QByteArray int double 转换

QByteArray 转换 

在操作sqlite时 有一个种类型 为blod ，对应就是QByteArray 

有时就需要将一些值 存入QBYTEARRAY，或者 从qbytearray取出值，例 如INT,DOUBLE依次放入BLOB，然后取出，相当 于数组

下面是一些转换

 

void  intToByte(int value,int step ,QByteArray &byteArray)

{

    byteArray[step] = (uchar)  (0x000000ff & value);

    byteArray[step+1] = (uchar) ((0x0000ff00 & value) >> 8);

    byteArray[step+2] = (uchar) ((0x00ff0000 & value) >> 16);

    byteArray[step+3] = (uchar) ((0xff000000 & value) >> 24);

}

int bytesToInt(QByteArray bytes,int step) {

    int addr = bytes[step] & 0x000000FF;

    addr |= ((bytes[step+1] << 8) & 0x0000FF00);

    addr |= ((bytes[step+2] << 16) & 0x00FF0000);

    addr |= ((bytes[step+3] << 24) & 0xFF000000);

    return addr;

}

//举例

下面会将多个INT依次放入QBYTEARRAY

QString str="INSERT INTO temData  VALUES (?)";

    QList<QVariant> lstParameter;

    len = _circleMap.size();

    step=0;

    QByteArray _modelCircleBytes;

    for (size_t i =0; i < len; i ++) {

        CircleItem m_CircleItem = _circleMap[i];

        intToByte(m_CircleItem.Cent.x,step,_modelCircleBytes);

        step=step+4;

        intToByte(m_CircleItem.Cent.y,step,_modelCircleBytes);

        step=step+4;

        intToByte(m_CircleItem.Rad,step,_modelCircleBytes);

        step=step+4;

    }

 lstParameter.push_back(_modelCircleBytes);

再执行数据库操作就实现将多个INT存入SQLITE的BLOB

取出时就调用另一个函数一样的操作

double的转换

//存入

step=0;

    QByteArray _modelLineBytes;

    for (size_t i =0; i < len; i ++) {

        //K,B就double采有MEMCPY

        _modelLineBytes.append(reinterpret_cast<const char*>(&(k)), sizeof(double));

        step=step+sizeof(double);

        _modelLineBytes.append(reinterpret_cast<const char*>(&(b)), sizeof(double));

        step=step+sizeof(double);

    }

取出

 if(tmpByteArray.size() !=0)

        {

            for(int i=0;i<tmpByteArray.size()/16;i++)

            {

                tmpLineItem.k =*reinterpret_cast< double*>(tmpByteArray.data()+step);

                step=step+sizeof(double);

                tmpLineItem.b = *reinterpret_cast< double*>(tmpByteArray.data()+step);

                step=step+sizeof(double);

            }

}