compress.lisp

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   2 ;;; Copyright (c) 2007 Zachary Beane, All Rights Reserved
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  28
  29 (in-package #:salza2)
  30
  31 (defun compress (input chains start end
  32                  literal-fun length-fun distance-fun)
  33   (declare (type input-buffer input)
  34            (type chains-buffer chains)
  35            (type input-index start end)
  36            (type function literal-fun length-fun distance-fun)
  37            (optimize speed))
  38   (let ((p start))
  39     (loop
  40      (when (= p end)
  41        (return))
  42      (multiple-value-bind (length distance)
  43          (longest-match p input chains end 4)
  44        (declare (type (integer 0 258) length)
  45                 (type (integer 0 32768) distance))
  46        (cond ((zerop length)
  47               (funcall literal-fun (aref input p))
  48               (setf p (logand (+ p 1) #xFFFF)))
  49              (t
  50               (funcall length-fun length)
  51               (funcall distance-fun distance)
  52               (setf p (logand (+ p length) #xFFFF))))))))