QByteArray转int

//注意大小端
 int MainWindow::byteAraryToInt(QByteArray arr, bool endian)
 {
 int res = 0;
 if (arr.size() == 4){
 if (endian == false)// 小端模式
 {
 res = arr.at(0) & 0x000000FF;
 res |= (arr.at(1) << 8) & 0x0000FF00;
 res |= (arr.at(2) << 16) & 0x00FF0000;
 res |= (arr.at(3) << 24) & 0xFF000000;
 }
 else // 大端模式
 {
 res = (arr.at(0) << 24) & 0xFF000000;
 res |= (arr.at(1) << 16) & 0x00FF0000;
 res |= arr.at(2) << 8 & 0x0000FF00;
 res |= arr.at(3) & 0x000000FF;
 }
 }else if(arr.size() == 2){
 if (endian == false){
 res |= arr.at(0) << 8 & 0x0000FF00;
 res |= arr.at(1) & 0x000000FF;
 }else{
 res = arr.at(0) & 0x000000FF;
 res |= (arr.at(1) << 8) & 0x0000FF00;
 }
 }
 return res;
 }