mirror of
https://github.com/curl/curl.git
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223 lines
5.3 KiB
C
223 lines
5.3 KiB
C
/*****************************************************************************
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* _ _ ____ _
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* Project ___| | | | _ \| |
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* / __| | | | |_) | |
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* | (__| |_| | _ <| |___
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* \___|\___/|_| \_\_____|
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*
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* $Id$
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*
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* This example source code introduces an fopen()/fread()/fclose() emulation
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* for URL reads. Using an approach similar to this, you could replace your
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* program's fopen() with this url_fopen() and fread() with url_fread() and
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* it should be possible to read remote streams instead of (only) local files.
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*
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* See the main() function at the bottom that shows a tiny app in action.
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*
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* This source code is a proof of concept. It will need further attention to
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* become production-use useful and solid.
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*
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* This example requires libcurl 7.9.7 or later.
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*/
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#include <stdio.h>
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#include <string.h>
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#include <sys/time.h>
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#include <curl/curl.h>
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#include <curl/types.h>
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#include <curl/easy.h>
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struct data {
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int type;
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union {
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CURL *curl;
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FILE *file;
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} handle;
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/* TODO: We should perhaps document the biggest possible buffer chunk we can
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get from libcurl in one single callback... */
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char buffer[CURL_MAX_WRITE_SIZE];
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char *readptr; /* read from here */
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int bytes; /* bytes available from read pointer */
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CURLMcode m; /* stored from a previous url_fread() */
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};
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typedef struct data URL_FILE;
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/* we use a global one for convenience */
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CURLM *multi_handle;
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static
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size_t write_callback(char *buffer,
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size_t size,
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size_t nitems,
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void *userp)
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{
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URL_FILE *url = (URL_FILE *)userp;
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size *= nitems;
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memcpy(url->readptr, buffer, size);
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url->readptr += size;
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url->bytes += size;
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return size;
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}
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URL_FILE *url_fopen(char *url, char *operation)
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{
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/* this code could check for URLs or types in the 'url' and
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basicly use the real fopen() for standard files */
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URL_FILE *file;
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int still_running;
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file = (URL_FILE *)malloc(sizeof(URL_FILE));
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if(!file)
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return NULL;
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memset(file, 0, sizeof(URL_FILE));
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file->type = 1; /* marked as URL, use 0 for plain file */
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file->handle.curl = curl_easy_init();
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curl_easy_setopt(file->handle.curl, CURLOPT_URL, url);
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curl_easy_setopt(file->handle.curl, CURLOPT_FILE, file);
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curl_easy_setopt(file->handle.curl, CURLOPT_VERBOSE, FALSE);
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curl_easy_setopt(file->handle.curl, CURLOPT_WRITEFUNCTION, write_callback);
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if(!multi_handle)
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multi_handle = curl_multi_init();
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curl_multi_add_handle(multi_handle, file->handle.curl);
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while(CURLM_CALL_MULTI_PERFORM ==
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curl_multi_perform(multi_handle, &still_running));
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/* if still_running would be 0 now, we should return NULL */
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return file;
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}
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void url_fclose(URL_FILE *file)
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{
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/* make sure the easy handle is not in the multi handle anymore */
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curl_multi_remove_handle(multi_handle, file->handle.curl);
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/* cleanup */
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curl_easy_cleanup(file->handle.curl);
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}
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size_t url_fread(void *ptr, size_t size, size_t nmemb, URL_FILE *file)
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{
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fd_set fdread;
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fd_set fdwrite;
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fd_set fdexcep;
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int maxfd;
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struct timeval timeout;
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int rc;
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int still_running = 0;
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if(!file->bytes) { /* no data available at this point */
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file->readptr = file->buffer; /* reset read pointer */
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if(CURLM_CALL_MULTI_PERFORM == file->m) {
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while(CURLM_CALL_MULTI_PERFORM ==
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curl_multi_perform(multi_handle, &still_running)) {
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if(file->bytes) {
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printf("(fread) WOAH! THis happened!\n");
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break;
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}
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}
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if(!still_running) {
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printf("NO MORE RUNNING AROUND!\n");
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return 0;
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}
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}
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FD_ZERO(&fdread);
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FD_ZERO(&fdwrite);
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FD_ZERO(&fdexcep);
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/* set a suitable timeout to fail on */
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timeout.tv_sec = 500; /* 5 minutes */
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timeout.tv_usec = 0;
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/* get file descriptors from the transfers */
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curl_multi_fdset(multi_handle, &fdread, &fdwrite, &fdexcep, &maxfd);
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rc = select(maxfd+1, &fdread, &fdwrite, &fdexcep, &timeout);
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switch(rc) {
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case -1:
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/* select error */
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break;
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case 0:
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break;
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default:
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/* timeout or readable/writable sockets */
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do {
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file->m = curl_multi_perform(multi_handle, &still_running);
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if(file->bytes)
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/* we have received data, return that now */
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break;
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} while(CURLM_CALL_MULTI_PERFORM == file->m);
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if(!still_running)
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printf("NO MORE RUNNING AROUND!\n");
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break;
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}
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}
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else
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printf("(fread) Skip network read\n");
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if(file->bytes) {
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/* data already available, return that */
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int want = size * nmemb;
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if(file->bytes < want)
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want = file->bytes;
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memcpy(ptr, file->readptr, want);
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file->readptr += want;
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file->bytes -= want;
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printf("(fread) return %d bytes\n", want);
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return want;
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}
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return 0; /* no data available to return */
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}
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int main(int argc, char *argv[])
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{
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URL_FILE *handle;
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int nread;
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char buffer[256];
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handle = url_fopen("http://www.haxx.se", "r");
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if(!handle) {
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printf("couldn't url_fopen()\n");
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}
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do {
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nread = url_fread(buffer, sizeof(buffer), 1, handle);
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printf("We got: %d bytes\n", nread);
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} while(nread);
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url_fclose(handle);
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return 0;
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}
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