module Pipes.Text.IO
(
- -- * Text IO
+ -- * Simple line-based Text IO
+ -- $lineio
+
+ fromHandleLn
+ , toHandleLn
+ , stdinLn
+ , stdoutLn
+ , stdoutLn'
+ , readFileLn
+ , writeFileLn
+
+
+ -- * Simple streaming text IO
-- $textio
-- * Caveats
-- $caveats
-- * Producers
- fromHandle
- , fromHandleLn
+ , fromHandle
, stdin
, readFile
- , readFileLn
+
-- * Consumers
, toHandle
, stdout
, writeFile
+
+ -- * Re-exports
+ , MonadSafe(..)
+ , runSafeT
+ , runSafeP
+ , Safe.withFile
) where
import qualified System.IO as IO
import qualified Data.Text.IO as T
import Pipes
import qualified Pipes.Safe.Prelude as Safe
-import Pipes.Safe (MonadSafe(..))
+import Pipes.Safe (MonadSafe(..), runSafeT, runSafeP)
import Prelude hiding (readFile, writeFile)
+{- $lineio
+ Line-based operations are marked with a final \-@Ln@, like 'stdinLn', 'readFileLn'. They are
+ drop-in replacements for the line-based operations in @Pipes.Prelude@ and
+ @Pipes.Safe.Prelude@ - the final \-@Ln@ being added where necessary.
+ With them, one is producing, piping and consuming semantically significant individual texts,
+ understood as lines, just as one would pipe 'Int's. The standard materials from @Pipes@ and @Pipes.Prelude@ and
+ @Data.Text@ are all you need to interact with these lines as you read or write them.
+ You can use these operations without using any of the other material in this package.
+
+ Thus, to take a trivial case, here we upper-case three lines from standard input and write
+ them to a file.
+
+>>> import Pipes
+>>> import qualified Pipes.Prelude as P
+>>> import qualified Pipes.Text.IO as Text
+>>> import qualified Data.Text as T
+>>> Text.runSafeT $ runEffect $ Text.stdinLn >-> P.take 3 >-> P.map T.toUpper >-> Text.writeFileLn "threelines.txt"
+one<Enter>
+two<Enter>
+three<Enter>
+>>> :! cat "threelines.txt"
+ONE
+TWO
+THREE
+
+ The point of view is very much that of @Pipes.Prelude@ and the user who needs no more
+ can use them ignoring the rest of this package.
+
+ The line-based operations are, however, subject to a number of caveats.
+ First, where they read from a handle, they will of course happily
+ accumulate indefinitely long lines. This is likely to be legitimate for input
+ typed in by a user, and for locally produced log files and other known material, but
+ otherwise not. See the post on
+ <http://www.haskellforall.com/2013/09/perfect-streaming-using-pipes-bytestring.html perfect streaming>
+ to see why @pipes-bytestring@ and this package take a different approach. Furthermore,
+ like those in @Data.Text.IO@, the operations use the system encoding and @T.hGetLine@
+ and thus are slower than the \'official\' route, which would use bytestring IO and
+ the encoding and decoding functions in @Pipes.Text.Encoding@. Finally, they will generate
+ text exceptions after the fashion of @Data.Text.Encoding@ rather than returning the
+ undigested bytes in the style of @Pipes.Text.Encoding@
+
+-}
+
+
+{-| Read separate lines of 'Text' from 'IO.stdin' using 'T.getLine'
+ This function will accumulate indefinitely long strict 'Text's. See the caveats above.
+
+ Terminates on end of input
+-}
+stdinLn :: MonadIO m => Producer' T.Text m ()
+stdinLn = fromHandleLn IO.stdin
+{-# INLINABLE stdinLn #-}
+
+
+{-| Write 'String's to 'IO.stdout' using 'putStrLn'
+
+ Unlike 'toHandle', 'stdoutLn' gracefully terminates on a broken output pipe
+-}
+stdoutLn :: MonadIO m => Consumer' T.Text m ()
+stdoutLn = go
+ where
+ go = do
+ str <- await
+ x <- liftIO $ try (T.putStrLn str)
+ case x of
+ Left (G.IOError { G.ioe_type = G.ResourceVanished
+ , G.ioe_errno = Just ioe })
+ | Errno ioe == ePIPE
+ -> return ()
+ Left e -> liftIO (throwIO e)
+ Right () -> go
+{-# INLINABLE stdoutLn #-}
+
+{-| Write lines of 'Text's to 'IO.stdout'.
+
+ This does not handle a broken output pipe, but has a polymorphic return
+ value.
+-}
+stdoutLn' :: MonadIO m => Consumer' T.Text m r
+stdoutLn' = for cat (\str -> liftIO (T.putStrLn str))
+{-# INLINABLE stdoutLn' #-}
+
+{-# RULES
+ "p >-> stdoutLn'" forall p .
+ p >-> stdoutLn' = for p (\str -> liftIO (T.putStrLn str))
+ #-}
+
+{-| Read separate lines of 'Text' from a 'IO.Handle' using 'T.hGetLine'.
+ This operation will accumulate indefinitely large strict texts. See the caveats above.
+
+ Terminates on end of input
+-}
+fromHandleLn :: MonadIO m => IO.Handle -> Producer' Text m ()
+fromHandleLn h = go where
+ getLine :: IO (Either G.IOException Text)
+ getLine = try (T.hGetLine h)
+
+ go = do txt <- liftIO getLine
+ case txt of
+ Left e -> return ()
+ Right y -> do yield y
+ go
+{-# INLINABLE fromHandleLn #-}
+
+-- to do: investigate differences from the above:
+-- fromHandleLn :: MonadIO m => IO.Handle -> Producer' T.Text m ()
+-- fromHandleLn h = go
+-- where
+-- go = do
+-- eof <- liftIO $ IO.hIsEOF h
+-- unless eof $ do
+-- str <- liftIO $ T.hGetLine h
+-- yield str
+-- go
+-- {-# INLINABLE fromHandleLn #-}
+
+
+-- | Write separate lines of 'Text' to a 'IO.Handle' using 'T.hPutStrLn'
+toHandleLn :: MonadIO m => IO.Handle -> Consumer' T.Text m r
+toHandleLn handle = for cat (\str -> liftIO (T.hPutStrLn handle str))
+{-# INLINABLE toHandleLn #-}
+
+{-# RULES
+ "p >-> toHandleLn handle" forall p handle .
+ p >-> toHandleLn handle = for p (\str -> liftIO (T.hPutStrLn handle str))
+ #-}
+
+
+{-| Stream separate lines of text from a file. This operation will accumulate
+ indefinitely long strict text chunks. See the caveats above.
+-}
+readFileLn :: MonadSafe m => FilePath -> Producer Text m ()
+readFileLn file = Safe.withFile file IO.ReadMode fromHandleLn
+{-# INLINE readFileLn #-}
+
+
+
+{-| Write lines to a file, automatically opening and closing the file as
+ necessary
+-}
+writeFileLn :: (MonadSafe m) => FilePath -> Consumer' Text m r
+writeFileLn file = Safe.withFile file IO.WriteMode toHandleLn
+{-# INLINABLE writeFileLn #-}
+
+
+
{- $textio
Where pipes @IO@ replaces lazy @IO@, @Producer Text IO r@ replaces lazy 'Text'.
- This module exports some convenient functions for producing and consuming
- pipes 'Text' in @IO@, namely, 'readFile', 'writeFile', 'fromHandle', 'toHandle',
- 'stdin' and 'stdout'. Some caveats described below.
+ The official IO of this package and the pipes ecosystem generally would use the
+ IO functions in @Pipes.ByteString@ and the encoding and decoding material in
+ @Pipes.Text.Encoding@.
+
+ The streaming functions exported here, namely, 'readFile', 'writeFile', 'fromHandle', 'toHandle',
+ 'stdin' and 'stdout' simplify this and use the system encoding on the model of @Data.Text.IO@
+ and @Data.Text.Lazy.IO@ Some caveats described below.
The main points are as in
<https://hackage.haskell.org/package/pipes-bytestring-1.0.0/docs/Pipes-ByteString.html Pipes.ByteString>:
> main = runEffect $ Text.stdin >-> Text.stdout
+ These programs, unlike the corresponding programs written with the line-based functions,
+ will pass along a 1 terabyte line without affecting memory use.
-}
* Like the functions in @Data.Text.IO@ , they use Text exceptions, not the standard Pipes protocols.
- Something like
-
-> view utf8 . Bytes.fromHandle :: Handle -> Producer Text IO (Producer ByteString m ())
-
- yields a stream of Text, and follows
- standard pipes protocols by reverting to (i.e. returning) the underlying byte stream
- upon reaching any decoding error. (See especially the pipes-binary package.)
-
- By contrast, something like
-
-> Text.fromHandle :: Handle -> Producer Text IO ()
-
- supplies a stream of text returning '()', which is convenient for many tasks,
- but violates the pipes @pipes-binary@ approach to decoding errors and
- throws an exception of the kind characteristic of the @text@ library instead.
-
-
-}
{-| Convert a 'IO.Handle' into a text stream using a text size
{-# INLINABLE fromHandle#-}
-fromHandleLn :: MonadIO m => IO.Handle -> Producer Text m ()
-fromHandleLn h = go where
- getLine :: IO (Either G.IOException Text)
- getLine = try (T.hGetLine h)
-
- go = do txt <- liftIO getLine
- case txt of
- Left e -> return ()
- Right y -> do yield y
- go
-{-# INLINABLE fromHandleLn #-}
-
-- | Stream text from 'stdin'
stdin :: MonadIO m => Producer Text m ()
stdin = fromHandle IO.stdin
{-# INLINE readFile #-}
-{-| Stream lines of text from a file
--}
-readFileLn :: MonadSafe m => FilePath -> Producer Text m ()
-readFileLn file = Safe.withFile file IO.ReadMode fromHandleLn
-{-# INLINE readFileLn #-}
-
{-| Stream text to 'stdout'
projects / github / fretlink / text-pipes.git / commitdiff
