text-1.2.4.1: src/Data/Text/Internal/Fusion.hs
{-# LANGUAGE BangPatterns, MagicHash #-}
-- |
-- Module : Data.Text.Internal.Fusion
-- Copyright : (c) Tom Harper 2008-2009,
-- (c) Bryan O'Sullivan 2009-2010,
-- (c) Duncan Coutts 2009
--
-- License : BSD-style
-- Maintainer : bos@serpentine.com
-- Stability : experimental
-- Portability : GHC
--
-- /Warning/: this is an internal module, and does not have a stable
-- API or name. Functions in this module may not check or enforce
-- preconditions expected by public modules. Use at your own risk!
--
-- Text manipulation functions represented as fusible operations over
-- streams.
module Data.Text.Internal.Fusion
(
-- * Types
Stream(..)
, Step(..)
-- * Creation and elimination
, stream
, unstream
, reverseStream
, length
-- * Transformations
, reverse
-- * Construction
-- ** Scans
, reverseScanr
-- ** Accumulating maps
, mapAccumL
-- ** Generation and unfolding
, unfoldrN
-- * Indexing
, index
, findIndex
, countChar
) where
import Prelude (Bool(..), Char, Maybe(..), Monad(..), Int,
Num(..), Ord(..), ($), (&&),
fromIntegral, otherwise)
import Data.Bits ((.&.))
import Data.Text.Internal (Text(..))
import Data.Text.Internal.Private (runText)
import Data.Text.Internal.Unsafe.Char (ord, unsafeChr, unsafeWrite)
import Data.Text.Internal.Unsafe.Shift (shiftL, shiftR)
import qualified Data.Text.Array as A
import qualified Data.Text.Internal.Fusion.Common as S
import Data.Text.Internal.Fusion.Types
import Data.Text.Internal.Fusion.Size
import qualified Data.Text.Internal as I
import qualified Data.Text.Internal.Encoding.Utf16 as U16
default(Int)
-- | /O(n)/ Convert a 'Text' into a 'Stream Char'.
stream :: Text -> Stream Char
stream (Text arr off len) = Stream next off (betweenSize (len `shiftR` 1) len)
where
!end = off+len
next !i
| i >= end = Done
| n >= 0xD800 && n <= 0xDBFF = Yield (U16.chr2 n n2) (i + 2)
| otherwise = Yield (unsafeChr n) (i + 1)
where
n = A.unsafeIndex arr i
n2 = A.unsafeIndex arr (i + 1)
{-# INLINE [0] stream #-}
-- | /O(n)/ Convert a 'Text' into a 'Stream Char', but iterate
-- backwards.
reverseStream :: Text -> Stream Char
reverseStream (Text arr off len) = Stream next (off+len-1) (betweenSize (len `shiftR` 1) len)
where
{-# INLINE next #-}
next !i
| i < off = Done
| n >= 0xDC00 && n <= 0xDFFF = Yield (U16.chr2 n2 n) (i - 2)
| otherwise = Yield (unsafeChr n) (i - 1)
where
n = A.unsafeIndex arr i
n2 = A.unsafeIndex arr (i - 1)
{-# INLINE [0] reverseStream #-}
-- | /O(n)/ Convert a 'Stream Char' into a 'Text'.
unstream :: Stream Char -> Text
unstream (Stream next0 s0 len) = runText $ \done -> do
-- Before encoding each char we perform a buffer realloc check assuming
-- worst case encoding size of two 16-bit units for the char. Just add an
-- extra space to the buffer so that we do not end up reallocating even when
-- all the chars are encoded as single unit.
let mlen = upperBound 4 len + 1
arr0 <- A.new mlen
let outer !arr !maxi = encode
where
-- keep the common case loop as small as possible
encode !si !di =
case next0 si of
Done -> done arr di
Skip si' -> encode si' di
Yield c si'
-- simply check for the worst case
| maxi < di + 1 -> realloc si di
| otherwise -> do
n <- unsafeWrite arr di c
encode si' (di + n)
-- keep uncommon case separate from the common case code
{-# NOINLINE realloc #-}
realloc !si !di = do
let newlen = (maxi + 1) * 2
arr' <- A.new newlen
A.copyM arr' 0 arr 0 di
outer arr' (newlen - 1) si di
outer arr0 (mlen - 1) s0 0
{-# INLINE [0] unstream #-}
{-# RULES "STREAM stream/unstream fusion" forall s. stream (unstream s) = s #-}
-- ----------------------------------------------------------------------------
-- * Basic stream functions
length :: Stream Char -> Int
length = S.lengthI
{-# INLINE[0] length #-}
-- | /O(n)/ Reverse the characters of a string.
reverse :: Stream Char -> Text
reverse (Stream next s len0)
| isEmpty len0 = I.empty
| otherwise = I.text arr off' len'
where
len0' = upperBound 4 (larger len0 4)
(arr, (off', len')) = A.run2 (A.new len0' >>= loop s (len0'-1) len0')
loop !s0 !i !len marr =
case next s0 of
Done -> return (marr, (j, len-j))
where j = i + 1
Skip s1 -> loop s1 i len marr
Yield x s1 | i < least -> {-# SCC "reverse/resize" #-} do
let newLen = len `shiftL` 1
marr' <- A.new newLen
A.copyM marr' (newLen-len) marr 0 len
write s1 (len+i) newLen marr'
| otherwise -> write s1 i len marr
where n = ord x
least | n < 0x10000 = 0
| otherwise = 1
m = n - 0x10000
lo = fromIntegral $ (m `shiftR` 10) + 0xD800
hi = fromIntegral $ (m .&. 0x3FF) + 0xDC00
write t j l mar
| n < 0x10000 = do
A.unsafeWrite mar j (fromIntegral n)
loop t (j-1) l mar
| otherwise = do
A.unsafeWrite mar (j-1) lo
A.unsafeWrite mar j hi
loop t (j-2) l mar
{-# INLINE [0] reverse #-}
-- | /O(n)/ Perform the equivalent of 'scanr' over a list, only with
-- the input and result reversed.
reverseScanr :: (Char -> Char -> Char) -> Char -> Stream Char -> Stream Char
reverseScanr f z0 (Stream next0 s0 len) = Stream next (Scan1 z0 s0) (len+1) -- HINT maybe too low
where
{-# INLINE next #-}
next (Scan1 z s) = Yield z (Scan2 z s)
next (Scan2 z s) = case next0 s of
Yield x s' -> let !x' = f x z
in Yield x' (Scan2 x' s')
Skip s' -> Skip (Scan2 z s')
Done -> Done
{-# INLINE reverseScanr #-}
-- | /O(n)/ Like 'unfoldr', 'unfoldrN' builds a stream from a seed
-- value. However, the length of the result is limited by the
-- first argument to 'unfoldrN'. This function is more efficient than
-- 'unfoldr' when the length of the result is known.
unfoldrN :: Int -> (a -> Maybe (Char,a)) -> a -> Stream Char
unfoldrN n = S.unfoldrNI n
{-# INLINE [0] unfoldrN #-}
-------------------------------------------------------------------------------
-- ** Indexing streams
-- | /O(n)/ stream index (subscript) operator, starting from 0.
index :: Stream Char -> Int -> Char
index = S.indexI
{-# INLINE [0] index #-}
-- | The 'findIndex' function takes a predicate and a stream and
-- returns the index of the first element in the stream
-- satisfying the predicate.
findIndex :: (Char -> Bool) -> Stream Char -> Maybe Int
findIndex = S.findIndexI
{-# INLINE [0] findIndex #-}
-- | /O(n)/ The 'count' function returns the number of times the query
-- element appears in the given stream.
countChar :: Char -> Stream Char -> Int
countChar = S.countCharI
{-# INLINE [0] countChar #-}
-- | /O(n)/ Like a combination of 'map' and 'foldl''. Applies a
-- function to each element of a 'Text', passing an accumulating
-- parameter from left to right, and returns a final 'Text'.
mapAccumL :: (a -> Char -> (a,Char)) -> a -> Stream Char -> (a, Text)
mapAccumL f z0 (Stream next0 s0 len) = (nz, I.text na 0 nl)
where
(na,(nz,nl)) = A.run2 (A.new mlen >>= \arr -> outer arr mlen z0 s0 0)
where mlen = upperBound 4 len
outer arr top = loop
where
loop !z !s !i =
case next0 s of
Done -> return (arr, (z,i))
Skip s' -> loop z s' i
Yield x s'
| j >= top -> {-# SCC "mapAccumL/resize" #-} do
let top' = (top + 1) `shiftL` 1
arr' <- A.new top'
A.copyM arr' 0 arr 0 top
outer arr' top' z s i
| otherwise -> do d <- unsafeWrite arr i c
loop z' s' (i+d)
where (z',c) = f z x
j | ord c < 0x10000 = i
| otherwise = i + 1
{-# INLINE [0] mapAccumL #-}