refactor http2 file (#864)

* refactor http2 file

* move fileBlockSize to HTTP2.File

src/Simplex/Messaging/Transport/HTTP2/File.hs

@@ -0,0 +1,43 @@
+{-# LANGUAGE LambdaCase #-}
+{-# LANGUAGE MultiWayIf #-}
+
+module Simplex.Messaging.Transport.HTTP2.File where
+
+import Data.ByteString.Builder (Builder, byteString)
+import Data.ByteString (ByteString)
+import qualified Data.ByteString as B
+import Data.Int (Int64)
+import Data.Word (Word32)
+import GHC.IO.Handle.Internals (ioe_EOF)
+import System.IO (Handle)
+
+fileBlockSize :: Int
+fileBlockSize = 16384
+
+hReceiveFile :: (Int -> IO ByteString) -> Handle -> Word32 -> IO Int64
+hReceiveFile _ _ 0 = pure 0
+hReceiveFile getBody h size = get $ fromIntegral size
+  where
+    get sz = do
+      ch <- getBody fileBlockSize
+      let chSize = fromIntegral $ B.length ch
+      if
+          | chSize > sz -> pure (chSize - sz)
+          | chSize > 0 -> B.hPut h ch >> get (sz - chSize)
+          | otherwise -> pure (- fromIntegral sz)
+
+hSendFile :: Handle -> (Builder -> IO ()) -> Word32 -> IO ()
+hSendFile h send = go
+  where
+    go 0 = pure ()
+    go sz =
+      getFileChunk h sz >>= \ch -> do
+        send $ byteString ch
+        go $ sz - fromIntegral (B.length ch)
+
+getFileChunk :: Handle -> Word32 -> IO ByteString
+getFileChunk h sz = do
+  ch <- B.hGet h fileBlockSize
+  if B.null ch
+    then ioe_EOF
+    else pure $ B.take (fromIntegral sz) ch -- sz >= xftpBlockSize