stream - C++ Stringstream - copying with rd_buf changes const object -

given 1 stringstream object, copy another. according :

how copy 1 stringstream object in c++?

(among others), proper way use rdbuf() member. however, seems cause issues, particularly if stringstream const.

for example:

void dosomething(stringstream & ss) {     stringstream sstmp;      cout << "pos 1: " << ss.tellg() << "\n";     sstmp << ss.rdbuf();     cout << "pos 2: " << ss.tellg() << "\n"; //        sstmp.rdbuf()->pubseekpos(0, ios_base::in | ios_base::out);      cout << "string: " << sstmp.str() << "\n"; }  int main(void) {     stringstream ss;     ss << "hello";      dosomething(ss);     dosomething(ss);      return 0; } 

the output is

pos 1: 0 pos 2: 5 string: hello pos 1: 5 pos 2: 5 string:  

the first call dosomething() changed internal pointer, , seems if stringstream const (left out here tellg() not const). way remedy seekg(), can't called on const streams. attempted way (commented out in code) without success.

so can done either:

1. copy (const) stringstream without changing it, or

2. reset position on const object?

note: compiled using gcc 4.8.1 on arch linux

the straightforward way make string , copy way: sstmp.str(ss.str());

the less obvious approach utilize fact can gain non-const access rdbuf const stringstream.

i made several changes code compiles, , updated code directly set rdbuf's position, should want, outputting:

string: hello string: hello 

-

#include <sstream> #include <iostream>  void dosomething(const std::stringstream& ss) {     std::stringstream sstmp;      sstmp << ss.rdbuf();     ss.rdbuf()->pubseekpos(0, std::ios_base::in);      std::cout << "string: " << sstmp.str() << "\n"; }  int main() {     std::stringstream ss;     ss << "hello";      dosomething(ss);     dosomething(ss);      return 0; }