FastString.lhs 19 KB
Newer Older
1
%
2
% (c) The University of Glasgow, 1997-2006
3
%
4
\begin{code}
5
{-# LANGUAGE BangPatterns #-}
6 7 8 9
{-# OPTIONS -fno-warn-unused-imports #-}
-- XXX GHC 6.9 seems to be confused by unpackCString# being used only in
--     a RULE

10 11 12 13
{-# OPTIONS_GHC -O -funbox-strict-fields #-}
-- We always optimise this, otherwise performance of a non-optimised
-- compiler is severely affected

14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
-- |
-- 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'.
31 32
module FastString
       (
Ian Lynagh's avatar
Ian Lynagh committed
33 34
        -- * FastStrings
        FastString(..),     -- not abstract, for now.
35

Ian Lynagh's avatar
Ian Lynagh committed
36
        -- ** Construction
37
        fsLit,
38
        mkFastString,
Ian Lynagh's avatar
Ian Lynagh committed
39
        mkFastStringBytes,
40
        mkFastStringByteList,
Ian Lynagh's avatar
Ian Lynagh committed
41
        mkFastStringForeignPtr,
42
#if defined(__GLASGOW_HASKELL__)
Ian Lynagh's avatar
Ian Lynagh committed
43
        mkFastString#,
44
#endif
Ian Lynagh's avatar
Ian Lynagh committed
45 46
        mkZFastString,
        mkZFastStringBytes,
47

Ian Lynagh's avatar
Ian Lynagh committed
48 49 50
        -- ** Deconstruction
        unpackFS,           -- :: FastString -> String
        bytesFS,            -- :: FastString -> [Word8]
51

Ian Lynagh's avatar
Ian Lynagh committed
52 53 54
        -- ** Encoding
        isZEncoded,
        zEncodeFS,
55

Ian Lynagh's avatar
Ian Lynagh committed
56
        -- ** Operations
57
        uniqueOfFS,
Ian Lynagh's avatar
Ian Lynagh committed
58 59 60
        lengthFS,
        nullFS,
        appendFS,
61 62
        headFS,
        tailFS,
Ian Lynagh's avatar
Ian Lynagh committed
63
        concatFS,
64
        consFS,
Ian Lynagh's avatar
Ian Lynagh committed
65
        nilFS,
66

Ian Lynagh's avatar
Ian Lynagh committed
67
        -- ** Outputing
68 69
        hPutFS,

Ian Lynagh's avatar
Ian Lynagh committed
70 71 72
        -- ** Internal
        getFastStringTable,
        hasZEncoding,
73

Ian Lynagh's avatar
Ian Lynagh committed
74 75
        -- * LitStrings
        LitString,
76 77 78
        
        -- ** Construction
        sLit,
79
#if defined(__GLASGOW_HASKELL__)
Ian Lynagh's avatar
Ian Lynagh committed
80
        mkLitString#,
81
#endif
Ian Lynagh's avatar
Ian Lynagh committed
82
        mkLitString,
83 84
        
        -- ** Deconstruction
Ian Lynagh's avatar
Ian Lynagh committed
85
        unpackLitString,
86 87 88
        
        -- ** Operations
        lengthLS
89 90
       ) where

91
#include "HsVersions.h"
92

93
import Encoding
94 95
import FastTypes
import FastFunctions
96
import Panic
97
import Util
98

99
import Foreign.C
100
import GHC.Exts
101
import System.IO
102
import System.IO.Unsafe ( unsafePerformIO )
103
import Data.Data
104
import Data.IORef       ( IORef, newIORef, readIORef, writeIORef )
Ian Lynagh's avatar
Ian Lynagh committed
105 106
import Data.Maybe       ( isJust )
import Data.Char        ( ord )
107

108
import GhcIO ( IO(..) )
109

110
#if __GLASGOW_HASKELL__ >= 701
111
import Foreign.Safe
112 113
import GHC.Ptr.Unsafe   ( Ptr(..) )
#else
114
import Foreign hiding ( unsafePerformIO )
Ian Lynagh's avatar
Ian Lynagh committed
115
import GHC.Ptr          ( Ptr(..) )
116 117
#endif

Ian Lynagh's avatar
Ian Lynagh committed
118 119 120
#if defined(__GLASGOW_HASKELL__)
import GHC.Base         ( unpackCString# )
#endif
121

122 123
#define hASH_TBL_SIZE          4091
#define hASH_TBL_SIZE_UNBOXED  4091#
124 125


126 127 128 129 130
{-|
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.
131

132 133 134 135
'FastString's support a memoized conversion to the Z-encoding via zEncodeFS.
-}

data FastString = FastString {
Ian Lynagh's avatar
Ian Lynagh committed
136 137 138
      uniq    :: {-# UNPACK #-} !Int, -- unique id
      n_bytes :: {-# UNPACK #-} !Int, -- number of bytes
      n_chars :: {-# UNPACK #-} !Int, -- number of chars
139 140
      buf     :: {-# UNPACK #-} !(ForeignPtr Word8),
      enc     :: FSEncoding
141
  } deriving Typeable
142 143

data FSEncoding
Ian Lynagh's avatar
Ian Lynagh committed
144
    -- including strings that don't need any encoding
145
  = ZEncoded
Ian Lynagh's avatar
Ian Lynagh committed
146
    -- A UTF-8 string with a memoized Z-encoding
147
  | UTF8Encoded {-# UNPACK #-} !(IORef (Maybe FastString))
148

149 150
instance Eq FastString where
  f1 == f2  =  uniq f1 == uniq f2
151

152
instance Ord FastString where
Ian Lynagh's avatar
Ian Lynagh committed
153
    -- Compares lexicographically, not by unique
154
    a <= b = case cmpFS a b of { LT -> True;  EQ -> True;  GT -> False }
Ian Lynagh's avatar
Ian Lynagh committed
155
    a <  b = case cmpFS a b of { LT -> True;  EQ -> False; GT -> False }
156
    a >= b = case cmpFS a b of { LT -> False; EQ -> True;  GT -> True  }
Ian Lynagh's avatar
Ian Lynagh committed
157 158 159 160 161
    a >  b = case cmpFS a b of { LT -> False; EQ -> False; GT -> True  }
    max x y | x >= y    =  x
            | otherwise =  y
    min x y | x <= y    =  x
            | otherwise =  y
162
    compare a b = cmpFS a b
163

164 165 166
instance Show FastString where
   show fs = show (unpackFS fs)

167 168 169 170 171 172
instance Data FastString where
  -- don't traverse?
  toConstr _   = abstractConstr "FastString"
  gunfold _ _  = error "gunfold"
  dataTypeOf _ = mkNoRepType "FastString"

173 174 175
cmpFS :: FastString -> FastString -> Ordering
cmpFS (FastString u1 l1 _ buf1 _) (FastString u2 l2 _ buf2 _) =
  if u1 == u2 then EQ else
Isaac Dupree's avatar
Isaac Dupree committed
176 177 178 179 180 181 182 183 184 185 186
  case unsafeMemcmp buf1 buf2 (min l1 l2) `compare` 0 of
     LT -> LT
     EQ -> compare l1 l2
     GT -> GT

unsafeMemcmp :: ForeignPtr a -> ForeignPtr b -> Int -> Int
unsafeMemcmp buf1 buf2 l =
      inlinePerformIO $
        withForeignPtr buf1 $ \p1 ->
        withForeignPtr buf2 $ \p2 ->
          memcmp p1 p2 l
187

188
#ifndef __HADDOCK__
Ian Lynagh's avatar
Ian Lynagh committed
189
foreign import ccall unsafe "ghc_memcmp"
190 191
  memcmp :: Ptr a -> Ptr b -> Int -> IO Int
#endif
192

193 194
-- -----------------------------------------------------------------------------
-- Construction
195

196
{-
197 198 199 200
Internally, the compiler will maintain a fast string symbol
table, providing sharing and fast comparison. Creation of
new @FastString@s then covertly does a lookup, re-using the
@FastString@ if there was a hit.
201
-}
202

Ian Lynagh's avatar
Ian Lynagh committed
203
data FastStringTable =
204
 FastStringTable
205
    {-# UNPACK #-} !Int
206
    (MutableArray# RealWorld [FastString])
207

208
{-# NOINLINE string_table #-}
209
string_table :: IORef FastStringTable
Ian Lynagh's avatar
Ian Lynagh committed
210
string_table =
211
 unsafePerformIO $ do
212 213 214 215
   tab <- IO $ \s1# -> case newArray# hASH_TBL_SIZE_UNBOXED [] s1# of
                           (# s2#, arr# #) ->
                               (# s2#, FastStringTable 0 arr# #)
   newIORef tab
216 217 218 219 220

lookupTbl :: FastStringTable -> Int -> IO [FastString]
lookupTbl (FastStringTable _ arr#) (I# i#) =
  IO $ \ s# -> readArray# arr# i# s#

221 222
updTbl :: IORef FastStringTable -> FastStringTable -> Int -> [FastString] -> IO ()
updTbl fs_table_var (FastStringTable uid arr#) (I# i#) ls = do
223
  (IO $ \ s# -> case writeArray# arr# i# ls s# of { s2# -> (# s2#, () #) })
224
  writeIORef fs_table_var (FastStringTable (uid+1) arr#)
225

226
mkFastString# :: Addr# -> FastString
227
mkFastString# a# = mkFastStringBytes ptr (ptrStrLength ptr)
228
  where ptr = Ptr a#
229

230
mkFastStringBytes :: Ptr Word8 -> Int -> FastString
231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248
mkFastStringBytes ptr len = unsafePerformIO $ do
  ft@(FastStringTable uid _) <- readIORef string_table
  let
   h = hashStr ptr len
   add_it ls = do
        fs <- copyNewFastString uid ptr len
        updTbl string_table ft h (fs:ls)
        {- _trace ("new: " ++ show f_str)   $ -}
        return fs
  --
  lookup_result <- lookupTbl ft h
  case lookup_result of
    [] -> add_it []
    ls -> do
       b <- bucket_match ls len ptr
       case b of
         Nothing -> add_it ls
         Just v  -> {- _trace ("re-use: "++show v) $ -} return v
249 250

mkZFastStringBytes :: Ptr Word8 -> Int -> FastString
251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268
mkZFastStringBytes ptr len = unsafePerformIO $ do
  ft@(FastStringTable uid _) <- readIORef string_table
  let
   h = hashStr ptr len
   add_it ls = do
        fs <- copyNewZFastString uid ptr len
        updTbl string_table ft h (fs:ls)
        {- _trace ("new: " ++ show f_str)   $ -}
        return fs
  --
  lookup_result <- lookupTbl ft h
  case lookup_result of
    [] -> add_it []
    ls -> do
       b <- bucket_match ls len ptr
       case b of
         Nothing -> add_it ls
         Just v  -> {- _trace ("re-use: "++show v) $ -} return v
269 270 271 272 273 274

-- | 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.
mkFastStringForeignPtr :: Ptr Word8 -> ForeignPtr Word8 -> Int -> IO FastString
mkFastStringForeignPtr ptr fp len = do
275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292
  ft@(FastStringTable uid _) <- readIORef string_table
--  _trace ("hashed: "++show (I# h)) $
  let
    h = hashStr ptr len
    add_it ls = do
        fs <- mkNewFastString uid ptr fp len
        updTbl string_table ft h (fs:ls)
        {- _trace ("new: " ++ show f_str)   $ -}
        return fs
  --
  lookup_result <- lookupTbl ft h
  case lookup_result of
    [] -> add_it []
    ls -> do
       b <- bucket_match ls len ptr
       case b of
         Nothing -> add_it ls
         Just v  -> {- _trace ("re-use: "++show v) $ -} return v
293 294 295

mkZFastStringForeignPtr :: Ptr Word8 -> ForeignPtr Word8 -> Int -> IO FastString
mkZFastStringForeignPtr ptr fp len = do
296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314
  ft@(FastStringTable uid _) <- readIORef string_table
--  _trace ("hashed: "++show (I# h)) $
  let
    h = hashStr ptr len
    add_it ls = do
        fs <- mkNewZFastString uid ptr fp len
        updTbl string_table ft h (fs:ls)
        {- _trace ("new: " ++ show f_str)   $ -}
        return fs
  --
  lookup_result <- lookupTbl ft h
  case lookup_result of
    [] -> add_it []
    ls -> do
       b <- bucket_match ls len ptr
       case b of
         Nothing -> add_it ls
         Just v  -> {- _trace ("re-use: "++show v) $ -} return v

315

316 317
-- | Creates a UTF-8 encoded 'FastString' from a 'String'
mkFastString :: String -> FastString
Ian Lynagh's avatar
Ian Lynagh committed
318
mkFastString str =
319 320 321 322 323
  inlinePerformIO $ do
    let l = utf8EncodedLength str
    buf <- mallocForeignPtrBytes l
    withForeignPtr buf $ \ptr -> do
      utf8EncodeString ptr str
Ian Lynagh's avatar
Ian Lynagh committed
324
      mkFastStringForeignPtr ptr buf l
325

326 327
-- | Creates a 'FastString' from a UTF-8 encoded @[Word8]@
mkFastStringByteList :: [Word8] -> FastString
Ian Lynagh's avatar
Ian Lynagh committed
328
mkFastStringByteList str =
329 330 331 332 333
  inlinePerformIO $ do
    let l = Prelude.length str
    buf <- mallocForeignPtrBytes l
    withForeignPtr buf $ \ptr -> do
      pokeArray (castPtr ptr) str
Ian Lynagh's avatar
Ian Lynagh committed
334
      mkFastStringForeignPtr ptr buf l
335 336 337

-- | Creates a Z-encoded 'FastString' from a 'String'
mkZFastString :: String -> FastString
Ian Lynagh's avatar
Ian Lynagh committed
338
mkZFastString str =
339 340 341 342 343
  inlinePerformIO $ do
    let l = Prelude.length str
    buf <- mallocForeignPtrBytes l
    withForeignPtr buf $ \ptr -> do
      pokeCAString (castPtr ptr) str
Ian Lynagh's avatar
Ian Lynagh committed
344
      mkZFastStringForeignPtr ptr buf l
345

346
bucket_match :: [FastString] -> Int -> Ptr Word8 -> IO (Maybe FastString)
347 348 349
bucket_match [] _ _ = return Nothing
bucket_match (v@(FastString _ l _ buf _):ls) len ptr
      | len == l  =  do
Ian Lynagh's avatar
Ian Lynagh committed
350 351 352 353 354
         b <- cmpStringPrefix ptr buf len
         if b then return (Just v)
              else bucket_match ls len ptr
      | otherwise =
         bucket_match ls len ptr
355

356 357
mkNewFastString :: Int -> Ptr Word8 -> ForeignPtr Word8 -> Int
                -> IO FastString
358 359 360 361 362
mkNewFastString uid ptr fp len = do
  ref <- newIORef Nothing
  n_chars <- countUTF8Chars ptr len
  return (FastString uid len n_chars fp (UTF8Encoded ref))

363 364 365
mkNewZFastString :: Int -> Ptr Word8 -> ForeignPtr Word8 -> Int
                 -> IO FastString
mkNewZFastString uid _ fp len = do
366 367
  return (FastString uid len len fp ZEncoded)

368
copyNewFastString :: Int -> Ptr Word8 -> Int -> IO FastString
369 370 371 372 373 374
copyNewFastString uid ptr len = do
  fp <- copyBytesToForeignPtr ptr len
  ref <- newIORef Nothing
  n_chars <- countUTF8Chars ptr len
  return (FastString uid len n_chars fp (UTF8Encoded ref))

375
copyNewZFastString :: Int -> Ptr Word8 -> Int -> IO FastString
376 377 378 379
copyNewZFastString uid ptr len = do
  fp <- copyBytesToForeignPtr ptr len
  return (FastString uid len len fp ZEncoded)

380
copyBytesToForeignPtr :: Ptr Word8 -> Int -> IO (ForeignPtr Word8)
381 382 383 384 385 386 387 388 389 390 391 392 393
copyBytesToForeignPtr ptr len = do
  fp <- mallocForeignPtrBytes len
  withForeignPtr fp $ \ptr' -> copyBytes ptr' ptr len
  return fp

cmpStringPrefix :: Ptr Word8 -> ForeignPtr Word8 -> Int -> IO Bool
cmpStringPrefix ptr fp len =
  withForeignPtr fp $ \ptr' -> do
    r <- memcmp ptr ptr' len
    return (r == 0)


hashStr  :: Ptr Word8 -> Int -> Int
394
 -- use the Addr to produce a hash value between 0 & m (inclusive)
395
hashStr (Ptr a#) (I# len#) = loop 0# 0#
Ian Lynagh's avatar
Ian Lynagh committed
396
   where
397
    loop h n | n GHC.Exts.==# len# = I# h
Ian Lynagh's avatar
Ian Lynagh committed
398
             | otherwise  = loop h2 (n GHC.Exts.+# 1#)
399 400 401
          where !c = ord# (indexCharOffAddr# a# n)
                !h2 = (c GHC.Exts.+# (h GHC.Exts.*# 128#)) `remInt#`
                      hASH_TBL_SIZE#
402

403 404
-- -----------------------------------------------------------------------------
-- Operations
405

406 407 408
-- | Returns the length of the 'FastString' in characters
lengthFS :: FastString -> Int
lengthFS f = n_chars f
409

410
-- | Returns @True@ if the 'FastString' is Z-encoded
411 412
isZEncoded :: FastString -> Bool
isZEncoded fs | ZEncoded <- enc fs = True
Ian Lynagh's avatar
Ian Lynagh committed
413
              | otherwise          = False
414

415
-- | Returns @True@ if this 'FastString' is not Z-encoded but already has
416 417
-- a Z-encoding cached (used in producing stats).
hasZEncoding :: FastString -> Bool
418
hasZEncoding (FastString _ _ _ _ enc) =
419 420 421 422 423
  case enc of
    ZEncoded -> False
    UTF8Encoded ref ->
      inlinePerformIO $ do
        m <- readIORef ref
Ian Lynagh's avatar
Ian Lynagh committed
424
        return (isJust m)
425

426
-- | Returns @True@ if the 'FastString' is empty
427 428 429
nullFS :: FastString -> Bool
nullFS f  =  n_bytes f == 0

430
-- | Unpacks and decodes the FastString
431
unpackFS :: FastString -> String
Ian Lynagh's avatar
Ian Lynagh committed
432
unpackFS (FastString _ n_bytes _ buf enc) =
433 434
  inlinePerformIO $ withForeignPtr buf $ \ptr ->
    case enc of
Ian Lynagh's avatar
Ian Lynagh committed
435 436
        ZEncoded      -> peekCAStringLen (castPtr ptr,n_bytes)
        UTF8Encoded _ -> utf8DecodeString ptr n_bytes
437 438

bytesFS :: FastString -> [Word8]
439
bytesFS (FastString _ n_bytes _ buf _) =
440 441 442
  inlinePerformIO $ withForeignPtr buf $ \ptr ->
    peekArray n_bytes ptr

443
-- | Returns a Z-encoded version of a 'FastString'.  This might be the
444 445 446 447 448
-- original, if it was already Z-encoded.  The first time this
-- function is applied to a particular 'FastString', the results are
-- memoized.
--
zEncodeFS :: FastString -> FastString
449
zEncodeFS fs@(FastString _ _ _ _ enc) =
450 451 452 453
  case enc of
    ZEncoded -> fs
    UTF8Encoded ref ->
      inlinePerformIO $ do
454 455 456 457 458 459 460
        m <- readIORef ref
        case m of
          Just fs -> return fs
          Nothing -> do
            let efs = mkZFastString (zEncodeString (unpackFS fs))
            writeIORef ref (Just efs)
            return efs
461 462

appendFS :: FastString -> FastString -> FastString
ich@christoph-bauer.net's avatar
ich@christoph-bauer.net committed
463 464 465 466 467 468 469 470 471 472 473 474
appendFS fs1 fs2 =
  inlinePerformIO $ do
    r <- mallocForeignPtrBytes len
    withForeignPtr r $ \ r' -> do
    withForeignPtr (buf fs1) $ \ fs1Ptr -> do
    withForeignPtr (buf fs2) $ \ fs2Ptr -> do
        copyBytes r' fs1Ptr len1
        copyBytes (advancePtr r' len1) fs2Ptr len2
        mkFastStringForeignPtr r' r len
  where len  = len1 + len2
        len1 = lengthFS fs1
        len2 = lengthFS fs2
475 476 477 478 479

concatFS :: [FastString] -> FastString
concatFS ls = mkFastString (Prelude.concat (map unpackFS ls)) -- ToDo: do better

headFS :: FastString -> Char
480 481
headFS (FastString _ 0 _ _ _) = panic "headFS: Empty FastString"
headFS (FastString _ _ _ buf enc) =
482 483
  inlinePerformIO $ withForeignPtr buf $ \ptr -> do
    case enc of
Ian Lynagh's avatar
Ian Lynagh committed
484 485 486 487 488
      ZEncoded -> do
         w <- peek (castPtr ptr)
         return (castCCharToChar w)
      UTF8Encoded _ ->
         return (fst (utf8DecodeChar ptr))
489 490

tailFS :: FastString -> FastString
491
tailFS (FastString _ 0 _ _ _) = panic "tailFS: Empty FastString"
Ian Lynagh's avatar
Ian Lynagh committed
492
tailFS (FastString _ n_bytes _ buf enc) =
493 494 495
  inlinePerformIO $ withForeignPtr buf $ \ptr -> do
    case enc of
      ZEncoded -> do
Ian Lynagh's avatar
Ian Lynagh committed
496
        return $! mkZFastStringBytes (ptr `plusPtr` 1) (n_bytes - 1)
497
      UTF8Encoded _ -> do
Ian Lynagh's avatar
Ian Lynagh committed
498 499 500
         let (_,ptr') = utf8DecodeChar ptr
         let off = ptr' `minusPtr` ptr
         return $! mkFastStringBytes (ptr `plusPtr` off) (n_bytes - off)
501 502 503 504

consFS :: Char -> FastString -> FastString
consFS c fs = mkFastString (c : unpackFS fs)

505 506
uniqueOfFS :: FastString -> FastInt
uniqueOfFS (FastString u _ _ _ _) = iUnbox u
507

508
nilFS :: FastString
509
nilFS = mkFastString ""
510

511 512 513 514 515 516
-- -----------------------------------------------------------------------------
-- Stats

getFastStringTable :: IO [[FastString]]
getFastStringTable = do
  tbl <- readIORef string_table
517
  buckets <- mapM (lookupTbl tbl) [0 .. hASH_TBL_SIZE]
518 519
  return buckets

520 521 522
-- -----------------------------------------------------------------------------
-- Outputting 'FastString's

523 524
-- |Outputs a 'FastString' with /no decoding at all/, that is, you
-- get the actual bytes in the 'FastString' written to the 'Handle'.
525
hPutFS :: Handle -> FastString -> IO ()
526 527 528
hPutFS handle (FastString _ len _ fp _)
  | len == 0  = return ()
  | otherwise = do withForeignPtr fp $ \ptr -> hPutBuf handle ptr len
529

530 531
-- ToDo: we'll probably want an hPutFSLocal, or something, to output
-- in the current locale's encoding (for error messages and suchlike).
532

533 534
-- -----------------------------------------------------------------------------
-- LitStrings, here for convenience only.
535

536 537 538 539 540 541 542
-- hmm, not unboxed (or rather FastPtr), interesting
--a.k.a. Ptr CChar, Ptr Word8, Ptr (), hmph.  We don't
--really care about C types in naming, where we can help it.
type LitString = Ptr Word8
--Why do we recalculate length every time it's requested?
--If it's commonly needed, we should perhaps have
--data LitString = LitString {-#UNPACK#-}!(FastPtr Word8) {-#UNPACK#-}!FastInt
543

544
#if defined(__GLASGOW_HASKELL__)
545
mkLitString# :: Addr# -> LitString
546
mkLitString# a# = Ptr a#
Ian Lynagh's avatar
Ian Lynagh committed
547
#endif
548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565
--can/should we use FastTypes here?
--Is this likely to be memory-preserving if only used on constant strings?
--should we inline it? If lucky, that would make a CAF that wouldn't
--be computationally repeated... although admittedly we're not
--really intending to use mkLitString when __GLASGOW_HASKELL__...
--(I wonder, is unicode / multi-byte characters allowed in LitStrings
-- at all?)
{-# INLINE mkLitString #-}
mkLitString :: String -> LitString
mkLitString s =
 unsafePerformIO (do
   p <- mallocBytes (length s + 1)
   let
     loop :: Int -> String -> IO ()
     loop n cs | n `seq` null cs = pokeByteOff p n (0 :: Word8)
     loop n (c:cs) = do
        pokeByteOff p n (fromIntegral (ord c) :: Word8)
        loop (1+n) cs
Ian Lynagh's avatar
Ian Lynagh committed
566 567 568
     -- XXX GHC isn't smart enough to know that we have already covered
     -- this case.
     loop _ [] = panic "mkLitString"
569 570 571 572 573 574 575 576 577 578 579 580
   loop 0 s
   return p
 )

unpackLitString :: LitString -> String
unpackLitString p_ = case pUnbox p_ of
 p -> unpack (_ILIT(0))
  where
    unpack n = case indexWord8OffFastPtrAsFastChar p n of
      ch -> if ch `eqFastChar` _CLIT('\0')
            then [] else cBox ch : unpack (n +# _ILIT(1))

581 582
lengthLS :: LitString -> Int
lengthLS = ptrStrLength
583 584 585 586 587 588 589 590 591 592 593 594

-- for now, use a simple String representation
--no, let's not do that right now - it's work in other places
#if 0
type LitString = String

mkLitString :: String -> LitString
mkLitString = id

unpackLitString :: LitString -> String
unpackLitString = id

595 596
lengthLS :: LitString -> Int
lengthLS = length
597 598

#endif
599 600 601 602

-- -----------------------------------------------------------------------------
-- under the carpet

Ian Lynagh's avatar
Ian Lynagh committed
603
foreign import ccall unsafe "ghc_strlen"
604
  ptrStrLength :: Ptr Word8 -> Int
605

606
-- NB. does *not* add a '\0'-terminator.
607 608
-- We only use CChar here to be parallel to the imported
-- peekC(A)StringLen.
609 610 611
pokeCAString :: Ptr CChar -> String -> IO ()
pokeCAString ptr str =
  let
612
        go [] _     = return ()
Ian Lynagh's avatar
Ian Lynagh committed
613
        go (c:cs) n = do pokeElemOff ptr n (castCharToCChar c); go cs (n+1)
614 615 616
  in
  go str 0

Ian Lynagh's avatar
Ian Lynagh committed
617 618 619 620 621 622 623 624 625 626 627 628
{-# NOINLINE sLit #-}
sLit :: String -> LitString
sLit x  = mkLitString x

{-# NOINLINE fsLit #-}
fsLit :: String -> FastString
fsLit x = mkFastString x

{-# RULES "slit"
    forall x . sLit  (unpackCString# x) = mkLitString#  x #-}
{-# RULES "fslit"
    forall x . fsLit (unpackCString# x) = mkFastString# x #-}
629
\end{code}