92 lines
2.4 KiB
Haskell
92 lines
2.4 KiB
Haskell
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{-# LANGUAGE BangPatterns #-}
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{-# LANGUAGE DeriveDataTypeable #-}
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{-# LANGUAGE TypeFamilies #-}
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{-# LANGUAGE RebindableSyntax #-}
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{-# LANGUAGE NoImplicitPrelude #-}
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-- |
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-- Module : Basement.String.Encoding.ASCII7
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-- License : BSD-style
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-- Maintainer : Foundation
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-- Stability : experimental
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-- Portability : portable
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--
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{-# LANGUAGE MagicHash #-}
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module Basement.String.Encoding.ASCII7
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( ASCII7(..)
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, ASCII7_Invalid(..)
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) where
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import Basement.Compat.Base
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import Basement.Compat.Primitive
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import Basement.Types.OffsetSize
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import Basement.Numerical.Additive
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import Basement.Monad
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import Basement.Bits
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import GHC.Prim (int2Word#, ord#)
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import GHC.Word
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import GHC.Types
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import Basement.UArray
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import Basement.UArray.Mutable (MUArray)
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import Basement.MutableBuilder
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import Basement.String.Encoding.Encoding
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-- | validate a given byte is within ASCII characters encoring size
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--
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-- This function check the 8th bit is set to 0
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--
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isAscii :: Word8 -> Bool
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isAscii w = (w .&. 0x80) == 0
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{-# INLINE isAscii #-}
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data ASCII7_Invalid
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= ByteOutOfBound Word8
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| CharNotAscii Char
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deriving (Typeable, Show, Eq)
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instance Exception ASCII7_Invalid
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data ASCII7 = ASCII7
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instance Encoding ASCII7 where
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type Unit ASCII7 = Word8
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type Error ASCII7 = ASCII7_Invalid
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encodingNext _ = next
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encodingWrite _ = write
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-- | consume an Ascii7 char and return the Unicode point and the position
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-- of the next possible Ascii7 char
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--
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next :: (Offset Word8 -> Word8)
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-- ^ method to access a given byte
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-> Offset Word8
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-- ^ index of the byte
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-> Either ASCII7_Invalid (Char, Offset Word8)
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-- ^ either successfully validated the ASCII char and returned the
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-- next index or fail with an error
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next getter off
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| isAscii w8 = Right (toChar w, off + 1)
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| otherwise = Left $ ByteOutOfBound w8
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where
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!w8@(W8# w) = getter off
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toChar :: Word8# -> Char
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toChar a = C# (word8ToChar# w)
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-- Write ascii char
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--
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-- > build 64 $ sequence_ write "this is a simple list of char..."
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--
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write :: (PrimMonad st, Monad st)
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=> Char
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-- ^ expecting it to be a valid Ascii character.
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-- otherwise this function will throw an exception
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-> Builder (UArray Word8) (MUArray Word8) Word8 st err ()
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write c
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| c < toEnum 0x80 = builderAppend $ w8 c
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| otherwise = throw $ CharNotAscii c
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where
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w8 :: Char -> Word8
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w8 (C# ch) = W8# (wordToWord8# (int2Word# (ord# ch)))
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