IReadFile* file not reading my struct

[pararealist]

Hi,

I have a little problem that is driving me crazy.
I have a struct:

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        //! Struct for camera data.
        struct CAMDATA
        {
            vector3df Pos;
            vector3df Rot;
        };      
        CAMDATA *m_camdata;
 

and

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m_camdata = new CAMDATA();
 

Then my write and read functions.

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//Save camera position data.
void CApplication::saveCameraData()
{
    //get camera position.
    m_camdata[0].Pos = m_camera->getAbsolutePosition();
    m_camdata[0].Rot = getCameraRotation();
 
    IWriteFile* file =
        m_smgr->getFileSystem()->createAndWriteFile( "campos/campos.gsx", false);
    if(file)
    {
        file->write(&m_camdata, sizeof(m_camdata));
        file->drop();
    }
}
 
//Load camera position data.
bool CApplication::loadCameraData()
{
    if( (m_smgr->getFileSystem()->existFile("campos/campos.gsx")) )
    {       
        IReadFile* file = m_smgr->getFileSystem()->createMemoryReadFile((char*)&m_camdata,
                            sizeof(m_camdata), "campos/campos.gsx", false);
 
        if(file)
        {
            long lSize = file->getSize();
 
            file->read(&m_camdata, lSize );
            file->drop();
 
            m_defpos = m_camdata.Pos;
            m_defrot = m_camdata.Rot;
 
            return true;
        }
    }
    return false;
}
 

When i debug the write function camdata contains the pos and rot data.
It writes to file.
When i debug the read function it only reads 0,0,0 for both.

It seems the write function is not writing to the file.
Is there something wrong with the write function and then by default the read one?
Thanks for any help.

[randomMesh]

You only write 4 bytes since sizeof a pointer is 4 on most systems. sizeof does not do what you expect.

Next time try to post a minimal compilable example.

[pararealist]

Thanks for your reply.
I could not post full code as these functions are in my application class.
So sizeof is the culprit here?
What is the way to get the correct size then?
I will experiment with pure c++ methods of read writing to file then instead of the irrlicht calls.

[serengeor]

So sizeof is the culprit here?

No, what it gave you was what you asked it for, size of a pointer. If you need to know the size of the object use it on an object or class itself.

[hendu]

Print it out.

printf("sizeof(CAMDATA) = %lu, sizeof(m_camdata) = %lu\n", sizeof(CAMDATA), sizeof(m_camdata))

[pararealist]

These both give the same result.

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sizeof(CAMDATA) = 24 , sizeof(m_camdata) = 24
 

I now use oftream and ifstream which writes and reads it correctly.

BUT
i am doing a separate little project to get my head around what you are telling me
as i prefer to use the irrlicht functions again later.

Thank you.
I am 59 retired, and programming to keep my brain active stop me becoming senile, so thanks for your patience .