#include <iostream>
#include <format>
#include "utf8.h"

std::string u16_to_u8_unchecked(const std::u16string& u16)
{
	std::string str;
	utf8::unchecked::utf16to8(u16.begin(), u16.end(), std::back_inserter(str));
	return str;
}

int main()
{
	std::u16string u16 = u"Simple test!";

	std::string u8_checked = utf8::utf16to8(u16);
	std::string u8_unchecked = u16_to_u8_unchecked(u16);

	std::cout << std::format("{}\n{}\n", u8_checked, u8_unchecked);
	std::cout << std::format("{} {} {}\n", u8_checked == u8_unchecked, u8_checked.size(), u8_unchecked.size());

	return 0;
}

Simple test!
Simple test
false 12 11