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+/*****************************************************************************
+ *
+ * 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.
+ */
+
+#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 suceeded 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;
+
+ /* only attempt to fill buffer if transactions still running and buffer
+ * doesnt 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 */
+ curl_multi_fdset(multi_handle, &fdread, &fdwrite, &fdexcep, &maxfd);
+
+ /* In a real-world program you OF COURSE check the return code of the
+ function calls. On success, the value of maxfd is guaranteed to be
+ greater or equal than -1. We call select(maxfd + 1, ...), specially
+ in case of (maxfd == -1), we call select(0, ...), which is basically
+ equal to sleep. */
+
+ 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,int want)
+{
+ /* sort out buffer */
+ if((file->buffer_pos - want) <=0) {
+ /* ditch buffer - write will recreate */
+ if(file->buffer)
+ 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
+ basicly 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;
+ }
+
+ if(file->buffer)
+ 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,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*/
+ if(file->buffer)
+ free(file->buffer);
+
+ file->buffer=NULL;
+ file->buffer_pos=0;
+ file->buffer_len=0;
+
+ break;
+
+ default: /* unknown or supported type - oh dear */
+ break;
+ }
+}
+
+/* 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;
+
+ int 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("fgets.test","w+");
+ 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("fread.test","w+");
+ 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("rewind.test","w+");
+ 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 */
+}
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