Le 21/10/2013 12:24, Renaud Gaujoux a écrit :
Hi,
this is somehow a general C++ question, but it could be of interest to
all Rcpp users (I think).
Still for the purpose of RcppOctave, I would like to redirect cout and
cerr streams that are used by Octave to Rprintf REprintf respectively.
Currently I redirect these streams to 2 temporary stringstreams (via the
std::cout.rdbuf get/set methods ) which buffer the output/errors
messages and print them at the end of the Octave call. The standard
streams are restored on exiting the function (in a class destructor).
However, I would like to do this without buffering, i.e. that messages
are printed as they come through the stream. This should be possible
through the definition of a std::stream child class with some method
overload that output the formatted messages as they are pushed into the
stream.
Anybody knows which class and method(s) need to be overloaded, or have
hints on how to achieve this in an -- aesthetic -- way?
Thank you.
Bests,
Renaud
Hello,
Rcpp11 does this by default now instead of the behavior that is in Rcpp,
which depends on the Rcpp::Rcout and Rcpp::cerr. See e.g.
https://github.com/romainfrancois/Rcpp11/blob/master/src/Rcpp11_init.cpp
In Rcpp, you would just have to grab the rdbuf of cout, remember it, set
it to something different and then later reset it. You can take
advantage of C++ constructor/destructor anddo something like this:
class Sinker {
public:
Sinker(): remembered_buffer(std::cout.rdbuf() ){
std::cout.rdbuf( Rcout.rdbuf() ) ;
}
~Sinker(){
std::cout.rdbuf( remembered_buffer ) ;
}
private:
std::streambuf* remembered_buffer ;
} ;
Then, whenever you want this redirection, you just have to create a
Sinker object:
void foo(){
Sinker bar ;
// call whatever that uses cout
}
Romain
--
Romain Francois
Professional R Enthusiast
+33(0) 6 28 91 30 30
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