; -*- Mode: Scheme; Syntax: Scheme; Package: bare-machine; -*-

;;;; ASCII character conversion

(define ascii-chars
  (string-append "........."
		 (list->string '(#\tab #\newline #\. #\page))
		 "..................."
		 " !\"#$%&'()*+,-./0123456789:;<=>?"
		 "@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_"
		 "`abcdefghijklmnopqrstuvwxyz{|}~"))

(define native-chars
  (let ((t (make-table)))
    (let loop ((a (string->list ascii-chars))
	       (i 0)
	       (least    #f)
	       (greatest #f))
      (cond ((null? a)
	     (let ((v (make-vector (+ (- greatest least) 1))))
	       (do ((i least (+ i 1)))
		   ((> i greatest) (cons least v))
		 (vector-set! v (- i least) (table-ref t i)))))
	    (else
	     (let ((n (char->integer (car a))))
	       (table-set! t n i)
	       (loop (cdr a)
		     (+ i 1)
		     (if least    (min least    n) n)
		     (if greatest (max greatest n) n))))))))

(define (char->ascii char)
  (vector-ref (cdr native-chars)
	      (- (char->integer char) (car native-chars))))

(define[subst] (ascii->char n)
  (string-ref ascii-chars n))