Parsing

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"

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

An exception raised when parsing fails.