ghc-6.12.2: The GHC APISource codeContentsIndex
FastString
Contents
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.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.

Synopsis
data FastString = FastString {
uniq :: !Int
n_bytes :: !Int
n_chars :: !Int
buf :: !(ForeignPtr Word8)
enc :: FSEncoding
}
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
uniq :: !Int
n_bytes :: !Int
n_chars :: !Int
buf :: !(ForeignPtr Word8)
enc :: FSEncoding
show/hide Instances
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
uniqueOfFS :: FastString -> FastIntSource
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
nilFS :: 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
type LitString = Ptr Word8Source
Construction
sLit :: String -> LitStringSource
mkLitString# :: Addr# -> LitStringSource
mkLitString :: String -> LitStringSource
Deconstruction
unpackLitString :: LitString -> StringSource
Operations
lengthLS :: LitString -> IntSource
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