The strstream returned a char * that was very difficult to manage, as nowhere was it stated how it had been allocated. It was thus impossible to know if you should delete it or call free() on it or do something else entirely. About the only really satisfactory way to deallocate it was to hand … Read more
Personally, I find it very rare that I want to perform streaming into and out of the same string stream. Usually I want to either initialize a stream from a string and then parse it; or stream things to a string stream and then extract the result and store it. If you’re streaming to and … Read more
You can also use the built in find_first_of and find_first_not_of to find the first “numberstring” in any string. std::string first_numberstring(std::string const & str) { char const* digits = “0123456789”; std::size_t const n = str.find_first_of(digits); if (n != std::string::npos) { std::size_t const m = str.find_first_not_of(digits, n); return str.substr(n, m != std::string::npos ? m-n : m); } … Read more
Indeed, streams are non-copyable (though they are movable). Depending on your usage, the following works quite well: #include <iostream> #include <sstream> int main() { std::stringstream ss1; ss1 << “some ” << 123 << ” stuff” << std::flush; std::stringstream ss2; ss2 << ss1.rdbuf(); // copy everything inside ss1’s buffer to ss2’s buffer std::cout << ss1.str() << … Read more
std::ifstream has a method rdbuf(), that returns a pointer to a filebuf. You can then “push” this filebuf into your stringstream: #include <fstream> #include <sstream> int main() { std::ifstream file( “myFile” ); if ( file ) { std::stringstream buffer; buffer << file.rdbuf(); file.close(); // operations on the buffer… } } EDIT: As Martin York remarks … Read more
stringstream.str() returns a temporary string object that’s destroyed at the end of the full expression. If you get a pointer to a C string from that (stringstream.str().c_str()), it will point to a string which is deleted where the statement ends. That’s why your code prints garbage. You could copy that temporary string object to some … Read more
Typically to ‘reset’ a stringstream you need to both reset the underlying sequence to an empty string with str and to clear any fail and eof flags with clear. parser.str( std::string() ); parser.clear(); Typically what happens is that the first >> reaches the end of the string and sets the eof bit, although it successfully … Read more
Another version… Use strtol, wrapping it inside a simple function to hide its complexity : inline bool isInteger(const std::string & s) { if(s.empty() || ((!isdigit(s[0])) && (s[0] != ‘-‘) && (s[0] != ‘+’))) return false; char * p; strtol(s.c_str(), &p, 10); return (*p == 0); } Why strtol ? As far as I love C++, … Read more
#include <iostream> #include <sstream> std::string input = “abc,def,ghi”; std::istringstream ss(input); std::string token; while(std::getline(ss, token, ‘,’)) { std::cout << token << ‘\n’; } abc def ghi
From this reference: If extraction fails (e.g. if a letter was entered where a digit is expected), value is left unmodified and failbit is set (until C++11) If extraction fails, zero is written to value and failbit is set. If extraction results in the value too large or too small to fit in value, std::numeric_limits::max() … Read more