| Safe Haskell | Safe-Inferred |
|---|---|
| Language | Haskell2010 |
GHC.Data.FastString
Description
There are two principal string types used internally by GHC:
- A compact, hash-consed, representation of character strings.
- Generated by
fsLit. - You can get a
Uniquefrom them. - Equality test is O(1) (it uses the Unique).
- Comparison is O(1) or O(n):
- O(n) but deterministic with lexical comparison (
lexicalCompareFS) - O(1) but non-deterministic with Unique comparison (
uniqCompareFS) - Turn into
SDocwithftext.
- Pointer and size of a Latin-1 encoded string.
- Practically no operations.
- Outputting them is fast.
- Generated by
mkPtrString#. - Length of string literals (mkPtrString# "abc"#) is computed statically
- Turn into
SDocwithptext - 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 PtrString unless you want the facilities of FastString.
Synopsis
- bytesFS :: FastString -> ByteString
- fastStringToByteString :: FastString -> ByteString
- mkFastStringByteString :: ByteString -> FastString
- fastZStringToByteString :: FastZString -> ByteString
- unsafeMkByteString :: String -> ByteString
- fastStringToShortByteString :: FastString -> ShortByteString
- mkFastStringShortByteString :: ShortByteString -> FastString
- data FastZString
- hPutFZS :: Handle -> FastZString -> IO ()
- zString :: FastZString -> String
- zStringTakeN :: Int -> FastZString -> String
- lengthFZS :: FastZString -> Int
- data FastString = FastString {
- uniq :: !Int
- n_chars :: !Int
- fs_sbs :: !ShortByteString
- fs_zenc :: FastZString
- newtype NonDetFastString = NonDetFastString FastString
- newtype LexicalFastString = LexicalFastString FastString
- fsLit :: String -> FastString
- mkFastString :: String -> FastString
- mkFastStringBytes :: Ptr Word8 -> Int -> FastString
- mkFastStringByteList :: [Word8] -> FastString
- mkFastString# :: Addr# -> FastString
- unpackFS :: FastString -> String
- unconsFS :: FastString -> Maybe (Char, FastString)
- zEncodeFS :: FastString -> FastZString
- uniqueOfFS :: FastString -> Int
- lengthFS :: FastString -> Int
- nullFS :: FastString -> Bool
- appendFS :: FastString -> FastString -> FastString
- concatFS :: [FastString] -> FastString
- consFS :: Char -> FastString -> FastString
- nilFS :: FastString
- lexicalCompareFS :: FastString -> FastString -> Ordering
- uniqCompareFS :: FastString -> FastString -> Ordering
- hPutFS :: Handle -> FastString -> IO ()
- getFastStringTable :: IO [[[FastString]]]
- getFastStringZEncCounter :: IO Int
- data PtrString = PtrString !(Ptr Word8) !Int
- mkPtrString# :: Addr# -> PtrString
- unpackPtrString :: PtrString -> String
- unpackPtrStringTakeN :: Int -> PtrString -> String
- lengthPS :: PtrString -> Int
ByteString
bytesFS :: FastString -> ByteString Source #
Gives the Modified UTF-8 encoded bytes corresponding to a FastString
fastStringToByteString :: FastString -> ByteString Source #
Deprecated: Use bytesFS instead
Gives the Modified UTF-8 encoded bytes corresponding to a FastString
mkFastStringByteString :: ByteString -> FastString Source #
Create a FastString by copying an existing ByteString
ShortByteString
mkFastStringShortByteString :: ShortByteString -> FastString Source #
Create a FastString from an existing ShortByteString without
copying.
FastZString
data FastZString Source #
Instances
| NFData FastZString Source # | |
Defined in GHC.Data.FastString Methods rnf :: FastZString -> () Source # | |
zString :: FastZString -> String Source #
zStringTakeN :: Int -> FastZString -> String Source #
zStringTakeN n =
but is performed in \(O(\min(n,l))\) rather than \(O(l)\),
where \(l\) is the length of the take n . zStringFastZString.
lengthFZS :: FastZString -> Int Source #
FastStrings
data FastString Source #
A FastString is a UTF-8 encoded string together with a unique ID. All
FastStrings are stored in a global hashtable to support fast O(1)
comparison.
It is also associated with a lazy reference to the Z-encoding of this string which is used by the compiler internally.
Constructors
| FastString | |
Fields
| |
Instances
newtype NonDetFastString Source #
Non-deterministic FastString
This is a simple FastString wrapper with an Ord instance using
uniqCompareFS (i.e. which compares FastStrings on their Uniques). Hence it
is not deterministic from one run to the other.
Constructors
| NonDetFastString FastString |
Instances
newtype LexicalFastString Source #
Lexical FastString
This is a simple FastString wrapper with an Ord instance using
lexicalCompareFS (i.e. which compares FastStrings on their String
representation). Hence it is deterministic from one run to the other.
Constructors
| LexicalFastString FastString |
Instances
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]
mkFastString# :: Addr# -> FastString Source #
Deconstruction
unpackFS :: FastString -> String Source #
Lazily unpacks and decodes the FastString
unconsFS :: FastString -> Maybe (Char, FastString) Source #
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 #
concatFS :: [FastString] -> FastString Source #
consFS :: Char -> FastString -> FastString Source #
nilFS :: FastString Source #
lexicalCompareFS :: FastString -> FastString -> Ordering Source #
Compare FastString lexically
If you don't care about the lexical ordering, use uniqCompareFS instead.
uniqCompareFS :: FastString -> FastString -> Ordering Source #
Compare FastString by their Unique (not lexically).
Much cheaper than lexicalCompareFS but non-deterministic!
Outputting
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 #
PtrStrings
A PtrString is a pointer to some array of Latin-1 encoded chars.
Construction
Deconstruction
unpackPtrString :: PtrString -> String Source #
unpackPtrStringTakeN :: Int -> PtrString -> String Source #
unpackPtrStringTakeN n =
but is performed in \(O(\min(n,l))\) rather than \(O(l)\),
where \(l\) is the length of the take n . unpackPtrStringPtrString.