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to get entire buffer from stringstream

Started by seifer503 Jan 21, 2008 at 7:25 PM 4 replies 1.3k views

Original Post

Jan 21, 2008 at 7:25 PM

I'm trying to create a template function to convert text to various data types:


template<typename Output, typename Input>
Output lexical_cast(Input &input) {
	std::stringstream ss;
	ss << input;
	Output output;
	ss >> output;
	return output;
}

int main () {
	using namespace std;

	string s;
	int i;
	char buf[] = "7 Hello World";

	s = lexical_cast<string>(buf);
	i = lexical_cast<int>(buf);
	
	cout << "String: " << s << " Int: " << i;
	cin.get();
	return 0;
}

However, I cannot get the entire buffer to fill the string. It only contains "7" instead of "7 Hello World". I realize I can use the str() member function of stringstream, but I want the solution to be general. Is there a way to accomplish this?

Sc4Freak

Jan 21, 2008 at 7:53 PM

The std::stringstream::str() function should do what you want.

But in the end, why not just use boost::lexical_cast?

seifer503

Jan 21, 2008 at 8:31 PM

I'm trying to deserialize a vector from XML and I want to be able to use any data type. For example I want to be able to call a function like: template GetVectorFromXml(string xml, vector). Is this possible?

the_edd

Jan 22, 2008 at 2:50 AM

You can ether overload << and >> for std::vector<> or provide some kind of specialization for the case where Output is std::string.

Template function specialization is a little funky, so I'd go through a helper template class with a static member function. Something like:

template<typename To>struct lexical_conversion{    template<typename From>    static To convert(const From &f) { /* as before */ }};template<>struct lexical_conversion<std::string>{    template<typename From>    static std::string convert(const From &f) { /* use std::getline() */ }};template<typename To, typename From>To my_lexical_cast(const From &from){    return lexical_conversion<To>::convert(from);}

seifer503

Jan 22, 2008 at 11:25 AM

That was just what I needed, thank you! Are there any other types I should create specializations for? (BTW, I can't use Boost, since the project I'm working does not have it at this point)

Zahlman

Jan 22, 2008 at 11:49 AM

Quote:
Original post by seifer503
That was just what I needed, thank you! Are there any other types I should create specializations for? (BTW, I can't use Boost, since the project I'm working does not have it at this point)

Zuh?

Boost is not some monolithic thing. Just download the pieces you need and add them.

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