Convert a unicode String In C++ To Upper Case

Question

How we can convert a multi language string or unicode string to upper/lower case in C or C++.

Answer 1

I found 2 solution of that problem_

1. setlocale(LC_CTYPE, "en_US.UTF-8"); // the locale will be the UTF-8 enabled English

std::wstring str = L"Zoë Saldaña played in La maldición del padre Cardona.ëèñ";

std::wcout << str << std::endl;

for (wstring::iterator it = str.begin(); it != str.end(); ++it)
    *it = towupper(*it);

std::wcout << "toUpper_onGCC_LLVM_1 :: "<< str << std::endl;

this is working on LLVM GCC 4.2 Compiler.

2. std::locale::global(std::locale("en_US.UTF-8")); // the locale will be the UTF-8 enabled English

std::wcout.imbue(std::locale());
const std::ctype<wchar_t>& f = std::use_facet< std::ctype<wchar_t> >(std::locale());

std::wstring str = L"Chloëè";//"Zoë Saldaña played in La maldición del padre Cardona.";

f.toupper(&str[0], &str[0] + str.size());   

std::wcout << str << std::endl;

This is working in Apple LLVM 4.2.

Both case i ran on Xocde. But I am finding a way to run this code in Eclipse with g++ Compiler.

Answer 2

You can iterate through a wstring and use towupper / towlower

for (wstring::iterator it = a.begin(); it != a.end(); ++it)
        *it = towupper(*it);

Answer 3

For C I would use toupper after adjusting the C locale in the current thread.

setlocale(LC_CTYPE, "en_US.UTF8");

For C++ I would use the toupper method of std::ctype<char>:

std::locale loc;

auto& f = std::use_facet<std::ctype<char>>(loc);

char str[80] = "Hello World";

f.toupper(str, str+strlen(str));

Answer 4

In Windows, consider CharUpperBuffW and CharLowerBuffW for mixed-language applications where locale is unknown. These functions handle diacritics where toupper() does not.

Answer 5

With quite a lot of difficulty if you're going to do it right.

The usual use-case for this is for comparison purposes, but the problem is more general than that.

There is a fairly detailed paper from C++ Report circa 2000 from Matt Austern here (PDF)

Answer 6

If you want a sane and mature solution, look at IBM's ICU. Here's an example:

#include <iostream>
#include <unicode/unistr.h>
#include <string>

int main(){
    icu::UnicodeString us("óóßChloë");
    us.toUpper(); //convert to uppercase in-place
    std::string s;
    us.toUTF8String(s);
    std::cout<<"Upper: "<<s<<"\n";

    us.toLower(); //convert to lowercase in-place
    s.clear();
    us.toUTF8String(s);
    std::cout<<"Lower: "<<s<<"\n";
    return 0;
}

Output:

Upper: ÓÓSSCHLOË
Lower: óósschloë

Note: In the later step SS isn't being treated as capital of German ß