Unverified Commit 8cf6c170 authored by Daniel Stenberg's avatar Daniel Stenberg
Browse files

examples/10-at-a-time.c: improve readability and simplify 

 - use better variable names to explain their purposes
 - convert logic to curl_multi_wait()
parent 754ae103

docs/examples/10-at-a-time.c

+25 −72
Original line number Diff line number Diff line
@@ -5,7 +5,7 @@ 
 *                            | (__| |_| |  _ <| |___

 *                             \___|\___/|_| \_\_____|

 *

 * Copyright (C) 1998 - 2018, Daniel Stenberg, <daniel@haxx.se>, et al.

 * Copyright (C) 1998 - 2019, Daniel Stenberg, <daniel@haxx.se>, et al.

 *

 * This software is licensed as described in the file COPYING, which

 * you should have received as part of this distribution. The terms
@@ -20,10 +20,8 @@ 
 *

 ***************************************************************************/

/* <DESC>

 * Source code using the multi interface to download many

 * files, with a capped maximum amount of simultaneous transfers.

 * Download many files in parallel, in the same thread.

 * </DESC>

 * Written by Michael Wallner

 */



#include <errno.h>
@@ -84,27 +82,23 @@ static const char *urls[] = { 
  "https://www.un.org",

};



#define MAX 10 /* number of simultaneous transfers */

#define CNT sizeof(urls)/sizeof(char *) /* total number of transfers to do */

#define MAX_PARALLEL 10 /* number of simultaneous transfers */

#define NUM_URLS sizeof(urls)/sizeof(char *) /* total number of transfers to do */



static size_t cb(char *d, size_t n, size_t l, void *p)

static size_t write_cb(char *data, size_t n, size_t l, void *userp)

{

  /* take care of the data here, ignored in this example */

  (void)d;

  (void)p;

  (void)data;

  (void)userp;

  return n*l;

}



static void init(CURLM *cm, int i)

static void add_transfer(CURLM *cm, int i)

{

  CURL *eh = curl_easy_init();



  curl_easy_setopt(eh, CURLOPT_WRITEFUNCTION, cb);

  curl_easy_setopt(eh, CURLOPT_HEADER, 0L);

  curl_easy_setopt(eh, CURLOPT_WRITEFUNCTION, write_cb);

  curl_easy_setopt(eh, CURLOPT_URL, urls[i]);

  curl_easy_setopt(eh, CURLOPT_PRIVATE, urls[i]);

  curl_easy_setopt(eh, CURLOPT_VERBOSE, 0L);



  curl_multi_add_handle(cm, eh);

}
@@ -112,64 +106,23 @@ int main(void) 
{

  CURLM *cm;

  CURLMsg *msg;

  long L;

  unsigned int C = 0;

  int M, Q, U = -1;

  fd_set R, W, E;

  struct timeval T;

  unsigned int transfers = 0;

  int msgs_left = -1;

  int still_alive = 1;



  curl_global_init(CURL_GLOBAL_ALL);



  cm = curl_multi_init();



  /* we can optionally limit the total amount of connections this multi handle

     uses */

  curl_multi_setopt(cm, CURLMOPT_MAXCONNECTS, (long)MAX);



  for(C = 0; C < MAX; ++C) {

    init(cm, C);

  }



  while(U) {

    curl_multi_perform(cm, &U);



    if(U) {

      FD_ZERO(&R);

      FD_ZERO(&W);

      FD_ZERO(&E);



      if(curl_multi_fdset(cm, &R, &W, &E, &M)) {

        fprintf(stderr, "E: curl_multi_fdset\n");

        return EXIT_FAILURE;

      }



      if(curl_multi_timeout(cm, &L)) {

        fprintf(stderr, "E: curl_multi_timeout\n");

        return EXIT_FAILURE;

      }

      if(L == -1)

        L = 100;

  /* Limit the amount of simultaneous connections curl should allow: */

  curl_multi_setopt(cm, CURLMOPT_MAXCONNECTS, (long)MAX_PARALLEL);



      if(M == -1) {

#ifdef WIN32

        Sleep(L);

#else

        sleep((unsigned int)L / 1000);

#endif

      }

      else {

        T.tv_sec = L/1000;

        T.tv_usec = (L%1000)*1000;

  for(transfers = 0; transfers < MAX_PARALLEL; transfers++)

    add_transfer(cm, transfers);



        if(0 > select(M + 1, &R, &W, &E, &T)) {

          fprintf(stderr, "E: select(%i,,,,%li): %i: %s\n",

              M + 1, L, errno, strerror(errno));

          return EXIT_FAILURE;

        }

      }

    }

  do {

    curl_multi_perform(cm, &still_alive);



    while((msg = curl_multi_info_read(cm, &Q))) {

    while((msg = curl_multi_info_read(cm, &msgs_left))) {

      if(msg->msg == CURLMSG_DONE) {

        char *url;

        CURL *e = msg->easy_handle;
@@ -182,13 +135,13 @@ int main(void) 
      else {

        fprintf(stderr, "E: CURLMsg (%d)\n", msg->msg);

      }

      if(C < CNT) {

        init(cm, C++);

        U++; /* just to prevent it from remaining at 0 if there are more

                URLs to get */

      }

    }

      if(transfers < NUM_URLS)

        add_transfer(cm, transfers++);

    }

    if(still_alive)

      curl_multi_wait(cm, NULL, 0, 1000, NULL);



  } while(still_alive || (transfers < NUM_URLS));



  curl_multi_cleanup(cm);

  curl_global_cleanup();