HORIZON HASKELLDocslts/ghc-9.10.xc74966e2026-09-27Search names, modules, packages, or :: a typeCtrl K

GHC 9.10.3 · lts/ghc-9.10.x · c74966e · 2026-09-27

Modulestreamly-core-0.2.2Haskell2010

Streamly.Internal.FileSystem.File

Read and write streams and arrays to and from files specified by their paths in the file system. Unlike the handle based APIs which can have a read/write session consisting of multiple reads and writes to the handle, these APIs are one shot read or write APIs. These APIs open the file handle, perform the requested operation and close the handle. Thease are safer compared to the handle based APIs as there is no possibility of a file descriptor leakage.

import qualified Streamly.Internal.FileSystem.File as File
  • 28 values

Streaming IO

0 declarations

Stream data to or from a file or device sequentially. When reading, the stream is lazy and generated on-demand as the consumer consumes it. Read IO requests to the IO device are performed in chunks limited to a maximum size of 32KiB, this is referred to as defaultChunkSize in the documentation. One IO request may or may not read the full chunk. If the whole stream is not consumed, it is possible that we may read slightly more from the IO device than what the consumer needed. Unless specified otherwise in the API, writes are collected into chunks of defaultChunkSize before they are written to the IO device.

File IO Using Handle

valuewithFile
  1. :: (MonadIO m, MonadCatch m)
  2. => FilePath
  3. -> IOMode
  4. -> Handle -> Stream m a
  5. -> Stream m a
#

withFile name mode act opens a file using openFile and passes the resulting handle to the computation act. The handle will be closed on exit from withFile, whether by normal termination or by raising an exception. If closing the handle raises an exception, then this exception will be raised by withFile rather than any exception raised by act.

Pre-release

Streams

valueread :: (MonadIO m, MonadCatch m) => FilePath -> Stream m Word8
#

Generate a stream of bytes from a file specified by path. The stream ends when EOF is encountered. File is locked using multiple reader and single writer locking mode.

Pre-release

valuereadChunks
  1. :: (MonadIO m, MonadCatch m)
  2. => FilePath
  3. -> Stream m (Array Word8)
#

readChunks file reads a stream of arrays from file file. The maximum size of a single array is limited to defaultChunkSize. The actual size read may be less than defaultChunkSize.

readChunks = readChunksWith defaultChunkSize

Pre-release

Unfolds

valuereader :: (MonadIO m, MonadCatch m) => Unfold m FilePath Word8
#

Unfolds a file path into a byte stream. IO requests to the device are performed in sizes of Streamly.Internal.Data.Array.Type.defaultChunkSize.

Pre-release

valuechunkReaderWith :: (MonadIO m, MonadCatch m) => Unfold m (Int, FilePath) (Array Word8)
#

Unfold the tuple (bufsize, filepath) into a stream of Word8 arrays. Read requests to the IO device are performed using a buffer of size bufsize. The size of an array in the resulting stream is always less than or equal to bufsize.

Pre-release

valuechunkReaderFromToWith :: (MonadIO m, MonadCatch m) => Unfold m (Int, Int, Int, FilePath) (Array Word8)
#

Unfold the tuple (from, to, bufsize, filepath) into a stream of Word8 arrays. Read requests to the IO device are performed using a buffer of size bufsize starting from absolute offset of from till the absolute position of to. The size of an array in the resulting stream is always less than or equal to bufsize.

Pre-release

valuechunkReader :: (MonadIO m, MonadCatch m) => Unfold m FilePath (Array Word8)
#

Unfolds a FilePath into a stream of Word8 arrays. Requests to the IO device are performed using a buffer of size Streamly.Internal.Data.Array.Type.defaultChunkSize. The size of arrays in the resulting stream are therefore less than or equal to Streamly.Internal.Data.Array.Type.defaultChunkSize.

Pre-release

Write To File

valueputChunk :: FilePath -> Array a -> IO ()
#

Write an array to a file. Overwrites the file if it exists.

Pre-release

Folds

valuewrite :: (MonadIO m, MonadCatch m) => FilePath -> Fold m Word8 ()
#

Write a byte stream to a file. Accumulates the input in chunks of up to Streamly.Internal.Data.Array.Type.defaultChunkSize before writing to the IO device.

Pre-release

valuewriteWith :: (MonadIO m, MonadCatch m) => Int -> FilePath -> Fold m Word8 ()
#

writeWith chunkSize handle writes the input stream to handle. Bytes in the input stream are collected into a buffer until we have a chunk of size chunkSize and then written to the IO device.

Pre-release

Writing Streams

valuefromBytes :: (MonadIO m, MonadCatch m) => FilePath -> Stream m Word8 -> m ()
#

Write a byte stream to a file. Combines the bytes in chunks of size up to A.defaultChunkSize before writing. If the file exists it is truncated to zero size before writing. If the file does not exist it is created. File is locked using single writer locking mode.

Pre-release

Append To File

valuewriteAppend
  1. :: (MonadIO m, MonadCatch m)
  2. => FilePath
  3. -> Stream m Word8
  4. -> m ()
#

Append a byte stream to a file. Combines the bytes in chunks of size up to A.defaultChunkSize before writing. If the file exists then the new data is appended to the file. If the file does not exist it is created. File is locked using single writer locking mode.

Pre-release

Deprecated

8 declarations