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ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. The directory name has changed: no version number in the expanded directory now.
author Franz Glasner <fzglas.hg@dom66.de>
date Mon, 15 Sep 2025 11:43:07 +0200
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1:1d09e1dec1d9 2:b50eed0cc0ef
1 /*****************************************************************************
2 *
3 * This example source code introduces a c library buffered I/O interface to
4 * URL reads it supports fopen(), fread(), fgets(), feof(), fclose(),
5 * rewind(). Supported functions have identical prototypes to their normal c
6 * lib namesakes and are preceaded by url_ .
7 *
8 * Using this code you can replace your program's fopen() with url_fopen()
9 * and fread() with url_fread() and it become possible to read remote streams
10 * instead of (only) local files. Local files (ie those that can be directly
11 * fopened) will drop back to using the underlying clib implementations
12 *
13 * See the main() function at the bottom that shows an app that retrieves from
14 * a specified url using fgets() and fread() and saves as two output files.
15 *
16 * Copyright (c) 2003, 2017 Simtec Electronics
17 *
18 * Re-implemented by Vincent Sanders <vince@kyllikki.org> with extensive
19 * reference to original curl example code
20 *
21 * Redistribution and use in source and binary forms, with or without
22 * modification, are permitted provided that the following conditions
23 * are met:
24 * 1. Redistributions of source code must retain the above copyright
25 * notice, this list of conditions and the following disclaimer.
26 * 2. Redistributions in binary form must reproduce the above copyright
27 * notice, this list of conditions and the following disclaimer in the
28 * documentation and/or other materials provided with the distribution.
29 * 3. The name of the author may not be used to endorse or promote products
30 * derived from this software without specific prior written permission.
31 *
32 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
33 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
34 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
35 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
36 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
37 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
38 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
39 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
40 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
41 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
42 *
43 * This example requires libcurl 7.9.7 or later.
44 */
45 /* <DESC>
46 * implements an fopen() abstraction allowing reading from URLs
47 * </DESC>
48 */
49
50 #include <stdio.h>
51 #include <string.h>
52 #ifndef WIN32
53 # include <sys/time.h>
54 #endif
55 #include <stdlib.h>
56 #include <errno.h>
57
58 #include <curl/curl.h>
59
60 enum fcurl_type_e {
61 CFTYPE_NONE = 0,
62 CFTYPE_FILE = 1,
63 CFTYPE_CURL = 2
64 };
65
66 struct fcurl_data
67 {
68 enum fcurl_type_e type; /* type of handle */
69 union {
70 CURL *curl;
71 FILE *file;
72 } handle; /* handle */
73
74 char *buffer; /* buffer to store cached data*/
75 size_t buffer_len; /* currently allocated buffers length */
76 size_t buffer_pos; /* end of data in buffer*/
77 int still_running; /* Is background url fetch still in progress */
78 };
79
80 typedef struct fcurl_data URL_FILE;
81
82 /* exported functions */
83 URL_FILE *url_fopen(const char *url, const char *operation);
84 int url_fclose(URL_FILE *file);
85 int url_feof(URL_FILE *file);
86 size_t url_fread(void *ptr, size_t size, size_t nmemb, URL_FILE *file);
87 char *url_fgets(char *ptr, size_t size, URL_FILE *file);
88 void url_rewind(URL_FILE *file);
89
90 /* we use a global one for convenience */
91 static CURLM *multi_handle;
92
93 /* curl calls this routine to get more data */
94 static size_t write_callback(char *buffer,
95 size_t size,
96 size_t nitems,
97 void *userp)
98 {
99 char *newbuff;
100 size_t rembuff;
101
102 URL_FILE *url = (URL_FILE *)userp;
103 size *= nitems;
104
105 rembuff = url->buffer_len - url->buffer_pos; /* remaining space in buffer */
106
107 if(size > rembuff) {
108 /* not enough space in buffer */
109 newbuff = realloc(url->buffer, url->buffer_len + (size - rembuff));
110 if(newbuff == NULL) {
111 fprintf(stderr, "callback buffer grow failed\n");
112 size = rembuff;
113 }
114 else {
115 /* realloc succeeded increase buffer size*/
116 url->buffer_len += size - rembuff;
117 url->buffer = newbuff;
118 }
119 }
120
121 memcpy(&url->buffer[url->buffer_pos], buffer, size);
122 url->buffer_pos += size;
123
124 return size;
125 }
126
127 /* use to attempt to fill the read buffer up to requested number of bytes */
128 static int fill_buffer(URL_FILE *file, size_t want)
129 {
130 fd_set fdread;
131 fd_set fdwrite;
132 fd_set fdexcep;
133 struct timeval timeout;
134 int rc;
135 CURLMcode mc; /* curl_multi_fdset() return code */
136
137 /* only attempt to fill buffer if transactions still running and buffer
138 * doesn't exceed required size already
139 */
140 if((!file->still_running) || (file->buffer_pos > want))
141 return 0;
142
143 /* attempt to fill buffer */
144 do {
145 int maxfd = -1;
146 long curl_timeo = -1;
147
148 FD_ZERO(&fdread);
149 FD_ZERO(&fdwrite);
150 FD_ZERO(&fdexcep);
151
152 /* set a suitable timeout to fail on */
153 timeout.tv_sec = 60; /* 1 minute */
154 timeout.tv_usec = 0;
155
156 curl_multi_timeout(multi_handle, &curl_timeo);
157 if(curl_timeo >= 0) {
158 timeout.tv_sec = curl_timeo / 1000;
159 if(timeout.tv_sec > 1)
160 timeout.tv_sec = 1;
161 else
162 timeout.tv_usec = (curl_timeo % 1000) * 1000;
163 }
164
165 /* get file descriptors from the transfers */
166 mc = curl_multi_fdset(multi_handle, &fdread, &fdwrite, &fdexcep, &maxfd);
167
168 if(mc != CURLM_OK) {
169 fprintf(stderr, "curl_multi_fdset() failed, code %d.\n", mc);
170 break;
171 }
172
173 /* On success the value of maxfd is guaranteed to be >= -1. We call
174 select(maxfd + 1, ...); specially in case of (maxfd == -1) there are
175 no fds ready yet so we call select(0, ...) --or Sleep() on Windows--
176 to sleep 100ms, which is the minimum suggested value in the
177 curl_multi_fdset() doc. */
178
179 if(maxfd == -1) {
180 #ifdef _WIN32
181 Sleep(100);
182 rc = 0;
183 #else
184 /* Portable sleep for platforms other than Windows. */
185 struct timeval wait = { 0, 100 * 1000 }; /* 100ms */
186 rc = select(0, NULL, NULL, NULL, &wait);
187 #endif
188 }
189 else {
190 /* Note that on some platforms 'timeout' may be modified by select().
191 If you need access to the original value save a copy beforehand. */
192 rc = select(maxfd + 1, &fdread, &fdwrite, &fdexcep, &timeout);
193 }
194
195 switch(rc) {
196 case -1:
197 /* select error */
198 break;
199
200 case 0:
201 default:
202 /* timeout or readable/writable sockets */
203 curl_multi_perform(multi_handle, &file->still_running);
204 break;
205 }
206 } while(file->still_running && (file->buffer_pos < want));
207 return 1;
208 }
209
210 /* use to remove want bytes from the front of a files buffer */
211 static int use_buffer(URL_FILE *file, size_t want)
212 {
213 /* sort out buffer */
214 if(file->buffer_pos <= want) {
215 /* ditch buffer - write will recreate */
216 free(file->buffer);
217 file->buffer = NULL;
218 file->buffer_pos = 0;
219 file->buffer_len = 0;
220 }
221 else {
222 /* move rest down make it available for later */
223 memmove(file->buffer,
224 &file->buffer[want],
225 (file->buffer_pos - want));
226
227 file->buffer_pos -= want;
228 }
229 return 0;
230 }
231
232 URL_FILE *url_fopen(const char *url, const char *operation)
233 {
234 /* this code could check for URLs or types in the 'url' and
235 basically use the real fopen() for standard files */
236
237 URL_FILE *file;
238 (void)operation;
239
240 file = calloc(1, sizeof(URL_FILE));
241 if(!file)
242 return NULL;
243
244 file->handle.file = fopen(url, operation);
245 if(file->handle.file)
246 file->type = CFTYPE_FILE; /* marked as URL */
247
248 else {
249 file->type = CFTYPE_CURL; /* marked as URL */
250 file->handle.curl = curl_easy_init();
251
252 curl_easy_setopt(file->handle.curl, CURLOPT_URL, url);
253 curl_easy_setopt(file->handle.curl, CURLOPT_WRITEDATA, file);
254 curl_easy_setopt(file->handle.curl, CURLOPT_VERBOSE, 0L);
255 curl_easy_setopt(file->handle.curl, CURLOPT_WRITEFUNCTION, write_callback);
256
257 if(!multi_handle)
258 multi_handle = curl_multi_init();
259
260 curl_multi_add_handle(multi_handle, file->handle.curl);
261
262 /* lets start the fetch */
263 curl_multi_perform(multi_handle, &file->still_running);
264
265 if((file->buffer_pos == 0) && (!file->still_running)) {
266 /* if still_running is 0 now, we should return NULL */
267
268 /* make sure the easy handle is not in the multi handle anymore */
269 curl_multi_remove_handle(multi_handle, file->handle.curl);
270
271 /* cleanup */
272 curl_easy_cleanup(file->handle.curl);
273
274 free(file);
275
276 file = NULL;
277 }
278 }
279 return file;
280 }
281
282 int url_fclose(URL_FILE *file)
283 {
284 int ret = 0;/* default is good return */
285
286 switch(file->type) {
287 case CFTYPE_FILE:
288 ret = fclose(file->handle.file); /* passthrough */
289 break;
290
291 case CFTYPE_CURL:
292 /* make sure the easy handle is not in the multi handle anymore */
293 curl_multi_remove_handle(multi_handle, file->handle.curl);
294
295 /* cleanup */
296 curl_easy_cleanup(file->handle.curl);
297 break;
298
299 default: /* unknown or supported type - oh dear */
300 ret = EOF;
301 errno = EBADF;
302 break;
303 }
304
305 free(file->buffer);/* free any allocated buffer space */
306 free(file);
307
308 return ret;
309 }
310
311 int url_feof(URL_FILE *file)
312 {
313 int ret = 0;
314
315 switch(file->type) {
316 case CFTYPE_FILE:
317 ret = feof(file->handle.file);
318 break;
319
320 case CFTYPE_CURL:
321 if((file->buffer_pos == 0) && (!file->still_running))
322 ret = 1;
323 break;
324
325 default: /* unknown or supported type - oh dear */
326 ret = -1;
327 errno = EBADF;
328 break;
329 }
330 return ret;
331 }
332
333 size_t url_fread(void *ptr, size_t size, size_t nmemb, URL_FILE *file)
334 {
335 size_t want;
336
337 switch(file->type) {
338 case CFTYPE_FILE:
339 want = fread(ptr, size, nmemb, file->handle.file);
340 break;
341
342 case CFTYPE_CURL:
343 want = nmemb * size;
344
345 fill_buffer(file, want);
346
347 /* check if there's data in the buffer - if not fill_buffer()
348 * either errored or EOF */
349 if(!file->buffer_pos)
350 return 0;
351
352 /* ensure only available data is considered */
353 if(file->buffer_pos < want)
354 want = file->buffer_pos;
355
356 /* xfer data to caller */
357 memcpy(ptr, file->buffer, want);
358
359 use_buffer(file, want);
360
361 want = want / size; /* number of items */
362 break;
363
364 default: /* unknown or supported type - oh dear */
365 want = 0;
366 errno = EBADF;
367 break;
368
369 }
370 return want;
371 }
372
373 char *url_fgets(char *ptr, size_t size, URL_FILE *file)
374 {
375 size_t want = size - 1;/* always need to leave room for zero termination */
376 size_t loop;
377
378 switch(file->type) {
379 case CFTYPE_FILE:
380 ptr = fgets(ptr, (int)size, file->handle.file);
381 break;
382
383 case CFTYPE_CURL:
384 fill_buffer(file, want);
385
386 /* check if there's data in the buffer - if not fill either errored or
387 * EOF */
388 if(!file->buffer_pos)
389 return NULL;
390
391 /* ensure only available data is considered */
392 if(file->buffer_pos < want)
393 want = file->buffer_pos;
394
395 /*buffer contains data */
396 /* look for newline or eof */
397 for(loop = 0; loop < want; loop++) {
398 if(file->buffer[loop] == '\n') {
399 want = loop + 1;/* include newline */
400 break;
401 }
402 }
403
404 /* xfer data to caller */
405 memcpy(ptr, file->buffer, want);
406 ptr[want] = 0;/* always null terminate */
407
408 use_buffer(file, want);
409
410 break;
411
412 default: /* unknown or supported type - oh dear */
413 ptr = NULL;
414 errno = EBADF;
415 break;
416 }
417
418 return ptr;/*success */
419 }
420
421 void url_rewind(URL_FILE *file)
422 {
423 switch(file->type) {
424 case CFTYPE_FILE:
425 rewind(file->handle.file); /* passthrough */
426 break;
427
428 case CFTYPE_CURL:
429 /* halt transaction */
430 curl_multi_remove_handle(multi_handle, file->handle.curl);
431
432 /* restart */
433 curl_multi_add_handle(multi_handle, file->handle.curl);
434
435 /* ditch buffer - write will recreate - resets stream pos*/
436 free(file->buffer);
437 file->buffer = NULL;
438 file->buffer_pos = 0;
439 file->buffer_len = 0;
440
441 break;
442
443 default: /* unknown or supported type - oh dear */
444 break;
445 }
446 }
447
448 #define FGETSFILE "fgets.test"
449 #define FREADFILE "fread.test"
450 #define REWINDFILE "rewind.test"
451
452 /* Small main program to retrieve from a url using fgets and fread saving the
453 * output to two test files (note the fgets method will corrupt binary files if
454 * they contain 0 chars */
455 int main(int argc, char *argv[])
456 {
457 URL_FILE *handle;
458 FILE *outf;
459
460 size_t nread;
461 char buffer[256];
462 const char *url;
463
464 if(argc < 2)
465 url = "http://192.168.7.3/testfile";/* default to testurl */
466 else
467 url = argv[1];/* use passed url */
468
469 /* copy from url line by line with fgets */
470 outf = fopen(FGETSFILE, "wb+");
471 if(!outf) {
472 perror("couldn't open fgets output file\n");
473 return 1;
474 }
475
476 handle = url_fopen(url, "r");
477 if(!handle) {
478 printf("couldn't url_fopen() %s\n", url);
479 fclose(outf);
480 return 2;
481 }
482
483 while(!url_feof(handle)) {
484 url_fgets(buffer, sizeof(buffer), handle);
485 fwrite(buffer, 1, strlen(buffer), outf);
486 }
487
488 url_fclose(handle);
489
490 fclose(outf);
491
492
493 /* Copy from url with fread */
494 outf = fopen(FREADFILE, "wb+");
495 if(!outf) {
496 perror("couldn't open fread output file\n");
497 return 1;
498 }
499
500 handle = url_fopen("testfile", "r");
501 if(!handle) {
502 printf("couldn't url_fopen() testfile\n");
503 fclose(outf);
504 return 2;
505 }
506
507 do {
508 nread = url_fread(buffer, 1, sizeof(buffer), handle);
509 fwrite(buffer, 1, nread, outf);
510 } while(nread);
511
512 url_fclose(handle);
513
514 fclose(outf);
515
516
517 /* Test rewind */
518 outf = fopen(REWINDFILE, "wb+");
519 if(!outf) {
520 perror("couldn't open fread output file\n");
521 return 1;
522 }
523
524 handle = url_fopen("testfile", "r");
525 if(!handle) {
526 printf("couldn't url_fopen() testfile\n");
527 fclose(outf);
528 return 2;
529 }
530
531 nread = url_fread(buffer, 1, sizeof(buffer), handle);
532 fwrite(buffer, 1, nread, outf);
533 url_rewind(handle);
534
535 buffer[0]='\n';
536 fwrite(buffer, 1, 1, outf);
537
538 nread = url_fread(buffer, 1, sizeof(buffer), handle);
539 fwrite(buffer, 1, nread, outf);
540
541 url_fclose(handle);
542
543 fclose(outf);
544
545 return 0;/* all done */
546 }