Maintainer	i@ak3n.com
Safe Haskell	Safe-Inferred
Language	Haskell2010

System.IO.LineIndexedCursor

Description

Line-indexed file reader.

Lazily builds the index with the line numbers while reading the file making it possible to rewind to them quickly later.

The indices are stored using a list, with a fixed length capacity, and Array. Each new element is added to the list and when the capacity is reached, the list items get flushed to the array for faster access. The list's capacity can be configured using mkLineIndexedCursorWithCapacity.

Synopsis

data LineIndexedCursor = LineIndexedCursor {
- getCurrentLine :: IO (Maybe ByteString)
- getCurrentLineUnsafe :: IO ByteString
- getCurrentLineNumber :: IO Integer
- doFullScan :: IO ()
- goToLine :: Integer -> IO Integer
- getHandle :: Handle
- getCursorState :: IO [Integer]
}
mkLineIndexedCursor :: Handle -> IO LineIndexedCursor
mkLineIndexedCursorWithCapacity :: Handle -> Integer -> IO LineIndexedCursor

Documentation

data LineIndexedCursor #

ADT with methods, hiding the internal state.

getCurrentLine, getCurrentLineUnsafe, doFullScan, and goToLine, all throw IOError.

Constructors

LineIndexedCursor

Fields

getCurrentLine :: IO (Maybe ByteString)
Same as getCurrentLineUnsafe but safely handles EOF.
getCurrentLineUnsafe :: IO ByteString
A wrapper around hGetLine. Throws the same exceptions.
getCurrentLineNumber :: IO Integer
Returns the current line number.
doFullScan :: IO ()
Reads from the latest known line until EOF to build the full index.
goToLine :: Integer -> IO Integer
Rewinds the file handle to the requsted line number. Stops at the EOF if it's too big, returning the reached line number.
getHandle :: Handle
Returns the file Handle.
getCursorState :: IO [Integer]
Returns the current state of the cursor — all known line indexes.

mkLineIndexedCursor :: Handle -> IO LineIndexedCursor #

Builds LineIndexedCursor. Resets the file handle's ofsset to the beginning.

Use hSetNewlineMode if you want to configure NewlineMode.

mkLineIndexedCursorWithCapacity :: Handle -> Integer -> IO LineIndexedCursor #

Same as mkLineIndexedCursor but allows to configure the list's capacity.