thodg/cl-unix-cybernetics/core/properties.lisp

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• Hash : b0ab5bb5
  Author : Thomas de Grivel
  Date : 2022-12-04T18:50:53
  

  cl-unix-cybernetics

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• core/properties.lisp

• ;; cl-unix-cybernetics
  ;; Copyright 2013-2022 Thomas de Grivel <thodg@kmx.io>
  ;;
  ;; Permission is hereby granted to use this software granted
  ;; the above copyright notice and this permission paragraph
  ;; are included in all copies and substantial portions of this
  ;; software.
  ;;
  ;; THIS SOFTWARE IS PROVIDED "AS-IS" WITHOUT ANY GUARANTEE OF
  ;; PURPOSE AND PERFORMANCE. IN NO EVENT WHATSOEVER SHALL THE
  ;; AUTHOR BE CONSIDERED LIABLE FOR THE USE AND PERFORMANCE OF
  ;; THIS SOFTWARE.
  
  (in-package :cl-unix-cybernetics)
  
  ;;  Properties implemented as property lists
  
  (defun properties (&rest keys-and-values)
    (apply #'list keys-and-values))
  
  (defmacro properties* (&rest vars)
    (when (and (consp (first vars))
               (endp (rest vars)))
      (setq vars (first vars)))
    (let ((properties))
      (loop
         (when (endp vars)
           (return))
         (let ((v (pop vars)))
           (push (make-keyword v) properties)
           (push v properties)))
      (cons 'list
            (nreverse properties))))
  
  (defmacro values* (&rest vars)
    (when (and (consp (first vars))
               (endp (rest vars)))
      (setq vars (first vars)))
    `(values ,@vars))
  
  (defmacro get-property (property properties)
    `(getf ,properties ,property +undefined+))
  
  (defun get-properties (keys properties)
    (let ((plist))
      (loop
         (when (endp keys)
           (return))
         (let* ((k (pop keys))
                (v (get-property k properties)))
           (unless (eq v +undefined+)
             (push k plist)
             (push v plist))))
      (nreverse plist)))
  
  (defmethod compare-property-values (resource property value1 value2)
    (equalp value1 value2))
  
  (defmethod compare-property-values (resource property
                                      (value1 local-time:timestamp)
                                      (value2 local-time:timestamp))
    (local-time:timestamp= value1 value2))
  
  (defmethod merge-property-values (resource property (old null) new)
    new)
  
  (defmethod merge-property-values (resource property old new)
    (unless (compare-property-values resource property old new)
      (warn "Conflicting values for property ~A in
  ~A
   old: ~S
   new: ~S
  Keeping old value by default."
            property resource old new)
      old))
  
  (defun merge-properties (resource &rest properties)
    (let* ((result (pop properties))
           (tail (last result)))
      (flet ((push-result (&rest args)
               (dolist (x args)
                 (let ((new-tail (list x)))
                   (if (endp result)
                       (setf result new-tail
                             tail new-tail)
                       (setf (cdr tail) new-tail
                             tail new-tail))))))
        (dolist (plist properties)
          (loop
             (when (endp plist)
               (return))
             (let* ((key (pop plist))
                    (val (pop plist))
                    (result-val (getf result key +undefined+)))
               (cond ((eq result-val +undefined+)
                      (push-result key val))
                     ((not (equalp result-val val))
                      (setf (getf result key)
                            (merge-property-values resource key result-val val))))))))
      result))
  

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