anchor.diff:    ;; use regular CL functions to create the file and check its length
     (let ((path (ensure-file-exists path size)))
   
  -  ;; the file is now created and the correct size 
  -  (let ((fd (with-foreign-string (s path)
  -	      (%open s 
  -		     2 ;; o_rdwr
  -		     600)))) ;; rw
  -    (when (< fd 0)
  -      (get-last-error))
  -    (let ((ptr (%mmap (null-pointer) 
  -		      size 
  -		      3 ;; prot_read | prot_write
  -		      1 ;; map_shared
  -		      fd 
  -		      0)))
  -      (when (invalid-pointer-p ptr)
  -	(%close fd)
  +    ;; the file is now created and the correct size 
  +    (let ((fd (with-foreign-string (s path)
  +		(%open s 
  +		       2 ;; o_rdwr
  +		       600)))) ;; rw
  +      (when (< fd 0)
   	(get-last-error))
  -      (make-mapping :fd fd
  -		    :ptr ptr
  -		    :size size)))))
  +      (let ((ptr (%mmap (null-pointer) 
  +			size 
  +			3 ;; prot_read | prot_write
  +			1 ;; map_shared
  +			fd 
  +			0)))
  +	(when (invalid-pointer-p ptr)
  +	  (%close fd)
  +	  (get-last-error))
  +	(make-mapping :fd fd
  +		      :ptr ptr
  +		      :size size)))))
     
   (defun close-mapping (mapping)
     "Close the file mapping."
  
positive.code:   ;; make sure the file actually exists before mapping it 
    (let ((path (ensure-file-exists path size)))
  
    (let ((fhandle (with-foreign-string (s path)
  		   (%create-file s 
  				 #xC0000000 ;; access == generic_read|generic_write
  				 3 ;; mode == share_read|share_write
  				 (null-pointer) ;; attrs
  				 4 ;; disposition == open always
  				 128 ;; flags == file attribute normal
  				 (null-pointer)))))
      (when (invalid-handle-p fhandle)
        (get-last-error))
      
      (let ((mhandle (%create-file-mapping fhandle
  					 (null-pointer) ;; attrs
  					 4 ;; protect == page_readwrite
  					 0 ;; high
  					 0 ;; low
  					 (null-pointer))))
        (when (null-pointer-p mhandle)
  	(%close-handle fhandle)
  	(get-last-error))
        (let ((ptr (%map-view-of-file mhandle
  				    #x001f ;; access == filemapallaccess
  				    0 ;; low
  				    0 ;; high
  				    size)))
  	(when (null-pointer-p ptr)
  	  (%close-handle mhandle)
  	  (%close-handle fhandle)
  	  (get-last-error))
  	(make-mapping :fhandle fhandle
  		      :mhandle mhandle
  		      :ptr ptr
  		      :size size))))))
  
  (defun close-mapping (mapping)
    "Closes the mapping structure."
  
negative.code: 
  (defun remap (mapping size)
    "Remap the file. SIZE should be the new size."
    (declare (type mapping mapping)
  	   (type integer size))
    (%munmap (mapping-ptr mapping)
  	   (mapping-size mapping))
    ;; write a byte at size
  