ghc-8.2.2: The GHC API

Safe Haskell | None
Language | Haskell2010

FastString

Contents

- ByteString
- FastZString
- FastStrings
  - Construction
  - Deconstruction
  - Encoding
  - Operations
  - Outputing
  - Internal
- LitStrings
  - Construction
  - Deconstruction
  - Operations

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

- fastStringToByteString :: FastString -> ByteString
- mkFastStringByteString :: ByteString -> FastString
- fastZStringToByteString :: FastZString -> ByteString
- unsafeMkByteString :: String -> ByteString
- hashByteString :: ByteString -> Int
- data FastZString
- hPutFZS :: Handle -> FastZString -> IO ()
- zString :: FastZString -> String
- lengthFZS :: FastZString -> Int
- data FastString = FastString {
  - uniq :: !Int
  - n_chars :: !Int
  - fs_bs :: !ByteString
  - fs_ref :: !(IORef (Maybe FastZString))
  }
- fsLit :: String -> FastString
- mkFastString :: String -> FastString
- mkFastStringBytes :: Ptr Word8 -> Int -> FastString
- mkFastStringByteList :: [Word8] -> FastString
- mkFastStringForeignPtr :: Ptr Word8 -> ForeignPtr Word8 -> Int -> IO FastString
- mkFastString# :: Addr# -> FastString
- unpackFS :: FastString -> String
- bytesFS :: FastString -> [Word8]
- zEncodeFS :: FastString -> FastZString
- uniqueOfFS :: FastString -> Int
- lengthFS :: FastString -> Int
- nullFS :: FastString -> Bool
- appendFS :: FastString -> FastString -> FastString
- headFS :: FastString -> Char
- tailFS :: FastString -> FastString
- concatFS :: [FastString] -> FastString
- consFS :: Char -> FastString -> FastString
- nilFS :: FastString
- hPutFS :: Handle -> FastString -> IO ()
- getFastStringTable :: IO [[FastString]]
- hasZEncoding :: FastString -> Bool
- type LitString = Ptr Word8
- sLit :: String -> LitString
- mkLitString# :: Addr# -> LitString
- mkLitString :: String -> LitString
- unpackLitString :: LitString -> String
- lengthLS :: LitString -> Int

# ByteString

fastStringToByteString :: FastString -> ByteString #

mkFastStringByteString :: ByteString -> FastString #

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 #

unsafeMkByteString :: String -> ByteString #

hashByteString :: ByteString -> Int #

# FastZString

data FastZString #

Instances

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

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

zString :: FastZString -> String #

lengthFZS :: FastZString -> Int #

# FastStrings

data FastString #

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.

`FastString`s 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 # pprPrec :: Rational -> FastString -> SDoc #
Uniquable FastString # |
Methods getUnique :: FastString -> Unique #
Binary FastString # |
Methods put_ :: BinHandle -> FastString -> IO () # put :: BinHandle -> FastString -> IO (Bin * FastString) # get :: BinHandle -> IO FastString #

## Construction

fsLit :: String -> FastString #

mkFastString :: String -> FastString #

Creates a UTF-8 encoded `FastString` from a `String`

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

mkFastStringByteList :: [Word8] -> FastString #

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

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

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 #

## Deconstruction

unpackFS :: FastString -> String #

Unpacks and decodes the FastString

bytesFS :: FastString -> [Word8] #

Gives the UTF-8 encoded bytes corresponding to a `FastString`

## Encoding

zEncodeFS :: FastString -> FastZString #

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 #

lengthFS :: FastString -> Int #

Returns the length of the `FastString` in characters

nullFS :: FastString -> Bool #

Returns `True` if the `FastString` is empty

appendFS :: FastString -> FastString -> FastString #

headFS :: FastString -> Char #

tailFS :: FastString -> FastString #

concatFS :: [FastString] -> FastString #

consFS :: Char -> FastString -> FastString #

nilFS :: FastString #

## Outputing

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

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]] #

hasZEncoding :: FastString -> Bool #

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 #

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

## Construction

sLit :: String -> LitString #

mkLitString# :: Addr# -> LitString #

Wrap an unboxed address into a `LitString`.

mkLitString :: String -> LitString #

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 #

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

## Operations

lengthLS :: LitString -> Int #

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