IOHasBufFS` interface for I/O using user-supplied buffers

.stylish-haskell.yaml

@@ -21,7 +21,7 @@ steps:
   #
   #     # Should export lists be sorted?  Sorting is only performed within the
   #     # export section, as delineated by Haddock comments.
-      sort: true
+      sort: false
   #
   #     # See `separate_lists` for the `imports` step.
       separate_lists: true

fs-api/CHANGELOG.md

@@ -2,6 +2,19 @@
 
 ## next release -- ????-??-??
 
+### Breaking
+
+* New `primitive ^>=0.9` dependency
+
+### Non-breaking
+
+* Add new `HasBufFS` interface for performing I/O using pointer buffers. Note
+  that it is likely that this interfaced is unified with the `HasFS` interface
+  in the future.
+* Add compound functions, built from primitives in `HasBufFS`: `hGetAllAt`,
+  `hGetBufExactly`, `hPutBufExactly`, `hGetBufExactlyAt` and `hPutBufExactlyAt`
+* Provide an instantiation of the `HasBufFS` interface for `IO`.
+
 ### Patch
 
 * Make internal error comparison function more lenient on MacOS systems.

fs-api/fs-api.cabal

@@ -10,7 +10,7 @@ license-files:
 
 copyright:       2019-2023 Input Output Global Inc (IOG)
 author:          IOG Engineering Team
-maintainer:      operations@iohk.io, Joris Dral
+maintainer:      operations@iohk.io, Joris Dral (joris@well-typed.com)
 category:        System
 build-type:      Simple
 extra-doc-files: CHANGELOG.md
@@ -45,6 +45,7 @@ library
     , directory   >=1.3  && <1.4
     , filepath    >=1.4  && <1.5
     , io-classes  >=0.3  && <1.5
+    , primitive   ^>=0.9
     , text        >=1.2  && <2.2
 
   if os(windows)
@@ -69,3 +70,24 @@ library
     -Wall -Wcompat -Wincomplete-uni-patterns
     -Wincomplete-record-updates -Wpartial-fields -Widentities
     -Wredundant-constraints -Wmissing-export-lists -Wunused-packages
+
+test-suite fs-api-test
+  type:             exitcode-stdio-1.0
+  hs-source-dirs:   test
+  main-is:          Main.hs
+  other-modules:    Test.System.FS.IO
+  default-language: Haskell2010
+  build-depends:
+    , base
+    , bytestring
+    , fs-api
+    , primitive
+    , tasty
+    , tasty-quickcheck
+    , temporary
+
+  ghc-options:
+    -Wall -Wcompat -Wincomplete-uni-patterns
+    -Wincomplete-record-updates -Wpartial-fields -Widentities
+    -Wredundant-constraints -Wmissing-export-lists -Wunused-packages
+    -fno-ignore-asserts

fs-api/src-unix/System/FS/IO/Internal.hs

@@ -9,11 +9,15 @@ module System.FS.IO.Internal (
   , getSize
   , open
   , pread
+  , preadBuf
+  , pwriteBuf
   , read
+  , readBuf
   , sameError
   , seek
   , truncate
   , write
+  , writeBuf
   ) where
 
 import           Prelude hiding (read, truncate)
@@ -29,8 +33,9 @@ import           System.FS.API.Types (AllowExisting (..), OpenMode (..),
 import           System.FS.IO.Internal.Error (sameError)
 import           System.FS.IO.Internal.Handle
 import qualified System.Posix as Posix
-import           System.Posix (Fd)
-import           System.Posix.IO.ByteString.Ext (fdPreadBuf)
+import           System.Posix (ByteCount, Fd (..), FileOffset)
+import qualified System.Posix.IO.ByteString.Ext as Posix (fdPreadBuf,
+                     fdPwriteBuf)
 
 type FHandle = HandleOS Fd
 
@@ -130,10 +135,28 @@ read h bytes = withOpenHandle "read" h $ \fd ->
     Internal.createUptoN (fromIntegral bytes) $ \ptr ->
       fromIntegral <$> Posix.fdReadBuf fd ptr (fromIntegral bytes)
 
+readBuf :: FHandle -> Ptr Word8 -> ByteCount -> IO ByteCount
+readBuf f buf c = withOpenHandle "readBuf" f $ \fd -> Posix.fdReadBuf fd buf c
+
+writeBuf :: FHandle -> Ptr Word8 -> ByteCount -> IO ByteCount
+writeBuf f buf c = withOpenHandle "writeBuf" f $ \fd -> Posix.fdWriteBuf fd buf c
+
 pread :: FHandle -> Word64 -> Word64 -> IO ByteString
 pread h bytes offset = withOpenHandle "pread" h $ \fd ->
     Internal.createUptoN (fromIntegral bytes) $ \ptr ->
-      fromIntegral <$> fdPreadBuf fd ptr (fromIntegral bytes) (fromIntegral offset)
+      fromIntegral <$> Posix.fdPreadBuf fd ptr (fromIntegral bytes) (fromIntegral offset)
+
+-- | @'preadBuf' fh buf c off@ reads @c@ bytes into the buffer @buf@ from the file
+-- handle @fh@ at the file offset @off@. This does not move the position of the
+-- file handle.
+preadBuf :: FHandle -> Ptr Word8 -> ByteCount -> FileOffset -> IO ByteCount
+preadBuf h buf c off = withOpenHandle "preadBuf" h $ \fd -> Posix.fdPreadBuf fd buf c off
+
+-- | @'pwriteBuf' fh buf c off@ writes @c@ bytes from the data in the buffer
+-- @buf@ to the file handle @fh@ at the file offset @off@. This does not move
+-- the position of the file handle.
+pwriteBuf :: FHandle -> Ptr Word8 -> ByteCount -> FileOffset -> IO ByteCount
+pwriteBuf h buf c off = withOpenHandle "pwriteBuf" h $ \fd -> Posix.fdPwriteBuf fd buf c off
 
 -- | Truncates the file managed by the input 'FHandle' to the input size.
 truncate :: FHandle -> Word64 -> IO ()

fs-api/src-win32/System/FS/IO/Internal.hs

@@ -8,11 +8,15 @@ module System.FS.IO.Internal (
   , getSize
   , open
   , pread
+  , preadBuf
+  , pwriteBuf
   , read
+  , readBuf
   , sameError
   , seek
   , truncate
   , write
+  , writeBuf
   ) where
 
 import           Prelude hiding (read, truncate)
@@ -26,6 +30,7 @@ import           Foreign (Int64, Ptr)
 import           System.FS.API.Types (AllowExisting (..), FsError (..),
                      FsErrorType (..), OpenMode (..), SeekMode (..))
 import           System.FS.IO.Internal.Handle
+import           System.Posix.Types
 import           System.Win32
 
 type FHandle = HandleOS HANDLE
@@ -78,6 +83,14 @@ read fh bytes = withOpenHandle "read" fh $ \h ->
 getCurrentFileOffset :: HANDLE -> IO Int64
 getCurrentFileOffset h = setFilePointerEx h 0 fILE_CURRENT
 
+readBuf :: FHandle -> Ptr Word8 -> ByteCount -> IO ByteCount
+readBuf fh buf c = withOpenHandle "readBuf" fh $ \h ->
+    fromIntegral <$> win32_ReadFile h buf (fromIntegral c) Nothing
+
+writeBuf :: FHandle -> Ptr Word8 -> ByteCount -> IO ByteCount
+writeBuf fh buf c = withOpenHandle "writeBuf" fh $ \h ->
+    fromIntegral <$> win32_WriteFile h buf (fromIntegral c) Nothing
+
 pread :: FHandle -> Word64 -> Word64 -> IO ByteString
 pread fh bytes pos = withOpenHandle "pread" fh $ \h ->
   Internal.createUptoN (fromIntegral bytes) $ \ptr -> do
@@ -87,6 +100,22 @@ pread fh bytes pos = withOpenHandle "pread" fh $ \h ->
     _ <- setFilePointerEx h initialOffset fILE_BEGIN
     return n
 
+preadBuf :: FHandle -> Ptr Word8 -> ByteCount -> FileOffset -> IO ByteCount
+preadBuf fh buf c off = withOpenHandle "preadBuf" fh $ \h -> do
+    initialOffset <- getCurrentFileOffset h
+    _ <- setFilePointerEx h (fromIntegral off) fILE_BEGIN
+    n <- fromIntegral <$> win32_ReadFile h buf (fromIntegral c) Nothing
+    _ <- setFilePointerEx h initialOffset fILE_BEGIN
+    return n
+
+pwriteBuf :: FHandle -> Ptr Word8 -> ByteCount -> FileOffset -> IO ByteCount
+pwriteBuf fh buf c off = withOpenHandle "pwriteBuf" fh $ \h -> do
+    initialOffset <- getCurrentFileOffset h
+    _ <- setFilePointerEx h (fromIntegral off) fILE_BEGIN
+    n <- fromIntegral <$> win32_WriteFile h buf (fromIntegral c) Nothing
+    _ <- setFilePointerEx h initialOffset fILE_BEGIN
+    return n
+
 -- We only allow truncate in AppendMode, but Windows do not support it, so we manually seek to the end.
 -- It is important that the logical end of the handle stays alligned to the physical end of the file.
 truncate :: FHandle -> Word64 -> IO ()