creating and storing QByteArray from std::vector raw data

user4592357

i'm creating a QByteArray from std::vector's raw data, and storing the byte array in variant list.
QByteArray docs say deep copy of data is made (https://doc.qt.io/qt-5/qbytearray.html#QByteArray-1).
but when i print the byte array when it is stored and when it is used, i get different bytes.

this is my code, am i doing something incorrectly?

	std::vector<unsigned char> bytes;
	auto writtenBytes = encodePoints(points, bytes);

	QByteArray baOffsets(reinterpret_cast<const char *>(bytes.data()), writtenBytes);
	m_queryBoundValues.append(baOffsets);

jsulm

@user4592357 said in creating and storing QByteArray from std::vector raw data:

but when i print the byte array when it is stored and when it is used

How do you print and what do you mean by "stored" and "used"?

user4592357

@jsulm

std::cout << baOffsets.toStdString() << std::endl;

i mean, i store the byte array in m_queryBoundValues, then read it from there (in another function, so i think vector data is deleted by then).

jsulm

@user4592357 Try to compare https://doc.qt.io/qt-5/qbytearray.html#length instead of printing as string (0 bytes are interpreted as end-of-string).
Also, how do you use and print m_queryBoundValues?
Do you have an example of what is printed for both?

user4592357

@jsulm
okay, m_queryBoundValues is QVariantList, so i'm actually converting byte array to variant while storing it.
i'm using the byte array as QSql::ParamType(QSql::In | QSql::Binary) type bound value for sql query, but i just checked there's no variant to byte array conversion...

i was also getting this error, so i'm thinking the lack of conversion may be the problem?

~$ c++filt _ZN8QVariantaSERKS_
QVariant::operator=(QVariant const&)

i have a nested data structure:

// type aliases
using tQueryBoundValues = QVariantList; // bound values for one query
using tQueryValues2Type = QPair<tQueryBoundValues, QSql::ParamType>;
using tAllQueriesBoundValues = QList<tQueryValues2Type>; // bound values for list of queries
using tTable2AllQueriesValues = QHash<QString, tAllQueriesBoundValues>; // bound values for all queries
using tQuery2BoundData = QHash<EQuery, tTable2AllQueriesValues>;

tQuery2BoundData m_mapQuery2BoundValues;

this is the usage:

for (EQuery queryType : m_mapQuery2BoundValues.keys())
{
  QString sQueryPattern = pQueries->get(queryType);
  const auto &queryTableDataMap = m_mapQuery2BoundValues[queryType];

  for (const QString &sTable : queryTableDataMap.keys())
  {
    m_sqlQuery.prepare(sTable.isEmpty() ? sQueryPattern : sQueryPattern.arg(sTable));

    for (const auto &boundValueType : queryTableDataMap[sTable])
      m_sqlQuery.addBindValue(QVariant::fromValue(boundValueType.first), boundValueType.second);

    if (!m_sqlQuery.execBatch())
      return err = makeErrorString(m_sqlQuery.lastError().text()), false;
  }
}

user4592357

@jsulm
nevermind, i found what i was missing, i bound less parameter than i actually had in my query, so i got that error.