Safe Haskell	None
Language	Haskell2010

FastString

Contents

ByteString
FastZString
FastStrings
LitStrings

Description

There are two principal string types used internally by GHC:

FastString

A compact, hash-consed, representation of character strings.
Comparison is O(1), and you can get a Unique from them.
Generated by fsLit.
Turn into SDoc with ftext.

LitString

Just a wrapper for the Addr# of a C string (Ptr CChar).
Practically no operations.
Outputing them is fast.
Generated by sLit.
Turn into SDoc with ptext
Requires manual memory management. Improper use may lead to memory leaks or dangling pointers.
It assumes Latin-1 as the encoding, therefore it cannot represent arbitrary Unicode strings.

Use LitString unless you want the facilities of FastString.

Synopsis

ByteString

fastStringToByteString :: FastString -> ByteString Source #

mkFastStringByteString :: ByteString -> FastString Source #

Create a FastString from an existing ForeignPtr; the difference between this and mkFastStringBytes is that we don't have to copy the bytes if the string is new to the table.

fastZStringToByteString :: FastZString -> ByteString Source #

unsafeMkByteString :: String -> ByteString Source #

hashByteString :: ByteString -> Int Source #

FastZString

data FastZString Source #

Instances

NFData FastZString #
Methods rnf :: FastZString -> () Source #

hPutFZS :: Handle -> FastZString -> IO () Source #

zString :: FastZString -> String Source #

lengthFZS :: FastZString -> Int Source #

FastStrings

data FastString Source #

A FastString is an array of bytes, hashed to support fast O(1) comparison. It is also associated with a character encoding, so that we know how to convert a FastString to the local encoding, or to the Z-encoding used by the compiler internally.

FastStrings support a memoized conversion to the Z-encoding via zEncodeFS.

Constructors

FastString
Fields uniq :: !Int n_chars :: !Int fs_bs :: !ByteString fs_ref :: !(IORef (Maybe FastZString))

Instances

Eq FastString #
Methods (==) :: FastString -> FastString -> Bool # (/=) :: FastString -> FastString -> Bool #
Data FastString #
Methods gfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> FastString -> c FastString Source # gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c FastString Source # toConstr :: FastString -> Constr Source # dataTypeOf :: FastString -> DataType Source # dataCast1 :: Typeable (* -> ) t => (forall d. Data d => c (t d)) -> Maybe (c FastString) Source # dataCast2 :: Typeable ( -> * -> *) t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c FastString) Source # gmapT :: (forall b. Data b => b -> b) -> FastString -> FastString Source # gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> FastString -> r Source # gmapQr :: (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> FastString -> r Source # gmapQ :: (forall d. Data d => d -> u) -> FastString -> [u] Source # gmapQi :: Int -> (forall d. Data d => d -> u) -> FastString -> u Source # gmapM :: Monad m => (forall d. Data d => d -> m d) -> FastString -> m FastString Source # gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> FastString -> m FastString Source # gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> FastString -> m FastString Source #
Ord FastString #
Methods compare :: FastString -> FastString -> Ordering # (<) :: FastString -> FastString -> Bool # (<=) :: FastString -> FastString -> Bool # (>) :: FastString -> FastString -> Bool # (>=) :: FastString -> FastString -> Bool # max :: FastString -> FastString -> FastString # min :: FastString -> FastString -> FastString #
Show FastString #
Methods showsPrec :: Int -> FastString -> ShowS Source # show :: FastString -> String Source # showList :: [FastString] -> ShowS Source #
IsString FastString #
Methods fromString :: String -> FastString Source #
Monoid FastString #
Methods mempty :: FastString Source # mappend :: FastString -> FastString -> FastString Source # mconcat :: [FastString] -> FastString Source #
Outputable FastString #
Methods ppr :: FastString -> SDoc Source # pprPrec :: Rational -> FastString -> SDoc Source #
Uniquable FastString #
Methods getUnique :: FastString -> Unique Source #
Binary FastString #
Methods put_ :: BinHandle -> FastString -> IO () Source # put :: BinHandle -> FastString -> IO (Bin * FastString) Source # get :: BinHandle -> IO FastString Source #

Construction

fsLit :: String -> FastString Source #

mkFastString :: String -> FastString Source #

Creates a UTF-8 encoded FastString from a String

mkFastStringBytes :: Ptr Word8 -> Int -> FastString Source #

mkFastStringByteList :: [Word8] -> FastString Source #

Creates a FastString from a UTF-8 encoded [Word8]

mkFastStringForeignPtr :: Ptr Word8 -> ForeignPtr Word8 -> Int -> IO FastString Source #

Create a FastString from an existing ForeignPtr; the difference between this and mkFastStringBytes is that we don't have to copy the bytes if the string is new to the table.

mkFastString# :: Addr# -> FastString Source #

Deconstruction

unpackFS :: FastString -> String Source #

Unpacks and decodes the FastString

bytesFS :: FastString -> [Word8] Source #

Gives the UTF-8 encoded bytes corresponding to a FastString

Encoding

zEncodeFS :: FastString -> FastZString Source #

Returns a Z-encoded version of a FastString. This might be the original, if it was already Z-encoded. The first time this function is applied to a particular FastString, the results are memoized.

Operations

uniqueOfFS :: FastString -> Int Source #

lengthFS :: FastString -> Int Source #

Returns the length of the FastString in characters

nullFS :: FastString -> Bool Source #

Returns True if the FastString is empty

appendFS :: FastString -> FastString -> FastString Source #

headFS :: FastString -> Char Source #

tailFS :: FastString -> FastString Source #

concatFS :: [FastString] -> FastString Source #

consFS :: Char -> FastString -> FastString Source #

nilFS :: FastString Source #

Outputing

hPutFS :: Handle -> FastString -> IO () Source #

Outputs a FastString with no decoding at all, that is, you get the actual bytes in the FastString written to the Handle.

Internal

getFastStringTable :: IO [[FastString]] Source #

hasZEncoding :: FastString -> Bool Source #

Returns True if this FastString is not Z-encoded but already has a Z-encoding cached (used in producing stats).

LitStrings

type LitString = Ptr Word8 Source #

A LitString is a pointer to some null-terminated array of bytes.

Construction

sLit :: String -> LitString Source #

mkLitString# :: Addr# -> LitString Source #

Wrap an unboxed address into a LitString.

mkLitString :: String -> LitString Source #

Encode a String into a newly allocated LitString using Latin-1 encoding. The original string must not contain non-Latin-1 characters (above codepoint 0xff).

Deconstruction

unpackLitString :: LitString -> String Source #

Decode a LitString back into a String using Latin-1 encoding. This does not free the memory associated with LitString.

Operations

lengthLS :: LitString -> Int Source #

Compute the length of a LitString, which must necessarily be null-terminated.