Function latin1_to_utf8

cpp/fory/util/string_util.h:96–130

Convert Latin1 encoded bytes to UTF-8 string. Latin1 (ISO-8859-1) maps bytes 0-127 to ASCII and bytes 128-255 to Unicode code points U+0080 to U+00FF.

// Latin1 (ISO-8859-1) maps bytes 0-127 to ASCII and bytes 128-255 to
// Unicode code points U+0080 to U+00FF.
inline std::string latin1_to_utf8(const uint8_t *data, size_t length) {
  if (length == 0) {
    return std::string();
  }

  // Fast path: if all bytes are ASCII, direct copy
  if (is_ascii_fallback(reinterpret_cast<const char *>(data), length)) {
    return std::string(reinterpret_cast<const char *>(data), length);
  }

  // Calculate exact output size to avoid reallocation
  // ASCII bytes (< 128) need 1 byte, non-ASCII need 2 bytes in UTF-8
  size_t utf8_len = 0;
  for (size_t i = 0; i < length; ++i) {
    utf8_len += (data[i] < 128) ? 1 : 2;
  }

  std::string result;
  result.resize(utf8_len);
  char *out = &result[0];

  for (size_t i = 0; i < length; ++i) {
    uint8_t byte = data[i];
    if (byte < 128) {
      *out++ = static_cast<char>(byte);
    } else {
      // Latin1 byte 128-255 maps to U+0080 to U+00FF
      // UTF-8 encoding: 110xxxxx 10xxxxxx
      *out++ = static_cast<char>(0xC0 | (byte >> 6));
      *out++ = static_cast<char>(0x80 | (byte & 0x3F));
    }
  }

  return result;
}

// Convert UTF-16 code units to UTF-8 string.
// Handles surrogate pairs for characters outside BMP.