C/C++ multiple pointers?

Ok so I've been thinking about this for some time, and i can only come up with one solution. My problem is the following: -> Im handeling a USB flash -> I split its size in 3 parts -> I have 3 threads, each one with a pointer, and the 3 parts are distributed to the tree threads;

Now this is the part that bugs my head: If i only have one handle handeling the usb and if, for each thread, i set a pointer using the only handle i have, it will be a reall mess.

Theard 1 sets the pointer to 0;

Thread 2 sets the pointer to 100;

Thread 3 sets the pointer to 500;

The pointer will be, for each thread, at 500 because it will be the last place he will be.

I want to make so that every thread starts in a individual place. I think the only solution to my problem is to have diferent handles for each thread, but i find that solution pretty bad and unpractic. I would love if someone knows of a better solution to my problem! Regardless, thanks!

This is the 2 functions im using (hanlde and the pointer):

Pointer:

DWORD WINAPI SetFilePointer( _In_ HANDLE hFile, _In_ LONG lDistanceToMove, _Inout_opt_ PLONG lpDistanceToMoveHigh, _In_ DWORD dwMoveMethod );

Handler:

    HANDLE WINAPI CreateFile(
      _In_     LPCTSTR               lpFileName,
      _In_     DWORD                 dwDesiredAccess,
  _In_     DWORD                 dwShareMode,
  _In_opt_ LPSECURITY_ATTRIBUTES lpSecurityAttributes,
  _In_     DWORD                 dwCreationDisposition,
  _In_opt_ HANDLE                hTemplateFile
  _In_     DWORD                 dwFlagsAndAttributes,
);

Solution

You cannot have multiple file pointers to the same file (or rather, same file object). There are few ways around that:

open same file (device in your case) several times, that will get you independent file objects and each will have its own current position.
use I/O operations which don't use current position pointers, e.g. async I/O like WriteFileEx
(as a variation on the previous idea) use memory-mapped I/O, i.e. MapViewOfFile