DOCERR: AllocSelector & FreeSelector documentação incompletos

     UINT codeSelector, dataSelector;

   _asm {
        mov ax, cs
        mov codeSelector, ax
        }

   dataSelector = AllocSelector(codeSelector);
   if (!dataSelector)
      return NULL;

   // Change dataSelector from a code selector into a data selector
   if (PrestoChangoSelector(codeSelector, dataSelector))
      {
      // Set the desired base address and limit
      SetSelectorBase(dataSelector, dwLinearBase);
      DPMISetSelectorLimit(dataSelector, dwLimit);
      }
   else
      {
      // If you get here, you couldn't change dataSelector so you need
      // to free it because you can't use it as a code selector
      FreeSelector(dataSelector);
      return NULL;
      }

   // You now have a single data selector. Use it, and then free it by
   // calling FreeSelector.
				

    // The application creates, uses, and frees a huge pointer here
   char __huge * hpMem;

   hpMem = CreateHugePointer (dwBaseAddress, dwLength);

   // hpMem now points to a region of pre-allocated memory, such
   // as a memory-mapped hardware device's buffer. Use it as you
   // would any pointer.

   FreeHugePointer (hpMem);

// The following three functions show how to allocate an array
// of tiled selectors that point to a specified region of memory.

/*--------------------------------------------------------------
  This function creates a huge pointer with the proper number
  of selectors to access physical memory. The huge pointer may be
  used by C or C++ code. dwLinearBase is a 32-bit linear address,
  and dwLength is the number of bytes that the huge pointer will
  be able to access. This function returns the huge pointer if it
  succeeds, or it returns NULL if it fails.
--------------------------------------------------------------*/ 

void __huge * CreateHugePointer (DWORD dwLinearBase,
                                 DWORD dwLength)
   {
   WORD tempSelector = NULL;
   WORD codeSelector = NULL;
   WORD dataSelector = NULL;
   DWORD dwLimit;

   /*
     A segment's limit is defined as the last accessible offset in
     the segment. Because the limit is the last accessible offset, it
     is the desired length of the segment minus 1. For example, if
     you want a 64K segment, then you need a limit of 0xFFFF, not
     0x10000, because the segment contains byte offsets 0 to 0xFFFF.
     Note that a segment with a limit of 0 is actually a single byte
     in length. Thus, this function considers a length of zero
     invalid.
   */ 
   if (dwLength == 0)
      return NULL;

   dwLimit = dwLength - 1;
   /*
     Allocate a single temporary selector by making a copy of the
     code segment selector and converting the copy to a data
     selector. Code segments are always less than or equal to
     64K in length, so you are guaranteed to get a single temporary
     selector and be sure to free a single selector.

     Once you have the temporary selector, set its base address and
     limit to the desired values, which may be larger than 64K.
     Because the memory must be accessed by 16-bit code, you must
     allocate an array of tiled selectors. The temporary selector is
     used to force AllocSelector to allocate an array of the proper
     number of tiled selectors, each with the proper base and limit.
     Then you can free the single temporary selector.

     If you fail anywhere along the way, clean up whatever has been
     done, and return NULL.
   */ 

   _asm {
        mov ax, cs
        mov codeSelector, ax
        }

   tempSelector = AllocSelector (codeSelector);
   if (!tempSelector)
      return NULL;

   /*
     If you can successfully change the tempSelector into a
     data selector, set its base address and limit to the
     desired base and limit, and then allocate the real selector
     array. Otherwise, prepare to return NULL.

     SetSelectorLimit does not handle the granularity bit of
     selectors properly, which limits its usefulness only to ranges
     of addresses less than 1MB in length. This function calls
     DPMISetSelectorLimit, a function defined below, to overcome
     this limitation and allow you to create arrays of tiled
     selectors that can access more than 1MB.
   */ 
   if (PrestoChangoSelector (codeSelector, tempSelector))
      {
      SetSelectorBase(tempSelector, dwLinearBase);
      DPMISetSelectorLimit(tempSelector, dwLimit);
      dataSelector = AllocSelector(tempSelector);
      }
   else
      dataSelector = NULL;

   // Clean up temp selector
   DPMISetSelectorLimit(tempSelector, 0L);
   FreeSelector(tempSelector);

   // dataSelector will be NULL if it could not be allocated
   // successfully, making this function return NULL.
   return (void __huge *)MAKELONG(0, dataSelector);
   }

/*--------------------------------------------------------------
  This function frees pointers allocated by CreateHugePointer.
  It correctly frees all tiled selectors created to access the
  block of physical memory. It is very important that you call
  this on all pointers created by CreateHugePointer and that you
  do not call this function on pointers allocated by any way
  other than using CreateHugePointer.
--------------------------------------------------------------*/ 

void FreeHugePointer (void __huge * hPtr)
   {
   if (hPtr)
      FreeSelector (HIWORD(hPtr));
   }

/*--------------------------------------------------------------
  This function sets the limit of a selector using DPMI Function
  0008h (Set Segment Limit). This function is necessary if the
  segment size is greater than 1 MB because the Windows
  SetSelectorLimit() API function does not correctly set selector
  limits greater than 1 MB.

  Segments that are larger than 1MB are actually page granular,
  meaning that in the descriptor, the limit field is actually
  stored as the number of 4K pages rather than bytes. When you
  specify a limit greater than 1MB, this function rounds it up
  to the nearest page boundary.

  No matter the size of the segment, this function always accepts
  selector limits in number of bytes, never pages. The conversion
  between bytes and pages is handled internally.

  Note that this function takes a segment limit, which is one less
  than the number of bytes in the segment.
--------------------------------------------------------------*/ 

   BOOL DPMISetSelectorLimit (UINT selector, DWORD dwLimit)
   {
      BOOL bRetVal=TRUE;

   // If the limit is >= 1MB, we need to make the limit a mulitple
   // of the page size or DPMISetSelectorLimit will fail.

      if( dwLimit >= 0x100000 )
         dwLimit |= 0x0FFF;

      __asm
      {
         mov  ax, 0008h
         mov  bx, selector
         mov  cx, word ptr [dwLimit+2]
         mov  dx, word ptr [dwLimit]
         int  31h
         jnc  success
         mov  bRetVal, FALSE
       success:
      }
      return bRetVal;
   }