{-# LANGUAGE CPP #-} {-# OPTIONS_GHC -fno-warn-missing-methods #-} -- | -- Module : Data.Text.Internal.Fusion.Internal -- Copyright : (c) Roman Leshchinskiy 2008, -- (c) Bryan O'Sullivan 2009 -- -- License : BSD-style -- Maintainer : bos@serpentine.com -- Stability : experimental -- Portability : portable -- -- /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! -- -- Size hints. module Data.Text.Internal.Fusion.Size ( Size , exactly , exactSize , maxSize , betweenSize , unknownSize , smaller , larger , upperBound , lowerBound , compareSize , isEmpty ) where #if defined(ASSERTS) import Control.Exception (assert) #endif data Size = Between {-# UNPACK #-} !Int {-# UNPACK #-} !Int -- ^ Lower and upper bounds on size. | Unknown -- ^ Unknown size. deriving (Eq, Show) exactly :: Size -> Maybe Int exactly (Between na nb) | na == nb = Just na exactly _ = Nothing {-# INLINE exactly #-} exactSize :: Int -> Size exactSize n = #if defined(ASSERTS) assert (n >= 0) #endif Between n n {-# INLINE exactSize #-} maxSize :: Int -> Size maxSize n = #if defined(ASSERTS) assert (n >= 0) #endif Between 0 n {-# INLINE maxSize #-} betweenSize :: Int -> Int -> Size betweenSize m n = #if defined(ASSERTS) assert (m >= 0) assert (n >= m) #endif Between m n {-# INLINE betweenSize #-} unknownSize :: Size unknownSize = Unknown {-# INLINE unknownSize #-} instance Num Size where (+) = addSize (-) = subtractSize (*) = mulSize fromInteger = f where f = exactSize . fromInteger {-# INLINE f #-} add :: Int -> Int -> Int add m n | mn >= 0 = mn | otherwise = overflowError where mn = m + n {-# INLINE add #-} addSize :: Size -> Size -> Size addSize (Between ma mb) (Between na nb) = Between (add ma na) (add mb nb) addSize _ _ = Unknown {-# INLINE addSize #-} subtractSize :: Size -> Size -> Size subtractSize (Between ma mb) (Between na nb) = Between (max (ma-nb) 0) (max (mb-na) 0) subtractSize a@(Between 0 _) Unknown = a subtractSize (Between _ mb) Unknown = Between 0 mb subtractSize _ _ = Unknown {-# INLINE subtractSize #-} mul :: Int -> Int -> Int mul m n | m <= maxBound `quot` n = m * n | otherwise = overflowError {-# INLINE mul #-} mulSize :: Size -> Size -> Size mulSize (Between ma mb) (Between na nb) = Between (mul ma na) (mul mb nb) mulSize _ _ = Unknown {-# INLINE mulSize #-} -- | Minimum of two size hints. smaller :: Size -> Size -> Size smaller a@(Between ma mb) b@(Between na nb) | mb <= na = a | nb <= ma = b | otherwise = Between (ma `min` na) (mb `min` nb) smaller a@(Between 0 _) Unknown = a smaller (Between _ mb) Unknown = Between 0 mb smaller Unknown b@(Between 0 _) = b smaller Unknown (Between _ nb) = Between 0 nb smaller Unknown Unknown = Unknown {-# INLINE smaller #-} -- | Maximum of two size hints. larger :: Size -> Size -> Size larger a@(Between ma mb) b@(Between na nb) | ma >= nb = a | na >= mb = b | otherwise = Between (ma `max` na) (mb `max` nb) larger _ _ = Unknown {-# INLINE larger #-} -- | Compute the maximum size from a size hint, if possible. upperBound :: Int -> Size -> Int upperBound _ (Between _ n) = n upperBound k _ = k {-# INLINE upperBound #-} -- | Compute the maximum size from a size hint, if possible. lowerBound :: Int -> Size -> Int lowerBound _ (Between n _) = n lowerBound k _ = k {-# INLINE lowerBound #-} compareSize :: Size -> Int -> Maybe Ordering compareSize (Between ma mb) n | mb < n = Just LT | ma > n = Just GT | ma == n && mb == n = Just EQ compareSize _ _ = Nothing isEmpty :: Size -> Bool isEmpty (Between _ n) = n <= 0 isEmpty _ = False {-# INLINE isEmpty #-} overflowError :: Int overflowError = error "Data.Text.Internal.Fusion.Size: size overflow"