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.
49 # include <sys/time.h>
54 #include <curl/curl.h>
64 enum fcurl_type_e type; /* type of handle */
68 } handle; /* handle */
70 char *buffer; /* buffer to store cached data*/
71 size_t buffer_len; /* currently allocated buffers length */
72 size_t buffer_pos; /* end of data in buffer*/
73 int still_running; /* Is background url fetch still in progress */
76 typedef struct fcurl_data URL_FILE;
78 /* exported functions */
79 URL_FILE *url_fopen(const char *url,const char *operation);
80 int url_fclose(URL_FILE *file);
81 int url_feof(URL_FILE *file);
82 size_t url_fread(void *ptr, size_t size, size_t nmemb, URL_FILE *file);
83 char * url_fgets(char *ptr, size_t size, URL_FILE *file);
84 void url_rewind(URL_FILE *file);
86 /* we use a global one for convenience */
89 /* curl calls this routine to get more data */
90 static size_t write_callback(char *buffer,
98 URL_FILE *url = (URL_FILE *)userp;
101 rembuff=url->buffer_len - url->buffer_pos; /* remaining space in buffer */
104 /* not enough space in buffer */
105 newbuff=realloc(url->buffer,url->buffer_len + (size - rembuff));
107 fprintf(stderr,"callback buffer grow failed\n");
111 /* realloc suceeded increase buffer size*/
112 url->buffer_len+=size - rembuff;
117 memcpy(&url->buffer[url->buffer_pos], buffer, size);
118 url->buffer_pos += size;
123 /* use to attempt to fill the read buffer up to requested number of bytes */
124 static int fill_buffer(URL_FILE *file, size_t want)
129 struct timeval timeout;
132 /* only attempt to fill buffer if transactions still running and buffer
133 * doesnt exceed required size already
135 if((!file->still_running) || (file->buffer_pos > want))
138 /* attempt to fill buffer */
141 long curl_timeo = -1;
147 /* set a suitable timeout to fail on */
148 timeout.tv_sec = 60; /* 1 minute */
151 curl_multi_timeout(multi_handle, &curl_timeo);
152 if(curl_timeo >= 0) {
153 timeout.tv_sec = curl_timeo / 1000;
154 if(timeout.tv_sec > 1)
157 timeout.tv_usec = (curl_timeo % 1000) * 1000;
160 /* get file descriptors from the transfers */
161 curl_multi_fdset(multi_handle, &fdread, &fdwrite, &fdexcep, &maxfd);
163 /* In a real-world program you OF COURSE check the return code of the
164 function calls. On success, the value of maxfd is guaranteed to be
165 greater or equal than -1. We call select(maxfd + 1, ...), specially
166 in case of (maxfd == -1), we call select(0, ...), which is basically
169 rc = select(maxfd+1, &fdread, &fdwrite, &fdexcep, &timeout);
178 /* timeout or readable/writable sockets */
179 curl_multi_perform(multi_handle, &file->still_running);
182 } while(file->still_running && (file->buffer_pos < want));
186 /* use to remove want bytes from the front of a files buffer */
187 static int use_buffer(URL_FILE *file,int want)
189 /* sort out buffer */
190 if((file->buffer_pos - want) <=0) {
191 /* ditch buffer - write will recreate */
200 /* move rest down make it available for later */
201 memmove(file->buffer,
203 (file->buffer_pos - want));
205 file->buffer_pos -= want;
210 URL_FILE *url_fopen(const char *url,const char *operation)
212 /* this code could check for URLs or types in the 'url' and
213 basicly use the real fopen() for standard files */
218 file = malloc(sizeof(URL_FILE));
222 memset(file, 0, sizeof(URL_FILE));
224 if((file->handle.file=fopen(url,operation)))
225 file->type = CFTYPE_FILE; /* marked as URL */
228 file->type = CFTYPE_CURL; /* marked as URL */
229 file->handle.curl = curl_easy_init();
231 curl_easy_setopt(file->handle.curl, CURLOPT_URL, url);
232 curl_easy_setopt(file->handle.curl, CURLOPT_WRITEDATA, file);
233 curl_easy_setopt(file->handle.curl, CURLOPT_VERBOSE, 0L);
234 curl_easy_setopt(file->handle.curl, CURLOPT_WRITEFUNCTION, write_callback);
237 multi_handle = curl_multi_init();
239 curl_multi_add_handle(multi_handle, file->handle.curl);
241 /* lets start the fetch */
242 curl_multi_perform(multi_handle, &file->still_running);
244 if((file->buffer_pos == 0) && (!file->still_running)) {
245 /* if still_running is 0 now, we should return NULL */
247 /* make sure the easy handle is not in the multi handle anymore */
248 curl_multi_remove_handle(multi_handle, file->handle.curl);
251 curl_easy_cleanup(file->handle.curl);
261 int url_fclose(URL_FILE *file)
263 int ret=0;/* default is good return */
267 ret=fclose(file->handle.file); /* passthrough */
271 /* make sure the easy handle is not in the multi handle anymore */
272 curl_multi_remove_handle(multi_handle, file->handle.curl);
275 curl_easy_cleanup(file->handle.curl);
278 default: /* unknown or supported type - oh dear */
285 free(file->buffer);/* free any allocated buffer space */
292 int url_feof(URL_FILE *file)
298 ret=feof(file->handle.file);
302 if((file->buffer_pos == 0) && (!file->still_running))
306 default: /* unknown or supported type - oh dear */
314 size_t url_fread(void *ptr, size_t size, size_t nmemb, URL_FILE *file)
320 want=fread(ptr,size,nmemb,file->handle.file);
326 fill_buffer(file,want);
328 /* check if theres data in the buffer - if not fill_buffer()
329 * either errored or EOF */
330 if(!file->buffer_pos)
333 /* ensure only available data is considered */
334 if(file->buffer_pos < want)
335 want = file->buffer_pos;
337 /* xfer data to caller */
338 memcpy(ptr, file->buffer, want);
340 use_buffer(file,want);
342 want = want / size; /* number of items */
345 default: /* unknown or supported type - oh dear */
354 char *url_fgets(char *ptr, size_t size, URL_FILE *file)
356 size_t want = size - 1;/* always need to leave room for zero termination */
361 ptr = fgets(ptr,size,file->handle.file);
365 fill_buffer(file,want);
367 /* check if theres data in the buffer - if not fill either errored or
369 if(!file->buffer_pos)
372 /* ensure only available data is considered */
373 if(file->buffer_pos < want)
374 want = file->buffer_pos;
376 /*buffer contains data */
377 /* look for newline or eof */
378 for(loop=0;loop < want;loop++) {
379 if(file->buffer[loop] == '\n') {
380 want=loop+1;/* include newline */
385 /* xfer data to caller */
386 memcpy(ptr, file->buffer, want);
387 ptr[want]=0;/* allways null terminate */
389 use_buffer(file,want);
393 default: /* unknown or supported type - oh dear */
399 return ptr;/*success */
402 void url_rewind(URL_FILE *file)
406 rewind(file->handle.file); /* passthrough */
410 /* halt transaction */
411 curl_multi_remove_handle(multi_handle, file->handle.curl);
414 curl_multi_add_handle(multi_handle, file->handle.curl);
416 /* ditch buffer - write will recreate - resets stream pos*/
426 default: /* unknown or supported type - oh dear */
431 /* Small main program to retrive from a url using fgets and fread saving the
432 * output to two test files (note the fgets method will corrupt binary files if
433 * they contain 0 chars */
434 int main(int argc, char *argv[])
444 url="http://192.168.7.3/testfile";/* default to testurl */
446 url=argv[1];/* use passed url */
448 /* copy from url line by line with fgets */
449 outf=fopen("fgets.test","w+");
451 perror("couldn't open fgets output file\n");
455 handle = url_fopen(url, "r");
457 printf("couldn't url_fopen() %s\n", url);
462 while(!url_feof(handle)) {
463 url_fgets(buffer,sizeof(buffer),handle);
464 fwrite(buffer,1,strlen(buffer),outf);
472 /* Copy from url with fread */
473 outf=fopen("fread.test","w+");
475 perror("couldn't open fread output file\n");
479 handle = url_fopen("testfile", "r");
481 printf("couldn't url_fopen() testfile\n");
487 nread = url_fread(buffer, 1,sizeof(buffer), handle);
488 fwrite(buffer,1,nread,outf);
497 outf=fopen("rewind.test","w+");
499 perror("couldn't open fread output file\n");
503 handle = url_fopen("testfile", "r");
505 printf("couldn't url_fopen() testfile\n");
510 nread = url_fread(buffer, 1,sizeof(buffer), handle);
511 fwrite(buffer,1,nread,outf);
515 fwrite(buffer,1,1,outf);
517 nread = url_fread(buffer, 1,sizeof(buffer), handle);
518 fwrite(buffer,1,nread,outf);
526 return 0;/* all done */