{-# LANGUAGE BangPatterns, CPP, Rank2Types #-} {-# OPTIONS_HADDOCK not-home #-} ----------------------------------------------------------------------------- -- | -- Module : Data.Text.Internal.Builder -- Copyright : (c) 2013 Bryan O'Sullivan -- (c) 2010 Johan Tibell -- License : BSD3-style (see LICENSE) -- -- Maintainer : Johan Tibell <johan.tibell@gmail.com> -- Stability : experimental -- Portability : portable to Hugs and 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! -- -- Efficient construction of lazy @Text@ values. The principal -- operations on a @Builder@ are @singleton@, @fromText@, and -- @fromLazyText@, which construct new builders, and 'mappend', which -- concatenates two builders. -- -- To get maximum performance when building lazy @Text@ values using a -- builder, associate @mappend@ calls to the right. For example, -- prefer -- -- > singleton 'a' `mappend` (singleton 'b' `mappend` singleton 'c') -- -- to -- -- > singleton 'a' `mappend` singleton 'b' `mappend` singleton 'c' -- -- as the latter associates @mappend@ to the left. -- ----------------------------------------------------------------------------- module Data.Text.Internal.Builder ( -- * Public API -- ** The Builder type Builder , toLazyText , toLazyTextWith -- ** Constructing Builders , singleton , fromText , fromLazyText , fromString -- ** Flushing the buffer state , flush -- * Internal functions , append' , ensureFree , writeN ) where import Control.Monad.ST (ST, runST) import Data.Bits ((.&.)) import Data.Monoid (Monoid(..)) import Data.Text.Internal (Text(..)) import Data.Text.Internal.Lazy (smallChunkSize) import Data.Text.Unsafe (inlineInterleaveST) import Data.Text.Internal.Unsafe.Char (ord, unsafeWrite) import Data.Text.Internal.Unsafe.Shift (shiftR) import Prelude hiding (map, putChar) import qualified Data.String as String import qualified Data.Text as S import qualified Data.Text.Array as A import qualified Data.Text.Lazy as L ------------------------------------------------------------------------ -- | A @Builder@ is an efficient way to build lazy @Text@ values. -- There are several functions for constructing builders, but only one -- to inspect them: to extract any data, you have to turn them into -- lazy @Text@ values using @toLazyText@. -- -- Internally, a builder constructs a lazy @Text@ by filling arrays -- piece by piece. As each buffer is filled, it is \'popped\' off, to -- become a new chunk of the resulting lazy @Text@. All this is -- hidden from the user of the @Builder@. newtype Builder = Builder { -- Invariant (from Data.Text.Lazy): -- The lists include no null Texts. runBuilder :: forall s. (Buffer s -> ST s [S.Text]) -> Buffer s -> ST s [S.Text] } instance Monoid Builder where mempty = empty {-# INLINE mempty #-} mappend = append {-# INLINE mappend #-} mconcat = foldr mappend mempty {-# INLINE mconcat #-} instance String.IsString Builder where fromString = fromString {-# INLINE fromString #-} instance Show Builder where show = show . toLazyText instance Eq Builder where a == b = toLazyText a == toLazyText b instance Ord Builder where a <= b = toLazyText a <= toLazyText b ------------------------------------------------------------------------ -- | /O(1)./ The empty @Builder@, satisfying -- -- * @'toLazyText' 'empty' = 'L.empty'@ -- empty :: Builder empty = Builder (\ k buf -> k buf) {-# INLINE empty #-} -- | /O(1)./ A @Builder@ taking a single character, satisfying -- -- * @'toLazyText' ('singleton' c) = 'L.singleton' c@ -- singleton :: Char -> Builder singleton c = writeAtMost 2 $ \ marr o -> if n < 0x10000 then A.unsafeWrite marr o (fromIntegral n) >> return 1 else do A.unsafeWrite marr o lo A.unsafeWrite marr (o+1) hi return 2 where n = ord c m = n - 0x10000 lo = fromIntegral $ (m `shiftR` 10) + 0xD800 hi = fromIntegral $ (m .&. 0x3FF) + 0xDC00 {-# INLINE singleton #-} ------------------------------------------------------------------------ -- | /O(1)./ The concatenation of two builders, an associative -- operation with identity 'empty', satisfying -- -- * @'toLazyText' ('append' x y) = 'L.append' ('toLazyText' x) ('toLazyText' y)@ -- append :: Builder -> Builder -> Builder append (Builder f) (Builder g) = Builder (f . g) {-# INLINE [0] append #-} -- TODO: Experiment to find the right threshold. copyLimit :: Int copyLimit = 128 -- This function attempts to merge small @Text@ values instead of -- treating each value as its own chunk. We may not always want this. -- | /O(1)./ A @Builder@ taking a 'S.Text', satisfying -- -- * @'toLazyText' ('fromText' t) = 'L.fromChunks' [t]@ -- fromText :: S.Text -> Builder fromText t@(Text arr off l) | S.null t = empty | l <= copyLimit = writeN l $ \marr o -> A.copyI marr o arr off (l+o) | otherwise = flush `append` mapBuilder (t :) {-# INLINE [1] fromText #-} {-# RULES "fromText/pack" forall s . fromText (S.pack s) = fromString s #-} -- | /O(1)./ A Builder taking a @String@, satisfying -- -- * @'toLazyText' ('fromString' s) = 'L.fromChunks' [S.pack s]@ -- fromString :: String -> Builder fromString str = Builder $ \k (Buffer p0 o0 u0 l0) -> let loop !marr !o !u !l [] = k (Buffer marr o u l) loop marr o u l s@(c:cs) | l <= 1 = do arr <- A.unsafeFreeze marr let !t = Text arr o u marr' <- A.new chunkSize ts <- inlineInterleaveST (loop marr' 0 0 chunkSize s) return $ t : ts | otherwise = do n <- unsafeWrite marr (o+u) c loop marr o (u+n) (l-n) cs in loop p0 o0 u0 l0 str where chunkSize = smallChunkSize {-# INLINE fromString #-} -- | /O(1)./ A @Builder@ taking a lazy @Text@, satisfying -- -- * @'toLazyText' ('fromLazyText' t) = t@ -- fromLazyText :: L.Text -> Builder fromLazyText ts = flush `append` mapBuilder (L.toChunks ts ++) {-# INLINE fromLazyText #-} ------------------------------------------------------------------------ -- Our internal buffer type data Buffer s = Buffer {-# UNPACK #-} !(A.MArray s) {-# UNPACK #-} !Int -- offset {-# UNPACK #-} !Int -- used units {-# UNPACK #-} !Int -- length left ------------------------------------------------------------------------ -- | /O(n)./ Extract a lazy @Text@ from a @Builder@ with a default -- buffer size. The construction work takes place if and when the -- relevant part of the lazy @Text@ is demanded. toLazyText :: Builder -> L.Text toLazyText = toLazyTextWith smallChunkSize -- | /O(n)./ Extract a lazy @Text@ from a @Builder@, using the given -- size for the initial buffer. The construction work takes place if -- and when the relevant part of the lazy @Text@ is demanded. -- -- If the initial buffer is too small to hold all data, subsequent -- buffers will be the default buffer size. toLazyTextWith :: Int -> Builder -> L.Text toLazyTextWith chunkSize m = L.fromChunks (runST $ newBuffer chunkSize >>= runBuilder (m `append` flush) (const (return []))) -- | /O(1)./ Pop the strict @Text@ we have constructed so far, if any, -- yielding a new chunk in the result lazy @Text@. flush :: Builder flush = Builder $ \ k buf@(Buffer p o u l) -> if u == 0 then k buf else do arr <- A.unsafeFreeze p let !b = Buffer p (o+u) 0 l !t = Text arr o u ts <- inlineInterleaveST (k b) return $! t : ts ------------------------------------------------------------------------ -- | Sequence an ST operation on the buffer withBuffer :: (forall s. Buffer s -> ST s (Buffer s)) -> Builder withBuffer f = Builder $ \k buf -> f buf >>= k {-# INLINE withBuffer #-} -- | Get the size of the buffer withSize :: (Int -> Builder) -> Builder withSize f = Builder $ \ k buf@(Buffer _ _ _ l) -> runBuilder (f l) k buf {-# INLINE withSize #-} -- | Map the resulting list of texts. mapBuilder :: ([S.Text] -> [S.Text]) -> Builder mapBuilder f = Builder (fmap f .) ------------------------------------------------------------------------ -- | Ensure that there are at least @n@ many elements available. ensureFree :: Int -> Builder ensureFree !n = withSize $ \ l -> if n <= l then empty else flush `append'` withBuffer (const (newBuffer (max n smallChunkSize))) {-# INLINE [0] ensureFree #-} writeAtMost :: Int -> (forall s. A.MArray s -> Int -> ST s Int) -> Builder writeAtMost n f = ensureFree n `append'` withBuffer (writeBuffer f) {-# INLINE [0] writeAtMost #-} -- | Ensure that @n@ many elements are available, and then use @f@ to -- write some elements into the memory. writeN :: Int -> (forall s. A.MArray s -> Int -> ST s ()) -> Builder writeN n f = writeAtMost n (\ p o -> f p o >> return n) {-# INLINE writeN #-} writeBuffer :: (A.MArray s -> Int -> ST s Int) -> Buffer s -> ST s (Buffer s) writeBuffer f (Buffer p o u l) = do n <- f p (o+u) return $! Buffer p o (u+n) (l-n) {-# INLINE writeBuffer #-} newBuffer :: Int -> ST s (Buffer s) newBuffer size = do arr <- A.new size return $! Buffer arr 0 0 size {-# INLINE newBuffer #-} ------------------------------------------------------------------------ -- Some nice rules for Builder -- This function makes GHC understand that 'writeN' and 'ensureFree' -- are *not* recursive in the precense of the rewrite rules below. -- This is not needed with GHC 7+. append' :: Builder -> Builder -> Builder append' (Builder f) (Builder g) = Builder (f . g) {-# INLINE append' #-} {-# RULES "append/writeAtMost" forall a b (f::forall s. A.MArray s -> Int -> ST s Int) (g::forall s. A.MArray s -> Int -> ST s Int) ws. append (writeAtMost a f) (append (writeAtMost b g) ws) = append (writeAtMost (a+b) (\marr o -> f marr o >>= \ n -> g marr (o+n) >>= \ m -> let s = n+m in s `seq` return s)) ws "writeAtMost/writeAtMost" forall a b (f::forall s. A.MArray s -> Int -> ST s Int) (g::forall s. A.MArray s -> Int -> ST s Int). append (writeAtMost a f) (writeAtMost b g) = writeAtMost (a+b) (\marr o -> f marr o >>= \ n -> g marr (o+n) >>= \ m -> let s = n+m in s `seq` return s) "ensureFree/ensureFree" forall a b . append (ensureFree a) (ensureFree b) = ensureFree (max a b) "flush/flush" append flush flush = flush #-}