--- /dev/null
+dist
+dist-*
+cabal-dev
+*.o
+*.hi
+*.hie
+*.chi
+*.chs.h
+*.dyn_o
+*.dyn_hi
+.hpc
+.hsenv
+.cabal-sandbox/
+cabal.sandbox.config
+*.prof
+*.aux
+*.hp
+*.eventlog
+.stack-work/
+cabal.project.local
+cabal.project.local~
+.HTF/
+.ghc.environment.*
+*.output
+packagedb
+cache
+build
\ No newline at end of file
--- /dev/null
+# Revision history for line-indexed-file-cursor
+
+## 0.1.0.0 -- YYYY-mm-dd
+
+* First version. Released on an unsuspecting world.
--- /dev/null
+Copyright (c) 2023 Evgenii Akentev
+
+Permission is hereby granted, free of charge, to any person obtaining
+a copy of this software and associated documentation files (the
+"Software"), to deal in the Software without restriction, including
+without limitation the rights to use, copy, modify, merge, publish,
+distribute, sublicense, and/or sell copies of the Software, and to
+permit persons to whom the Software is furnished to do so, subject to
+the following conditions:
+
+The above copyright notice and this permission notice shall be included
+in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
--- /dev/null
+cabal-version: 3.0
+name: line-indexed-cursor
+version: 0.1.0.0
+license: MIT
+license-file: LICENSE
+author: Evgenii Akentev
+maintainer: i@ak3n.com
+category: Development
+build-type: Simple
+extra-doc-files: CHANGELOG.md
+
+common warnings
+ ghc-options:
+ -Wall -Wnoncanonical-monad-instances -Wincomplete-uni-patterns
+ -Wincomplete-record-updates -Wredundant-constraints -Widentities
+ -Wunused-packages -Wmissing-deriving-strategies
+
+
+library
+ import: warnings
+ exposed-modules: System.IO.LineIndexedCursor
+ build-depends: base ^>=4.18.0.0, bytestring ^>= 0.11
+ hs-source-dirs: src
+ default-language: Haskell2010
+
+test-suite line-indexed-cursor-test
+ import: warnings
+ default-language: Haskell2010
+ type: exitcode-stdio-1.0
+ hs-source-dirs: test
+ main-is: Main.hs
+ build-depends:
+ base >= 4.7 && < 5,
+ hspec >= 2.10 && < 3,
+ line-indexed-cursor
--- /dev/null
+{-# LANGUAGE DuplicateRecordFields #-}
+{-# LANGUAGE RecordWildCards #-}
+
+-----------------------------------------------------------------------------
+-- |
+-- Module : System.IO.LineIndexedCursor
+-- Maintainer : i@ak3n.com
+--
+-- Line-indexed file reader.
+--
+-- Lazily builds the index of line numbers while reading the file
+-- making it possible to rewind to them quickly later.
+-----------------------------------------------------------------------------
+
+module System.IO.LineIndexedCursor (
+ LineIndexedCursor(..), mkLineIndexedCursor
+ ) where
+
+import Data.ByteString (ByteString, hGetLine)
+import Control.Concurrent.MVar
+import System.IO (Handle, hTell, hSeek, SeekMode(..), hIsEOF)
+
+-- | ADT with methods, hiding the internal state.
+data LineIndexedCursor = LineIndexedCursor
+ {
+ -- | Same as 'hGetLine' but safe.
+ getCurrentLine :: IO (Maybe ByteString)
+
+
+ -- | Rewinds to the requsted line number. Stops at EOF if it's too big.
+ -- Returns the reached line number.
+ , goToLine :: Integer -> IO Integer
+
+ -- | Returns the file 'Handle'.
+ , getHandle :: Handle
+ }
+
+data CursorHandle = CursorHandle
+ { fileHandle :: Handle
+ , linesIdx :: MVar ([Integer], Integer)
+ }
+
+{- |
+
+Builds 'LineIndexedCursor'.
+
+Resets the file handle's ofsset to the beginning.
+
+Use 'System.IO.hSetNewlineMode' if you want to configure 'System.IO.NewlineMode'.
+
+-}
+mkLineIndexedCursor :: Handle -> IO LineIndexedCursor
+mkLineIndexedCursor fileHandle = do
+ -- reset the handle's offset to the beginning
+ hSeek fileHandle AbsoluteSeek 0
+
+ linesIdx <- newMVar ([0], 0)
+
+ let cursorHandle = CursorHandle fileHandle linesIdx
+ pure $ LineIndexedCursor
+ { getCurrentLine = getCurrentLine' cursorHandle
+ , goToLine = goToLine' cursorHandle
+ , getHandle = fileHandle
+ }
+
+getCurrentLine' :: CursorHandle -> IO (Maybe ByteString)
+getCurrentLine' CursorHandle{..} =
+ hIsEOF fileHandle >>= \isEOF -> if isEOF then pure Nothing else do
+ line <- hGetLine fileHandle
+ offset <- hTell fileHandle
+ modifyMVar_ linesIdx $ \(idx, size) -> pure $
+ if (not $ offset `elem` idx)
+ then (offset : idx, size + 1)
+ else (idx, size)
+ pure $ Just line
+
+goToLine' :: CursorHandle -> Integer -> IO Integer
+goToLine' CursorHandle{..} ln = do
+ modifyMVar linesIdx $ \(idx, size) -> do
+ if ln > size then do
+ hSeek fileHandle AbsoluteSeek (idx !! 0)
+ -- try to read until the requested line number
+ idxTail <- readUntil (ln - size) []
+ let newSize = size + (fromIntegral $ length idxTail)
+ pure ((idxTail ++ idx, newSize), newSize)
+ else do
+ let nextSeekIndex = fromIntegral $ size - ln
+ hSeek fileHandle AbsoluteSeek (idx !! nextSeekIndex)
+ pure ((idx, size), ln)
+ where
+ readUntil 0 idx = pure idx
+ readUntil counter idx =
+ hIsEOF fileHandle >>= \isEOF -> if isEOF then pure idx else do
+ _ <- hGetLine fileHandle
+ offset <- hTell fileHandle
+ readUntil (counter - 1) (fromInteger offset : idx)
\ No newline at end of file
--- /dev/null
+{-# LANGUAGE OverloadedStrings #-}
+
+module Main (main) where
+
+import System.IO
+import System.IO.LineIndexedCursor
+
+import Test.Hspec
+
+main :: IO ()
+main = hspec $ do
+ let
+ mkCursor = do
+ h <- openFile "test/testdata" ReadMode
+ c <- mkLineIndexedCursor h
+ pure (h, c)
+
+ before mkCursor . after (\(h, _) -> hClose h)
+ $ describe "System.IO.LineIndexedCursor" $ do
+
+ it "getCurrentLine works" $ \(_, c) -> do
+ l <- getCurrentLine c
+ l `shouldBe` Just "Lorem ipsum dolor sit amet, consectetur adipiscing elit."
+
+ it "goToLine works" $ \(_, c) -> do
+ ln <- goToLine c 10
+ ln `shouldBe` 10
+
+ l <- getCurrentLine c
+ l `shouldBe` Just "Sed elementum velit sit amet orci mollis tincidunt."
+
+ it "goToLine is too big" $ \(_, c) -> do
+ l <- getCurrentLine c
+ l `shouldBe` Just "Lorem ipsum dolor sit amet, consectetur adipiscing elit."
+
+ ln <- goToLine c 30
+ ln `shouldBe` 20
+
+ l' <- getCurrentLine c
+ l' `shouldBe` Nothing
+
+ it "read line, then go to beginning and forth" $ \(_, c) -> do
+ l <- getCurrentLine c
+ l `shouldBe` Just "Lorem ipsum dolor sit amet, consectetur adipiscing elit."
+
+ _ <- getCurrentLine c
+ _ <- getCurrentLine c
+ _ <- getCurrentLine c
+ _ <- getCurrentLine c
+ _ <- getCurrentLine c
+
+ ln <- goToLine c 0
+ ln `shouldBe` 0
+
+ l' <- getCurrentLine c
+ l' `shouldBe` Just "Lorem ipsum dolor sit amet, consectetur adipiscing elit."
+
+ ln' <- goToLine c 5
+ ln' `shouldBe` 5
+
+ l'' <- getCurrentLine c
+ l'' `shouldBe` Just "Curabitur nec dui posuere, tincidunt turpis vitae, tincidunt magna."
+
+ ln'' <- goToLine c 6
+ ln'' `shouldBe` 6
+
+ ln''' <- goToLine c 7
+ ln''' `shouldBe` 7
+
+ ln'''' <- goToLine c 10
+ ln'''' `shouldBe` 10
--- /dev/null
+Lorem ipsum dolor sit amet, consectetur adipiscing elit.
+Sed eget lacus id nulla sagittis interdum sit amet ac quam.
+Vestibulum vehicula felis ac massa tincidunt, a elementum elit malesuada.
+Curabitur nec mi sit amet justo condimentum gravida.
+Pellentesque accumsan dolor at nisl pulvinar, ut bibendum diam egestas.
+Curabitur nec dui posuere, tincidunt turpis vitae, tincidunt magna.
+Duis fringilla orci vitae finibus fermentum.
+Pellentesque facilisis nisi sit amet urna elementum, nec blandit neque tincidunt.
+Duis efficitur odio non ipsum consequat lobortis.
+Curabitur faucibus tortor quis leo ultricies volutpat.
+Sed elementum velit sit amet orci mollis tincidunt.
+Aliquam vitae est vel odio pharetra fermentum.
+Morbi facilisis sem id scelerisque fermentum.
+Sed placerat lorem at commodo ornare.
+Suspendisse bibendum ex non eros bibendum molestie.
+Nullam sed elit quis arcu dapibus aliquam nec sed nunc.
+Sed sodales ex a dapibus lacinia.
+Duis at nunc et est maximus vestibulum.
+Fusce ut justo id ante vehicula dignissim.
+Praesent tincidunt eros vel viverra posuere.
\ No newline at end of file
projects / line-indexed-cursor.git / commitdiff