Re: [Cppcms-users] HTTP response and binary stream (libharu)

[Artyom B. <art...@ya...>]

Several points:
(a) You misunderstand meaning of "raw" output - "raw" means you are sending CGI output including headers etc on your own and CppCMS does not interfere with it. There only very-very specific cases you may actually need this - bottom line you don't need it.(b) std::ostream is just a character or more correctly octet stream, std::string is a container that keeps bytes/"C chars"/octets in it in string friendly way. You can put any binary data to it. 
Now in your case the problem is there"
app()->response().out() << buf << std::flush; or 
cppcms_buf << buf

Why? std::ostream assumes that buf is NUL terminated string so it would stop on NUL, and this what corrupts the stream.You need to use std::ostream::write, i.e.
out().write(buf,siz)
That's it

Artyom Beilis
 
      From: augustin <aug...@ov...>
 To: cpp...@li... 
 Sent: Thursday, September 17, 2015 4:16 PM
 Subject: Re: [Cppcms-users] HTTP response and binary stream (libharu)
   
On Thursday, September 17, 2015 07:07:21 PM Joerg Sonnenberger wrote:
> On Thu, Sep 17, 2015 at 05:52:03PM +0800, augustin wrote:
> > I am trying to get my cppcms application to output a PDF file (using
> > libharu). However, I seem to have a problem returning the binary output.
> > It seems that the cppcms internals are corrupting the stream.
> 
> Works fine for me, but I don't set raw mode or anything like that, just:
> 
> response().content_type("application/pdf");
> response().out() << pdf;
> 
> where pdf is a std::string.

Thanks, but pdf is not a std::string.
It is a HPDF_Doc from the libharu library, which is used to create documents 
following the PDF standard.
A PDF file may include binary streams.

I have no problem outputting HTML (std::string).
I have no problem outputting simple PDF files which only include a stream of 
strings.
But when I try creating more complex PDF files with drawings or pictures (i.e. 
PDF files including binary streams), the file gets corrupted and is not 
rendered properly.

Right now, I am learning about the complexities of having binary streams in 
C++. There are quite a few articles on the topic on the internet.

My main question is:
is it a problem in my own code, or is it a shortcoming of the cppcms library, 
that it cannot handle binary streams? Does cppcms need to be patched or should 
I handle the stream differently on my end?

thanks,



augustin.


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