On 2013-09-27 15:26, Daniel Stenberg wrote:
> On Fri, 27 Sep 2013, Ulf Samuelsson wrote:
>
>> Want to create a query with multiple fields, and get the result in a
>> C++ string
>>
>> Example: "http://www.myserver.com?field=1&field=2&field=3"
>>
>> The server need the query to be of the form
>> "application/x-www-form-urlencoded".
>
> Here's a very simple example showing how to send the POST:
>
> http://curl.haxx.se/libcurl/c/simplepost.html
>
> ... and you can combine that with the example showing how to receive
> the response back into a memory buffer:
>
> http://curl.haxx.se/libcurl/c/getinmemory.html
>
Thanks,
That worked.

The merged program is below.

BR
Ulf Samuelsson.

/***************************************************************************
  * _ _ ____ _
  * Project ___| | | | _ \| |
  * / __| | | | |_) | |
  * | (__| |_| | _ <| |___
  * \___|\___/|_| \_\_____|
  *
  * Copyright (C) 1998 - 2011, Daniel Stenberg, <daniel_at_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
  * are also available at http://curl.haxx.se/docs/copyright.html.
  *
  * You may opt to use, copy, modify, merge, publish, distribute and/or sell
  * copies of the Software, and permit persons to whom the Software is
  * furnished to do so, under the terms of the COPYING file.
  *
  * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY
OF ANY
  * KIND, either express or implied.
  *
  ***************************************************************************/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <curl/curl.h>

struct MemoryStruct {
   char *memory;
   size_t size;
};

static size_t
WriteMemoryCallback(void *contents, size_t size, size_t nmemb, void *userp)
{
   size_t realsize = size * nmemb;
   struct MemoryStruct *mem = (struct MemoryStruct *)userp;

   mem->memory = realloc(mem->memory, mem->size + realsize + 1);
   if(mem->memory == NULL) {
     /* out of memory! */
     printf("not enough memory (realloc returned NULL)\n");
     return 0;
   }

   memcpy(&(mem->memory[mem->size]), contents, realsize);
   mem->size += realsize;
   mem->memory[mem->size] = 0;

   return realsize;
}

int main(void)
{
   CURL *curl;
   CURLcode res;

   struct MemoryStruct chunk;

   static const char *postthis="Field=1&Field=2&Field=3";

   chunk.memory = malloc(1); /* will be grown as needed by the realloc
above */
   chunk.size = 0; /* no data at this point */

   curl_global_init(CURL_GLOBAL_ALL);
   curl = curl_easy_init();
   if(curl) {

     curl_easy_setopt(curl, CURLOPT_URL, "http://www.myserver.se/");

     /* send all data to this function */
     curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, WriteMemoryCallback);

     /* we pass our 'chunk' struct to the callback function */
     curl_easy_setopt(curl, CURLOPT_WRITEDATA, (void *)&chunk);

     /* some servers don't like requests that are made without a user-agent
      field, so we provide one */
     curl_easy_setopt(curl, CURLOPT_USERAGENT, "libcurl-agent/1.0");

     curl_easy_setopt(curl, CURLOPT_POSTFIELDS, postthis);

     /* if we don't provide POSTFIELDSIZE, libcurl will strlen() by
        itself */
     curl_easy_setopt(curl, CURLOPT_POSTFIELDSIZE, (long)strlen(postthis));

     /* Perform the request, res will get the return code */
     res = curl_easy_perform(curl);
     /* Check for errors */
     if(res != CURLE_OK) {
       fprintf(stderr, "curl_easy_perform() failed: %s\n",
               curl_easy_strerror(res));
     } else {
       /*
        * Now, our chunk.memory points to a memory block that is chunk.size
        * bytes big and contains the remote file.
        *
        * Do something nice with it!
        *
        * You should be aware of the fact that at this point we might
have an
        * allocated data block, and nothing has yet deallocated that
data. So when
        * you're done with it, you should free() it as a nice application.
        */

       // printf("%lu bytes retrieved\n", (long)chunk.size);
       printf("%s\n",chunk.memory);
     }

     /* always cleanup */
     curl_easy_cleanup(curl);

     if(chunk.memory)
       free(chunk.memory);

     /* we're done with libcurl, so clean it up */
     curl_global_cleanup();
   }
   return 0;
}

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Received on 2013-09-27