Reverse wstring in C++

Question

I need to reverse wstring. I have such code:

#include <iostream>
#include <string>
#include <locale>

int main() {
    std::wstring s;
    std::getline(std::wcin, s);
    for (const auto &i : s) {
        std::wcout << (int) i << " ";
    }
    std::wcout << std::endl;

    std::wcout << s << std::endl;

    std::reverse(s.begin(), s.end());
    std::wcout << s << std::endl;
    return 0;
}

ANSI characters are encoded in 1 byte, and I can easily reverse them:

echo -n "papa" | ./reverse
112 97 112 97
papa
apap

But when I enter cyrillic text, that are encoded more than 1 bytes, I get such output:

echo -n "папа" | ./reverse
208 191 208 176 208 191 208 176
папа
�пап�

How can I properly reverse that string?

P.S. I'm using OS X.

If the encoding is utf-8, then why do you use wide character types? — eerorika, Apr 30 '16 at 09:56
@user2079303 With `std::string` I get such output: `-48 -65 -48 -80 -48 -65 -48 -80 папа �пап�` — 0x1337, Apr 30 '16 at 09:59
Yes, I didn't imply that was your problem, just a confusion. — eerorika, Apr 30 '16 at 10:01
Did you see the answer at http://stackoverflow.com/questions/199260/how-do-i-reverse-a-utf-8-string-in-place? — Shachar Shemesh, Apr 30 '16 at 10:04

score 1 · Accepted Answer · edited May 23 '17 at 10:33

Your system, OS X, uses UTF-8. So there is no reason for you to use wstring or wchar_t. And indeed this is where the confusion comes from!

You see, when you call getline() with a wstring on OS X, it does not read wide characters at all. The characters are indeed four bytes each, but they hold the same 0-255 range of values that they would if you used a regular "narrow" string. So when you pipe your Cyrillic characters to your program, you end up with a wstring of length 8, because C++ doesn't understand UTF-8, but your terminal does (hence it looks like four characters in the terminal but 8 in C++).

A commenter on your question was right to point out this question: How do I reverse a UTF-8 string in place? - that is really all you need, once you realize that you aren't dealing with wide strings at all.

Reverse wstring in C++

1 Answers1