Moduleghc-9.10.3GHC2021

GHC.Data.FastString

There are two principal string types used internally by GHC:

FastString

A compact, hash-consed, representation of character strings.
Generated by fsLit.
You can get a Unique from 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 SDoc with ftext.

PtrString

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 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 PtrString unless you want the facilities of FastString.

5 types
36 values

Packageghc-9.10.3
Exports41
LanguageGHC2021
LicenceBSD-3-Clause
SourceFastString.hs

ByteString

5 declarations

valuebytesFS :: FastString -> ByteString

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

valuefastStringToByteString :: FastString -> ByteString

Deprecated. Use bytesFS instead

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

valuemkFastStringByteString :: ByteString -> FastString

Create a FastString by copying an existing ByteString

valuefastZStringToByteString :: FastZString -> ByteString

valueunsafeMkByteString :: String -> ByteString

ShortByteString

2 declarations

valuefastStringToShortByteString :: FastString -> ShortByteString

valuemkFastStringShortByteString :: ShortByteString -> FastString

Create a FastString from an existing ShortByteString without copying.

ShortText

1 declaration

valuefastStringToShortText :: FastString -> ShortText

FastZString

5 declarations

newtypenewtype FastZString

Instances1NFData

NFData FastZStringDefined in ghc-9.10.3 · GHC.Data.FastString

valuehPutFZS :: Handle -> FastZString -> IO ()

valuezString :: FastZString -> String

valuezStringTakeN :: Int -> FastZString -> String

zStringTakeN n = take n . zString but is performed in O(\min(n,l)) rather than O(l), where l is the length of the FastZString.

valuelengthFZS :: FastZString -> Int

FastStrings

3 declarations

datadata FastString

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
- uniq :: !Int
- n_chars :: !Int
- fs_sbs :: !ShortByteString
- fs_zenc :: FastZString
  Lazily computed Z-encoding of this string. See Note [Z-Encoding] in GHC.Utils.Encoding.
  Since FastStrings are globally memoized this is computed at most once for any given string.

Instances14Eq, Data, Show, IsString, Semigroup, Monoid, …

Eq FastStringDefined in ghc-9.10.3 · GHC.Data.FastString
Data FastStringDefined in ghc-9.10.3 · GHC.Data.FastString
Show FastStringDefined in ghc-9.10.3 · GHC.Data.FastString
IsString FastStringDefined in ghc-9.10.3 · GHC.Data.FastString
Semigroup FastStringDefined in ghc-9.10.3 · GHC.Data.FastString
Monoid FastStringDefined in ghc-9.10.3 · GHC.Data.FastString
NFData FastStringDefined in ghc-9.10.3 · GHC.Data.FastString
Outputable FastStringDefined in ghc-9.10.3 · GHC.Utils.Outputable
Uniquable FastStringDefined in ghc-9.10.3 · GHC.Types.Unique
Binary FastStringDefined in ghc-9.10.3 · GHC.Utils.Binary
ToJExpr FastStringDefined in ghc-9.10.3 · GHC.JS.Make
ToJExpr a => ToJExpr (UniqMap FastString a)Defined in ghc-9.10.3 · GHC.JS.Make
type Anno FastString = EpAnnCODefined in ghc-9.10.3 · GHC.Hs.Expr · orphan
type Anno (SourceText, RuleName) = EpAnnCODefined in ghc-9.10.3 · GHC.Hs.Decls · orphan

newtypenewtype NonDetFastString

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

Instances6Eq, Data, Ord, Show, Outputable, Binary

Eq NonDetFastStringDefined in ghc-9.10.3 · GHC.Data.FastString
Data NonDetFastStringDefined in ghc-9.10.3 · GHC.Data.FastString
Ord NonDetFastStringDefined in ghc-9.10.3 · GHC.Data.FastString
Show NonDetFastStringDefined in ghc-9.10.3 · GHC.Data.FastString
Outputable NonDetFastStringDefined in ghc-9.10.3 · GHC.Utils.Outputable
Binary NonDetFastStringDefined in ghc-9.10.3 · GHC.Utils.Binary

newtypenewtype LexicalFastString

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

Instances6Eq, Data, Ord, Show, Outputable, Binary

Eq LexicalFastStringDefined in ghc-9.10.3 · GHC.Data.FastString
Data LexicalFastStringDefined in ghc-9.10.3 · GHC.Data.FastString
Ord LexicalFastStringDefined in ghc-9.10.3 · GHC.Data.FastString
Show LexicalFastStringDefined in ghc-9.10.3 · GHC.Data.FastString
Outputable LexicalFastStringDefined in ghc-9.10.3 · GHC.Utils.Outputable
Binary LexicalFastStringDefined in ghc-9.10.3 · GHC.Utils.Binary

Construction

valuefsLit :: String -> FastString

valuemkFastString :: String -> FastString

Creates a UTF-8 encoded FastString from a String

valuemkFastStringBytes :: Ptr Word8 -> Int -> FastString

valuemkFastStringByteList :: [Word8] -> FastString

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

valuemkFastString# :: Addr# -> FastString

Deconstruction

valueunpackFS :: FastString -> String

Lazily unpacks and decodes the FastString

valueunconsFS :: FastString -> Maybe (Char, FastString)

Encoding

valuezEncodeFS :: 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

valueuniqueOfFS :: FastString -> Int

valuelengthFS :: FastString -> Int

Returns the length of the FastString in characters

valuenullFS :: FastString -> Bool

Returns True if the FastString is empty

valueappendFS :: FastString -> FastString -> FastString

valueconcatFS :: [FastString] -> FastString

valueconsFS :: Char -> FastString -> FastString

valuenilFS :: FastString

valuelexicalCompareFS :: FastString -> FastString -> Ordering

Compare FastString lexically

If you don't care about the lexical ordering, use uniqCompareFS instead.

valueuniqCompareFS :: FastString -> FastString -> Ordering

Compare FastString by their Unique (not lexically).

Much cheaper than lexicalCompareFS but non-deterministic!

Outputting

valuehPutFS :: 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

valuegetFastStringTable :: IO [[[FastString]]]

valuegetFastStringZEncCounter :: IO Int

PtrStrings

1 declaration

datadata PtrString

A PtrString is a pointer to some array of Latin-1 encoded chars.

Constructors

PtrString !(Ptr Word8) !Int

Construction

valuemkPtrString# :: Addr# -> PtrString

Wrap an unboxed address into a PtrString.

Deconstruction

valueunpackPtrString :: PtrString -> String

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

valueunpackPtrStringTakeN :: Int -> PtrString -> String

unpackPtrStringTakeN n = take n . unpackPtrString but is performed in O(\min(n,l)) rather than O(l), where l is the length of the PtrString.

Operations

valuelengthPS :: PtrString -> Int

Return the length of a PtrString