{-# OPTIONS -XMagicHash -XUnboxedTuples -XRecordWildCards -XNamedFieldPuns -XNoImplicitPrelude -cpp #-}
{-# LANGUAGE ForeignFunctionInterface #-}
-- | Implementation of the ideas in 
-- <http://www.cs.ubc.ca/local/reading/proceedings/spe91-95/spe/vol25/issue12/spe986.pdf>.
-- Inspired also by "Data.Map" and the OCaml version of ropes.
module Data.Rope(
  -- * The 'Rope' type
  Rope,
  -- * Introducing and eliminating 'Rope's
  empty,
  singleton,
  pack,
  unpack,
  fromByteString,
  toByteString,
  -- * Basic interface
  cons,
  snoc,
  append,
  head,
  uncons,
  last,
  tail,
  init,
  null,
  length,
  -- * Transforming 'Rope's
  map,
  reverse,
  intercalate,
  -- * Concatenations
  insert,
  -- * Reducing 'Rope's
  foldl,
  foldl',
  foldr,
  -- * Breaking 'Rope's
  take,
  drop,
  splitAt#,
  splitAt,
  breakByte,
  breaks,
  lines,
  -- * Indexing 'Rope's
  index,
  elemIndex,
  elemIndex',
  elemIndices,
  -- * Input and Output
  readFile,
  hGet,
  hGetLine,
  hGetContents,
  hPut,
  hPutStrLn,
  hPutStr,
  putStrLn,
  putStr,  

  ) where

import Foreign.Storable
import Foreign.ForeignPtr
import qualified Foreign.Concurrent as FC
import Foreign.Marshal.Array
import Foreign.Marshal.Utils
import Foreign.Ptr

import Foreign.C.Types

import qualified Data.ByteString.Internal as B
import Data.String
import Data.Word
import Control.Exception (finally)
#if __GLASGOW_HASKELL__ >=608
import GHC.IO (IO(IO),unsafePerformIO,unsafeInterleaveIO)
import GHC.Base (realWorld#)
import GHC.IO.Handle.Types
--import GHC.IO.Handle.Internals
import GHC.IO.Device as IODevice
#else
import System.IO.Unsafe
#endif
import Data.Maybe
import GHC.Conc (par)

import System.Posix (openFd,closeFd,defaultFileFlags,getFileStatus,
                     fileSize,OpenMode(..))

import System.IO (hGetBuf,hPutBuf,hSeek,hTell,
                  hPutChar, stdout, hClose)
import System.IO.Posix.MMap.Internal(c_mmap,c_munmap)

import qualified Prelude(length,map,splitAt)
import Prelude hiding (length,null,head,tail,last,init,map,reverse,
                       foldl,foldr,
                       take,drop,splitAt,lines,
                       putStrLn,putStr,readFile)
import Data.Bits hiding(rotateL,rotateR)

data Rope=
  Concat { sizeC:: !Int,
           length_:: !Int,
           l::Rope,
           r::Rope }
  | String { contents:: !(ForeignPtr Word8),
             i0:: !(ForeignPtr Int),
             offset:: !Int,
             length_:: !Int }

instance IsString Rope where
  fromString s=pack $ Prelude.map (fromIntegral.fromEnum) s


instance Show Rope where
  show s="\""++(Prelude.map (toEnum.fromIntegral) $ unpack s)++"\""

{-
instance Show Rope where
  show (s@String{})=show ((Prelude.map (toEnum.fromIntegral) $ unpack s)::String)
  show (Concat{l,r})="Concat { l="++(show l)++"\nr="++(show r)
-}

instance Eq Rope where
  (==) String{contents=ca,offset=oa,length_=la}
    String{contents=cb, offset=ob, length_=lb} =
    
    la==lb &&
    (inlinePerformIO $ (withForeignPtr ca $ \pa->
                         withForeignPtr cb $ \pb->do
                           x<-strncmp (pa`plusPtr`oa) (pb`plusPtr`ob) (fromIntegral la)
                           return $ x == 0))
  
  (==) a b=
    (length a == length b) &&
    (case (a,b) of
        (Concat{l,r}, _) -> 
          let (# x,y #)=splitAt# (length l) b in
          x==l && y==r
        (_,Concat{l,r})->
          let (# x,y #)=splitAt# (length l) a in
          x==l && y==r
        _->undefined) -- never happens
    
    
instance Ord Rope where
  compare (String{contents=ca,offset=oa,length_=la})
    (String{contents=cb, offset=ob, length_=lb}) =
    
    inlinePerformIO $ (withForeignPtr ca $ \pa->withForeignPtr cb $ \pb->do
                          x<-strncmp (pa`plusPtr`oa) (pb`plusPtr`ob) (fromIntegral $ min la lb)
                          if x==0 then return $ compare la lb else
                            return $ compare x 0)
  
  compare a_ b_=
    let (a,b)=if length a_<length b_ then (b_,a_) else (a_,b_) in
    case (a,b) of
      (_,Concat{l,r})->
        let (# x,y #)=splitAt# (length l) a in
        case compare x l of
          EQ->compare y r
          ord->ord
      (Concat{l,r},_)->
        let (# x,y #)=splitAt# (length l) b in
        case compare l x of
          EQ->compare r y
          ord->ord
      _->undefined --never happens


  
-- | leafLen est la taille standard des blocs de feuilles.
leafSize::Int
leafSize=0x10000

-- | O(log n). Appends the specified byte at the beginning of the 'Rope'.
cons::Word8->Rope->Rope
cons w x=append (singleton w) x
{-# INLINE cons #-}

-- | O(log n). Appends the specified byte at the end of the 'Rope'.
snoc::Rope->Word8->Rope
snoc x w=append x (singleton w)
{-# INLINE snoc #-}

-- | O(log n) First element of the 'Rope'. Raises an error if the argument is empty.
head::Rope->Word8
head (String{contents,offset,length_})
  |length_>0 = inlinePerformIO $ withForeignPtr contents $ \c->peekByteOff c offset
  |otherwise = error "head"
head (Concat{l})=head l

-- | O(log n). Returns the first element of the 'Rope', and the 'Rope' of the
-- remaining elements.
uncons::Rope->Maybe (Word8, Rope)
uncons (s@String{contents,offset,length_})
  | length_<=0 = Nothing
  | otherwise=
    let u=inlinePerformIO $ withForeignPtr contents $ \c->peekByteOff c offset in
    Just (u,s { contents,offset=offset+1,length_=length_-1 })
uncons (c@Concat{l,r,length_})=
  case uncons l of
    Just (x,y)->Just (x,balance $ c { l=y, length_=length_-1 })
    Nothing->uncons r

-- | O(log n). Last element of a 'Rope'.
last::Rope->Word8
last (String{contents,offset,length_})
  | length_<=0 = error "last"
  | otherwise = inlinePerformIO $ withForeignPtr contents $ \c->peekByteOff c $ offset+length_-1
last (Concat{l,r})
  |size r<=0 = last l
  |otherwise = last r


-- | O(log n) The elements after the head. An error is raised if the 'Rope' is empty.
tail::Rope->Rope
tail (s@String{offset,length_})
  | length_<=0 = error "tail"
  | otherwise = s { offset=offset+1,length_=length_-1 }
tail (c@Concat{l,r})
  | length l<=0 = tail r
  | otherwise = balance $ c { l=tail l }


-- | O(log n) The elements in the 'Rope' except the last one.
init::Rope->Rope
init (s@String{length_})
  | length_<=0 = error "init"
  | otherwise = s { length_=length_-1 }
init (s@Concat{r})=balance $ s { r=init r }

-- | O(1) Tests whether a 'Rope' is empty.
null::Rope->Bool
null x=length x==0

-- | O(1) Length of a 'Rope'.
length::Rope->Int
length (String{length_})=length_
length (Concat{length_})=length_

size::Rope->Int
size (Concat {sizeC})=sizeC
size _=1

-- | O(n). @'map' f r@ applies @f@ on each element of @r@ and returns the
-- concatenation of the result.
map::(Word8->Word8)->Rope->Rope
map f (String{contents,offset,length_})=
  unsafePerformIO $ withForeignPtr contents $ \c->do
    cont<-mallocForeignPtrBytes leafSize
    withForeignPtr cont $ \p->copyMap p (c`plusPtr`offset) length_
    
    i0<-mallocForeignPtr
    withForeignPtr i0 $ \i->poke i length_
    
    return $ String { contents=cont,offset=0,length_,i0 }

      where
        copyMap _ _ 0=return ()
        copyMap p p' len=do
          peek p' >>= ((poke p).f)
          copyMap (p`plusPtr`1) (p'`plusPtr`1) $ len-1

map f (Concat{l,r})=append (map f l) (map f r)

-- | O(n) efficient way to reverse a 'Rope'.
reverse::Rope->Rope
reverse (String{contents,offset,length_})=
  unsafePerformIO $ withForeignPtr contents $ \c->do
    cont<-mallocForeignPtrBytes leafSize
    withForeignPtr cont $ \p->
      copyRev (p`plusPtr`(length_-1)) (c`plusPtr`offset) length_
    
    i0<-mallocForeignPtr
    withForeignPtr i0 $ \i->poke i length_
    
    return $ String { contents=cont,offset=0,length_,i0 }

      where
        copyRev::Ptr Word8->Ptr Word8->Int->IO()
        copyRev _ _ 0=return ()
        copyRev p p' len=do
          peek p' >>= poke p
          copyRev (p`plusPtr`(-1)) (p'`plusPtr`1) $ len-1

reverse (Concat{l,r})=append (reverse r) (reverse l)

-- | O(n) intercalate an element between each element of the list of 'Rope's
-- and concatenates the result.
intercalate::Rope->[Rope]->Rope
intercalate rope list=
  intercalate_ list empty
  where
    intercalate_ [] x=x
    intercalate_ [h] x=append x h
    intercalate_ (h:s) x=intercalate_ s (append (append h rope) x)

-- | O(1) The empty 'Rope'
empty::Rope
empty=unsafePerformIO $ do
  contents<-mallocForeignPtrArray leafSize
  i0<-mallocForeignPtr
  withForeignPtr i0 $ \i->poke i (-1)
  return $ String { contents,i0,offset=0,length_=0 }

-- | O(1) Convert a 'Word8' into a 'Rope'
singleton::Word8->Rope
singleton c=unsafePerformIO $ do
  contents<-mallocForeignPtrArray leafSize
  withForeignPtr contents $ \con->poke con c
  i0<-mallocForeignPtr
  withForeignPtr i0 $ \i->poke i 1
  return $ String { contents,i0,offset=0,length_=1 }

-- | O(n) Convert a list of 'Word8' into a 'Rope'
pack::[Word8]->Rope
pack s=
  if Prelude.length s<=leafSize then unsafePerformIO $ do
    contents<-mallocForeignPtrArray leafSize
    i0<-mallocForeignPtr
    withForeignPtr i0 $ \i->poke i $ Prelude.length s
    withForeignPtr contents $ \c->fillPtr c s
    return $ String { contents, i0, offset=0, length_=Prelude.length s }
  else
    let (a,b)=Prelude.splitAt leafSize s in
    append (pack a) (pack b)

    where
      fillPtr::Storable a=>Ptr a->[a]->IO ()
      fillPtr _ []=return ()
      fillPtr ptr (h:t)=do
        poke ptr h
        fillPtr (plusPtr ptr 1) t



-- | O(n) Inverse conversion
unpack::Rope->[Word8]
unpack (Concat{l,r})=unpack l++unpack r
unpack (String{contents,offset,length_})=
  unsafePerformIO $
  mapM (\i->withForeignPtr contents $
            \c->peek (plusPtr c i)::IO Word8) [offset..(offset+length_-1)]


-- | O(log n) Concatenates two 'Rope's
append::Rope->Rope->Rope
append sa@(String {}) sb@(String{})
  |length sa + offset sa + length sb <= leafSize = unsafePerformIO $ do
    i0_<-withForeignPtr (i0 sa) $ peek
    let l=length sa
    if i0_<offset sa+l then do
      withForeignPtr (i0 sa) $ \i->poke i $ offset sa+l+length sb
      withForeignPtr (contents sa) $
        \ca->withForeignPtr (contents sb) $
             \cb->copyArray (ca`plusPtr`(l+offset sa)::Ptr Word8) 
                  (cb`plusPtr`(offset sb)) $ length sb
      return $ sa { length_=length sa+length sb }
      else
      return $ Concat { sizeC=3,
                        length_=length sa+length sb,
                        l=sa,
                        r=sb }

  |otherwise=
    Concat { sizeC=3,
             length_=length sa+length sb,
             l=sa,
             r=sb }

append x@String{} y@Concat{sizeC,l}=balance $ y { sizeC=1+sizeC,
                                                  length_=length x+length y,
                                                  l=append x l }
append x y = balance $ Concat { sizeC=size x+size y,
                                length_=length x+length y,
                                l=x,
                                r=y }



-- | O(log n) @'insert' a i b@ inserts 'Rope' @a@ in 'Rope' @b@ after the @i@th element of @b@.
insert::Rope->Int->Rope->Rope
insert a 0 b=append a b
insert a i (b@String{})=
  balance $ Concat { sizeC=size a+size b,
                     length_=length a+length b,
                     l=String { contents=contents b,
                                i0=i0 b,
                                offset=offset b,
                                length_=min i $ length b },
                     r=append a $ String { contents=contents b,
                                           i0=i0 b,
                                           offset=i+offset b,
                                           length_=max 0 $ (length b)-i }
                   }
  
insert a i (b@Concat{})
  |i>=(length $ r b) = balance $ b { r=insert a (i-(length $ r b)) $ r b }
  |otherwise = balance $ b { l=insert a i $ l b}
                    

delta,ratio::Int
delta=5
ratio=2

balance,rotateL,rotateR,singleL,singleR,doubleL,doubleR::Rope->Rope

balance x=case x of
  String{}->x
  Concat{l,r}
    | length l==0 -> r
    | length r==0 -> l
    | size r>=delta*size l -> rotateL x
    | size l>=delta*size r -> rotateR x
    | otherwise->x
  
rotateL x=case x of
  String{}->x
  Concat{r}->case r of
    String{}->x
    Concat{l=rl,r=rr}
      |size rl<ratio*size rr -> singleL x
      |otherwise -> doubleL x

rotateR x=case x of
  String{}->x
  Concat{l}->case l of
    String{}->x
    Concat{l=ll,r=lr}
      |size lr<ratio*size ll -> singleR x
      |otherwise -> doubleR x



singleL (a@String{})=a
singleL (b@Concat{})=
  case r b of
    d@Concat{}->
      let b'=append (l b) (l d)
             {- Concat { length_=(length $ l b)+(length $ l d),
                     sizeC=(size $ l b)+(size $ l d)+1,
                     l=l b,
                     r=l d } -}
      in
       Concat { length_=length b,
                sizeC=size b,
                r=r d,
                l=b' }
                             
    _->b

singleR (d@Concat{})=
  case l d of
    b@Concat{}->
      let d'=append (r b) (r d)
             {- Concat { length_=(length $ r b)+(length $ r d),
                     sizeC=(size $ r b)+(size $ r d)+1,
                     l=r b,
                     r=r d } -}
      in
       Concat { length_=length d,
                sizeC=size d,
                r=d',
                l=l b }
    _->d
singleR a=a
    

doubleL (a@Concat{})=singleL $ a { l=singleR $ l a }
doubleL a=a
doubleR (a@Concat{})=singleR $ a { r=singleL $ r a }
doubleR a=a

foreign import ccall unsafe "string.h memchr" memchr::Ptr Word8->Word8->CSize->IO (Ptr Word8)
foreign import ccall unsafe "string.h strncmp" strncmp::Ptr Word8->Ptr Word8->CSize->IO CInt

{-# INLINE inlinePerformIO #-}
inlinePerformIO::IO a->a
#ifdef __GLASGOW_HASKELL__
inlinePerformIO (IO m)=case m realWorld# of (# _, r #)->r
#else
inlinePerformIO=unsafePerformIO
#endif

-- | O(log n) returns the 'Word8' at given index in the 'Rope'
index::Rope->Int->Char
index c i
  |i>=length c = error $ "index trop grand : "++(show i)++", longueur = "++(show $ length c)
  |otherwise=index_ c i
    where 
      index_ (String{contents,offset}) i_=
        inlinePerformIO $ withForeignPtr contents $ 
        \con->do
          x<-peek $ plusPtr con (offset+i_) :: IO Word8
          return $ toEnum $ fromIntegral x
      index_ (Concat{r,l}) i_
        |i_>=length l = index_ r (i_-length l)
        |otherwise = index_ l i_


-- | O(n) returns the index of the first element equal to the query element. This implementation
-- uses memchr at leaves, and explores the rope in parallel (with 'GHC.Conc.par').

elemIndex::Word8->Rope->Maybe Int
elemIndex w rope=
  elemIndex_ 0 rope
  where
    elemIndex_ i (String{contents,offset,length_})=
      inlinePerformIO $ withForeignPtr contents $ \con->do
        ptr<-memchr (con`plusPtr`offset) w (fromIntegral length_)
        return $ if ptr==nullPtr then Nothing else Just $ i+offset+(ptr`minusPtr`con)
        
    elemIndex_ i (Concat{l,r})=
      let sl=elemIndex_ i l
          sr=elemIndex_ (i+length l) r
      in
       (sl`par`sr)`seq`(if isNothing sl then sr else sl)
       

-- | O(n) Same as 'elemIndex', but explores the 'Rope' sequentially. Useful for
-- 'Rope's loaded lazily with 'readFile'.

elemIndex'::Word8->Rope->Maybe Int
elemIndex' w rope=
  elemIndex_ 0 rope
  where
    elemIndex_ i (String{contents,offset,length_})=
      inlinePerformIO $ withForeignPtr contents $ \con->do
        ptr<-memchr (con`plusPtr`offset) w (fromIntegral length_)
        return $ if ptr==nullPtr then Nothing else Just $ i+offset+(ptr`minusPtr`con)
        
    elemIndex_ i (Concat{l,r})=
      case elemIndex_ i l of
        Nothing->elemIndex_ (i+length l) r
        a->a

-- | O(n) returns the list of all positions where the queried elements occurs in the 'Rope'.
-- This implementation uses memchr.

elemIndices::Word8->Rope->[Int]
elemIndices w rope=
  elemIndices_ 0 rope []
  where
    -- loop est une action IO, avec le foreignPtr deja enleve.
    -- Autant dire que ca va tres vite.
    loop::Ptr Word8->CInt->CSize->[Int]->IO [Int]
    loop _ _ 0 l=return l
    loop ptr i len l=do
      ptr'<-memchr ptr w len
      if ptr'==nullPtr then return [] else do
        let off=fromIntegral $ ptr'`minusPtr`ptr
        x<-loop (ptr'`plusPtr`1) (i+off+1) (len-fromIntegral off-1) l
        return $ (fromIntegral $ i+off):x
        
        
    elemIndices_ i (String{contents,offset,length_}) list=
      inlinePerformIO $ withForeignPtr contents $ \con->
      loop (con`plusPtr`offset) i (fromIntegral length_) list
        
    elemIndices_ i (Concat{l,r}) list=
      let sl=elemIndices_ i l sr
          sr=elemIndices_ (i+(fromIntegral $ length l)) r list
      in
       sl

-- | O(n). fold over a 'Rope'.
-- This implementation is not tail-recursive but never pushes more than
-- O(log n) calls on the stack.

foldl::(a->Word8->a)->a->Rope->a
foldl f a (String {contents,offset,length_})=
  unsafePerformIO $ withForeignPtr contents $
  \c->foldlBuf f a (c`plusPtr`offset) length_
      
foldl f a (Concat{l,r})=foldl f (foldl f a l) r

foldlBuf::(a->Word8->a)->a->Ptr Word8->Int->IO a
foldlBuf _ a _ 0=return a
foldlBuf f a p l=do
  c<-peek p
  foldlBuf f (f a c) (p`plusPtr`1) (l-1)

-- | O(n). like 'foldl' but strict.

foldl'::(a->Word8->a)->a->Rope->a
foldl' f a (String {contents,offset,length_})=
  unsafePerformIO $ withForeignPtr contents $
  \c->foldlBuf' f a (c`plusPtr`offset) length_
      
foldl' f a (Concat{l,r})=
  let b=foldl' f a l in b`seq`(foldl' f b r)

foldlBuf'::(a->Word8->a)->a->Ptr Word8->Int->IO a
foldlBuf' _ a _ 0=return a
foldlBuf' f a p l=do
  c<-peek p
  let b=f a c
  b`seq`foldlBuf' f b (p`plusPtr`1) (l-1)
  

-- | O(n). Right fold. Again not tail-recursive but never uses more than
-- O(log n) on the stack.
foldr::(Word8->a->a)->a->Rope->a
foldr f a (String{contents,offset,length_})=
  unsafePerformIO $ withForeignPtr contents $ 
  \p->foldrBuf f a (p`plusPtr`offset) length_

foldr f a (Concat{l,r})=foldr f (foldr f a r) l

foldrBuf::(Word8->a->a)->a->Ptr Word8->Int->IO a
foldrBuf _ a _ 0=return a
foldrBuf f a p l=do
  c<-peek $ p`plusPtr`(l-1)
  foldrBuf f (f c a) p (l-1)

take::Int->Rope->Rope
take i (s@String{length_})=s { length_=min length_ i }
take i (c@Concat{l,r})
  | i==length l = l
  | i<length l = take i l
  | otherwise = c { r=take (i-length l) r }

drop::Int->Rope->Rope
drop i (s@String{offset,length_})=s { offset=offset+(min i length_) }
drop i (c@Concat{l,r})
  | i==length l = r
  | i<length l = c { l=drop i l }
  | otherwise = drop (i-length l) r

splitAt# ::Int->Rope->(# Rope,Rope #)
splitAt# i (s@String{offset,length_})
  | i>=length_ = (# s,empty #)
  | otherwise = (# s { length_=i }, s { offset=offset+i,length_=length_-i} #)
splitAt# i (c@Concat{length_=l0,l,r})
  | i>=l0 = (# c,empty #)
  | i>=length_ l =
    let (# u,v #)=splitAt# (i-length_ l) r in
    (# c { length_=i, r=u }, v #)
  | otherwise = 
      let (# u,v #)=splitAt# i l in
      (# u, c { length_=i-length_ u, l=v } #)

-- | O(log n). @'splitAt' n xs@ is equivalent to (take n xs, drop n xs), but a little faster.
splitAt::Int->Rope->(Rope,Rope)
splitAt i r=
  let (# u,v #)=splitAt# i r in
  (u,v)

-- | O(n). @'breakByte' c r@ breaks 'Rope' @r@ before the first occurence of @c@.
breakByte::Word8->Rope->(Rope,Rope)
breakByte w rope_=
  let (_,b,c)=breakByte_ rope_ in
  (b,c)
  where
    breakByte_::Rope->(Bool,Rope,Rope)
    breakByte_ x@(String{contents,offset,length_})=
      inlinePerformIO $ withForeignPtr contents $ \con->do
        ptr<-memchr (con`plusPtr`offset) w (fromIntegral length_)
        return $ if ptr==nullPtr then (False, x, empty) else
                   (True,
                    x { length_=length_-(ptr`minusPtr`con)-1 }, 
                    x { offset=offset+(ptr`minusPtr`con) })
                   
    breakByte_ (Concat{l,r})=
      case breakByte_ l of
        (True,x,y)->(True,x,append y r)
        (False,x,_)->
          case breakByte_ r of
            (True,x',y')->(True,append x x',y')
            u@(False,_,_)->u

-- | O(n). @'breaks' w r@ breaks 'Rope' @r@ between each occurence of @w@ (non-inclusive).
-- This function is not tail-recursive, uses @memchr@ and constructs the list in parallel
-- using @'par'@.
    
breaks::Word8->Rope->[Rope]
breaks w rope_=
  let (a,_)=lines_ True rope_ in
  a
  where
    lines_::Bool->Rope->([Rope],Maybe Rope)
    lines_ isLast (str@String{contents,offset,length_})=
      if length_<=0 then ([],Nothing) else
        let off=inlinePerformIO $ withForeignPtr contents $ \con->do
              let pcon=con`plusPtr`offset
              ptr<-memchr pcon w (fromIntegral length_)
              if ptr==nullPtr then return Nothing else return $ Just (ptr`minusPtr`pcon)
        in
         case off of
           Nothing-> -- traceShow ("str",isLast, str) $ 
                    if isLast then 
                      if length str>0 then ([str],Nothing) else ([],Nothing)
                    else ([], Just str)
           Just diff->
             let line=str { length_=diff }
                 (a,b)=lines_ isLast (str{ offset=offset+diff+1,
                                           length_=length_-diff-1})
             in
              -- traceShow ("line",line:a,b) $
              (line:a,b)
             
    lines_ isLast (Concat{l,r})=
      let (ll,x)=lines_ False l
          (lr,y)=lines_ isLast r
      in
       (ll`par`lr)`seq`
       (case lr of
           []->case (x,y) of
             (Just xx, Just yy)->(ll,Just $ append xx yy)
             (Just _, Nothing)->(ll, x)
             (Nothing, _)->(ll, y)
             
           h:s->case x of { Nothing->(ll++lr,y); Just xx->(ll++((append xx h):s), y) }
       )
    
-- | O(n). Satisfies @lines r == breaks 0x0a r@.
lines::Rope->[Rope]
lines r=breaks 0x0a r

-- | Writes the contents of the 'Rope' on the specified 'Handle'.
hPut::Handle->Rope->IO()
hPut h (String{contents,offset,length_})=
  withForeignPtr contents $ \c->hPutBuf h (c`plusPtr`offset) length_
hPut h (Concat{l,r})=do
  hPut h l
  hPut h r

-- | synonym for 'hPut'.
hPutStr::Handle->Rope->IO()
hPutStr=hPut

-- | like 'hPut', but with a newline character at the end of the output
hPutStrLn::Handle->Rope->IO()
hPutStrLn handle r=do
  hPut handle r
  hPutChar handle '\n'
  
-- | Writes the contents of the 'Rope' on the standard output.
putStr::Rope->IO()
putStr=hPutStr stdout
  
-- | like 'putStr' but with a newline character at the end of the output
putStrLn::Rope->IO()
putStrLn=hPutStrLn stdout
  
-- | fromPtr encapsule un pointeur, un offset et une longueur dans un @Rope@..
fromPtr::ForeignPtr Word8->Int->Int->IO Rope
fromPtr fp offset s
  | s<=leafSize = withForeignPtr fp $ \p->do
    contents<-mallocForeignPtrBytes leafSize
    withForeignPtr contents $ \c->copyArray c (p`plusPtr`offset) s
              
    i0<-mallocForeignPtr
    withForeignPtr i0 $ \i->poke i s
    
    return $ String { contents,i0,offset=0,length_=s }

  | otherwise = do
    let sl=s`shiftR`1
        sr=sl+s.&.1
        sz=ceiling $ ((fromIntegral s)/(fromIntegral leafSize) :: Double)
    l<-unsafeInterleaveIO $ fromPtr fp offset sl
    r<-unsafeInterleaveIO $ fromPtr fp (offset+sl) sr
    return $ Concat { l,r,length_=s, sizeC=2*sz-1 }

-- | O(n) Conversion from a strict 'ByteString'
fromByteString::B.ByteString->Rope
fromByteString b=
  let (fp,off,len)=B.toForeignPtr b in
  unsafePerformIO $ fromPtr fp off len

-- | O(n) Conversion to a strict 'ByteString'
toByteString::Rope->B.ByteString
toByteString (String{contents,offset,length_})=
  B.fromForeignPtr contents offset length_
  
toByteString (c@Concat{length_=len})=
  B.unsafeCreate len $ \ptr->fill ptr c
    where
      fill p (Concat{l,r})=do
        fill p l
        fill (p`plusPtr`(length_ l)) r
      fill p (String{contents,offset,length_})=
        withForeignPtr contents $ \cc->copyBytes p (cc`plusPtr`offset) length_
  

-- | Lazy file reading, using @mmap@.
    
readFile::FilePath->IO Rope
readFile file=do
  stat<-getFileStatus file
  let s=fromIntegral $! fileSize stat
  fd<-openFd file ReadOnly Nothing $ defaultFileFlags
  p<-c_mmap s (fromIntegral fd)
  fp<-FC.newForeignPtr p $ do
    _<-c_munmap p s
    closeFd fd
  fromPtr fp 0 (fromIntegral s)



-- | Strict hGet. The whole rope is constructed.
hGet::Handle->Int->IO Rope
hGet handle length_=do
  position<-hTell handle
  buildRope handle position length_
  
buildRope::Handle->Integer->Int->IO Rope
buildRope handle position len
      | len<=leafSize = do
        
        contents<-mallocForeignPtrBytes leafSize
        length_<-withForeignPtr contents $ \c->do
          hSeek handle AbsoluteSeek position
          hGetBuf handle c len
        
        i0<-mallocForeignPtr
        withForeignPtr i0 $ \i->poke i len

        
        return $ String {contents,length_,offset=0,i0 }
        
      | otherwise =
        let a=len`shiftR`1
            b=a+(len.&.1)
        in do
          aa<-buildRope handle position a
          bb<-buildRope handle (position+fromIntegral a) b
          return $ Concat { length_=len,l=aa,r=bb,sizeC=size aa+size bb }
  
-- | Returns the next line in the input 'Handle'. If you need to iterate 'hGetLine',
-- it may be more efficient to first @mmap@ the file using 'readFile', or even load
-- it with then iterate
-- @'breakByte' 0x0a@ : 'hGetLine' allocates a buffer to read the file
-- and may waste most of this space if the lines are shorter than the standard buffer
-- size of this module.
hGetLine::Handle->IO Rope
hGetLine h=
  hGetLine' empty
  
  where
    hGetLine' x=do
      contents<-mallocForeignPtrBytes leafSize
      withForeignPtr contents $ \con->do
        l<-hGetBuf h con leafSize
        let readBytes=min l leafSize
        if readBytes<=0 then return x else do
          ptr<-memchr con 0x0a (fromIntegral readBytes)
          if ptr==nullPtr then do
            i0<-mallocForeignPtr
            withForeignPtr i0 $ \i->poke i readBytes
            let y=String { contents,i0,offset=0,length_=readBytes }
            hGetLine' (x`append`y)
          
            else do
          
            i0<-mallocForeignPtr
            let lineLen=ptr`minusPtr`con
                y=String { contents,i0,offset=0,length_=lineLen }
            withForeignPtr i0 $ \i->poke i lineLen
            hSeek h RelativeSeek (fromIntegral $ lineLen-readBytes+1)
            return $ x`append`y
          
-- | Reads the contents of a file handle strictly, then closes it.

hGetContents::Handle->IO Rope
hGetContents h=finally (hGetContents' empty) (hClose h)

  where
    hGetContents' r=do
      contents<-mallocForeignPtrBytes leafSize
      withForeignPtr contents $ \l->do
        x<-hGetBuf h l leafSize
        i0<-mallocForeignPtr
        withForeignPtr i0 $ \i->poke i x
        let y=String { contents,i0,offset=0,length_=x }

        if x==0 then return r else
          if x<leafSize then return $ r`append`y else
            hGetContents' $ r`append`y