summaryrefslogtreecommitdiff
path: root/docs/examples/fopen.c
blob: 7435264a7097b858c8e6dc869b3c6223bc12a9bc (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
/*****************************************************************************
 *
 * This example source code introduces a c library buffered I/O interface to
 * URL reads it supports fopen(), fread(), fgets(), feof(), fclose(),
 * rewind(). Supported functions have identical prototypes to their normal c
 * lib namesakes and are preceaded by url_ .
 *
 * Using this code you can replace your program's fopen() with url_fopen()
 * and fread() with url_fread() and it become possible to read remote streams
 * instead of (only) local files. Local files (ie those that can be directly
 * fopened) will drop back to using the underlying clib implementations
 *
 * See the main() function at the bottom that shows an app that retrives from a
 * specified url using fgets() and fread() and saves as two output files.
 *
 * Copyright (c) 2003 Simtec Electronics
 *
 * Re-implemented by Vincent Sanders <vince@kyllikki.org> with extensive
 * reference to original curl example code
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * This example requires libcurl 7.9.7 or later.
 */
/* <DESC>
 * implements an fopen() abstraction allowing reading from URLs
 * </DESC>
 */

#include <stdio.h>
#include <string.h>
#ifndef WIN32
#  include <sys/time.h>
#endif
#include <stdlib.h>
#include <errno.h>

#include <curl/curl.h>

enum fcurl_type_e {
  CFTYPE_NONE=0,
  CFTYPE_FILE=1,
  CFTYPE_CURL=2
};

struct fcurl_data
{
  enum fcurl_type_e type;     /* type of handle */
  union {
    CURL *curl;
    FILE *file;
  } handle;                   /* handle */

  char *buffer;               /* buffer to store cached data*/
  size_t buffer_len;          /* currently allocated buffers length */
  size_t buffer_pos;          /* end of data in buffer*/
  int still_running;          /* Is background url fetch still in progress */
};

typedef struct fcurl_data URL_FILE;

/* exported functions */
URL_FILE *url_fopen(const char *url, const char *operation);
int url_fclose(URL_FILE *file);
int url_feof(URL_FILE *file);
size_t url_fread(void *ptr, size_t size, size_t nmemb, URL_FILE *file);
char *url_fgets(char *ptr, size_t size, URL_FILE *file);
void url_rewind(URL_FILE *file);

/* we use a global one for convenience */
CURLM *multi_handle;

/* curl calls this routine to get more data */
static size_t write_callback(char *buffer,
                             size_t size,
                             size_t nitems,
                             void *userp)
{
  char *newbuff;
  size_t rembuff;

  URL_FILE *url = (URL_FILE *)userp;
  size *= nitems;

  rembuff=url->buffer_len - url->buffer_pos; /* remaining space in buffer */

  if(size > rembuff) {
    /* not enough space in buffer */
    newbuff=realloc(url->buffer, url->buffer_len + (size - rembuff));
    if(newbuff==NULL) {
      fprintf(stderr, "callback buffer grow failed\n");
      size=rembuff;
    }
    else {
      /* realloc succeeded increase buffer size*/
      url->buffer_len+=size - rembuff;
      url->buffer=newbuff;
    }
  }

  memcpy(&url->buffer[url->buffer_pos], buffer, size);
  url->buffer_pos += size;

  return size;
}

/* use to attempt to fill the read buffer up to requested number of bytes */
static int fill_buffer(URL_FILE *file, size_t want)
{
  fd_set fdread;
  fd_set fdwrite;
  fd_set fdexcep;
  struct timeval timeout;
  int rc;
  CURLMcode mc; /* curl_multi_fdset() return code */

  /* only attempt to fill buffer if transactions still running and buffer
   * doesn't exceed required size already
   */
  if((!file->still_running) || (file->buffer_pos > want))
    return 0;

  /* attempt to fill buffer */
  do {
    int maxfd = -1;
    long curl_timeo = -1;

    FD_ZERO(&fdread);
    FD_ZERO(&fdwrite);
    FD_ZERO(&fdexcep);

    /* set a suitable timeout to fail on */
    timeout.tv_sec = 60; /* 1 minute */
    timeout.tv_usec = 0;

    curl_multi_timeout(multi_handle, &curl_timeo);
    if(curl_timeo >= 0) {
      timeout.tv_sec = curl_timeo / 1000;
      if(timeout.tv_sec > 1)
        timeout.tv_sec = 1;
      else
        timeout.tv_usec = (curl_timeo % 1000) * 1000;
    }

    /* get file descriptors from the transfers */
    mc = curl_multi_fdset(multi_handle, &fdread, &fdwrite, &fdexcep, &maxfd);

    if(mc != CURLM_OK) {
      fprintf(stderr, "curl_multi_fdset() failed, code %d.\n", mc);
      break;
    }

    /* On success the value of maxfd is guaranteed to be >= -1. We call
       select(maxfd + 1, ...); specially in case of (maxfd == -1) there are
       no fds ready yet so we call select(0, ...) --or Sleep() on Windows--
       to sleep 100ms, which is the minimum suggested value in the
       curl_multi_fdset() doc. */

    if(maxfd == -1) {
#ifdef _WIN32
      Sleep(100);
      rc = 0;
#else
      /* Portable sleep for platforms other than Windows. */
      struct timeval wait = { 0, 100 * 1000 }; /* 100ms */
      rc = select(0, NULL, NULL, NULL, &wait);
#endif
    }
    else {
      /* Note that on some platforms 'timeout' may be modified by select().
         If you need access to the original value save a copy beforehand. */
      rc = select(maxfd+1, &fdread, &fdwrite, &fdexcep, &timeout);
    }

    switch(rc) {
    case -1:
      /* select error */
      break;

    case 0:
    default:
      /* timeout or readable/writable sockets */
      curl_multi_perform(multi_handle, &file->still_running);
      break;
    }
  } while(file->still_running && (file->buffer_pos < want));
  return 1;
}

/* use to remove want bytes from the front of a files buffer */
static int use_buffer(URL_FILE *file, size_t want)
{
  /* sort out buffer */
  if((file->buffer_pos - want) <=0) {
    /* ditch buffer - write will recreate */
    free(file->buffer);
    file->buffer=NULL;
    file->buffer_pos=0;
    file->buffer_len=0;
  }
  else {
    /* move rest down make it available for later */
    memmove(file->buffer,
            &file->buffer[want],
            (file->buffer_pos - want));

    file->buffer_pos -= want;
  }
  return 0;
}

URL_FILE *url_fopen(const char *url, const char *operation)
{
  /* this code could check for URLs or types in the 'url' and
     basically use the real fopen() for standard files */

  URL_FILE *file;
  (void)operation;

  file = malloc(sizeof(URL_FILE));
  if(!file)
    return NULL;

  memset(file, 0, sizeof(URL_FILE));

  if((file->handle.file=fopen(url, operation)))
    file->type = CFTYPE_FILE; /* marked as URL */

  else {
    file->type = CFTYPE_CURL; /* marked as URL */
    file->handle.curl = curl_easy_init();

    curl_easy_setopt(file->handle.curl, CURLOPT_URL, url);
    curl_easy_setopt(file->handle.curl, CURLOPT_WRITEDATA, file);
    curl_easy_setopt(file->handle.curl, CURLOPT_VERBOSE, 0L);
    curl_easy_setopt(file->handle.curl, CURLOPT_WRITEFUNCTION, write_callback);

    if(!multi_handle)
      multi_handle = curl_multi_init();

    curl_multi_add_handle(multi_handle, file->handle.curl);

    /* lets start the fetch */
    curl_multi_perform(multi_handle, &file->still_running);

    if((file->buffer_pos == 0) && (!file->still_running)) {
      /* if still_running is 0 now, we should return NULL */

      /* make sure the easy handle is not in the multi handle anymore */
      curl_multi_remove_handle(multi_handle, file->handle.curl);

      /* cleanup */
      curl_easy_cleanup(file->handle.curl);

      free(file);

      file = NULL;
    }
  }
  return file;
}

int url_fclose(URL_FILE *file)
{
  int ret=0;/* default is good return */

  switch(file->type) {
  case CFTYPE_FILE:
    ret=fclose(file->handle.file); /* passthrough */
    break;

  case CFTYPE_CURL:
    /* make sure the easy handle is not in the multi handle anymore */
    curl_multi_remove_handle(multi_handle, file->handle.curl);

    /* cleanup */
    curl_easy_cleanup(file->handle.curl);
    break;

  default: /* unknown or supported type - oh dear */
    ret=EOF;
    errno=EBADF;
    break;
  }

  free(file->buffer);/* free any allocated buffer space */
  free(file);

  return ret;
}

int url_feof(URL_FILE *file)
{
  int ret=0;

  switch(file->type) {
  case CFTYPE_FILE:
    ret=feof(file->handle.file);
    break;

  case CFTYPE_CURL:
    if((file->buffer_pos == 0) && (!file->still_running))
      ret = 1;
    break;

  default: /* unknown or supported type - oh dear */
    ret=-1;
    errno=EBADF;
    break;
  }
  return ret;
}

size_t url_fread(void *ptr, size_t size, size_t nmemb, URL_FILE *file)
{
  size_t want;

  switch(file->type) {
  case CFTYPE_FILE:
    want=fread(ptr, size, nmemb, file->handle.file);
    break;

  case CFTYPE_CURL:
    want = nmemb * size;

    fill_buffer(file, want);

    /* check if theres data in the buffer - if not fill_buffer()
     * either errored or EOF */
    if(!file->buffer_pos)
      return 0;

    /* ensure only available data is considered */
    if(file->buffer_pos < want)
      want = file->buffer_pos;

    /* xfer data to caller */
    memcpy(ptr, file->buffer, want);

    use_buffer(file, want);

    want = want / size;     /* number of items */
    break;

  default: /* unknown or supported type - oh dear */
    want=0;
    errno=EBADF;
    break;

  }
  return want;
}

char *url_fgets(char *ptr, size_t size, URL_FILE *file)
{
  size_t want = size - 1;/* always need to leave room for zero termination */
  size_t loop;

  switch(file->type) {
  case CFTYPE_FILE:
    ptr = fgets(ptr, (int)size, file->handle.file);
    break;

  case CFTYPE_CURL:
    fill_buffer(file, want);

    /* check if theres data in the buffer - if not fill either errored or
     * EOF */
    if(!file->buffer_pos)
      return NULL;

    /* ensure only available data is considered */
    if(file->buffer_pos < want)
      want = file->buffer_pos;

    /*buffer contains data */
    /* look for newline or eof */
    for(loop=0;loop < want;loop++) {
      if(file->buffer[loop] == '\n') {
        want=loop+1;/* include newline */
        break;
      }
    }

    /* xfer data to caller */
    memcpy(ptr, file->buffer, want);
    ptr[want]=0;/* allways null terminate */

    use_buffer(file, want);

    break;

  default: /* unknown or supported type - oh dear */
    ptr=NULL;
    errno=EBADF;
    break;
  }

  return ptr;/*success */
}

void url_rewind(URL_FILE *file)
{
  switch(file->type) {
  case CFTYPE_FILE:
    rewind(file->handle.file); /* passthrough */
    break;

  case CFTYPE_CURL:
    /* halt transaction */
    curl_multi_remove_handle(multi_handle, file->handle.curl);

    /* restart */
    curl_multi_add_handle(multi_handle, file->handle.curl);

    /* ditch buffer - write will recreate - resets stream pos*/
    free(file->buffer);
    file->buffer=NULL;
    file->buffer_pos=0;
    file->buffer_len=0;

    break;

  default: /* unknown or supported type - oh dear */
    break;
  }
}

#define FGETSFILE "fgets.test"
#define FREADFILE "fread.test"
#define REWINDFILE "rewind.test"

/* Small main program to retrive from a url using fgets and fread saving the
 * output to two test files (note the fgets method will corrupt binary files if
 * they contain 0 chars */
int main(int argc, char *argv[])
{
  URL_FILE *handle;
  FILE *outf;

  size_t nread;
  char buffer[256];
  const char *url;

  if(argc < 2)
    url="http://192.168.7.3/testfile";/* default to testurl */
  else
    url=argv[1];/* use passed url */

  /* copy from url line by line with fgets */
  outf=fopen(FGETSFILE, "wb+");
  if(!outf) {
    perror("couldn't open fgets output file\n");
    return 1;
  }

  handle = url_fopen(url, "r");
  if(!handle) {
    printf("couldn't url_fopen() %s\n", url);
    fclose(outf);
    return 2;
  }

  while(!url_feof(handle)) {
    url_fgets(buffer, sizeof(buffer), handle);
    fwrite(buffer, 1, strlen(buffer), outf);
  }

  url_fclose(handle);

  fclose(outf);


  /* Copy from url with fread */
  outf=fopen(FREADFILE, "wb+");
  if(!outf) {
    perror("couldn't open fread output file\n");
    return 1;
  }

  handle = url_fopen("testfile", "r");
  if(!handle) {
    printf("couldn't url_fopen() testfile\n");
    fclose(outf);
    return 2;
  }

  do {
    nread = url_fread(buffer, 1, sizeof(buffer), handle);
    fwrite(buffer, 1, nread, outf);
  } while(nread);

  url_fclose(handle);

  fclose(outf);


  /* Test rewind */
  outf=fopen(REWINDFILE, "wb+");
  if(!outf) {
    perror("couldn't open fread output file\n");
    return 1;
  }

  handle = url_fopen("testfile", "r");
  if(!handle) {
    printf("couldn't url_fopen() testfile\n");
    fclose(outf);
    return 2;
  }

  nread = url_fread(buffer, 1, sizeof(buffer), handle);
  fwrite(buffer, 1, nread, outf);
  url_rewind(handle);

  buffer[0]='\n';
  fwrite(buffer, 1, 1, outf);

  nread = url_fread(buffer, 1, sizeof(buffer), handle);
  fwrite(buffer, 1, nread, outf);

  url_fclose(handle);

  fclose(outf);

  return 0;/* all done */
}