RtlMoveMemory Problem?

This is a discussion on RtlMoveMemory Problem? within the C++ Programming forums, part of the General Programming Boards category; I'm just starting to work with c++(using Dev c++) and have ran into a problem. I was following a tutorial ...

  1. #1
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    Question 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!

  2. #2
    Algorithm Dissector iMalc's Avatar
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    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.

    You've also mismatched new and delete[]. I would guess that you meant to use new[] with an appropriate size.
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  3. #3
    and the Hat of Guessing tabstop's Avatar
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    Maybe you should make Bits point somewhere useful (via new) before trying to use it.

  4. #4
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    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++.

  5. #5
    and the Hat of Guessing tabstop's Avatar
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    Quote Originally Posted by DBProgrammer View Post
    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.

  6. #6
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    Thanks I got it working.

  7. #7
    C++まいる!Cをこわせ! Elysia's Avatar
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    When you do:
    T* myvar[size];
    That myvar is of mysize elements and points to... well, that's the problem. You don't know where. Probably nowhere good anyway. Probably to some memory you don't own, so the OS will bark when you try to write or read from there.
    Using the new keyword, on the other hand, asks the OS for some memory for storing n elements of type T and returns that address, so it's valid to read and write to/from there.
    Quote Originally Posted by Adak View Post
    io.h certainly IS included in some modern compilers. It is no longer part of the standard for C, but it is nevertheless, included in the very latest Pelles C versions.
    Quote Originally Posted by Salem View Post
    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

    Outside of your DOS world, your header file is meaningless.

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