{-# LANGUAGE CPP #-} #if __GLASGOW_HASKELL__ >= 701 {-# LANGUAGE Trustworthy #-} #endif -- -- | -- Module : Data.String.UTF8 -- Copyright : (c) Iavor S. Diatchki 2009 -- License : BSD3-style (see LICENSE) -- -- Maintainer : emertens@galois.com -- Stability : experimental -- Portability : portable -- {-# LANGUAGE MultiParamTypeClasses, UndecidableInstances #-} module Data.String.UTF8 ( -- * Representation UTF8 , UTF8Bytes() , fromString , toString , fromRep , toRep , G.replacement_char -- * Character based operations , uncons , splitAt , take , drop , span , break , foldl , foldr , length , lines , lines' -- * Representation based operations , null , decode , byteSplitAt , byteTake , byteDrop ) where import Prelude hiding (null,take,drop,span,break ,foldl,foldr,length,lines,splitAt) import qualified Codec.Binary.UTF8.Generic as G import Codec.Binary.UTF8.Generic (UTF8Bytes) -- | The type of strings that are represented using the UTF8 encoding. -- The parameter is the type of the container for the representation. newtype UTF8 string = Str string deriving (Eq,Ord) -- XXX: Is this OK? instance UTF8Bytes string index => Show (UTF8 string) where show x = show (toString x) fromRep :: string -> UTF8 string fromRep = Str toRep :: UTF8 string -> string toRep (Str x) = x -- | Converts a Haskell string into a UTF8 encoded string. -- Complexity: linear. fromString :: UTF8Bytes string index => String -> UTF8 string fromString xs = Str (G.fromString xs) -- | Convert a UTF8 encoded string into a Haskell string. -- Invalid characters are replaced by 'replacement_char'. -- Complexity: linear. toString :: UTF8Bytes string index => UTF8 string -> String toString (Str xs) = G.toString xs -- | Checks if there are no more bytes in the underlying representation. null :: UTF8Bytes string index => UTF8 string -> Bool null (Str x) = G.null x -- | Split after a given number of characters. -- Negative values are treated as if they are 0. -- See also 'bytesSplitAt'. splitAt :: UTF8Bytes string index => index -> UTF8 string -> (UTF8 string, UTF8 string) splitAt x (Str bs) = case G.splitAt x bs of (s1,s2) -> (Str s1, Str s2) -- | Split after a given number of bytes in the underlying representation. -- See also 'splitAt'. byteSplitAt :: UTF8Bytes string index => index -> UTF8 string -> (UTF8 string, UTF8 string) byteSplitAt n (Str x) = case G.bsplit n x of (as,bs) -> (Str as, Str bs) -- | Take only the given number of bytes from the underlying representation. -- See also 'take'. byteTake :: UTF8Bytes string index => index -> UTF8 string -> UTF8 string byteTake n (Str x) = Str (fst (G.bsplit n x)) -- | Drop the given number of bytes from the underlying representation. -- See also 'drop'. byteDrop :: UTF8Bytes string index => index -> UTF8 string -> UTF8 string byteDrop n (Str x) = Str (G.bdrop n x) -- | @take n s@ returns the first @n@ characters of @s@. -- If @s@ has less than @n@ characters, then we return the whole of @s@. take :: UTF8Bytes string index => index -> UTF8 string -> UTF8 string take n (Str bs) = Str (G.take n bs) -- | @drop n s@ returns the @s@ without its first @n@ characters. -- If @s@ has less than @n@ characters, then we return an empty string. drop :: UTF8Bytes string index => index -> UTF8 string -> UTF8 string drop n (Str bs) = Str (G.drop n bs) -- | Split a string into two parts: the first is the longest prefix -- that contains only characters that satisfy the predicate; the second -- part is the rest of the string. -- Invalid characters are passed as '\0xFFFD' to the predicate. span :: UTF8Bytes string index => (Char -> Bool) -> UTF8 string -> (UTF8 string, UTF8 string) span p (Str bs) = case G.span p bs of (s1,s2) -> (Str s1, Str s2) -- | Split a string into two parts: the first is the longest prefix -- that contains only characters that do not satisfy the predicate; the second -- part is the rest of the string. -- Invalid characters are passed as 'replacement_char' to the predicate. break :: UTF8Bytes string index => (Char -> Bool) -> UTF8 string -> (UTF8 string, UTF8 string) break p (Str bs) = case G.break p bs of (s1,s2) -> (Str s1, Str s2) -- | Get the first character of a byte string, if any. -- Invalid characters are replaced by 'replacement_char'. uncons :: UTF8Bytes string index => UTF8 string -> Maybe (Char, UTF8 string) uncons (Str x) = do (c,y) <- G.uncons x return (c, Str y) -- | Extract the first character for the underlying representation, -- if one is available. It also returns the number of bytes used -- in the representation of the character. -- See also 'uncons', 'dropBytes'. decode :: UTF8Bytes string index => UTF8 string -> Maybe (Char, index) decode (Str x) = G.decode x -- | Traverse a bytestring (right biased). foldr :: UTF8Bytes string index => (Char -> a -> a) -> a -> UTF8 string -> a foldr cons nil (Str cs) = G.foldr cons nil cs -- | Traverse a bytestring (left biased). -- This function is strict in the accumulator. foldl :: UTF8Bytes string index => (a -> Char -> a) -> a -> UTF8 string -> a foldl add acc (Str cs) = G.foldl add acc cs -- | Counts the number of characters encoded in the bytestring. -- Note that this includes replacement characters. -- The function is linear in the number of bytes in the representation. length :: UTF8Bytes string index => UTF8 string -> index length (Str b) = G.length b -- | Split a string into a list of lines. -- Lines are terminated by '\n' or the end of the string. -- Empty lines may not be terminated by the end of the string. -- See also 'lines\''. lines :: UTF8Bytes string index => UTF8 string -> [UTF8 string] lines (Str b) = map Str (G.lines b) -- XXX: unnecessary map -- | Split a string into a list of lines. -- Lines are terminated by '\n' or the end of the string. -- Empty lines may not be terminated by the end of the string. -- This function preserves the terminators. -- See also 'lines'. lines' :: UTF8Bytes string index => UTF8 string -> [UTF8 string] lines' (Str x) = map Str (G.lines' x) -- XXX: unnecessary map