Hello, I am trying to ofstream a file using the following code:

#include <curl.h>
#include <stdio.h>
#include <fstream.h>

struct callback_data {
  FILE *output;
};
 
static long file_is_comming(struct curl_fileinfo *finfo,
                            struct callback_data *data,
                            int remains);
 
static long file_is_downloaded(struct callback_data *data);
 
static size_t write_it(char *buff, size_t size, size_t nmemb,
                       struct callback_data *data);
 
int main(int argc, char **argv)
{

 ofstream file;
 file.open("file.txt");
 file << "Hello file\n";
 file.close();

  int rc = CURLE_OK;
 
  /* curl easy handle */ 
  CURL *handle;
 
  /* help data */ 
  struct callback_data data = { 0 };
 
  /* global initialization */ 
  rc = curl_global_init(CURL_GLOBAL_ALL);
  if(rc)
    return rc;
 
  /* initialization of easy handle */ 
  handle = curl_easy_init();
  if(!handle) {
    curl_global_cleanup();
    return CURLE_OUT_OF_MEMORY;
  }
 
  /* turn on wildcard matching */ 
  curl_easy_setopt(handle, CURLOPT_WILDCARDMATCH, 1L);
 
  /* callback is called before download of concrete file started */ 
  curl_easy_setopt(handle, CURLOPT_CHUNK_BGN_FUNCTION, file_is_comming);
 
  /* callback is called after data from the file have been transferred */ 
  curl_easy_setopt(handle, CURLOPT_CHUNK_END_FUNCTION, file_is_downloaded);
 
  /* this callback will write contents into files */ 
  curl_easy_setopt(handle, CURLOPT_WRITEFUNCTION, write_it);
 
  /* put transfer data into callbacks */ 
  curl_easy_setopt(handle, CURLOPT_CHUNK_DATA, &data);
  curl_easy_setopt(handle, CURLOPT_WRITEDATA, &data);
 
  /* curl_easy_setopt(handle, CURLOPT_VERBOSE, 1L); */ 
 
  /* set an URL containing wildcard pattern (only in the last part) */ 
  if(argc == 2)
    curl_easy_setopt(handle, CURLOPT_URL, argv[1]);
  else
    curl_easy_setopt(handle, CURLOPT_URL, "ftp://example.com//*");
 
  /* and start transfer! */
  rc = curl_easy_perform(handle);
 
  curl_easy_cleanup(handle);
  curl_global_cleanup();
  return rc;
}
 
static long file_is_comming(struct curl_fileinfo *finfo,
                            struct callback_data *data,
                            int remains)
{
  printf("%3d %40s %10luB ", remains, finfo->filename,
         (unsigned long)finfo->size);
 
  switch(finfo->filetype) {
  case CURLFILETYPE_DIRECTORY:
    printf(" DIR\n");
    break;
  case CURLFILETYPE_FILE:
    printf("FILE ");
    break;
  default:
    printf("OTHER\n");
    break;
  }
 
  if(finfo->filetype == CURLFILETYPE_FILE) {
    /* do not transfer files >= 50B */ 
    if(finfo->size > 50) {
      printf("SKIPPED\n");
      return CURL_CHUNK_BGN_FUNC_SKIP;
    }
 
    data->output = fopen(finfo->filename, "w");
    if(!data->output) {
      return CURL_CHUNK_BGN_FUNC_FAIL;
    }
  }
 
  return CURL_CHUNK_BGN_FUNC_OK;
}
 
static long file_is_downloaded(struct callback_data *data)
{
  if(data->output) {
    printf("DOWNLOADED\n");
    fclose(data->output);
    data->output = 0x0;
  }
  return CURL_CHUNK_END_FUNC_OK;
}
 
static size_t write_it(char *buff, size_t size, size_t nmemb,
                       struct callback_data *data)
{
  size_t written = 0;
  if(data->output)
    written = fwrite(buff, size, nmemb, data->output);
  else
    /* listing output */ 
    written = fwrite(buff, size, nmemb, stdout);
  return written;
}

And the program crashes when it's time to write data to a text file. Can someone, please, help me find out what the problem is?

In write_it (I guess that is where it crashes?), check what the value of 'buf' is, is it a valid pointer?

I don't know how this 'curl' library works though, so just guessing here

Thanks for the reply! I got this code here. I found the problem! I ignored "msvcrt", this causes the error, but when I remove "msvcrt" from ignored list the other code crashes... :(

Edited 5 Years Ago by SpecialForce: n/a

Check the compatibility. fwrite is "deprecated" on newer versions of windows. That might be the problem that causes the crash. Maybe running in compatibility mode or changing to code to use ofstream instead of fopen/fwrite.

This article has been dead for over six months. Start a new discussion instead.