#include <stdio.h>
#include <string.h>
#include <curl/curl.h>
 
const char data[]="this is what we post to the silly web server";
 
struct WriteThis {
  const char *readptr;
  long sizeleft;
};
 
static size_t read_callback(void *ptr, size_t size, size_t nmemb, void *userp)
{
  struct WriteThis *pooh = (struct WriteThis *)userp;
 
  if(size*nmemb < 1)
    return 0;
 
  if(pooh->sizeleft) {
    *(char *)ptr = pooh->readptr[0]; /* copy one single byte */ 
    pooh->readptr++;                 /* advance pointer */ 
    pooh->sizeleft--;                /* less data left */ 
    return 1;                        /* we return 1 byte at a time! */ 
  }
 
  return 0;                          /* no more data left to deliver */ 
}
 
int main(void)
{
  CURL *curl;
  CURLcode res;
 
  struct WriteThis pooh;
 
  pooh.readptr = data;
  pooh.sizeleft = (long)strlen(data);
 
  /* In windows, this will init the winsock stuff */ 
  res = curl_global_init(CURL_GLOBAL_DEFAULT);
  /* Check for errors */ 
  if(res != CURLE_OK) {
    fprintf(stderr, "curl_global_init() failed: %s\n",
            curl_easy_strerror(res));
    return 1;
  }
 
  /* get a curl handle */ 
  curl = curl_easy_init();
  if(curl) {
    /* First set the URL that is about to receive our POST. */ 
    curl_easy_setopt(curl, CURLOPT_URL, "http://example.com/index.cgi");
 
    /* Now specify we want to POST data */ 
    curl_easy_setopt(curl, CURLOPT_POST, 1L);
 
    /* we want to use our own read function */ 
    curl_easy_setopt(curl, CURLOPT_READFUNCTION, read_callback);
 
    /* pointer to pass to our read function */ 
    curl_easy_setopt(curl, CURLOPT_READDATA, &pooh);
 
    /* get verbose debug output please */ 
    curl_easy_setopt(curl, CURLOPT_VERBOSE, 1L);
 
    /*
      If you use POST to a HTTP 1.1 server, you can send data without knowing
      the size before starting the POST if you use chunked encoding. You
      enable this by adding a header like "Transfer-Encoding: chunked" with
      CURLOPT_HTTPHEADER. With HTTP 1.0 or without chunked transfer, you must
      specify the size in the request.
    */ 
#ifdef USE_CHUNKED
    {
      struct curl_slist *chunk = NULL;
 
      chunk = curl_slist_append(chunk, "Transfer-Encoding: chunked");
      res = curl_easy_setopt(curl, CURLOPT_HTTPHEADER, chunk);
      /* use curl_slist_free_all() after the *perform() call to free this
         list again */ 
    }
#else
    /* Set the expected POST size. If you want to POST large amounts of data,
       consider CURLOPT_POSTFIELDSIZE_LARGE */ 
    curl_easy_setopt(curl, CURLOPT_POSTFIELDSIZE, pooh.sizeleft);
#endif
 
#ifdef DISABLE_EXPECT
    /*
      Using POST with HTTP 1.1 implies the use of a "Expect: 100-continue"
      header.  You can disable this header with CURLOPT_HTTPHEADER as usual.
      NOTE: if you want chunked transfer too, you need to combine these two
      since you can only set one list of headers with CURLOPT_HTTPHEADER. */ 
 
    /* A less good option would be to enforce HTTP 1.0, but that might also
       have other implications. */ 
    {
      struct curl_slist *chunk = NULL;
 
      chunk = curl_slist_append(chunk, "Expect:");
      res = curl_easy_setopt(curl, CURLOPT_HTTPHEADER, chunk);
      /* use curl_slist_free_all() after the *perform() call to free this
         list again */ 
    }
#endif
 
    /* 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));
 
    /* always cleanup */ 
    curl_easy_cleanup(curl);
  }
  curl_global_cleanup();
  return 0;
}