Thread: RtlMoveMemory Problem?

I'm just starting to work with c++(using Dev c++) and have ran into a problem. I was following a tutorial and copied and pasted this function into my program, there where some errors but I managed to fix them so it would compile. Now it silently crashes on this line:

Code:

RtlMoveMemory(Bits, pDIB + sizeof(BITMAPINFOHEADER), bih.biSizeImage);

I have provided the function below and have surrounded the crashing line with stars. I would really appreciate any help.

Code:

BOOL CreateFromPackedDIBPointer(LPBYTE pDIB, int iFrame, int framenumber)
{
    if (pDIB!=NULL);
{
    
    //Creates a full-color (no palette) DIB from a pointer to a
    //full-color memory DIB

    //get the BitmapInfoHeader
    BITMAPINFOHEADER bih;
    
    RtlMoveMemory(&bih.biSize, pDIB, sizeof(BITMAPINFOHEADER));

    //now get the bitmap bits
    if (bih.biSizeImage < 1)
    {
        return FALSE;
    }

    BYTE* Bits=new BYTE;

//*****************************************************************************************
    RtlMoveMemory(Bits, pDIB + sizeof(BITMAPINFOHEADER), bih.biSizeImage);
//*****************************************************************************************

    //and BitmapInfo variable-length UDT
    BYTE memBitmapInfo[40];
    RtlMoveMemory(memBitmapInfo, &bih, sizeof(bih));

    BITMAPFILEHEADER bfh;
    bfh.bfType=19778;    //BM header
    bfh.bfSize=55 + bih.biSizeImage;
    bfh.bfReserved1=0;
    bfh.bfReserved2=0;
    bfh.bfOffBits=sizeof(BITMAPINFOHEADER) + sizeof(BITMAPFILEHEADER); //54
    
    FileName=("Frame-",(char)framenumber,".bmp");
    
    FILE* fp=fopen(FileName, "wb");
    if (fp!=NULL)
    {
        fwrite(&bfh, sizeof(bfh), 1, fp);
        fwrite(&memBitmapInfo, sizeof(memBitmapInfo), 1, fp);
        fwrite(Bits, bih.biSizeImage, 1, fp);
        fclose(fp);
    }
    else
    {
        TRACE0(_T("Error writing the bitmap file"));
        return FALSE;
    }

    delete [] Bits;
    return TRUE;
}
}

Thanks for reading!

Maybe you should make Bits point somewhere useful (via new) before trying to use it.

Like I said i'm just getting into c++ and copied and pasted this function but I will try to understand.

You're allocating a single byte and then copying bih.biSizeImage bytes into it. I would presume that bih.biSizeImage is a number greater than one.

Ok, that seems to make sense to me. How about this?

Code:

BYTE* Bits[sizeof(bih.biSizeImage)];

You've also mismatched new and delete[]. I would guess that you meant to use new[] with an appropriate size.

I don't really know why thats there since this function is in a for loop and it seems like it just gets redeclared anyway, but I probably misunderstand somthing.

Maybe you should make Bits point somewhere useful (via new) before trying to use it.

I don't really understand what you mean? Once again me being a "noob" at c++.

Originally Posted by DBProgrammer

Like I said i'm just getting into c++ and copied and pasted this function but I will try to understand.



Ok, that seems to make sense to me. How about this?

Code:

BYTE* Bits[sizeof(bih.biSizeImage)];

I don't really know why thats there since this function is in a for loop and it seems like it just gets redeclared anyway, but I probably misunderstand somthing.



I don't really understand what you mean? Once again me being a "noob" at c++.

I meant exactly what iMalc said, but without all the typing. You need bih.biSizeImage amount of space, as you just said in what I quoted right there, so get it:

Code:

BYTE *Bits = new BYTE[bih.biSizeImage];

And since you are doing new [] to get a bunch of memory, you need delete [] to get rid of it.

Thanks I got it working.