__character_formatter.hpp

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#pragma once
#if !defined(__XTD_CORE_INTERNAL__)
#error "Do not include this file: Internal use only"
#endif
 
#include "../char32.hpp"
#include <locale>

template<typename char_t, typename value_t>
[[nodiscard]] inline auto __character_formatter(const std::basic_string<char_t>& fmt, value_t value, const std::locale& loc) -> std::basic_string<char_t> {
  std::basic_string<char_t> result;
  xtd::char32 codepoint = static_cast<xtd::char32>(value);
  if (codepoint < 0x80)
    result.push_back(static_cast<char>(codepoint));
  else  if (codepoint < 0x800) {
    result.push_back(static_cast<char>((codepoint >> 6) | 0xc0));
    result.push_back(static_cast<char>((codepoint & 0x3f) | 0x80));
  } else if (codepoint < 0x10000) {
    result.push_back(static_cast<char>((codepoint >> 12) | 0xe0));
    result.push_back(static_cast<char>(((codepoint >> 6) & 0x3f) | 0x80));
    result.push_back(static_cast<char>((codepoint & 0x3f) | 0x80));
  } else {
    result.push_back(static_cast<char>((codepoint >> 18) | 0xf0));
    result.push_back(static_cast<char>(((codepoint >> 12) & 0x3f) | 0x80));
    result.push_back(static_cast<char>(((codepoint >> 6) & 0x3f) | 0x80));
    result.push_back(static_cast<char>((codepoint & 0x3f) | 0x80));
  }
  return result;
}