-- | This module provides support for parsing values from Text -- 'InputStream's using @attoparsec@. /Since: 1.4.0.0./ module System.IO.Streams.Attoparsec.Text ( -- * Parsing parseFromStream , parserToInputStream , ParseException(..) ) where ------------------------------------------------------------------------------ import Data.Attoparsec.Text (Parser) import Data.Text (Text) ------------------------------------------------------------------------------ import System.IO.Streams.Internal (InputStream) import qualified System.IO.Streams.Internal as Streams import System.IO.Streams.Internal.Attoparsec (ParseData (..), ParseException (..), parseFromStreamInternal) ------------------------------------------------------------------------------ -- | Supplies an @attoparsec@ 'Parser' with an 'InputStream', returning the -- final parsed value or throwing a 'ParseException' if parsing fails. -- -- 'parseFromStream' consumes only as much input as necessary to satisfy the -- 'Parser': any unconsumed input is pushed back onto the 'InputStream'. -- -- If the 'Parser' exhausts the 'InputStream', the end-of-stream signal is sent -- to attoparsec. -- -- Example: -- -- @ -- ghci> import "Data.Attoparsec.Text" -- ghci> is <- 'System.IO.Streams.fromList' [\"12345xxx\" :: 'Text'] -- ghci> 'parseFromStream' ('Data.Attoparsec.Text.takeWhile' 'Data.Char.isDigit') is -- \"12345\" -- ghci> 'System.IO.Streams.read' is -- Just \"xxx\" -- @ parseFromStream :: Parser r -> InputStream Text -> IO r parseFromStream = parseFromStreamInternal parse feed ------------------------------------------------------------------------------ -- | Given a 'Parser' yielding values of type @'Maybe' r@, transforms an -- 'InputStream' over byte strings to an 'InputStream' yielding values of type -- @r@. -- -- If the parser yields @Just x@, then @x@ will be passed along downstream, and -- if the parser yields @Nothing@, that will be interpreted as end-of-stream. -- -- Upon a parse error, 'parserToInputStream' will throw a 'ParseException'. -- -- Example: -- -- @ -- ghci> import "Control.Applicative" -- ghci> import "Data.Attoparsec.Text" -- ghci> is <- 'System.IO.Streams.fromList' [\"1 2 3 4 5\" :: 'Text'] -- ghci> let parser = ('Data.Attoparsec.Text.endOfInput' >> 'Control.Applicative.pure' 'Nothing') \<|\> (Just \<$\> ('Data.Attoparsec.Text.skipWhile' 'Data.Attoparsec.Text.isSpace' *> 'Data.Attoparsec.Text.decimal')) -- ghci> 'parserToInputStream' parser is >>= 'System.IO.Streams.toList' -- [1,2,3,4,5] -- ghci> is' \<- 'System.IO.Streams.fromList' [\"1 2xx3 4 5\" :: 'Text'] >>= 'parserToInputStream' parser -- ghci> 'read' is' -- Just 1 -- ghci> 'read' is' -- Just 2 -- ghci> 'read' is' -- *** Exception: Parse exception: Failed reading: takeWhile1 -- @ parserToInputStream :: Parser (Maybe r) -> InputStream Text -> IO (InputStream r) parserToInputStream = (Streams.makeInputStream .) . parseFromStream {-# INLINE parserToInputStream #-}