Add readChunksFromToWith, read ranges from Handle

src/Streamly/FileSystem/Handle.hs

@@ -79,6 +79,7 @@ module Streamly.FileSystem.Handle
     , readWithBufferOf
     , readChunks
     , readChunksWithBufferOf
+    , readChunksFromToWith
 
     -- ** Writing
     -- | 'TextEncoding', 'NewLineMode', and 'Buffering' options of the

src/Streamly/Internal/FileSystem/Handle.hs

@@ -105,7 +105,7 @@ import Foreign.ForeignPtr (withForeignPtr)
 import Foreign.Ptr (minusPtr, plusPtr)
 import Foreign.Storable (Storable(..))
 import GHC.ForeignPtr (mallocPlainForeignPtrBytes)
-import System.IO (Handle, hGetBufSome, hPutBuf)
+import System.IO (Handle, SeekMode(..), hGetBufSome, hPutBuf, hSeek)
 import Prelude hiding (read)
 
 import Streamly.Internal.BaseCompat
@@ -257,9 +257,32 @@ readChunksWithBufferOf = Unfold step return
 --
 --
 {-# INLINE_NORMAL readChunksFromToWith #-}
-readChunksFromToWith :: -- MonadIO m =>
+readChunksFromToWith :: MonadIO m =>
     Unfold m (Int, Int, Int, Handle) (Array Word8)
-readChunksFromToWith = undefined
+readChunksFromToWith = Unfold step inject
+
+    where
+
+    inject (from, to, buffSize, h) = do
+        liftIO $ hSeek h AbsoluteSeek $ fromIntegral from
+        return (to - from + 1, buffSize, h)
+
+    {-# INLINE_LATE step #-}
+    step (remaining, buffSize, h) =
+        if remaining <= 0
+        then return D.Stop
+        else
+            do
+            arr <- getChunk (min buffSize remaining) h
+            return $
+                case A.length arr of
+                    0 -> D.Stop
+                    len ->
+                        if (remaining - len) >= 0
+                        then
+                            D.Yield arr (remaining - len, buffSize, h)
+                        else
+                            error "Bug: getChunk returned array length more than expected"
 
 -- XXX read 'Array a' instead of Word8
 --

test/Streamly/Test/FileSystem/Handle.hs

@@ -61,6 +61,9 @@ testData = "This is the test data for FileSystem.Handle ??`!@#$%^&*~~))`]"
 testDataLarge :: String
 testDataLarge = concat $ replicate 6000 testData
 
+testBinData :: String
+testBinData = "01234567890123456789012345678901234567890123456789"
+
 executor :: (Handle -> SerialT IO Char) -> IO (SerialT IO Char)
 executor f =
     withSystemTempDirectory "fs_handle" $ \fp -> do
@@ -152,6 +155,53 @@ testWriteWithChunk =
                 let arr = Array.fromList ls
                 return (testDataLarge == utf8ToString arr)
 
+
+testReadChunksFromToWith :: Int -> Int -> Int -> String -> Property
+testReadChunksFromToWith from to buffSize expRes =
+    monadicIO $ do
+        res <- run go
+        assert res
+
+        where
+
+        go =
+            withSystemTempDirectory "fs_handle" $ \fp -> do
+                let fpathRead = fp </> "tmp_read.txt"
+                writeFile fpathRead testBinData
+                h <- openFile fpathRead ReadMode
+                ls <- Stream.toList $
+                    Stream.unfold
+                    Handle.readChunksFromToWith
+                    (from, to, buffSize, h)
+                return ( expRes == show ls)
+
+-- Test for first byte
+testReadChunksFromToWithFirstByte :: Property
+testReadChunksFromToWithFirstByte = testReadChunksFromToWith 0 0 15 "[[48]]"
+
+-- Test for second byte
+testReadChunksFromToWithSecondByte :: Property
+testReadChunksFromToWithSecondByte = testReadChunksFromToWith 1 1 15 "[[49]]"
+
+-- Test for second to 10th bytes
+testReadChunksFromToWithSecondToTenthBytes :: Property
+testReadChunksFromToWithSecondToTenthBytes =
+    testReadChunksFromToWith 1 10 15 "[[49,50,51,52,53,54,55,56,57,48]]"
+
+-- Test for offset of buffer size
+testReadChunksFromToWithBuffSizeOffset :: Property
+testReadChunksFromToWithBuffSizeOffset =
+    testReadChunksFromToWith 15 25 15 "[[53,54,55,56,57,48,49,50,51,52,53]]"
+
+-- Test with multi buffer size
+testReadChunksFromToWithMultiBuff :: Property
+testReadChunksFromToWithMultiBuff =
+    testReadChunksFromToWith
+    5 22 5 "[[53,54,55,56,57],[48,49,50,51,52],[53,54,55,56,57],[48,49,50]]"
+
+testReadChunksFromToWithRangeInvalid :: Property
+testReadChunksFromToWithRangeInvalid = testReadChunksFromToWith 15 5 15 "[]"
+
 moduleName :: String
 moduleName = "FileSystem.Handle"
 
@@ -166,6 +216,12 @@ main =
             prop "readWithBufferOf" $ testRead readWithBufferFromHandle
             prop "readChunks" $ testRead readChunksFromHandle
             prop "readChunksWithBufferOf" $ testRead readChunksWithBuffer
+            prop "readChunksFromToWithFirstByte" testReadChunksFromToWithFirstByte
+            prop "readChunksFromToWithSecondByte" testReadChunksFromToWithSecondByte
+            prop "readChunksFromToWithSecondToTenthBytes" testReadChunksFromToWithSecondToTenthBytes
+            prop "readChunksFromToWithBuffSizeOffset" testReadChunksFromToWithBuffSizeOffset
+            prop "readChunksFromToWithMultiBuff" testReadChunksFromToWithMultiBuff
+            prop "readChunksFromToWithRangeInvalid" testReadChunksFromToWithRangeInvalid
         describe "Write To Handle" $ do
             prop "write" $ testWrite Handle.write
             prop "writeWithBufferOf" $ testWrite $ Handle.writeWithBufferOf 1024