Re: [libmicrohttpd] issue in storing incrementally received data chunks from upload_data

[Kenneth Mastro]

I'm not an expert, but I kind of doubt that 'upload_data' is a
null-terminated string.  It probably just stops at the number of bytes that
were specified in 'upload_data_size' and has garbage after that.

So - your std::string.append call is probably adding more than it needs to
because it's looking for a null terminator for when to stop.  Try using the
'append' function that takes a size:

xmlDataString.append(upload_data, *upload_data_size);

As a side note - you may also want to consider using a stringstream instead
of a std::string.  Should be a lot more efficient than repeatedly calling
'append' like this.


Hope that helps.


Ken



On Tue, Feb 24, 2015 at 8:23 AM, dumitrița munteanu <dmt.munte...@gmail.com>
wrote:

>
> Hello all,
>
> I am using *MHD daemon server *in order to *send incrementally large
> strings containing xml data*.
>
> The size of the sent data chuck(from curls) is equal with the sum of the
> received data chucks
> (received data size in MHD daemon server  == sum of all upload_data_size
> for a specific connection).
>
> The problem is that *the string in which i append incrementally the data
> chunks as they arrive   is always bigger than the data it has been
> sent/received. *
>
> I do not understand where from comes this additional data and why my p
> ostXMLData variable gets always larger.
>
>
> My code looks like this:
>
> static postXMLData = "";
>
> static int AnswerToConnection (void *cls, struct MHD_Connection
> *connection,
> const char *url, const char *method, const char *version,
> const char *upload_data, size_t *upload_data_size, void **con_cls)
> {
>  static int i;
>
> // the first call - initialize data structures
> if (*con_cls == NULL)
> {
> *con_cls = &i;
>
> return MHD_YES;
> }
>
> // next calls - receive data incrementally
> if (*upload_data_size != 0)
> {
>           xmlDataString.append(upload_data);
>
> (*upload_data_size) = 0;
>
> return MHD_YES;
> }
>
> // last call -  upload_data_size = 0 - processed received data
> if (*upload_data_size == 0)
> {
> FILE *f; f=fopen("test_data_output_2.txt", "w"); fprintf(f, "%s", p
> ostXMLData .c_str()); fclose(f);
> }
>
>   int ret = pProcessRequest->SendPage(connection, ANSWER_PAGE);
>   return ret;
> }
>