1 | /* Copyright (C) 2007 Eric Blake |
---|
2 | * Permission to use, copy, modify, and distribute this software |
---|
3 | * is freely granted, provided that this notice is preserved. |
---|
4 | */ |
---|
5 | |
---|
6 | /* |
---|
7 | FUNCTION |
---|
8 | <<open_memstream>>, <<open_wmemstream>>---open a write stream around an arbitrary-length string |
---|
9 | |
---|
10 | INDEX |
---|
11 | open_memstream |
---|
12 | INDEX |
---|
13 | open_wmemstream |
---|
14 | |
---|
15 | SYNOPSIS |
---|
16 | #include <stdio.h> |
---|
17 | FILE *open_memstream(char **restrict <[buf]>, |
---|
18 | size_t *restrict <[size]>); |
---|
19 | |
---|
20 | #include <wchar.h> |
---|
21 | FILE *open_wmemstream(wchar_t **restrict <[buf]>, |
---|
22 | size_t *restrict <[size]>); |
---|
23 | |
---|
24 | DESCRIPTION |
---|
25 | <<open_memstream>> creates a seekable, byte-oriented <<FILE>> stream that |
---|
26 | wraps an arbitrary-length buffer, created as if by <<malloc>>. The current |
---|
27 | contents of *<[buf]> are ignored; this implementation uses *<[size]> |
---|
28 | as a hint of the maximum size expected, but does not fail if the hint |
---|
29 | was wrong. The parameters <[buf]> and <[size]> are later stored |
---|
30 | through following any call to <<fflush>> or <<fclose>>, set to the |
---|
31 | current address and usable size of the allocated string; although |
---|
32 | after fflush, the pointer is only valid until another stream operation |
---|
33 | that results in a write. Behavior is undefined if the user alters |
---|
34 | either *<[buf]> or *<[size]> prior to <<fclose>>. |
---|
35 | |
---|
36 | <<open_wmemstream>> is like <<open_memstream>> just with the associated |
---|
37 | stream being wide-oriented. The size set in <[size]> in subsequent |
---|
38 | operations is the number of wide characters. |
---|
39 | |
---|
40 | The stream is write-only, since the user can directly read *<[buf]> |
---|
41 | after a flush; see <<fmemopen>> for a way to wrap a string with a |
---|
42 | readable stream. The user is responsible for calling <<free>> on |
---|
43 | the final *<[buf]> after <<fclose>>. |
---|
44 | |
---|
45 | Any time the stream is flushed, a NUL byte is written at the current |
---|
46 | position (but is not counted in the buffer length), so that the string |
---|
47 | is always NUL-terminated after at most *<[size]> bytes (or wide characters |
---|
48 | in case of <<open_wmemstream>>). However, data previously written beyond |
---|
49 | the current stream offset is not lost, and the NUL value written during a |
---|
50 | flush is restored to its previous value when seeking elsewhere in the string. |
---|
51 | |
---|
52 | RETURNS |
---|
53 | The return value is an open FILE pointer on success. On error, |
---|
54 | <<NULL>> is returned, and <<errno>> will be set to EINVAL if <[buf]> |
---|
55 | or <[size]> is NULL, ENOMEM if memory could not be allocated, or |
---|
56 | EMFILE if too many streams are already open. |
---|
57 | |
---|
58 | PORTABILITY |
---|
59 | POSIX.1-2008 |
---|
60 | |
---|
61 | Supporting OS subroutines required: <<sbrk>>. |
---|
62 | */ |
---|
63 | |
---|
64 | #include <stdio.h> |
---|
65 | #include <wchar.h> |
---|
66 | #include <errno.h> |
---|
67 | #include <string.h> |
---|
68 | #include <sys/lock.h> |
---|
69 | #include <stdint.h> |
---|
70 | #include "local.h" |
---|
71 | |
---|
72 | #ifndef __LARGE64_FILES |
---|
73 | # define OFF_T off_t |
---|
74 | #else |
---|
75 | # define OFF_T _off64_t |
---|
76 | #endif |
---|
77 | |
---|
78 | /* Describe details of an open memstream. */ |
---|
79 | typedef struct memstream { |
---|
80 | void *storage; /* storage to free on close */ |
---|
81 | char **pbuf; /* pointer to the current buffer */ |
---|
82 | size_t *psize; /* pointer to the current size, smaller of pos or eof */ |
---|
83 | size_t pos; /* current position */ |
---|
84 | size_t eof; /* current file size */ |
---|
85 | size_t max; /* current malloc buffer size, always > eof */ |
---|
86 | union { |
---|
87 | char c; |
---|
88 | wchar_t w; |
---|
89 | } saved; /* saved character that lived at *psize before NUL */ |
---|
90 | int8_t wide; /* wide-oriented (>0) or byte-oriented (<0) */ |
---|
91 | } memstream; |
---|
92 | |
---|
93 | /* Write up to non-zero N bytes of BUF into the stream described by COOKIE, |
---|
94 | returning the number of bytes written or EOF on failure. */ |
---|
95 | static _READ_WRITE_RETURN_TYPE |
---|
96 | memwriter (struct _reent *ptr, |
---|
97 | void *cookie, |
---|
98 | const char *buf, |
---|
99 | _READ_WRITE_BUFSIZE_TYPE n) |
---|
100 | { |
---|
101 | memstream *c = (memstream *) cookie; |
---|
102 | char *cbuf = *c->pbuf; |
---|
103 | |
---|
104 | /* size_t is unsigned, but off_t is signed. Don't let stream get so |
---|
105 | big that user cannot do ftello. */ |
---|
106 | if (sizeof (OFF_T) == sizeof (size_t) && (ssize_t) (c->pos + n) < 0) |
---|
107 | { |
---|
108 | ptr->_errno = EFBIG; |
---|
109 | return EOF; |
---|
110 | } |
---|
111 | /* Grow the buffer, if necessary. Choose a geometric growth factor |
---|
112 | to avoid quadratic realloc behavior, but use a rate less than |
---|
113 | (1+sqrt(5))/2 to accomodate malloc overhead. Overallocate, so |
---|
114 | that we can add a trailing \0 without reallocating. The new |
---|
115 | allocation should thus be max(prev_size*1.5, c->pos+n+1). */ |
---|
116 | if (c->pos + n >= c->max) |
---|
117 | { |
---|
118 | size_t newsize = c->max * 3 / 2; |
---|
119 | if (newsize < c->pos + n + 1) |
---|
120 | newsize = c->pos + n + 1; |
---|
121 | cbuf = _realloc_r (ptr, cbuf, newsize); |
---|
122 | if (! cbuf) |
---|
123 | return EOF; /* errno already set to ENOMEM */ |
---|
124 | *c->pbuf = cbuf; |
---|
125 | c->max = newsize; |
---|
126 | } |
---|
127 | /* If we have previously done a seek beyond eof, ensure all |
---|
128 | intermediate bytes are NUL. */ |
---|
129 | if (c->pos > c->eof) |
---|
130 | memset (cbuf + c->eof, '\0', c->pos - c->eof); |
---|
131 | memcpy (cbuf + c->pos, buf, n); |
---|
132 | c->pos += n; |
---|
133 | /* If the user has previously written further, remember what the |
---|
134 | trailing NUL is overwriting. Otherwise, extend the stream. */ |
---|
135 | if (c->pos > c->eof) |
---|
136 | c->eof = c->pos; |
---|
137 | else if (c->wide > 0) |
---|
138 | c->saved.w = *(wchar_t *)(cbuf + c->pos); |
---|
139 | else |
---|
140 | c->saved.c = cbuf[c->pos]; |
---|
141 | cbuf[c->pos] = '\0'; |
---|
142 | *c->psize = (c->wide > 0) ? c->pos / sizeof (wchar_t) : c->pos; |
---|
143 | return n; |
---|
144 | } |
---|
145 | |
---|
146 | /* Seek to position POS relative to WHENCE within stream described by |
---|
147 | COOKIE; return resulting position or fail with EOF. */ |
---|
148 | static _fpos_t |
---|
149 | memseeker (struct _reent *ptr, |
---|
150 | void *cookie, |
---|
151 | _fpos_t pos, |
---|
152 | int whence) |
---|
153 | { |
---|
154 | memstream *c = (memstream *) cookie; |
---|
155 | OFF_T offset = (OFF_T) pos; |
---|
156 | |
---|
157 | if (whence == SEEK_CUR) |
---|
158 | offset += c->pos; |
---|
159 | else if (whence == SEEK_END) |
---|
160 | offset += c->eof; |
---|
161 | if (offset < 0) |
---|
162 | { |
---|
163 | ptr->_errno = EINVAL; |
---|
164 | offset = -1; |
---|
165 | } |
---|
166 | else if ((size_t) offset != offset) |
---|
167 | { |
---|
168 | ptr->_errno = ENOSPC; |
---|
169 | offset = -1; |
---|
170 | } |
---|
171 | #ifdef __LARGE64_FILES |
---|
172 | else if ((_fpos_t) offset != offset) |
---|
173 | { |
---|
174 | ptr->_errno = EOVERFLOW; |
---|
175 | offset = -1; |
---|
176 | } |
---|
177 | #endif /* __LARGE64_FILES */ |
---|
178 | else |
---|
179 | { |
---|
180 | if (c->pos < c->eof) |
---|
181 | { |
---|
182 | if (c->wide > 0) |
---|
183 | *(wchar_t *)((*c->pbuf) + c->pos) = c->saved.w; |
---|
184 | else |
---|
185 | (*c->pbuf)[c->pos] = c->saved.c; |
---|
186 | c->saved.w = L'\0'; |
---|
187 | } |
---|
188 | c->pos = offset; |
---|
189 | if (c->pos < c->eof) |
---|
190 | { |
---|
191 | if (c->wide > 0) |
---|
192 | { |
---|
193 | c->saved.w = *(wchar_t *)((*c->pbuf) + c->pos); |
---|
194 | *(wchar_t *)((*c->pbuf) + c->pos) = L'\0'; |
---|
195 | *c->psize = c->pos / sizeof (wchar_t); |
---|
196 | } |
---|
197 | else |
---|
198 | { |
---|
199 | c->saved.c = (*c->pbuf)[c->pos]; |
---|
200 | (*c->pbuf)[c->pos] = '\0'; |
---|
201 | *c->psize = c->pos; |
---|
202 | } |
---|
203 | } |
---|
204 | else if (c->wide > 0) |
---|
205 | *c->psize = c->eof / sizeof (wchar_t); |
---|
206 | else |
---|
207 | *c->psize = c->eof; |
---|
208 | } |
---|
209 | return (_fpos_t) offset; |
---|
210 | } |
---|
211 | |
---|
212 | /* Seek to position POS relative to WHENCE within stream described by |
---|
213 | COOKIE; return resulting position or fail with EOF. */ |
---|
214 | #ifdef __LARGE64_FILES |
---|
215 | static _fpos64_t |
---|
216 | memseeker64 (struct _reent *ptr, |
---|
217 | void *cookie, |
---|
218 | _fpos64_t pos, |
---|
219 | int whence) |
---|
220 | { |
---|
221 | _off64_t offset = (_off64_t) pos; |
---|
222 | memstream *c = (memstream *) cookie; |
---|
223 | |
---|
224 | if (whence == SEEK_CUR) |
---|
225 | offset += c->pos; |
---|
226 | else if (whence == SEEK_END) |
---|
227 | offset += c->eof; |
---|
228 | if (offset < 0) |
---|
229 | { |
---|
230 | ptr->_errno = EINVAL; |
---|
231 | offset = -1; |
---|
232 | } |
---|
233 | else if ((size_t) offset != offset) |
---|
234 | { |
---|
235 | ptr->_errno = ENOSPC; |
---|
236 | offset = -1; |
---|
237 | } |
---|
238 | else |
---|
239 | { |
---|
240 | if (c->pos < c->eof) |
---|
241 | { |
---|
242 | if (c->wide > 0) |
---|
243 | *(wchar_t *)((*c->pbuf) + c->pos) = c->saved.w; |
---|
244 | else |
---|
245 | (*c->pbuf)[c->pos] = c->saved.c; |
---|
246 | c->saved.w = L'\0'; |
---|
247 | } |
---|
248 | c->pos = offset; |
---|
249 | if (c->pos < c->eof) |
---|
250 | { |
---|
251 | if (c->wide > 0) |
---|
252 | { |
---|
253 | c->saved.w = *(wchar_t *)((*c->pbuf) + c->pos); |
---|
254 | *(wchar_t *)((*c->pbuf) + c->pos) = L'\0'; |
---|
255 | *c->psize = c->pos / sizeof (wchar_t); |
---|
256 | } |
---|
257 | else |
---|
258 | { |
---|
259 | c->saved.c = (*c->pbuf)[c->pos]; |
---|
260 | (*c->pbuf)[c->pos] = '\0'; |
---|
261 | *c->psize = c->pos; |
---|
262 | } |
---|
263 | } |
---|
264 | else if (c->wide > 0) |
---|
265 | *c->psize = c->eof / sizeof (wchar_t); |
---|
266 | else |
---|
267 | *c->psize = c->eof; |
---|
268 | } |
---|
269 | return (_fpos64_t) offset; |
---|
270 | } |
---|
271 | #endif /* __LARGE64_FILES */ |
---|
272 | |
---|
273 | /* Reclaim resources used by stream described by COOKIE. */ |
---|
274 | static int |
---|
275 | memcloser (struct _reent *ptr, |
---|
276 | void *cookie) |
---|
277 | { |
---|
278 | memstream *c = (memstream *) cookie; |
---|
279 | char *buf; |
---|
280 | |
---|
281 | /* Be nice and try to reduce any unused memory. */ |
---|
282 | buf = _realloc_r (ptr, *c->pbuf, |
---|
283 | c->wide > 0 ? (*c->psize + 1) * sizeof (wchar_t) |
---|
284 | : *c->psize + 1); |
---|
285 | if (buf) |
---|
286 | *c->pbuf = buf; |
---|
287 | _free_r (ptr, c->storage); |
---|
288 | return 0; |
---|
289 | } |
---|
290 | |
---|
291 | /* Open a memstream that tracks a dynamic buffer in BUF and SIZE. |
---|
292 | Return the new stream, or fail with NULL. */ |
---|
293 | static FILE * |
---|
294 | internal_open_memstream_r (struct _reent *ptr, |
---|
295 | char **buf, |
---|
296 | size_t *size, |
---|
297 | int wide) |
---|
298 | { |
---|
299 | FILE *fp; |
---|
300 | memstream *c; |
---|
301 | |
---|
302 | if (!buf || !size) |
---|
303 | { |
---|
304 | ptr->_errno = EINVAL; |
---|
305 | return NULL; |
---|
306 | } |
---|
307 | if ((fp = __sfp (ptr)) == NULL) |
---|
308 | return NULL; |
---|
309 | if ((c = (memstream *) _malloc_r (ptr, sizeof *c)) == NULL) |
---|
310 | { |
---|
311 | _newlib_sfp_lock_start (); |
---|
312 | fp->_flags = 0; /* release */ |
---|
313 | #ifndef __SINGLE_THREAD__ |
---|
314 | __lock_close_recursive (fp->_lock); |
---|
315 | #endif |
---|
316 | _newlib_sfp_lock_end (); |
---|
317 | return NULL; |
---|
318 | } |
---|
319 | /* Use *size as a hint for initial sizing, but bound the initial |
---|
320 | malloc between 64 bytes (same as asprintf, to avoid frequent |
---|
321 | mallocs on small strings) and 64k bytes (to avoid overusing the |
---|
322 | heap if *size was garbage). */ |
---|
323 | c->max = *size; |
---|
324 | if (wide == 1) |
---|
325 | c->max *= sizeof(wchar_t); |
---|
326 | if (c->max < 64) |
---|
327 | c->max = 64; |
---|
328 | #if (SIZE_MAX >= 64 * 1024) |
---|
329 | else if (c->max > 64 * 1024) |
---|
330 | c->max = 64 * 1024; |
---|
331 | #endif |
---|
332 | *size = 0; |
---|
333 | *buf = _malloc_r (ptr, c->max); |
---|
334 | if (!*buf) |
---|
335 | { |
---|
336 | _newlib_sfp_lock_start (); |
---|
337 | fp->_flags = 0; /* release */ |
---|
338 | #ifndef __SINGLE_THREAD__ |
---|
339 | __lock_close_recursive (fp->_lock); |
---|
340 | #endif |
---|
341 | _newlib_sfp_lock_end (); |
---|
342 | _free_r (ptr, c); |
---|
343 | return NULL; |
---|
344 | } |
---|
345 | if (wide == 1) |
---|
346 | **((wchar_t **)buf) = L'\0'; |
---|
347 | else |
---|
348 | **buf = '\0'; |
---|
349 | |
---|
350 | c->storage = c; |
---|
351 | c->pbuf = buf; |
---|
352 | c->psize = size; |
---|
353 | c->pos = 0; |
---|
354 | c->eof = 0; |
---|
355 | c->saved.w = L'\0'; |
---|
356 | c->wide = (int8_t) wide; |
---|
357 | |
---|
358 | _newlib_flockfile_start (fp); |
---|
359 | fp->_file = -1; |
---|
360 | fp->_flags = __SWR; |
---|
361 | fp->_cookie = c; |
---|
362 | fp->_read = NULL; |
---|
363 | fp->_write = memwriter; |
---|
364 | fp->_seek = memseeker; |
---|
365 | #ifdef __LARGE64_FILES |
---|
366 | fp->_seek64 = memseeker64; |
---|
367 | fp->_flags |= __SL64; |
---|
368 | #endif |
---|
369 | fp->_close = memcloser; |
---|
370 | ORIENT (fp, wide); |
---|
371 | _newlib_flockfile_end (fp); |
---|
372 | return fp; |
---|
373 | } |
---|
374 | |
---|
375 | FILE * |
---|
376 | _open_memstream_r (struct _reent *ptr, |
---|
377 | char **buf, |
---|
378 | size_t *size) |
---|
379 | { |
---|
380 | return internal_open_memstream_r (ptr, buf, size, -1); |
---|
381 | } |
---|
382 | |
---|
383 | FILE * |
---|
384 | _open_wmemstream_r (struct _reent *ptr, |
---|
385 | wchar_t **buf, |
---|
386 | size_t *size) |
---|
387 | { |
---|
388 | return internal_open_memstream_r (ptr, (char **)buf, size, 1); |
---|
389 | } |
---|
390 | |
---|
391 | #ifndef _REENT_ONLY |
---|
392 | FILE * |
---|
393 | open_memstream (char **buf, |
---|
394 | size_t *size) |
---|
395 | { |
---|
396 | return _open_memstream_r (_REENT, buf, size); |
---|
397 | } |
---|
398 | |
---|
399 | FILE * |
---|
400 | open_wmemstream (wchar_t **buf, |
---|
401 | size_t *size) |
---|
402 | { |
---|
403 | return _open_wmemstream_r (_REENT, buf, size); |
---|
404 | } |
---|
405 | #endif /* !_REENT_ONLY */ |
---|