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GHC 9.14.1 · lts/ghc-9.14.x · 45dd537 · 2026-10-11

Modulestreamly-core-0.3.1Haskell2010

Streamly.Internal.FileSystem.FileIO

  • 20 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. => Path
  3. -> IOMode
  4. -> Handle -> Stream m a
  5. -> Stream m a
#

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

The file is opened in binary mode as encoding, decoding, and newline translation can be handled explicitly by the streaming APIs.

The file is opened without buffering as buffering can be controlled explicitly by the streaming APIs.

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Streams

valueread :: (MonadIO m, MonadCatch m) => Path -> 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.

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valuereadChunksWith
  1. :: (MonadIO m, MonadCatch m)
  2. => Int
  3. -> Path
  4. -> Stream m (Array Word8)
#

readChunksWith size file reads a stream of arrays from file file. The maximum size of a single array is specified by size. The actual size read may be less than or equal to size.

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valuereadChunks :: (MonadIO m, MonadCatch m) => Path -> 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

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Unfolds

valuereader :: (MonadIO m, MonadCatch m) => Unfold m Path 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.

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valuechunkReaderWith :: (MonadIO m, MonadCatch m) => Unfold m (Int, Path) (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.

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

Unfolds a Path 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.

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Write To File

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

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

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Folds

valuewrite :: (MonadIO m, MonadCatch m) => Path -> 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.

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valuewriteWith :: (MonadIO m, MonadCatch m) => Int -> Path -> 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.

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valuewriteChunks :: (MonadIO m, MonadCatch m) => Path -> Fold m (Array a) ()
#

Write a stream of chunks to a file. Each chunk in the stream is written immediately to the device as a separate IO request, without coalescing or buffering.

Writing Streams

valuefromBytes :: (MonadIO m, MonadCatch m) => Path -> 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.

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Append To File

valuewriteAppend :: (MonadIO m, MonadCatch m) => Path -> Stream m Word8 -> 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.

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valuewriteAppendWith
  1. :: (MonadIO m, MonadCatch m)
  2. => Int
  3. -> Path
  4. -> Stream m Word8
  5. -> m ()
#

Like append but provides control over the write buffer. Output will be written to the IO device as soon as we collect the specified number of input elements.

Pre-release