FastString
Contents
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.Unique from them.
* Generated by fsLit.
* Turn into Outputable.SDoc with Outputable.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 Outputable.SDoc with Outputable.ptext
Use LitString unless you want the facilities of FastString.
- data FastString = FastString {}
- 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
- mkZFastString :: String -> FastString
- mkZFastStringBytes :: Ptr Word8 -> Int -> FastString
- unpackFS :: FastString -> String
- bytesFS :: FastString -> [Word8]
- isZEncoded :: FastString -> Bool
- zEncodeFS :: FastString -> FastString
- uniqueOfFS :: FastString -> FastInt
- 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
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 | |
Construction
fsLit :: String -> FastStringSource
mkFastString :: String -> FastStringSource
Creates a UTF-8 encoded FastString from a String
mkFastStringBytes :: Ptr Word8 -> Int -> FastStringSource
mkFastStringByteList :: [Word8] -> FastStringSource
Creates a FastString from a UTF-8 encoded [Word8]
mkFastStringForeignPtr :: Ptr Word8 -> ForeignPtr Word8 -> Int -> IO FastStringSource
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# -> FastStringSource
mkZFastString :: String -> FastStringSource
Creates a Z-encoded FastString from a String
mkZFastStringBytes :: Ptr Word8 -> Int -> FastStringSource
Deconstruction
unpackFS :: FastString -> StringSource
Unpacks and decodes the FastString
bytesFS :: FastString -> [Word8]Source
Encoding
isZEncoded :: FastString -> BoolSource
Returns True if the FastString is Z-encoded
zEncodeFS :: FastString -> FastStringSource
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
lengthFS :: FastString -> IntSource
Returns the length of the FastString in characters
nullFS :: FastString -> BoolSource
Returns True if the FastString is empty
appendFS :: FastString -> FastString -> FastStringSource
headFS :: FastString -> CharSource
tailFS :: FastString -> FastStringSource
concatFS :: [FastString] -> FastStringSource
consFS :: Char -> FastString -> FastStringSource
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 -> BoolSource
Returns True if this FastString is not Z-encoded but already has
a Z-encoding cached (used in producing stats).
LitStrings
Construction
mkLitString# :: Addr# -> LitStringSource
mkLitString :: String -> LitStringSource