;; Copyright (C) Johan Ceuppens 2013
;;
;; This program is free software: you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
;; the Free Software Foundation, either version 2 of the License, or
;; (at your option) any later version.
;;
;; This program is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;; GNU General Public License for more details.
;;
;; You should have received a copy of the GNU General Public License
;; along with this program.  If not, see <http://www.gnu.org/licenses/>.

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; Fixed chunk size gc, can be used in meta-gc.scm API
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
(load "stringutil.scm")

(define (make-sized-gc)
  (let ((*heap '())
	(*null '())
	(*max-datasize 1024)	
	(*datasize 0)	
	(*currentn 0) ;; right write mark	
	(*max-chunksize 8)	
	(*dynamic-data '())	
	)
    
    (define (malloc)
      (add-to-heap! 1)
      )

    (define (calloc nchunks)
      (add-to-heap! nchunks)
      )

    ;; private procedures
    
    (define (get-heap) *heap)
    
    ;; data is a string
    (define (get-data-size d) (string-length d))
    
    (define (generate-error msg)
      (cond ((eq? msg 'memory-exhausted)
	     (display "memory exhausted")(newline))
	    ))
    
    (define (add-to-heap! n)
      ((lambda (n)
	 (if (= n 0)
	     '()
	     (append (list (make-chunk)) (add-to-heap! (- n 1)))))))
    
    (define (make-chunk)
      (cons 'chunk *null))  
    
    ;;NOTE append null string after <8
    ;; data is a string
    (define (split-data data)
      (let ((split-data-func (lambda (datastr) 
			       (append (list (substring datastr 0 8))
4				       (cond ((< (string-length datastr) 8)
					      datastr)
					     (else
					      ;; this might be a guilism
					      (split-data-func (substring data 8 (string-length data)))))))
			     ))
	(split-data-func data)))

    (define (split-data2 data)
      (let ((split-data-func2 (lambda (datalist)
			       (append (sublist datalist 0 8)
				       (cond ((< (length datalist) 8)
					      datalist)
					     (else
					      (split-data-func2 (sublist datalist 8 (- (string-length datalist) 8)))))))))
	(map split-data-func2 (string->list data))))
    
    ;; FIX over *currentn
    (define (set-data-rec! lst n)
      (cond ((= n (length lst))
	     '())
	    ;; reverses
	    (else (append (list (list-ref lst n))
			  (set-data-rec! lst (- n 1))))))

    (define (set-data! chunk data)
      (let* ((lst (split-data data)))
	(set! *heap (set-data-rec! lst (length lst)))
	(set! *currentn (+ n *currentn))
	))
    
    (define (set-chunk-data! chunk)
      (set! *datasize (+ *datasize (get-data-size chunk)))
      (if (> *datasize *max-datasize) 
	  (generate-error 'memory-exhausted)
	  ;; The data is dynamically bound in this actor
	  (set-data! chunk *dynamic-data)
	  ))
    
    (define (dispatch msg)
      (cond ((eq? msg 'malloc) malloc)	
	    ((eq? msg 'calloc) calloc)
	    (else (display "make-gc : message not understood : ")(display msg)(newline))
	    ))
    dispatch))