Question

I have the following code which i copied from here:

/***************************************************************************
 *                                  _   _ ____  _
 *  Project                     ___| | | |  _ \| |
 *                             / __| | | | |_) | |
 *                            | (__| |_| |  _ <| |___
 *                             \___|\___/|_| \_\_____|
 *
 * Copyright (C) 1998 - 2011, Daniel Stenberg, <[e-mail]>, 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 <fcntl.h>
#include <sys/stat.h>
#include <unistd.h>

#include <curl/curl.h>
#include "printf_macro.h"

/*
 * This example shows a HTTP PUT operation. PUTs a file given as a command
 * line argument to the URL also given on the command line.
 *
 * This example also uses its own read callback.
 *
 * Here's an article on how to setup a PUT handler for Apache:
 * http://www.apacheweek.com/features/put
 */ 

static size_t read_callback(void *ptr, size_t size, size_t nmemb, void *stream)
{
  size_t retcode;

  /* in real-world cases, this would probably get this data differently
     as this fread() stuff is exactly what the library already would do
     by default internally */ 
  retcode = fread(ptr, size, nmemb, stream);

  fprintf(stderr, "*** We read %" _FMT_SIZE_T " bytes from file\n", retcode);

  return retcode;
}

int main(int argc, char **argv)
{
  CURL *curl;
  CURLcode res;
  FILE * hd_src ;
  int hd ;
  struct stat file_info;

  char *file;
  char *url;

  if(argc < 3)
    return 1;

  file= argv[1];
  url = argv[2];

  /* get the file size of the local file */ 
  hd = open(file, O_RDONLY) ;
  fstat(hd, &file_info);
  close(hd) ;

  /* get a FILE * of the same file, could also be made with
     fdopen() from the previous descriptor, but hey this is just
     an example! */ 
  hd_src = fopen(file, "rb");

  /* In windows, this will init the winsock stuff */ 
  curl_global_init(CURL_GLOBAL_ALL);

  /* get a curl handle */ 
  curl = curl_easy_init();
  if(curl) {
    /* we want to use our own read function */ 
    curl_easy_setopt(curl, CURLOPT_READFUNCTION, read_callback);

    /* enable uploading */ 
    curl_easy_setopt(curl, CURLOPT_UPLOAD, 1L);

    /* HTTP PUT please */ 
    curl_easy_setopt(curl, CURLOPT_PUT, 1L);

    /* specify target URL, and note that this URL should include a file
       name, not only a directory */ 
    curl_easy_setopt(curl, CURLOPT_URL, url);

    /* now specify which file to upload */ 
    curl_easy_setopt(curl, CURLOPT_READDATA, hd_src);

    /* provide the size of the upload, we specicially typecast the value
       to curl_off_t since we must be sure to use the correct data size */ 
    curl_easy_setopt(curl, CURLOPT_INFILESIZE_LARGE,
                     (curl_off_t)file_info.st_size);

    /* Now run off and do what you've been told! */ 
    res = curl_easy_perform(curl);

    /* always cleanup */ 
    curl_easy_cleanup(curl);
  }
  fclose(hd_src); /* close the local file */ 

  curl_global_cleanup();
  return 0;
}

It does require this header.

When i try to compile put.cpp as follows:

g++ put.cpp -lcurl

i get the following error:

put.cpp: In function `size_t read_callback(void*, size_t, size_t, void*)':
put.cpp:47: error: invalid conversion from `void*' to `FILE*'
put.cpp:47: error:   initializing argument 4 of `size_t fread(void*, size_t, size_t, FILE*)'

How can i fix this?

Answer 1

Change the signature of read_callback to type stream as FILE*