anchor.diff:        (unless final
           (skein-increment-counter tweak block-length))
         (skein-update-cipher block-length cipher-key cipher-tweak value tweak)
  -      (encrypt cipher buffer ciphertext)
  +      (funcall encryption-function cipher buffer 0 ciphertext 0)
         (skein-update-tweak tweak :first nil)
         (xor-block block-length ciphertext buffer 0 value 0)
         (setf buffer-length 0))
  
positive.code:       (loop until (<= message-length block-length) do
          (skein-increment-counter tweak block-length)
          (skein-update-cipher block-length cipher-key cipher-tweak value tweak)
          (encrypt cipher message ciphertext
                   :plaintext-start message-start
                   :plaintext-end (+ message-start block-length))
          (xor-block block-length ciphertext message message-start value 0)
          (incf message-start block-length)
          (decf message-length block-length)))
  
negative.code:            (type integer start end)
             #.(burn-baby-burn))
    (let* ((cipher (skein-cipher state))
           (encryption-function (encrypt-function cipher))
           (cipher-key (threefish-key cipher))
           (cipher-tweak (threefish-tweak cipher))
           (block-length (block-length state))
  