Std.Data.Parser

This module provide a simple resumable Parser, which is suitable for binary protocol and simple textual protocol parsing.

You can use Alternative instance to do backtracking, each branch will either succeed and may consume some input, or fail without consume anything. It's recommend to use peek to avoid backtracking if possible to get high performance.

Parser types

data Result a

Simple parsing result, that represent respectively:

• Success: the remaining unparsed data and the parsed value
• Failure: the remaining unparsed data and the error message
• Partial: that need for more input data, supply empty bytes to indicate endOfInput

Constructors

Success a !Bytes

Failure ParseError !Bytes

Partial (ParseStep a)

Instances

Functor Result

Defined in Std.Data.Parser.Base

Methods

fmap :: (a -> b) -> Result a -> Result b

(<$) :: a -> Result b -> Result a

Show a => Show (Result a)

Defined in Std.Data.Parser.Base

Methods

showsPrec :: Int -> Result a -> ShowS

show :: Result a -> String

showList :: [Result a] -> ShowS

type ParseError = [Text]

Type alias for error message

data Parser a

Simple CPSed parser

A parser takes a failure continuation, and a success one, while the success continuation is usually composed by Monad instance, the failure one is more like a reader part, which can be modified via <?>. If you build parsers from ground, a pattern like this can be used:

   xxParser = do
     ensureN errMsg ...            -- make sure we have some bytes
     Parser $  kf k inp ->        -- fail continuation, success continuation and input
       ...
       ... kf errMsg (if input not OK)
       ... k ... (if we get something useful for next parser)
 

Instances

Monad Parser

Defined in Std.Data.Parser.Base

Methods

(>>=) :: Parser a -> (a -> Parser b) -> Parser b

(>>) :: Parser a -> Parser b -> Parser b

return :: a -> Parser a

fail :: String -> Parser a

Functor Parser

Defined in Std.Data.Parser.Base

Methods

fmap :: (a -> b) -> Parser a -> Parser b

(<$) :: a -> Parser b -> Parser a

MonadFail Parser

Defined in Std.Data.Parser.Base

Methods

fail :: String -> Parser a

Applicative Parser

Defined in Std.Data.Parser.Base

Methods

pure :: a -> Parser a

(<*>) :: Parser (a -> b) -> Parser a -> Parser b

liftA2 :: (a -> b -> c) -> Parser a -> Parser b -> Parser c

(*>) :: Parser a -> Parser b -> Parser b

(<*) :: Parser a -> Parser b -> Parser a

Alternative Parser

Defined in Std.Data.Parser.Base

Methods

empty :: Parser a

(<|>) :: Parser a -> Parser a -> Parser a

some :: Parser a -> Parser [a]

many :: Parser a -> Parser [a]

MonadPlus Parser

Defined in Std.Data.Parser.Base

Methods

mzero :: Parser a

mplus :: Parser a -> Parser a -> Parser a

(<?>) :: Text -> Parser a -> Parser a infixr 0

Running a parser

parse :: Parser a -> Bytes -> (Bytes, Either ParseError a)

Parse the complete input, without resupplying, return the rest bytes

parse_ :: Parser a -> Bytes -> Either ParseError a

Parse the complete input, without resupplying

parseChunk :: Parser a -> Bytes -> Result a

Parse an input chunk

parseChunks :: Monad m => Parser a -> m Bytes -> Bytes -> m (Bytes, Either ParseError a)

Run a parser with an initial input string, and a monadic action that can supply more input if needed.

Note, once the monadic action return empty bytes, parsers will stop drawing more bytes (take it as endOfInput).

finishParsing :: Result a -> (Bytes, Either ParseError a)

Finish parsing and fetch result, feed empty bytes if it's Partial result.

runAndKeepTrack :: Parser a -> Parser (Result a, [Bytes])

Run a parser and keep track of all the input chunks it consumes. Once it's finished, return the final result (always Success or Failure) and all consumed chunks.

match :: Parser a -> Parser (Bytes, a)

Return both the result of a parse and the portion of the input that was consumed while it was being parsed.

Basic parsers

ensureN :: Int -> ParseError -> Parser ()

Ensure that there are at least n bytes available. If not, the computation will escape with Partial.

Since this parser is used in many other parsers, an extra error param is provide to attach custom error info.

endOfInput :: Parser ()

Test whether all input has been consumed, i.e. there are no remaining undecoded bytes. Fail if not atEnd.

atEnd :: Parser Bool

Test whether all input has been consumed, i.e. there are no remaining undecoded bytes.

Primitive decoders

decodePrim :: forall a. UnalignedAccess a => Parser a

decodePrimLE :: forall a. UnalignedAccess (LE a) => Parser a

decodePrimBE :: forall a. UnalignedAccess (BE a) => Parser a

More parsers

scan :: s -> (s -> Word8 -> Maybe s) -> Parser (Bytes, s)

A stateful scanner. The predicate consumes and transforms a state argument, and each transformed state is passed to successive invocations of the predicate on each byte of the input until one returns Nothing or the input ends.

This parser does not fail. It will return an empty string if the predicate returns Nothing on the first byte of input.

scanChunks :: s -> (s -> Bytes -> Either s (Bytes, Bytes, s)) -> Parser (Bytes, s)

Similar to scan, but working on Bytes chunks, The predicate consumes a Bytes chunk and transforms a state argument, and each transformed state is passed to successive invocations of the predicate on each chunk of the input until one chunk got splited to Right (V.Bytes, V.Bytes) or the input ends.

peekMaybe :: Parser (Maybe Word8)

Match any byte, to perform lookahead. Returns Nothing if end of input has been reached. Does not consume any input.

peek :: Parser Word8

Match any byte, to perform lookahead. Does not consume any input, but will fail if end of input has been reached.

satisfy :: (Word8 -> Bool) -> Parser Word8

The parser satisfy p succeeds for any byte for which the predicate p returns True. Returns the byte that is actually parsed.

digit = satisfy isDigit
    where isDigit w = w >= 48 && w <= 57

satisfyWith :: (Word8 -> a) -> (a -> Bool) -> Parser a

The parser satisfyWith f p transforms a byte, and succeeds if the predicate p returns True on the transformed value. The parser returns the transformed byte that was parsed.

word8 :: Word8 -> Parser ()

Match a specific byte.

char8 :: Char -> Parser ()

Match a specific 8bit char.

skipWord8 :: Parser ()

Skip a byte.

endOfLine :: Parser ()

Match either a single newline byte '\n', or a carriage return followed by a newline byte "\r\n".

skip :: Int -> Parser ()

skip N bytes.

skipWhile :: (Word8 -> Bool) -> Parser ()

Skip past input for as long as the predicate returns True.

skipSpaces :: Parser ()

Skip over white space using isSpace.

take :: Int -> Parser Bytes

takeTill :: (Word8 -> Bool) -> Parser Bytes

Consume input as long as the predicate returns False or reach the end of input, and return the consumed input.

takeWhile :: (Word8 -> Bool) -> Parser Bytes

Consume input as long as the predicate returns True or reach the end of input, and return the consumed input.

takeWhile1 :: (Word8 -> Bool) -> Parser Bytes

Similar to takeWhile, but requires the predicate to succeed on at least one byte of input: it will fail if the predicate never returns True or reach the end of input

bytes :: Bytes -> Parser ()

bytes s parses a sequence of bytes that identically match s.

bytesCI :: Bytes -> Parser ()

Same as bytes but ignoring case.

text :: Text -> Parser ()

text s parses a sequence of UTF8 bytes that identically match s.

Numeric parsers

Decimal

uint :: Integral a => Parser a

Parse and decode an unsigned decimal number.

int :: Integral a => Parser a

Parse a decimal number with an optional leading '+' or '-' sign character.

Hex

hex :: (Integral a, Bits a) => Parser a

Parse and decode an unsigned hex number. The hex digits 'a' through 'f' may be upper or lower case.

This parser does not accept a leading "0x" string, and consider sign bit part of the binary hex nibbles, i.e. 'parse hex "0xFF" == Right (-1 :: Int8)'

Fractional

rational :: Fractional a => Parser a

Parse a rational number.

The syntax accepted by this parser is the same as for double.

Note: this parser is not safe for use with inputs from untrusted sources. An input with a suitably large exponent such as "1e1000000000" will cause a huge Integer to be allocated, resulting in what is effectively a denial-of-service attack.

In most cases, it is better to use double or scientific instead.

float :: Parser Float

Parse a rational number and round to Float.

Single precision version of double.

double :: Parser Double

Parse a rational number and round to Double.

This parser accepts an optional leading sign character, followed by at least one decimal digit. The syntax similar to that accepted by the read function, with the exception that a trailing '.' or 'e' not followed by a number is not consumed.

Examples with behaviour identical to read:

parse_ double "3"     == ("", Right 3.0)
parse_ double "3.1"   == ("", Right 3.1)
parse_ double "3e4"   == ("", Right 30000.0)
parse_ double "3.1e4" == ("", Right 31000.0)

parse_ double ".3"    == (".3", Left ParserError)
parse_ double "e3"    == ("e3", Left ParserError)

Examples of differences from read:

parse_ double "3.foo" == (".foo", Right 3.0)
parse_ double "3e"    == ("e",    Right 3.0)
parse_ double "-3e"   == ("e",    Right -3.0)

This function does not accept string representations of "NaN" or "Infinity".

scientific :: Parser Scientific

Parse a scientific number.

The syntax accepted by this parser is the same as for double.

scientifically :: (Scientific -> a) -> Parser a

Parse a scientific number and convert to result using a user supply function.

The syntax accepted by this parser is the same as for double.

Stricter fractional(rfc8259)

rational' :: Fractional a => Parser a

Parse a rational number.

The syntax accepted by this parser is the same as for double'.

Note: this parser is not safe for use with inputs from untrusted sources. An input with a suitably large exponent such as "1e1000000000" will cause a huge Integer to be allocated, resulting in what is effectively a denial-of-service attack.

In most cases, it is better to use double' or scientific' instead.

float' :: Parser Float

Parse a rational number and round to Float using stricter grammer.

Single precision version of double'.

double' :: Parser Double

More strict number parsing(rfc8259).

scientific support parse 2314. and 21321exyz without eating extra dot or e via backtrack, this is not allowed in some strict grammer such as JSON, so we make an non-backtrack strict number parser separately using LL(1) lookahead. This parser also agree with read on extra dot or e handling:

parse_ double "3.foo" == Left ParseError
parse_ double "3e"    == Left ParseError

Leading zeros or + sign is also not allowed:

parse_ double "+3.14" == Left ParseError
parse_ double "0014" == Left ParseError

If you have a similar grammer, you can use this parser to save considerable time.

     number = [ minus ] int [ frac ] [ exp ]
     decimal-point = %x2E       ; .
     digit1-9 = %x31-39         ; 1-9
     e = %x65 / %x45            ; e E
     exp = e [ minus / plus ] 1*DIGIT
     frac = decimal-point 1*DIGIT

This function does not accept string representations of "NaN" or "Infinity". reference: https://tools.ietf.org/html/rfc8259#section-6

scientific' :: Parser Scientific

Parse a scientific number.

The syntax accepted by this parser is the same as for double'.

scientifically' :: (Scientific -> a) -> Parser a

Parse a scientific number and convert to result using a user supply function.

The syntax accepted by this parser is the same as for double'.

Misc

isSpace :: Word8 -> Bool

isSpace w = w == 32 || w - 9 <= 4 || w == 0xA0

isHexDigit :: Word8 -> Bool

A fast digit predicate.

isDigit :: Word8 -> Bool

A fast digit predicate.