-- module for things dealing with string constants needed by the compiler internally
{-# LANGUAGE NoImplicitPrelude, MagicHash #-}
{-# OPTIONS_JHC -fffi -funboxed-values #-}
module Jhc.String(
    eqString,
    eqUnpackedString,
    unpackStringFoldr,
    unpackString
    )where

import Jhc.Type.Basic
import Jhc.Prim.Prim

{-# VCONSTRUCTOR unpackString #-}
{-# NOINLINE unpackString #-}
unpackString :: Addr__ -> [Char]
unpackString addr = f addr where
    f addr = case constPeekByte addr of
        '\0'# -> []
        c -> (Char c:f (increment addr))

unpackStringFoldr :: Addr__ -> (Char -> b -> b) -> b -> b
unpackStringFoldr addr cons nil = f addr where
    f addr = case constPeekByte addr of
        '\0'# -> nil
        c -> (Char c `cons` f (increment addr))

{-# NOINLINE eqUnpackedString #-}
eqUnpackedString :: Addr__ -> [Char] -> Bool_
eqUnpackedString addr cs = f addr cs where
    f :: Addr__ -> [Char] -> Bool_
    f offset [] = case constPeekByte offset of '\0'# -> 1#; _ -> 0#
    f offset (Char c:cs) = case constPeekByte offset of
        '\0'# -> 0#
        uc -> case equalsChar uc c of
            0# -> 0#
            1# -> f (increment offset) cs

eqString :: [Char] -> [Char] -> Bool_
eqString [] [] = 1#
eqString (Char x:xs) (Char y:ys) = case equalsChar x y of
    0# -> 0#
    1# -> eqString xs ys
eqString _ _ = 0#

foreign import primitive increment :: Addr__ -> Addr__
foreign import primitive "Eq" equalsChar :: Char_ -> Char_ -> Bool_
foreign import primitive constPeekByte :: Addr__ -> Char_

{-
unpackFoldrString :: Addr__ -> (Char_ -> b -> b) -> b -> b
unpackFoldrString addr f e = unpack addr where
    unpack addr = case constPeekByte addr of
      '\NUL'# -> e
      ch  | ch `leChar_` '\x7F'# = ch `f` unpack (increment addr)
          | ch `leChar_` '\xDF'# = (((ch .&. '\x1f') `shiftL` 6#) .|. (constPeekByte (increment addr) .&. '\x3f')) `f` unpack (increment (increment addr))
           (chr# (((ord# ch                                  -# 0xC0#) `uncheckedIShiftL#`  6#) +#
                     (ord# (indexCharArray# addr (nh +# 1#)) -# 0x80#))) `f`
          unpack (nh +# 2#)
      | ch `leChar#` '\xEF'# =
           (chr# (((ord# ch                                  -# 0xE0#) `uncheckedIShiftL#` 12#) +#
                    ((ord# (indexCharArray# addr (nh +# 1#)) -# 0x80#) `uncheckedIShiftL#`  6#) +#
                     (ord# (indexCharArray# addr (nh +# 2#)) -# 0x80#))) `f`
          unpack (nh +# 3#)
      | otherwise            =
           (chr# (((ord# ch                                  -# 0xF0#) `uncheckedIShiftL#` 18#) +#
                    ((ord# (indexCharArray# addr (nh +# 1#)) -# 0x80#) `uncheckedIShiftL#` 12#) +#
                    ((ord# (indexCharArray# addr (nh +# 2#)) -# 0x80#) `uncheckedIShiftL#`  6#) +#
                     (ord# (indexCharArray# addr (nh +# 3#)) -# 0x80#))) `f`
          unpack (nh +# 4#)
      where
	ch = indexCharArray# addr nh

eqSingleChar :: Char_ -> [Char] -> Bool_
eqSingleChar ch (Char c:cs) = case equalsChar ch c of
    0# -> 0#
    1# -> case cs of
        [] -> 1#
        _ ->  0#

{-# NOINLINE eqUnpacked #-}
eqUnpacked :: Addr__ -> [Char] -> Bool_
eqUnpacked addr cs = f addr cs where
    f :: Addr__ -> [Char] -> Bool_
    f offset [] = case constPeekByte offset of '\0'# -> 1#;  _ -> 0#
    f offset (Char c:cs) = case constPeekByte offset of
        '\NUL'# -> 0#
        uc -> case equalsChar uc c of
            0# -> 0#
            1# -> f (increment offset) cs

-}