c# - p/Invoke WriteFile fails after 8 writes with access denied -

i using p/invoke c# write directly local hd. drive formatted doesn't contain data. trying write 512 bytes of 0s drive until drive complete full.

the code:

for (double idx = 0; idx < totalsectors; idx++)     {         file.write(writebuffer, (uint)writebuffer.length);  // write buffer         int val = pos += (int.parse(bps.tostring()) * int.parse(idx.tostring()));         file.movefilepointer(val);         application.doevents();     } 

as can see iterates process until sectors have been written to. however, reason after 8 iterations receive "access denied" error.

any ideas?

edit xanatos - stupid file position update has been fixed. however, file.movefilepointer() method takes int. casting val (int). method iterates 14 times before throwing "access denied" exception.

edit 2 borrowed code

write method looks this:

 public uint write(byte[] buffer, uint cbtowrite)     {         // returns bytes read         uint cbthatwerewritten = 0;         if (!writefile(_hfile, buffer, cbtowrite,          ref cbthatwerewritten, intptr.zero))             throwlastwin32err();         return cbthatwerewritten;     } 

and file.movefilepointer method looks this:

public void movefilepointer(int cbtomove,      movemethod fmovemethod)     {         if (_hfile != null)             if (setfilepointer(_hfile, cbtomove, intptr.zero,              fmovemethod) == invalid_set_file_pointer)                 throwlastwin32err();     } 

int bps = ... // use int! long totalsectors = ... // use long! long pos = 0; // use long!  (long idx = 0; idx < totalsectors; idx++) {     file.write(writebuffer, (uint)writebuffer.length);  // write buffer     pos += bps;     // file.movefilepointer(pos); // useless, file pointer moved                                   // file.write     application.doevents(); } 

done! increasing pos much!

val = pos += (int.parse(bps.tostring()) * int.parse(idx.tostring())); 

ignoring val, , ignoring parse(...tostring) it's:

pos += bps * idx; 

so

idx = 0, pos += 0 (pos = 0), // here it's wrong! initializing twice                               // same sector! idx = 1, pos += 1 * 512 (pos = 512),  idx = 2, pos += 2 * 512 (pos = 1536) wrong! 

as sidenote, in .net long 64 bits, big enough number of sectors of hard disk, or size.