnedAsPtr arr $ \ptr len -> do
         fptr <- newForeignPtr_ ptr
         performMajorGC
-        let arr1 = A.unsafeFromForeignPtr fptr len
-        arr1 `shouldBe` arr
+        A.unsafeFromForeignPtr fptr len `shouldReturn` arr
 
 reallocMA :: Property
 reallocMA =