void convertByteArrayToVector(const QByteArray &qba, vector<unsigned char> &vec)
{
 unsigned int size=qba.size();

 vec.resize(size, 0);

 for(unsigned int i=0; i<size; i++)
  vec[i]=(unsigned char)qba[i];
}


void convertVectorToByteArray(const vector<unsigned char> &vec, QByteArray &qba)
{
 unsigned int size=vec.size();

 qba.resize(size);

 for(unsigned int i=0; i<size; i++)
  qba[i]=(unsigned char)vec[i];
}

vector<unsigned char> v;
v.resize(100);
memcpy(&v[0], someArrayOfSize100, 100 * sizeof(unsigned char));

vector<unsigned char> buf;
...
(char *)(&buf[0])

vector<unsigned char> buf;
...
unsigned char *p = &*buf.begin();

vector<int> dataVec;

int dataArray[] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };
unsigned dataArraySize = sizeof(dataArray) / sizeof(int);

// Method 1: Copy the array to the vector using back_inserter.
{
    copy(&dataArray[0], &dataArray[dataArraySize], back_inserter(dataVec));
}

// Method 2: Same as 1 but pre-extend the vector by the size of the array using reserve
{
    dataVec.reserve(dataVec.size() + dataArraySize);
    copy(&dataArray[0], &dataArray[dataArraySize], back_inserter(dataVec));
}

// Method 3: Memcpy
{
    dataVec.resize(dataVec.size() + dataArraySize);
    memcpy(&dataVec[dataVec.size() - dataArraySize], &dataArray[0], dataArraySize * sizeof(int));
}

// Method 4: vector::insert
{
    dataVec.insert(dataVec.end(), &dataArray[0], &dataArray[dataArraySize]);
}

// Method 5: vector + vector
{
    vector<int> dataVec2(&dataArray[0], &dataArray[dataArraySize]);
    dataVec.insert(dataVec.end(), dataVec2.begin(), dataVec2.end());
}