I know one of the advantages of std::stringstream is that it is a std::istream so it may accept input from any type that defines operator<< to std::istream, and also from primitives types.
I am not going to use operator<<; instead I am just going to concatenate many strings. Does the implementation of std::stringstream make it faster than std::string for concatenating many strings?
There's no reason to expect std::string's appending functions to be slower than stringstream's insertion functions. std::string will generally be nothing more than a possible memory allocation/copy plus copying of the data into the memory. stringstream has to deal with things like locales, etc, even for basic write calls.
Also, std::string provides ways to minimize or eliminate anything but the first memory allocation. If you reserve sufficient space, every insertion is little more than a memcpy. That's not really possible with stringstream.
Even if it were faster than std::string's appending functions, you still have to copy the string out of the stringstream to do something with it. So that's another allocation + copy, which you won't need with std::string. Though at least C++20 looks set to remove that particular need.
You should use std::stringstream if you need formatting, not just for sticking some strings together.
<< for concatenation (it works with std::cout, std::cerr, std::stringstream) but it doesn't work with std::string. Do I really need to write a small wrapper around std::string just for this?operator<< that concatenates and that worked just fine. I just reserve the final size and after concatenating I move the string out. Feels like the stone age: string has append and operator+ while streams have write and operator<<...
In a recent set of benchmarks conducted on Quick-Bench, std::stringstream demonstrated lower performance compared to concatenating strings using the std::string += operator. This is a notable finding because appending multiple strings and literals is a frequent operation in string processing.
The benchmark compared the two methods under identical conditions with the goal of concatenating a long string composed of literals and small string objects. The results indicated that std::stringstream is less efficient.
Please find the detailed benchmark results here:
https://quick-bench.com/q/iR8hY3MmHXCSXe5vvY28C-6mQfY
It's important to note that while std::stringstream showed worse performance in this specific test case, actual performance can vary. Factors such as the compiler version, optimization settings, and the underlying hardware can all influence the results. Therefore, it is recommended to run benchmarks tailored to your application's specific use cases to determine the best approach.
.append()/operator+=?append()andoperator+=ostreamrather thanistream?