alex-3.2.5/data/AlexWrapper-basic-bytestring

{-# LINE 1 "templates/wrappers.hs" #-}
-- -----------------------------------------------------------------------------
-- Alex wrapper code.
--
-- This code is in the PUBLIC DOMAIN; you may copy it freely and use
-- it for any purpose whatsoever.


import Data.Word (Word8)


import Data.Int (Int64)
import qualified Data.Char
import qualified Data.ByteString.Lazy     as ByteString
import qualified Data.ByteString.Internal as ByteString (w2c)


type Byte = Word8

-- -----------------------------------------------------------------------------
-- The input type


data AlexInput = AlexInput { alexChar :: {-# UNPACK #-} !Char,      -- previous char
                             alexStr ::  !ByteString.ByteString,    -- current input string
                             alexBytePos :: {-# UNPACK #-} !Int64}  -- bytes consumed so far

alexInputPrevChar :: AlexInput -> Char
alexInputPrevChar = alexChar

alexGetByte (AlexInput {alexStr=cs,alexBytePos=n}) =
    case ByteString.uncons cs of
        Nothing -> Nothing
        Just (c, rest) ->
            Just (c, AlexInput {
                alexChar = ByteString.w2c c,
                alexStr =  rest,
                alexBytePos = n+1})


-- -----------------------------------------------------------------------------
-- Token positions

-- `Posn' records the location of a token in the input text.  It has three
-- fields: the address (number of chacaters preceding the token), line number
-- and column of a token within the file. `start_pos' gives the position of the
-- start of the file and `eof_pos' a standard encoding for the end of file.
-- `move_pos' calculates the new position after traversing a given character,
-- assuming the usual eight character tab stops.


-- -----------------------------------------------------------------------------
-- Monad (default and with ByteString input)


-- -----------------------------------------------------------------------------
-- Basic wrapper


-- -----------------------------------------------------------------------------
-- Basic wrapper, ByteString version


-- alexScanTokens :: ByteString.ByteString -> [token]
alexScanTokens str = go (AlexInput '\n' str 0)
  where go inp__ =
          case alexScan inp__ 0 of
                AlexEOF -> []
                AlexError _ -> error "lexical error"
                AlexSkip  inp__' _len  -> go inp__'
                AlexToken inp__' _ act ->
                  let len = alexBytePos inp__' - alexBytePos inp__ in
                  act (ByteString.take len (alexStr inp__)) : go inp__'


-- -----------------------------------------------------------------------------
-- Posn wrapper

-- Adds text positions to the basic model.


-- -----------------------------------------------------------------------------
-- Posn wrapper, ByteString version


-- -----------------------------------------------------------------------------
-- GScan wrapper

-- For compatibility with previous versions of Alex, and because we can.