Why this is not working ? libcurl & c++ - c++

Question

I am new to libcurl and am trying to get filelist from a server using ftp, going through the examples and some other posts here, I have come up with the following code. But when I run it, it returns error message :
Failed writing body (4294967295 != 129)
in the error string set by CURLOPT_ERRORBUFFER. The curl_easy_strerror( res ) returns:
Failed writing received data to disk/application
struct FtpFile
{
const char *filename;
FILE *stream;
};
static size_t fileWrite( void *buffer, size_t size, size_t nmemb, void *stream )
{
struct FtpFile *out=(struct FtpFile *)stream;
if(out && !out->stream)
{
out->stream=fopen(out->filename, "wb");
if(!out->stream)
{
cout << out->filename << " open failure [fileWrite] " << endl;
return -1;
}
}
size_t written = fwrite(buffer, size, nmemb, out->stream);
cout << written << endl;
if(written <= 0)
cout << "Nothing written : " << written;
return written;
}
void getFileList( const char* url, const char* fname )
{
CURL *curl;
CURLcode res;
FILE *ftpfile;
const char *errmsg;
ftpfile = fopen(fname, "wb");
if ( ftpfile == NULL )
{
cout << fname << " open failure [getFileList] " << endl ;
return;
}
curl = curl_easy_init();
if(curl)
{
curl_easy_setopt(curl, CURLOPT_URL, url);
curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, fileWrite);
curl_easy_setopt(curl, CURLOPT_WRITEDATA, ftpfile);
curl_easy_setopt(curl, CURLOPT_ERRORBUFFER, errmsg);
curl_easy_setopt(curl, CURLOPT_USERNAME, "username");
curl_easy_setopt(curl, CURLOPT_PASSWORD, "password");
curl_easy_setopt(curl, CURLOPT_FTPLISTONLY,TRUE);
res = curl_easy_perform(curl);
if(res != CURLE_OK)
{
fprintf( stderr, "curl_easy_perform() failed: %s\nError Message: %s\n", curl_easy_strerror( res ), errmsg );
}
curl_easy_cleanup(curl);
}
fclose(ftpfile);
}
int main(int argc, char *argv[])
{
getFileList( "ftp://ftp.example.com/public/somefolder/", "file-list.txt" );
system("PAUSE");
return EXIT_SUCCESS;
}

Answer 1

4294967295 is the 32 bit unsigned version of -1, which probably is what your callback returned and thus libcurl considered it an error and stopped everything.
Where is ->filename assigned?
You pass in a FILE * to CURLOPT_WRITEDATA and yet your callback reads it as a struct FtpFile *...

Answer 2

First, your fileWrite function should return the number of bytes written. fwrite returns the number of objects written. So you have to return written * size;
Then, as Daniel Stenberg notes, you are passing a FILE * to fileWrite but using it as a struct FtpFile *. Try this one instead:
static size_t fileWrite( void *buffer, size_t size, size_t nmemb, void *stream )
{
size_t written = fwrite(buffer, size, nmemb, (FILE*)stream);
std::cout << written * size << std::endl;
if(written <= 0)
std::cout << "Nothing written : " << written;
return written * size;
}