anchor.diff:  (defun temp-path (base ext)
     (format nil "~A.~A.~A" base ext (gentemp)))
   
  +(defun copy-stream (from to buffer)
  +  (let ((read (read-sequence buffer from)))
  +    (write-sequence buffer to :end read)
  +    (when (= read (length buffer))
  +      (copy-stream from to buffer))))
  +
   (defun concat-files (output-filepath &rest input-filepaths)
     (muffle
      (with-open-file (out output-filepath :element-type 'octet
  
positive.code:      (dolist (input-filepath input-filepaths)
         (with-open-file (in input-filepath :element-type 'octet)
           (write-bigendian-uint4 (file-length in) out)))
  
       (dolist (input-filepath input-filepaths)
         (with-open-file (in input-filepath :element-type 'octet)
           (let ((buf (make-array (file-length in) :element-type 'octet)))
             (read-sequence buf in)
             (write-sequence buf out)))))))
  
  ;;;;;;;;;;;;;;;;;;
  ;;; build function
  
negative.code: (declaim #.*fastest*
           (inline set-base set-chck set-opts))
  
  ;;;;;;;;;;;;
  ;;; constant
  (defconstant +BUFFER_SIZE+ 819200)
  
  ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
  ;;; da (abbreviation of "double array")
  (defstruct da
  