anchor.diff:  (defun decode-chunk (image scan s)
     "Reads and decodes either a whole scan (if no restarts) or restart interval"
     (let* ((nextbit (make-nextbit 0 0))
  -	 (ncomp (scan-ncomp scan))
  +         (ncomp (scan-ncomp scan))
            (nwidth (mul (descriptor-width image) (descriptor-ncomp image)))
            (dend (mul (descriptor-height image) nwidth))
  -	 (fr (make-array ncomp :initial-contents 
  +         (fr (make-array ncomp :initial-contents
                            (loop for i fixnum from 0 below ncomp ;collecting sampling rates for a components in the scan
                                  for cid fixnum = (first (svref (scan-cdesc scan) i))
                                  for pos fixnum = (position cid (descriptor-cid image))
  
positive.code:                  (if (= k 63)
                       (return zz)
                     (incf k))))))
            
  ;;; Decodes DC value
  (defun decode-dc (maxcode mincode valptr huffval nextbit s)
    "Decodes DC value"
  
negative.code:           for tc fixnum = (ash tcth -4)
            for th fixnum = (logand tcth 15)
            for tables = (if (zerop tc)
                             (svref (descriptor-huff-ac image) th)
                           (svref (descriptor-huff-dc image) th))
            for bits = (huffstruct-bits tables)
            for sum fixnum = 0 do
            (loop for i fixnum from 0 to 15
  