;;
;; Conversion of floating-point numbers between IEEE binary
;; representation and decimal string representation.
;;
;; Based on the gdtoa library by David M. Gay
;;

;;
;; This Chicken extension was written by Ivan Raikov.
;;
;; Permission to use, copy, modify, and distribute this software and
;; its documentation for any purpose and without fee is hereby
;; granted, provided that the above copyright notice appear in all
;; copies and that both that the copyright notice and this permission
;; notice appear in supporting documentation.
;;

(module fpio

 (export fp->string string->fp)
		   
 (import scheme chicken data-structures foreign)


(define (fp->string x . rest)
  (let-optionals rest ((ndig 0 ))
    (let* ((bufsize (max (+ ndig 20) 1024))
	   (buffer (make-blob bufsize)))
      (dtoa buffer x ndig bufsize))))


(define (string->fp s . rest)
  (let-optionals rest ((rounding 'toward-zero ))
      (strtord s (case rounding
		   ((toward-zero) 0)
		   ((nearest)     1)
		   ((toward+Inf)  2)
		   ((toward-Inf)  3)))))

#>
#include <gdtoa.h>
<#

;; strtord(CONST char *s, char **sp, int rounding, double *d)
;;	rounding_mode values:
;;		0 = toward zero
;;		1 = nearest
;;		2 = toward +Infinity
;;		3 = toward -Infinity
 
(define strtord 
  (foreign-lambda* double ((nonnull-c-string s) (integer rounding))
#<<END
   
    char *sp; double n;

    strtord (s, &sp, rounding, &n);

    C_return(n);    
END
))

(define dtoa
  (foreign-lambda* nonnull-c-string ((nonnull-blob b) (number x) (integer ndig) (unsigned-int bufsize))
#<<END

   double n = x;

   g_dfmt(b, &n, ndig, bufsize);

   C_return(b);
END
))


)