System.IO.Streams.Attoparsec

This module provides support for parsing values from InputStreams using attoparsec.

Parsing

parseFromStream :: Parser r -> InputStream ByteString -> IO r

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.ByteString.Char8
ghci> is <- fromList ["12345xxx" :: ByteString]
ghci> parseFromStream (takeWhile isDigit) is
"12345"
ghci> read is
Just "xxx"

parserToInputStream :: Parser (Maybe r) -> InputStream ByteString -> IO (InputStream r)

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.ByteString.Char8
ghci> is <- fromList ["1 2 3 4 5" :: ByteString]
ghci> let parser = (endOfInput >> pure Nothing) <|> (Just <$> (skipWhile isSpace *> decimal))
ghci> parserToInputStream parser is >>= toList
[1,2,3,4,5]
ghci> is' <- fromList ["1 2xx3 4 5" :: ByteString] >>= parserToInputStream parser
ghci> read is'
Just 1
ghci> read is'
Just 2
ghci> read is'
*** Exception: Parse exception: Failed reading: takeWhile1

data ParseException

An exception raised when parsing fails.

Constructors

ParseException String

Instances

Show ParseException

Exception ParseException

Typeable * ParseException