add install-includes: field
[packages/pretty.git] / Foreign / C / String.hs
1 {-# OPTIONS_GHC -fno-implicit-prelude #-}
2 -----------------------------------------------------------------------------
3 -- |
4 -- Module : Foreign.C.String
5 -- Copyright : (c) The FFI task force 2001
6 -- License : BSD-style (see the file libraries/base/LICENSE)
7 --
8 -- Maintainer : ffi@haskell.org
9 -- Stability : provisional
10 -- Portability : portable
11 --
12 -- Utilities for primitive marshalling of C strings.
13 --
14 -- The marshalling converts each Haskell character, representing a Unicode
15 -- code point, to one or more bytes in a manner that, by default, is
16 -- determined by the current locale. As a consequence, no guarantees
17 -- can be made about the relative length of a Haskell string and its
18 -- corresponding C string, and therefore all the marshalling routines
19 -- include memory allocation. The translation between Unicode and the
20 -- encoding of the current locale may be lossy.
21 --
22 -----------------------------------------------------------------------------
23
24 module Foreign.C.String ( -- representation of strings in C
25
26 -- * C strings
27
28 CString, -- = Ptr CChar
29 CStringLen, -- = (Ptr CChar, Int)
30
31 -- ** Using a locale-dependent encoding
32
33 -- | Currently these functions are identical to their @CAString@ counterparts;
34 -- eventually they will use an encoding determined by the current locale.
35
36 -- conversion of C strings into Haskell strings
37 --
38 peekCString, -- :: CString -> IO String
39 peekCStringLen, -- :: CStringLen -> IO String
40
41 -- conversion of Haskell strings into C strings
42 --
43 newCString, -- :: String -> IO CString
44 newCStringLen, -- :: String -> IO CStringLen
45
46 -- conversion of Haskell strings into C strings using temporary storage
47 --
48 withCString, -- :: String -> (CString -> IO a) -> IO a
49 withCStringLen, -- :: String -> (CStringLen -> IO a) -> IO a
50
51 charIsRepresentable, -- :: Char -> IO Bool
52
53 -- ** Using 8-bit characters
54
55 -- | These variants of the above functions are for use with C libraries
56 -- that are ignorant of Unicode. These functions should be used with
57 -- care, as a loss of information can occur.
58
59 castCharToCChar, -- :: Char -> CChar
60 castCCharToChar, -- :: CChar -> Char
61
62 peekCAString, -- :: CString -> IO String
63 peekCAStringLen, -- :: CStringLen -> IO String
64 newCAString, -- :: String -> IO CString
65 newCAStringLen, -- :: String -> IO CStringLen
66 withCAString, -- :: String -> (CString -> IO a) -> IO a
67 withCAStringLen, -- :: String -> (CStringLen -> IO a) -> IO a
68
69 -- * C wide strings
70
71 -- | These variants of the above functions are for use with C libraries
72 -- that encode Unicode using the C @wchar_t@ type in a system-dependent
73 -- way. The only encodings supported are
74 --
75 -- * UTF-32 (the C compiler defines @__STDC_ISO_10646__@), or
76 --
77 -- * UTF-16 (as used on Windows systems).
78
79 CWString, -- = Ptr CWchar
80 CWStringLen, -- = (Ptr CWchar, Int)
81
82 peekCWString, -- :: CWString -> IO String
83 peekCWStringLen, -- :: CWStringLen -> IO String
84 newCWString, -- :: String -> IO CWString
85 newCWStringLen, -- :: String -> IO CWStringLen
86 withCWString, -- :: String -> (CWString -> IO a) -> IO a
87 withCWStringLen, -- :: String -> (CWStringLen -> IO a) -> IO a
88
89 ) where
90
91 import Foreign.Marshal.Array
92 import Foreign.C.Types
93 import Foreign.Ptr
94 import Foreign.Storable
95
96 import Data.Word
97
98 #ifdef __GLASGOW_HASKELL__
99 import GHC.List
100 import GHC.Real
101 import GHC.Num
102 import GHC.IOBase
103 import GHC.Base
104 #else
105 import Data.Char ( chr, ord )
106 #define unsafeChr chr
107 #endif
108
109 -----------------------------------------------------------------------------
110 -- Strings
111
112 -- representation of strings in C
113 -- ------------------------------
114
115 -- | A C string is a reference to an array of C characters terminated by NUL.
116 type CString = Ptr CChar
117
118 -- | A string with explicit length information in bytes instead of a
119 -- terminating NUL (allowing NUL characters in the middle of the string).
120 type CStringLen = (Ptr CChar, Int)
121
122 -- exported functions
123 -- ------------------
124 --
125 -- * the following routines apply the default conversion when converting the
126 -- C-land character encoding into the Haskell-land character encoding
127
128 -- | Marshal a NUL terminated C string into a Haskell string.
129 --
130 peekCString :: CString -> IO String
131 peekCString = peekCAString
132
133 -- | Marshal a C string with explicit length into a Haskell string.
134 --
135 peekCStringLen :: CStringLen -> IO String
136 peekCStringLen = peekCAStringLen
137
138 -- | Marshal a Haskell string into a NUL terminated C string.
139 --
140 -- * the Haskell string may /not/ contain any NUL characters
141 --
142 -- * new storage is allocated for the C string and must be
143 -- explicitly freed using 'Foreign.Marshal.Alloc.free' or
144 -- 'Foreign.Marshal.Alloc.finalizerFree'.
145 --
146 newCString :: String -> IO CString
147 newCString = newCAString
148
149 -- | Marshal a Haskell string into a C string (ie, character array) with
150 -- explicit length information.
151 --
152 -- * new storage is allocated for the C string and must be
153 -- explicitly freed using 'Foreign.Marshal.Alloc.free' or
154 -- 'Foreign.Marshal.Alloc.finalizerFree'.
155 --
156 newCStringLen :: String -> IO CStringLen
157 newCStringLen = newCAStringLen
158
159 -- | Marshal a Haskell string into a NUL terminated C string using temporary
160 -- storage.
161 --
162 -- * the Haskell string may /not/ contain any NUL characters
163 --
164 -- * the memory is freed when the subcomputation terminates (either
165 -- normally or via an exception), so the pointer to the temporary
166 -- storage must /not/ be used after this.
167 --
168 withCString :: String -> (CString -> IO a) -> IO a
169 withCString = withCAString
170
171 -- | Marshal a Haskell string into a C string (ie, character array)
172 -- in temporary storage, with explicit length information.
173 --
174 -- * the memory is freed when the subcomputation terminates (either
175 -- normally or via an exception), so the pointer to the temporary
176 -- storage must /not/ be used after this.
177 --
178 withCStringLen :: String -> (CStringLen -> IO a) -> IO a
179 withCStringLen = withCAStringLen
180
181 -- | Determines whether a character can be accurately encoded in a 'CString'.
182 -- Unrepresentable characters are converted to @\'?\'@.
183 --
184 -- Currently only Latin-1 characters are representable.
185 charIsRepresentable :: Char -> IO Bool
186 charIsRepresentable c = return (ord c < 256)
187
188 -- single byte characters
189 -- ----------------------
190 --
191 -- ** NOTE: These routines don't handle conversions! **
192
193 -- | Convert a C byte, representing a Latin-1 character, to the corresponding
194 -- Haskell character.
195 castCCharToChar :: CChar -> Char
196 castCCharToChar ch = unsafeChr (fromIntegral (fromIntegral ch :: Word8))
197
198 -- | Convert a Haskell character to a C character.
199 -- This function is only safe on the first 256 characters.
200 castCharToCChar :: Char -> CChar
201 castCharToCChar ch = fromIntegral (ord ch)
202
203 -- | Marshal a NUL terminated C string into a Haskell string.
204 --
205 peekCAString :: CString -> IO String
206 #ifndef __GLASGOW_HASKELL__
207 peekCAString cp = do
208 cs <- peekArray0 nUL cp
209 return (cCharsToChars cs)
210 #else
211 peekCAString cp = do
212 l <- lengthArray0 nUL cp
213 if l <= 0 then return "" else loop "" (l-1)
214 where
215 loop s i = do
216 xval <- peekElemOff cp i
217 let val = castCCharToChar xval
218 val `seq` if i <= 0 then return (val:s) else loop (val:s) (i-1)
219 #endif
220
221 -- | Marshal a C string with explicit length into a Haskell string.
222 --
223 peekCAStringLen :: CStringLen -> IO String
224 #ifndef __GLASGOW_HASKELL__
225 peekCAStringLen (cp, len) = do
226 cs <- peekArray len cp
227 return (cCharsToChars cs)
228 #else
229 peekCAStringLen (cp, len)
230 | len <= 0 = return "" -- being (too?) nice.
231 | otherwise = loop [] (len-1)
232 where
233 loop acc i = do
234 xval <- peekElemOff cp i
235 let val = castCCharToChar xval
236 -- blow away the coercion ASAP.
237 if (val `seq` (i == 0))
238 then return (val:acc)
239 else loop (val:acc) (i-1)
240 #endif
241
242 -- | Marshal a Haskell string into a NUL terminated C string.
243 --
244 -- * the Haskell string may /not/ contain any NUL characters
245 --
246 -- * new storage is allocated for the C string and must be
247 -- explicitly freed using 'Foreign.Marshal.Alloc.free' or
248 -- 'Foreign.Marshal.Alloc.finalizerFree'.
249 --
250 newCAString :: String -> IO CString
251 #ifndef __GLASGOW_HASKELL__
252 newCAString = newArray0 nUL . charsToCChars
253 #else
254 newCAString str = do
255 ptr <- mallocArray0 (length str)
256 let
257 go [] n = pokeElemOff ptr n nUL
258 go (c:cs) n = do pokeElemOff ptr n (castCharToCChar c); go cs (n+1)
259 go str 0
260 return ptr
261 #endif
262
263 -- | Marshal a Haskell string into a C string (ie, character array) with
264 -- explicit length information.
265 --
266 -- * new storage is allocated for the C string and must be
267 -- explicitly freed using 'Foreign.Marshal.Alloc.free' or
268 -- 'Foreign.Marshal.Alloc.finalizerFree'.
269 --
270 newCAStringLen :: String -> IO CStringLen
271 #ifndef __GLASGOW_HASKELL__
272 newCAStringLen str = do
273 a <- newArray (charsToCChars str)
274 return (pairLength str a)
275 #else
276 newCAStringLen str = do
277 ptr <- mallocArray0 len
278 let
279 go [] n = n `seq` return () -- make it strict in n
280 go (c:cs) n = do pokeElemOff ptr n (castCharToCChar c); go cs (n+1)
281 go str 0
282 return (ptr, len)
283 where
284 len = length str
285 #endif
286
287 -- | Marshal a Haskell string into a NUL terminated C string using temporary
288 -- storage.
289 --
290 -- * the Haskell string may /not/ contain any NUL characters
291 --
292 -- * the memory is freed when the subcomputation terminates (either
293 -- normally or via an exception), so the pointer to the temporary
294 -- storage must /not/ be used after this.
295 --
296 withCAString :: String -> (CString -> IO a) -> IO a
297 #ifndef __GLASGOW_HASKELL__
298 withCAString = withArray0 nUL . charsToCChars
299 #else
300 withCAString str f =
301 allocaArray0 (length str) $ \ptr ->
302 let
303 go [] n = pokeElemOff ptr n nUL
304 go (c:cs) n = do pokeElemOff ptr n (castCharToCChar c); go cs (n+1)
305 in do
306 go str 0
307 f ptr
308 #endif
309
310 -- | Marshal a Haskell string into a C string (ie, character array)
311 -- in temporary storage, with explicit length information.
312 --
313 -- * the memory is freed when the subcomputation terminates (either
314 -- normally or via an exception), so the pointer to the temporary
315 -- storage must /not/ be used after this.
316 --
317 withCAStringLen :: String -> (CStringLen -> IO a) -> IO a
318 #ifndef __GLASGOW_HASKELL__
319 withCAStringLen str act = withArray (charsToCChars str) $ act . pairLength str
320 #else
321 withCAStringLen str f =
322 allocaArray len $ \ptr ->
323 let
324 go [] n = n `seq` return () -- make it strict in n
325 go (c:cs) n = do pokeElemOff ptr n (castCharToCChar c); go cs (n+1)
326 in do
327 go str 0
328 f (ptr,len)
329 where
330 len = length str
331 #endif
332
333 -- auxiliary definitions
334 -- ----------------------
335
336 -- C's end of string character
337 --
338 nUL :: CChar
339 nUL = 0
340
341 -- pair a C string with the length of the given Haskell string
342 --
343 pairLength :: String -> a -> (a, Int)
344 pairLength = flip (,) . length
345
346 #ifndef __GLASGOW_HASKELL__
347 -- cast [CChar] to [Char]
348 --
349 cCharsToChars :: [CChar] -> [Char]
350 cCharsToChars xs = map castCCharToChar xs
351
352 -- cast [Char] to [CChar]
353 --
354 charsToCChars :: [Char] -> [CChar]
355 charsToCChars xs = map castCharToCChar xs
356 #endif
357
358 -----------------------------------------------------------------------------
359 -- Wide strings
360
361 -- representation of wide strings in C
362 -- -----------------------------------
363
364 -- | A C wide string is a reference to an array of C wide characters
365 -- terminated by NUL.
366 type CWString = Ptr CWchar
367
368 -- | A wide character string with explicit length information in bytes
369 -- instead of a terminating NUL (allowing NUL characters in the middle
370 -- of the string).
371 type CWStringLen = (Ptr CWchar, Int)
372
373 -- | Marshal a NUL terminated C wide string into a Haskell string.
374 --
375 peekCWString :: CWString -> IO String
376 peekCWString cp = do
377 cs <- peekArray0 wNUL cp
378 return (cWcharsToChars cs)
379
380 -- | Marshal a C wide string with explicit length into a Haskell string.
381 --
382 peekCWStringLen :: CWStringLen -> IO String
383 peekCWStringLen (cp, len) = do
384 cs <- peekArray len cp
385 return (cWcharsToChars cs)
386
387 -- | Marshal a Haskell string into a NUL terminated C wide string.
388 --
389 -- * the Haskell string may /not/ contain any NUL characters
390 --
391 -- * new storage is allocated for the C wide string and must
392 -- be explicitly freed using 'Foreign.Marshal.Alloc.free' or
393 -- 'Foreign.Marshal.Alloc.finalizerFree'.
394 --
395 newCWString :: String -> IO CWString
396 newCWString = newArray0 wNUL . charsToCWchars
397
398 -- | Marshal a Haskell string into a C wide string (ie, wide character array)
399 -- with explicit length information.
400 --
401 -- * new storage is allocated for the C wide string and must
402 -- be explicitly freed using 'Foreign.Marshal.Alloc.free' or
403 -- 'Foreign.Marshal.Alloc.finalizerFree'.
404 --
405 newCWStringLen :: String -> IO CWStringLen
406 newCWStringLen str = do
407 a <- newArray (charsToCWchars str)
408 return (pairLength str a)
409
410 -- | Marshal a Haskell string into a NUL terminated C wide string using
411 -- temporary storage.
412 --
413 -- * the Haskell string may /not/ contain any NUL characters
414 --
415 -- * the memory is freed when the subcomputation terminates (either
416 -- normally or via an exception), so the pointer to the temporary
417 -- storage must /not/ be used after this.
418 --
419 withCWString :: String -> (CWString -> IO a) -> IO a
420 withCWString = withArray0 wNUL . charsToCWchars
421
422 -- | Marshal a Haskell string into a NUL terminated C wide string using
423 -- temporary storage.
424 --
425 -- * the Haskell string may /not/ contain any NUL characters
426 --
427 -- * the memory is freed when the subcomputation terminates (either
428 -- normally or via an exception), so the pointer to the temporary
429 -- storage must /not/ be used after this.
430 --
431 withCWStringLen :: String -> (CWStringLen -> IO a) -> IO a
432 withCWStringLen str act = withArray (charsToCWchars str) $ act . pairLength str
433
434 -- auxiliary definitions
435 -- ----------------------
436
437 wNUL :: CWchar
438 wNUL = 0
439
440 cWcharsToChars :: [CWchar] -> [Char]
441 charsToCWchars :: [Char] -> [CWchar]
442
443 #ifdef mingw32_HOST_OS
444
445 -- On Windows, wchar_t is 16 bits wide and CWString uses the UTF-16 encoding.
446
447 -- coding errors generate Chars in the surrogate range
448 cWcharsToChars = map chr . fromUTF16 . map fromIntegral
449 where
450 fromUTF16 (c1:c2:wcs)
451 | 0xd800 <= c1 && c1 <= 0xdbff && 0xdc00 <= c2 && c2 <= 0xdfff =
452 ((c1 - 0xd800)*0x400 + (c2 - 0xdc00) + 0x10000) : fromUTF16 wcs
453 fromUTF16 (c:wcs) = c : fromUTF16 wcs
454 fromUTF16 [] = []
455
456 charsToCWchars = foldr utf16Char [] . map ord
457 where
458 utf16Char c wcs
459 | c < 0x10000 = fromIntegral c : wcs
460 | otherwise = let c' = c - 0x10000 in
461 fromIntegral (c' `div` 0x400 + 0xd800) :
462 fromIntegral (c' `mod` 0x400 + 0xdc00) : wcs
463
464 #else /* !mingw32_HOST_OS */
465
466 cWcharsToChars xs = map castCWcharToChar xs
467 charsToCWchars xs = map castCharToCWchar xs
468
469 -- These conversions only make sense if __STDC_ISO_10646__ is defined
470 -- (meaning that wchar_t is ISO 10646, aka Unicode)
471
472 castCWcharToChar :: CWchar -> Char
473 castCWcharToChar ch = chr (fromIntegral ch )
474
475 castCharToCWchar :: Char -> CWchar
476 castCharToCWchar ch = fromIntegral (ord ch)
477
478 #endif /* !mingw32_HOST_OS */