I'm confused as to what exactly is going on in this code

Here is some code I found for loading Milkshape3f files (ms3d).
When I found it, it was for the most part uncommented, so I added some before posting.

Code:

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        ifstream inputFile( filename, ios::in | ios::binary | ios::nocreate );
        if ( inputFile.fail())
                return false;        // "Couldn't open the model file."

        inputFile.seekg( 0, ios::end );                        //GO TO THE END OF THE FILE
        long fileSize = inputFile.tellg();                //SEE HOW BIG THE FILE IS
        inputFile.seekg( 0, ios::beg );                        //POSITION BACK TO THE BEGINNING SO YOU CAN READ EVERYTHING IN

        byte *pBuffer = new byte[fileSize];                //CREATE A BUFFER TO HOLD EVERYTHING IN THE FILE
        inputFile.read( pBuffer, fileSize );        //READ EVERYTHING INTO PBUFFER UNTIL FILESIZE IS REACHED
        inputFile.close();

        const byte *pPtr = pBuffer;                               
        MS3DHeader *pHeader = ( MS3DHeader* )pPtr;       
       
        //pPTR CONTAINS EVERYTHING IN THE MS3D FILE
        pPtr += sizeof( MS3DHeader );                               

        if ( strncmp( pHeader->m_ID, "MS3D000000", 10 ) != 0 )
                return false; // "Not a valid Milkshape3D model file."

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So basically the buffer contains everything that was stored in the ms3d file. Everything in the ms3d file is read into pBuffer until the filesize is reached (the end of the file).

pPtr is assigned to everything in pBuffer. pHeader (which is a milkshape 3d header) is assigned to pPtr. the sizeof a milkshape 3d header is added to pPtr. Then information in the header is checked to make sure it is a valid ms3d file. The thing I dont' get is why is the sizeof a header added to pPtr (pPtr is everything in pBuffer, pBuffer is everything that is in the file). Shouldn't the header information already be in the file without having to modify any of the buffers?

Not quite sure what you mean. pHeader points to the beginning of the buffer (the header) and pPtr points to the rest of the buffer (after the header, thus adding sizeof(MS3DHeader) to the pointer).

I am curoius shouldnt this

( filename, ios::in | ios::binary | ios::nocreate );

be this

(filename, ios::in || ios::binary || ios::nocreate)


I am curious because I never seen just '|' before. Can anyone explain this to me, plz?


:confused:
I am curious...

Quote:

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-"God must like crazy people!"

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I am one of his crazy people!

:D

The single | is used when you are combining bits. Each of the ios bits are refenced in these names and you combine them together using the single |. The || is used as an or in an if (or similar) statement.

I don't see why the size of a MS3DHeader must be added to pPtr, unless it is just some way of keeping track what you have done with the file.

throughout the entire model loading routine the size of various data types are added to pPtr.

Quote:

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Originally posted by bonkey
The single | is used when you are combining bits. Each of the ios bits are refenced in these names and you combine them together using the single |. The || is used as an or in an if (or similar) statement.

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Thanks BONKEY for the lesson. Cool, learned something different.
Thnxs!
cj

Yes. You add the sizeof() to skip over the header and have pPtr point to the rest of the file, that way pHeader points to the header, and pPtr points to the data.
pPtr->pBuffer
[Header] // Equal to sizeof(MS3DHeader)
[Rest of File]

pBuffer
pHeader->[Header]
pPtr->[Rest of File]

Quote:

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Originally posted by Shadow12345
I don't see why the size of a MS3DHeader must be added to pPtr, unless it is just some way of keeping track what you have done with the file.

throughout the entire model loading routine the size of various data types are added to pPtr.

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pPtr points to the data you're currently interested in, and since pHeader points to the header all the time you can skip it with pPtr.

Try this program and you'll see how it works:

Code:

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#include <iostream.h>

#define Loop(n) for(int i=0; i<n; i++)
#define NrOfIntegers 6

int main()
{
  int Data[NrOfIntegers] = {6, 5, 4, 3, 2, 1};
  int* Pointer = Data;

  //Loop 6 times
  Loop(NrOfIntegers)
  {
      //Print the integers in the array
      cout << *Pointer << endl;
      Pointer++;
  }

  return 0;
}

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Yes, actually, what you both (Eibro and Magos) said makes sense. That program did help too, i just imagined pointer was pPtr and data was the file. The higher the value of pointer the further into the file it will look. I think it clicked.