Thread: Loading files into memory

I stopped coding for about a year and a half ago. So I'm trying to find things to brush up on. At the moment it's file i/o.

I'm not exactly sure what is wrong with my code, but when I go to check what I loaded into memory by outputting it to the consol, I am getting weird numbers.

Code:

#include <fstream>

using namespace std;

class BitmapPic
{
    private:
            
        //bitmap fileheader(info about file)
        typedef struct Bitmap_FileHeader
        {
            unsigned short bfType;//WORD
            unsigned long bfSize;//DWORD
            unsigned short bfReserved1;
            unsigned short bfReserved2;
            unsigned long bfOffBits;
        };//total:14 bytes
        
        //bitmap infoheader:(info on contents of file)
        typedef struct Bitmap_InfoHeader
        {
            unsigned long biSize;//DWORD
            unsigned long biWidth;
            unsigned long biHeigth;
            unsigned short biPlanes;//WORD
            unsigned short biBitCount;
            unsigned long biCompression;
            unsigned long biSizeImage;
            unsigned long biXPelsPerMeter;
            unsigned long biYPelsPerMeter;
            unsigned long biClrUsed;
            unsigned long biClrImportant;
        };//total: 40 bytes
        
        //structure for containing pixel values.
        typedef struct RGBQuad
        {
            unsigned char rgbBlue;
            unsigned char rgbGreen;
            unsigned char rgbRed;
            unsigned char rgbReserved;
        };

    public:

        Bitmap_FileHeader bmfh;
        Bitmap_InfoHeader bmih;
        RGBQuad aColors[];
        
        void LBmp(char file[]);
};

void BitmapPic::LBmp(char file[])
{
    ifstream infile(file,ios::binary|ios::in);
    infile.read(reinterpret_cast<char*>(&bmfh),sizeof(Bitmap_FileHeader));
    infile.read(reinterpret_cast<char*>(&bmih),sizeof(Bitmap_InfoHeader));
}

The only value that seems to come out true is the first one which is always going to be "19778"

bfSize comes out as 0
biWidth comes out as 18808832
biHeigth comes out as 65536 (2^16)

Easy check: what does your compiler say sizeof(Bitmap_FileHeader) and sizeof(Bitmap_InfoHeader) are? I wouldn't be surprised if the first, at least, is not actually 14.

sizeof(bmp.bmfh) = 16
sizeof(bmp.bmih) = 40

how can I fix that? I'm pretty sure I am using the right sized data in my structures.

You can either make a function that reads in the appropriate bits of the struct separately, or you can do something compiler-specific to "pack" the structure together so that there's no padding bytes in it.

Holy sweet Jesus, Sebastiani! There is a name from back when I was really active on the forums. I hope the years have been kind to you old friend.

it worked, reading it in piece by piece. I wanted to avoid that but meh... actually I did try sizeof(Bitmap_FileHeader) before I just forgot totally about it. I knew it had to do with bytes getting stored in the wrong spot somewhere. For some dumb reason I didn't think "oh my struct is 16bytes and it's only 14bytes"

Anyways, thanks everyone

side note: I'm just practice I/O, I'd like to try loading something like JPEG's into memory once I get a bit better. (eventually for texture mapping in OpenGL). I'd rather texture map other files than uncompressed bmp files. I know I could always use an image library like devIL but I'm just weird =P.

why would they add padding bytes to structs anyways?