Function assign_utf8_in_place

app/src/DataModel/Frame.h:895–919

* @brief Writes UTF-8 bytes into a QString, reusing the destination buffer for ASCII payloads. The * widen runs branchless (OR-accumulating the high bit instead of an in-loop early return) so * it auto-vectorizes; a single non-ASCII byte then redoes the rare frame via * QString::fromUtf8. */

 * QString::fromUtf8.
 */
SS_FORCE_INLINE void assign_utf8_in_place(QString& dst, QByteArrayView src)
{
  const char* p     = src.data();
  const qsizetype n = src.size();

  Q_ASSERT(n >= 0);

  if (!(dst.isDetached() && dst.capacity() >= n)) {
    dst = QString();
    dst.reserve(qMax<qsizetype>(n, 8));
  }

  dst.resize(n);
  QChar* out = dst.data();

  uchar nonAscii = 0;
  for (qsizetype i = 0; i < n; ++i) {
    const uchar c  = static_cast<uchar>(p[i]);
    nonAscii      |= c;
    out[i]         = QChar(static_cast<char16_t>(c));
  }

  if (nonAscii & 0x80) [[unlikely]]
    dst = QString::fromUtf8(p, n);
}

/**
 * @brief Copies per-frame volatile state (source id + dataset values) into a structure-matched dst.