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  1. #include <iostream>
  2. #include <string>
  3.  
  4. std::string utf16_to_utf8(const std::wstring& wstr) {
  5.     std::string result;
  6.  
  7.     for (size_t i = 0; i < wstr.size(); ++i) {
  8.         wchar_t wc = wstr[i];
  9.  
  10.         if (wc <= 0x7F) {  // ASCII (1-byte UTF-8)
  11.             result.push_back(static_cast<char>(wc));
  12.         } else if (wc <= 0x7FF) {  // 2-byte UTF-8
  13.             result.push_back(0xC0 | ((wc >> 6) & 0x1F));
  14.             result.push_back(0x80 | (wc & 0x3F));
  15.         } else if (wc >= 0xD800 && wc <= 0xDFFF) {  // Surrogate pair (UTF-16)
  16.             if (i + 1 < wstr.size()) {
  17.                 wchar_t high = wc;
  18.                 wchar_t low = wstr[++i];
  19.  
  20.                 if (high >= 0xD800 && high <= 0xDBFF && low >= 0xDC00 && low <= 0xDFFF) {
  21.                     uint32_t codepoint = ((high - 0xD800) << 10) + (low - 0xDC00) + 0x10000;
  22.                     result.push_back(0xF0 | ((codepoint >> 18) & 0x07));
  23.                     result.push_back(0x80 | ((codepoint >> 12) & 0x3F));
  24.                     result.push_back(0x80 | ((codepoint >> 6) & 0x3F));
  25.                     result.push_back(0x80 | (codepoint & 0x3F));
  26.                 }
  27.             }
  28.         } else {  // 3-byte UTF-8
  29.             result.push_back(0xE0 | ((wc >> 12) & 0x0F));
  30.             result.push_back(0x80 | ((wc >> 6) & 0x3F));
  31.             result.push_back(0x80 | (wc & 0x3F));
  32.         }
  33.     }
  34.  
  35.     return result;
  36. }
  37.  
  38. int main() {
  39.     std::wstring wide_text = L"A – B";  // Unicode text
  40.     std::string utf8_text = utf16_to_utf8(wide_text);
  41.  
  42.     std::cout << "UTF-8: " << utf8_text << std::endl;
  43.     return 0;
  44. }
Success #stdin #stdout 0.01s 5288KB
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Standard input is empty
stdout
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UTF-8: A – B
https://ideone.com/xgNvTO
language:
C++ (gcc 8.3)
created:
20 hours ago
visibility:
public

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