How to print UTF-8 symbols by entering decimal number? - c++

Question

For example I enter decimal number 210 that is symbol "Ò".
For example code
int a = 210;
wcout << wchar_t (a);
works fine, but before "wcout" I use "cout" and they are not compatible.
int main() {
string a = "\u";
string b = "210";
string c = a + b;
cout << b + a << endl;
cout << "Second cout message...";
}
ERROR:
main.cpp:4:15: error: \u used with no
following hex digits
string a = "\u";
^~
1 error generated.
compiler exit status 1

Answer 1

You can use std::wcrtomb to convert wide character to multi byte string. See https://en.cppreference.com/w/cpp/string/multibyte/wcrtomb
#include <iostream>
#include <cwchar>
#include <clocale>
int main() {
std::setlocale(LC_ALL, "en_US.utf8");
wchar_t wc = 127820;
char mbstr[5]{};
std::mbstate_t state{};
std::wcrtomb(mbstr, wc, &state);
std::cout << mbstr << std::endl;
}
https://ideone.com/QVMppe
Also if you are interested in what Unicode is and how it is encoded with variable width character encoding, see https://en.wikipedia.org/wiki/UTF-8

Answer 2

UTF-8 is very easy to encode manually, eg:
std::string toUTF8(uint32_t cp)
{
char utf8[4];
int len = 0;
if (cp <= 0x007F)
{
utf8[0] = static_cast<char>(cp);
len = 1;
}
else
{
if (cp <= 0x07FF)
{
utf8[0] = 0xC0;
len = 2;
}
else if (cp <= 0xFFFF)
{
utf8[0] = 0xE0;
len = 3;
}
else if (cp <= 0x10FFFF)
{
utf8[0] = 0xF0;
len = 4;
}
else
throw std::invalid_argument("invalid codepoint");
for(int i = 1; i < len; ++i)
{
utf8[len-i] = static_cast<char>(0x80 | (cp & 0x3F));
cp >>= 6;
}
utf8[0] |= static_cast<char>(cp);
}
return std::string(utf8, len);
}
int main()
{
std::string utf8 = toUTF8(210);
std::cout << utf8;
}
Live Demo
Make sure your console actually supports displaying UTF-8 text.