Annotation of embedaddon/curl/docs/examples/fopen.c, revision 1.1
1.1 ! misho 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 - 2019 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: }
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