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>
56 enum fcurl_type_e { CFTYPE_NONE=0, CFTYPE_FILE=1, CFTYPE_CURL=2 };
60 enum fcurl_type_e type; /* type of handle */
64 } handle; /* handle */
66 char *buffer; /* buffer to store cached data*/
67 int buffer_len; /* currently allocated buffers length */
68 int buffer_pos; /* end of data in buffer*/
69 int still_running; /* Is background url fetch still in progress */
72 typedef struct fcurl_data URL_FILE;
74 /* exported functions */
75 URL_FILE *url_fopen(const char *url,const char *operation);
76 int url_fclose(URL_FILE *file);
77 int url_feof(URL_FILE *file);
78 size_t url_fread(void *ptr, size_t size, size_t nmemb, URL_FILE *file);
79 char * url_fgets(char *ptr, int size, URL_FILE *file);
80 void url_rewind(URL_FILE *file);
82 /* we use a global one for convenience */
85 /* curl calls this routine to get more data */
87 write_callback(char *buffer,
95 URL_FILE *url = (URL_FILE *)userp;
98 rembuff=url->buffer_len - url->buffer_pos; /* remaining space in buffer */
102 /* not enough space in buffer */
103 newbuff=realloc(url->buffer,url->buffer_len + (size - rembuff));
106 fprintf(stderr,"callback buffer grow failed\n");
111 /* realloc suceeded increase buffer size*/
112 url->buffer_len+=size - rembuff;
115 /*printf("Callback buffer grown to %d bytes\n",url->buffer_len);*/
119 memcpy(&url->buffer[url->buffer_pos], buffer, size);
120 url->buffer_pos += size;
122 /*fprintf(stderr, "callback %d size bytes\n", size);*/
127 /* use to attempt to fill the read buffer up to requested number of bytes */
129 fill_buffer(URL_FILE *file,int want,int waittime)
134 struct timeval timeout;
137 /* only attempt to fill buffer if transactions still running and buffer
138 * doesnt exceed required size already
140 if((!file->still_running) || (file->buffer_pos > want))
143 /* attempt to fill buffer */
147 long curl_timeo = -1;
153 /* set a suitable timeout to fail on */
154 timeout.tv_sec = 60; /* 1 minute */
157 curl_multi_timeout(multi_handle, &curl_timeo);
158 if(curl_timeo >= 0) {
159 timeout.tv_sec = curl_timeo / 1000;
160 if(timeout.tv_sec > 1)
163 timeout.tv_usec = (curl_timeo % 1000) * 1000;
166 /* get file descriptors from the transfers */
167 curl_multi_fdset(multi_handle, &fdread, &fdwrite, &fdexcep, &maxfd);
169 /* In a real-world program you OF COURSE check the return code of the
170 function calls. On success, the value of maxfd is guaranteed to be
171 greater or equal than -1. We call select(maxfd + 1, ...), specially
172 in case of (maxfd == -1), we call select(0, ...), which is basically
175 rc = select(maxfd+1, &fdread, &fdwrite, &fdexcep, &timeout);
186 /* timeout or readable/writable sockets */
187 curl_multi_perform(multi_handle, &file->still_running);
190 } while(file->still_running && (file->buffer_pos < want));
194 /* use to remove want bytes from the front of a files buffer */
196 use_buffer(URL_FILE *file,int want)
198 /* sort out buffer */
199 if((file->buffer_pos - want) <=0)
201 /* ditch buffer - write will recreate */
211 /* move rest down make it available for later */
212 memmove(file->buffer,
214 (file->buffer_pos - want));
216 file->buffer_pos -= want;
224 url_fopen(const char *url,const char *operation)
226 /* this code could check for URLs or types in the 'url' and
227 basicly use the real fopen() for standard files */
232 file = malloc(sizeof(URL_FILE));
236 memset(file, 0, sizeof(URL_FILE));
238 if((file->handle.file=fopen(url,operation)))
240 file->type = CFTYPE_FILE; /* marked as URL */
244 file->type = CFTYPE_CURL; /* marked as URL */
245 file->handle.curl = curl_easy_init();
247 curl_easy_setopt(file->handle.curl, CURLOPT_URL, url);
248 curl_easy_setopt(file->handle.curl, CURLOPT_WRITEDATA, file);
249 curl_easy_setopt(file->handle.curl, CURLOPT_VERBOSE, 0L);
250 curl_easy_setopt(file->handle.curl, CURLOPT_WRITEFUNCTION, write_callback);
253 multi_handle = curl_multi_init();
255 curl_multi_add_handle(multi_handle, file->handle.curl);
257 /* lets start the fetch */
258 curl_multi_perform(multi_handle, &file->still_running);
260 if((file->buffer_pos == 0) && (!file->still_running))
262 /* if still_running is 0 now, we should return NULL */
264 /* make sure the easy handle is not in the multi handle anymore */
265 curl_multi_remove_handle(multi_handle, file->handle.curl);
268 curl_easy_cleanup(file->handle.curl);
279 url_fclose(URL_FILE *file)
281 int ret=0;/* default is good return */
286 ret=fclose(file->handle.file); /* passthrough */
290 /* make sure the easy handle is not in the multi handle anymore */
291 curl_multi_remove_handle(multi_handle, file->handle.curl);
294 curl_easy_cleanup(file->handle.curl);
297 default: /* unknown or supported type - oh dear */
305 free(file->buffer);/* free any allocated buffer space */
313 url_feof(URL_FILE *file)
320 ret=feof(file->handle.file);
324 if((file->buffer_pos == 0) && (!file->still_running))
327 default: /* unknown or supported type - oh dear */
336 url_fread(void *ptr, size_t size, size_t nmemb, URL_FILE *file)
343 want=fread(ptr,size,nmemb,file->handle.file);
349 fill_buffer(file,want,1);
351 /* check if theres data in the buffer - if not fill_buffer()
352 * either errored or EOF */
353 if(!file->buffer_pos)
356 /* ensure only available data is considered */
357 if(file->buffer_pos < want)
358 want = file->buffer_pos;
360 /* xfer data to caller */
361 memcpy(ptr, file->buffer, want);
363 use_buffer(file,want);
365 want = want / size; /* number of items - nb correct op - checked
368 /*printf("(fread) return %d bytes %d left\n", want,file->buffer_pos);*/
371 default: /* unknown or supported type - oh dear */
381 url_fgets(char *ptr, int size, URL_FILE *file)
383 int want = size - 1;/* always need to leave room for zero termination */
389 ptr = fgets(ptr,size,file->handle.file);
393 fill_buffer(file,want,1);
395 /* check if theres data in the buffer - if not fill either errored or
397 if(!file->buffer_pos)
400 /* ensure only available data is considered */
401 if(file->buffer_pos < want)
402 want = file->buffer_pos;
404 /*buffer contains data */
405 /* look for newline or eof */
406 for(loop=0;loop < want;loop++)
408 if(file->buffer[loop] == '\n')
410 want=loop+1;/* include newline */
415 /* xfer data to caller */
416 memcpy(ptr, file->buffer, want);
417 ptr[want]=0;/* allways null terminate */
419 use_buffer(file,want);
421 /*printf("(fgets) return %d bytes %d left\n", want,file->buffer_pos);*/
424 default: /* unknown or supported type - oh dear */
430 return ptr;/*success */
434 url_rewind(URL_FILE *file)
439 rewind(file->handle.file); /* passthrough */
443 /* halt transaction */
444 curl_multi_remove_handle(multi_handle, file->handle.curl);
447 curl_multi_add_handle(multi_handle, file->handle.curl);
449 /* ditch buffer - write will recreate - resets stream pos*/
459 default: /* unknown or supported type - oh dear */
467 /* Small main program to retrive from a url using fgets and fread saving the
468 * output to two test files (note the fgets method will corrupt binary files if
469 * they contain 0 chars */
471 main(int argc, char *argv[])
482 url="http://192.168.7.3/testfile";/* default to testurl */
486 url=argv[1];/* use passed url */
489 /* copy from url line by line with fgets */
490 outf=fopen("fgets.test","w+");
493 perror("couldn't open fgets output file\n");
497 handle = url_fopen(url, "r");
500 printf("couldn't url_fopen() %s\n", url);
505 while(!url_feof(handle))
507 url_fgets(buffer,sizeof(buffer),handle);
508 fwrite(buffer,1,strlen(buffer),outf);
516 /* Copy from url with fread */
517 outf=fopen("fread.test","w+");
520 perror("couldn't open fread output file\n");
524 handle = url_fopen("testfile", "r");
526 printf("couldn't url_fopen() testfile\n");
532 nread = url_fread(buffer, 1,sizeof(buffer), handle);
533 fwrite(buffer,1,nread,outf);
542 outf=fopen("rewind.test","w+");
545 perror("couldn't open fread output file\n");
549 handle = url_fopen("testfile", "r");
551 printf("couldn't url_fopen() testfile\n");
556 nread = url_fread(buffer, 1,sizeof(buffer), handle);
557 fwrite(buffer,1,nread,outf);
561 fwrite(buffer,1,1,outf);
563 nread = url_fread(buffer, 1,sizeof(buffer), handle);
564 fwrite(buffer,1,nread,outf);
572 return 0;/* all done */