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|
-- |
-- Module : Basement.String.Encoding.Encoding
-- License : BSD-style
-- Maintainer : Foundation
-- Stability : experimental
-- Portability : portable
--
{-# LANGUAGE FlexibleContexts #-}
module Basement.String.Encoding.Encoding
( Encoding(..)
, convertFromTo
) where
import Basement.Compat.Base
import Basement.Types.OffsetSize
import Basement.Monad
import Basement.PrimType
import Basement.MutableBuilder
import Basement.Numerical.Additive
import Basement.UArray (UArray)
import Basement.UArray.Mutable (MUArray)
import qualified Basement.UArray as Vec
class Encoding encoding where
-- | the unit element use for the encoding.
-- i.e. Word8 for ASCII7 or UTF8, Word16 for UTF16...
--
type Unit encoding
-- | define the type of error handling you want to use for the
-- next function.
--
-- > type Error UTF8 = Either UTF8_Invalid
--
type Error encoding
-- | consume an `Unit encoding` and return the Unicode point and the position
-- of the next possible `Unit encoding`
--
encodingNext :: encoding
-- ^ only used for type deduction
-> (Offset (Unit encoding) -> Unit encoding)
-- ^ method to access a given `Unit encoding`
-- (see `unsafeIndexer`)
-> Offset (Unit encoding)
-- ^ offset of the `Unit encoding` where starts the
-- encoding of a given unicode
-> Either (Error encoding) (Char, Offset (Unit encoding)) -- ^ either successfully validated the `Unit encoding`
-- and returned the next offset or fail with an
-- `Error encoding`
-- Write a unicode point encoded into one or multiple `Unit encoding`
--
-- > build 64 $ sequence_ (write UTF8) "this is a simple list of char..."
--
encodingWrite :: (PrimMonad st, Monad st)
=> encoding
-- ^ only used for type deduction
-> Char
-- ^ the unicode character to encode
-> Builder (UArray (Unit encoding))
(MUArray (Unit encoding))
(Unit encoding) st err ()
-- | helper to convert a given Array in a given encoding into an array
-- with another encoding.
--
-- This is a helper to convert from one String encoding to another.
-- This function is (quite) slow and needs some work.
--
-- ```
-- let s16 = ... -- string in UTF16
-- -- create s8, a UTF8 String
-- let s8 = runST $ convertWith UTF16 UTF8 (toBytes s16)
--
-- print s8
-- ```
--
convertFromTo :: ( PrimMonad st, Monad st
, Encoding input, PrimType (Unit input)
, Encoding output, PrimType (Unit output)
)
=> input
-- ^ Input's encoding type
-> output
-- ^ Output's encoding type
-> UArray (Unit input)
-- ^ the input raw array
-> st (Either (Offset (Unit input), Error input) (UArray (Unit output)))
convertFromTo inputEncodingTy outputEncodingTy bytes
| Vec.null bytes = return . return $ mempty
| otherwise = Vec.unsafeIndexer bytes $ \t -> Vec.builderBuild 64 (loop azero t)
where
lastUnit = Vec.length bytes
loop off getter
| off .==# lastUnit = return ()
| otherwise = case encodingNext inputEncodingTy getter off of
Left err -> mFail (off, err)
Right (c, noff) -> encodingWrite outputEncodingTy c >> loop noff getter
|
