1 /*****************************************************************************
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_ .
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
13 * See the main() function at the bottom that shows an app that retrives from a
14 * specified url using fgets() and fread() and saves as two output files.
16 * Copyright (c) 2003 Simtec Electronics
18 * Re-implemented by Vincent Sanders <vince@kyllikki.org> with extensive
19 * reference to original curl example code
21 * Redistribution and use in source and binary forms, with or without
22 * modification, are permitted provided that the following conditions
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.
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.
43 * This example requires libcurl 7.9.7 or later.
46 * implements an fopen() abstraction allowing reading from URLs
53 # include <sys/time.h>
58 #include <curl/curl.h>
68 enum fcurl_type_e type; /* type of handle */
72 } handle; /* handle */
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 */
80 typedef struct fcurl_data URL_FILE;
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);
90 /* we use a global one for convenience */
93 /* curl calls this routine to get more data */
94 static size_t write_callback(char *buffer,
102 URL_FILE *url = (URL_FILE *)userp;
105 rembuff=url->buffer_len - url->buffer_pos; /* remaining space in buffer */
108 /* not enough space in buffer */
109 newbuff=realloc(url->buffer,url->buffer_len + (size - rembuff));
111 fprintf(stderr,"callback buffer grow failed\n");
115 /* realloc succeeded increase buffer size*/
116 url->buffer_len+=size - rembuff;
121 memcpy(&url->buffer[url->buffer_pos], buffer, size);
122 url->buffer_pos += size;
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)
133 struct timeval timeout;
135 CURLMcode mc; /* curl_multi_fdset() return code */
137 /* only attempt to fill buffer if transactions still running and buffer
138 * doesn't exceed required size already
140 if((!file->still_running) || (file->buffer_pos > want))
143 /* attempt to fill buffer */
146 long curl_timeo = -1;
152 /* set a suitable timeout to fail on */
153 timeout.tv_sec = 60; /* 1 minute */
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)
162 timeout.tv_usec = (curl_timeo % 1000) * 1000;
165 /* get file descriptors from the transfers */
166 mc = curl_multi_fdset(multi_handle, &fdread, &fdwrite, &fdexcep, &maxfd);
170 fprintf(stderr, "curl_multi_fdset() failed, code %d.\n", mc);
174 /* On success the value of maxfd is guaranteed to be >= -1. We call
175 select(maxfd + 1, ...); specially in case of (maxfd == -1) there are
176 no fds ready yet so we call select(0, ...) --or Sleep() on Windows--
177 to sleep 100ms, which is the minimum suggested value in the
178 curl_multi_fdset() doc. */
185 /* Portable sleep for platforms other than Windows. */
186 struct timeval wait = { 0, 100 * 1000 }; /* 100ms */
187 rc = select(0, NULL, NULL, NULL, &wait);
191 /* Note that on some platforms 'timeout' may be modified by select().
192 If you need access to the original value save a copy beforehand. */
193 rc = select(maxfd+1, &fdread, &fdwrite, &fdexcep, &timeout);
203 /* timeout or readable/writable sockets */
204 curl_multi_perform(multi_handle, &file->still_running);
207 } while(file->still_running && (file->buffer_pos < want));
211 /* use to remove want bytes from the front of a files buffer */
212 static int use_buffer(URL_FILE *file, size_t want)
214 /* sort out buffer */
215 if((file->buffer_pos - want) <=0) {
216 /* ditch buffer - write will recreate */
223 /* move rest down make it available for later */
224 memmove(file->buffer,
226 (file->buffer_pos - want));
228 file->buffer_pos -= want;
233 URL_FILE *url_fopen(const char *url,const char *operation)
235 /* this code could check for URLs or types in the 'url' and
236 basically use the real fopen() for standard files */
241 file = malloc(sizeof(URL_FILE));
245 memset(file, 0, sizeof(URL_FILE));
247 if((file->handle.file=fopen(url,operation)))
248 file->type = CFTYPE_FILE; /* marked as URL */
251 file->type = CFTYPE_CURL; /* marked as URL */
252 file->handle.curl = curl_easy_init();
254 curl_easy_setopt(file->handle.curl, CURLOPT_URL, url);
255 curl_easy_setopt(file->handle.curl, CURLOPT_WRITEDATA, file);
256 curl_easy_setopt(file->handle.curl, CURLOPT_VERBOSE, 0L);
257 curl_easy_setopt(file->handle.curl, CURLOPT_WRITEFUNCTION, write_callback);
260 multi_handle = curl_multi_init();
262 curl_multi_add_handle(multi_handle, file->handle.curl);
264 /* lets start the fetch */
265 curl_multi_perform(multi_handle, &file->still_running);
267 if((file->buffer_pos == 0) && (!file->still_running)) {
268 /* if still_running is 0 now, we should return NULL */
270 /* make sure the easy handle is not in the multi handle anymore */
271 curl_multi_remove_handle(multi_handle, file->handle.curl);
274 curl_easy_cleanup(file->handle.curl);
284 int url_fclose(URL_FILE *file)
286 int ret=0;/* default is good return */
290 ret=fclose(file->handle.file); /* passthrough */
294 /* make sure the easy handle is not in the multi handle anymore */
295 curl_multi_remove_handle(multi_handle, file->handle.curl);
298 curl_easy_cleanup(file->handle.curl);
301 default: /* unknown or supported type - oh dear */
307 free(file->buffer);/* free any allocated buffer space */
313 int url_feof(URL_FILE *file)
319 ret=feof(file->handle.file);
323 if((file->buffer_pos == 0) && (!file->still_running))
327 default: /* unknown or supported type - oh dear */
335 size_t url_fread(void *ptr, size_t size, size_t nmemb, URL_FILE *file)
341 want=fread(ptr,size,nmemb,file->handle.file);
347 fill_buffer(file,want);
349 /* check if theres data in the buffer - if not fill_buffer()
350 * either errored or EOF */
351 if(!file->buffer_pos)
354 /* ensure only available data is considered */
355 if(file->buffer_pos < want)
356 want = file->buffer_pos;
358 /* xfer data to caller */
359 memcpy(ptr, file->buffer, want);
361 use_buffer(file,want);
363 want = want / size; /* number of items */
366 default: /* unknown or supported type - oh dear */
375 char *url_fgets(char *ptr, size_t size, URL_FILE *file)
377 size_t want = size - 1;/* always need to leave room for zero termination */
382 ptr = fgets(ptr, (int)size, file->handle.file);
386 fill_buffer(file,want);
388 /* check if theres data in the buffer - if not fill either errored or
390 if(!file->buffer_pos)
393 /* ensure only available data is considered */
394 if(file->buffer_pos < want)
395 want = file->buffer_pos;
397 /*buffer contains data */
398 /* look for newline or eof */
399 for(loop=0;loop < want;loop++) {
400 if(file->buffer[loop] == '\n') {
401 want=loop+1;/* include newline */
406 /* xfer data to caller */
407 memcpy(ptr, file->buffer, want);
408 ptr[want]=0;/* allways null terminate */
410 use_buffer(file,want);
414 default: /* unknown or supported type - oh dear */
420 return ptr;/*success */
423 void url_rewind(URL_FILE *file)
427 rewind(file->handle.file); /* passthrough */
431 /* halt transaction */
432 curl_multi_remove_handle(multi_handle, file->handle.curl);
435 curl_multi_add_handle(multi_handle, file->handle.curl);
437 /* ditch buffer - write will recreate - resets stream pos*/
445 default: /* unknown or supported type - oh dear */
450 /* Small main program to retrive from a url using fgets and fread saving the
451 * output to two test files (note the fgets method will corrupt binary files if
452 * they contain 0 chars */
453 int main(int argc, char *argv[])
463 url="http://192.168.7.3/testfile";/* default to testurl */
465 url=argv[1];/* use passed url */
467 /* copy from url line by line with fgets */
468 outf=fopen("fgets.test","w+");
470 perror("couldn't open fgets output file\n");
474 handle = url_fopen(url, "r");
476 printf("couldn't url_fopen() %s\n", url);
481 while(!url_feof(handle)) {
482 url_fgets(buffer,sizeof(buffer),handle);
483 fwrite(buffer,1,strlen(buffer),outf);
491 /* Copy from url with fread */
492 outf=fopen("fread.test","w+");
494 perror("couldn't open fread output file\n");
498 handle = url_fopen("testfile", "r");
500 printf("couldn't url_fopen() testfile\n");
506 nread = url_fread(buffer, 1, sizeof(buffer), handle);
507 fwrite(buffer,1,nread,outf);
516 outf=fopen("rewind.test","w+");
518 perror("couldn't open fread output file\n");
522 handle = url_fopen("testfile", "r");
524 printf("couldn't url_fopen() testfile\n");
529 nread = url_fread(buffer, 1,sizeof(buffer), handle);
530 fwrite(buffer,1,nread,outf);
534 fwrite(buffer,1,1,outf);
536 nread = url_fread(buffer, 1,sizeof(buffer), handle);
537 fwrite(buffer,1,nread,outf);
545 return 0;/* all done */