path: root/scanf.scm

;;;;"scanf.scm" implemenation of formated input
;Copyright (C) 1996, 1997 Aubrey Jaffer
;
;Permission to copy this software, to modify it, to redistribute it,
;to distribute modified versions, and to use it for any purpose is
;granted, subject to the following restrictions and understandings.
;
;1.  Any copy made of this software must include this copyright notice
;in full.
;
;2.  I have made no warrantee or representation that the operation of
;this software will be error-free, and I am under no obligation to
;provide any services, by way of maintenance, update, or otherwise.
;
;3.  In conjunction with products arising from the use of this
;material, there shall be no use of my name in any advertising,
;promotional, or sales literature without prior written consent in
;each case.

;;; Originally jjb@isye.gatech.edu (John Bartholdi) wrote some public
;;; domain code for a subset of scanf, but it was too difficult to
;;; extend to POSIX pattern compliance.  Jan 96, I rewrote the scanf
;;; functions starting from the POSIX man pages.

(require 'string-port)

(define (stdio:scan-and-set format-string input-port . args)
  (define setters args)
  (if (equal? '(#f) args) (set! args #f))
  (cond
   ((not (equal? "" format-string))
    (call-with-input-string
     format-string
     (lambda (format-port)

       (define items '())
       (define chars-scanned 0)
       (define assigned-count 0)

       (define (char-non-numeric? c) (not (char-numeric? c)))

       (define (flush-whitespace port)
	 (do ((c (peek-char port) (peek-char port))
	      (i 0 (+ 1 i)))
	     ((or (eof-object? c) (not (char-whitespace? c))) i)
	   (read-char port)))

       (define (flush-whitespace-input)
	 (set! chars-scanned (+ (flush-whitespace input-port) chars-scanned)))

       (define (read-input-char)
	 (set! chars-scanned (+ 1 chars-scanned))
	 (read-char input-port))

       (define (add-item report-field? next-item)
	 (cond (args
		(cond ((and report-field? (null? setters))
		       (slib:error 'scanf "not enough variables for format"
				   format-string))
		      ((not next-item) (return))
		      ((not report-field?) (loop1))
		      (else
		       (let ((suc ((car setters) next-item)))
			 (cond ((not (boolean? suc))
				(slib:warn 'scanf "setter returned non-boolean"
					   suc)))
			 (set! setters (cdr setters))
			 (cond ((not suc) (return))
			       ((eqv? -1 report-field?) (loop1))
			       (else
				(set! assigned-count (+ 1 assigned-count))
				(loop1)))))))
	       ((not next-item) (return))
	       (report-field? (set! items (cons next-item items))
			      (loop1))
	       (else (loop1))))

       (define (return)
	 (cond ((and (zero? chars-scanned)
		     (eof-object? (peek-char input-port)))
		(peek-char input-port))
	       (args assigned-count)
	       (else (reverse items))))

       (define (read-string width separator?)
	 (cond (width
		(let ((str (make-string width)))
		  (do ((i 0 (+ 1 i)))
		      ((>= i width)
		       str)
		    (let ((c (peek-char input-port)))
		      (cond ((eof-object? c)
			     (set! str (substring str 0 i))
			     (set! i width))
			    ((separator? c)
			     (set! str (if (zero? i) "" (substring str 0 i)))
			     (set! i width))
			    (else
			     (string-set! str i (read-input-char))))))))
	       (else
		(do ((c (peek-char input-port) (peek-char input-port))
		     (l '() (cons c l)))
		    ((or (eof-object? c) (separator? c))
		     (list->string (reverse l)))
		  (read-input-char)))))

       (define (read-word width separator?)
	 (let ((l (read-string width separator?)))
	   (if (zero? (string-length l)) #f l)))

       (define (loop1)
	 (define fc (read-char format-port))
	 (cond
	  ((eof-object? fc)
	   (return))
	  ((char-whitespace? fc)
	   (flush-whitespace format-port)
	   (flush-whitespace-input)
	   (loop1))
	  ((eqv? #\% fc)		; interpret next format
	   (set! fc (read-char format-port))
	   (let ((report-field? (not (eqv? #\* fc)))
		 (width #f))

	     (define (width--) (if width (set! width (+ -1 width))))

	     (define (read-u)
	       (string->number (read-string width char-non-numeric?)))

	     (define (read-o)
	       (string->number
		(read-string
		 width
		 (lambda (c) (not (memv c '(#\0 #\1 #\2 #\3 #\4 #\5 #\6 #\7)))))
		8))

	     (define (read-x)
	       (string->number
		(read-string
		 width
		 (lambda (c) (not (memv (char-downcase c)
					'(#\0 #\1 #\2 #\3 #\4 #\5 #\6 #\7 #\8
					      #\9 #\a #\b #\c #\d #\e #\f)))))
		16))

	     (define (read-radixed-unsigned)
	       (let ((c (peek-char input-port)))
		 (case c
		   ((#\0) (read-input-char)
			  (width--)
			  (set! c (peek-char input-port))
			  (case c
			    ((#\x #\X) (read-input-char)
				       (width--)
				       (read-x))
			    (else (read-o))))
		   (else (read-u)))))

	     (define (read-ui)
	       (let* ((dot? #f)
		      (mantissa (read-word
				 width
				 (lambda (c)
				   (not (or (char-numeric? c)
					    (cond (dot? #f)
						  ((eqv? #\. c)
						   (set! dot? #t)
						   #t)
						  (else #f)))))))
		      (exponent (cond
				 ((not mantissa) #f)
				 ((and (or (not width) (> width 1))
				       (memv (peek-char input-port) '(#\E #\e)))
				  (read-input-char)
				  (width--)
				  (let* ((expsign
					  (case (peek-char input-port)
					    ((#\-) (read-input-char)
						   (width--)
						   "-")
					    ((#\+) (read-input-char)
						   (width--)
						   "+")
					    (else "")))
					 (expint
					  (and
					   (or (not width) (positive? width))
					   (read-word width char-non-numeric?))))
				    (and expint (string-append
						 "e" expsign expint))))
				 (else #f))))
		 (and mantissa
		      (string->number
		       (string-append
			"#i" (or mantissa "") (or exponent ""))))))

	     (define (read-signed proc)
	       (case (peek-char input-port)
		 ((#\-) (read-input-char)
			(width--)
			(let ((ret (proc)))
			  (and ret (- ret))))
		 ((#\+) (read-input-char)
			(width--)
			(proc))
		 (else (proc))))

	     ;;(trace read-word read-signed read-ui read-radixed-unsigned read-x read-o read-u)

	     (cond ((not report-field?) (set! fc (read-char format-port))))
	     (if (char-numeric? fc) (set! width 0))
	     (do () ((or (eof-object? fc) (char-non-numeric? fc)))
	       (set! width (+ (* 10 width) (string->number (string fc))))
	       (set! fc (read-char format-port)))
	     (case fc			;ignore h,l,L modifiers.
	       ((#\h #\l #\L) (set! fc (read-char format-port))))
	     (case fc
	       ((#\n) (if (not report-field?)
			  (slib:error 'scanf "not saving %n??"))
		      (add-item -1 chars-scanned)) ;-1 is special flag.
	       ((#\c #\C)
		(if (not width) (set! width 1))
		(let ((str (make-string width)))
		  (do ((i 0 (+ 1 i))
		       (c (peek-char input-port) (peek-char input-port)))
		      ((or (>= i width)
			   (eof-object? c))
		       (add-item report-field? (substring str 0 i)))
		    (string-set! str i (read-input-char)))))
	       ((#\s #\S)
		;;(flush-whitespace-input)
		(add-item report-field? (read-word width char-whitespace?)))
	       ((#\[)
		(set! fc (read-char format-port))
		(let ((allbut #f))
		  (case fc
		    ((#\^) (set! allbut #t)
			   (set! fc (read-char format-port))))

		  (let scanloop ((scanset (list fc)))
		    (set! fc (read-char format-port))
		    (case fc
		      ((#\-)
		       (set! fc (peek-char format-port))
		       (cond
			((and (char<? (car scanset) fc)
			      (not (eqv? #\] fc)))
			 (set! fc (char->integer fc))
			 (do ((i (char->integer (car scanset)) (+ 1 i)))
			     ((> i fc) (scanloop scanset))
			   (set! scanset (cons (integer->char i) scanset))))
			(else (scanloop (cons #\- scanset)))))
		      ((#\])
		       (add-item report-field?
				 (read-word
				  width
				  (if allbut (lambda (c) (memv c scanset))
				      (lambda (c) (not (memv c scanset)))))))
		      (else (cond
			     ((eof-object? fc)
			      (slib:error 'scanf "unmatched [ in format"))
			     (else (scanloop (cons fc scanset)))))))))
	       ((#\o #\O)
		;;(flush-whitespace-input)
		(add-item report-field? (read-o)))
	       ((#\u #\U)
		;;(flush-whitespace-input)
		(add-item report-field? (read-u)))
	       ((#\d #\D)
		;;(flush-whitespace-input)
		(add-item report-field? (read-signed read-u)))
	       ((#\x #\X)
		;;(flush-whitespace-input)
		(add-item report-field? (read-x)))
	       ((#\e #\E #\f #\F #\g #\G)
		;;(flush-whitespace-input)
		(add-item report-field? (read-signed read-ui)))
	       ((#\i)
		;;(flush-whitespace-input)
		(add-item report-field? (read-signed read-radixed-unsigned)))
	       ((#\%)
		(cond ((or width (not report-field?))
		       (slib:error 'SCANF "%% has modifiers?"))
		      ((eqv? #\% (read-input-char))
		       (loop1))
		      (else (return))))
	       (else (slib:error 'SCANF
				 "Unknown format directive:" fc)))))
	  ((eqv? (peek-char input-port) fc)
	   (read-input-char)
	   (loop1))
	  (else (return))))
       ;;(trace flush-whitespace-input flush-whitespace add-item return read-string read-word loop1)
       (loop1))))
   (args 0)
   (else '())))

;;;This implements a Scheme-oriented version of SCANF: returns a list of
;;;objects read (rather than set!-ing values).

(define (scanf-read-list format-string . optarg)
  (define input-port
    (cond ((null? optarg) (current-input-port))
	  ((not (null? (cdr optarg)))
	   (slib:error 'scanf-read-list 'wrong-number-of-args optarg))
	  (else (car optarg))))
  (cond ((input-port? input-port)
	 (stdio:scan-and-set format-string input-port #f))
	((string? input-port)
	 (call-with-input-string
	  input-port (lambda (input-port)
		       (stdio:scan-and-set format-string input-port #f))))
	(else (slib:error 'scanf-read-list "argument 2 not a port"
			  input-port))))

(define (stdio:setter-procedure sexp)
  (let ((v (gentemp)))
    (cond ((symbol? sexp) `(lambda (,v) (set! ,sexp ,v) #t))
	  ((not (and (pair? sexp) (list? sexp)))
	   (slib:error 'scanf "setter expression not understood" sexp))
	  (else
	   (case (car sexp)
	     ((vector-ref) `(lambda (,v) (vector-set! ,@(cdr sexp) ,v) #t))
	     ((substring)
	      (require 'rev2-procedures)
	      `(lambda (,v) (substring-move-left!
			     ,v 0 (min (string-length ,v)
				       (- ,(cadddr sexp) ,(caddr sexp)))
			     ,(cadr sexp) ,(caddr sexp))
		       #t))
	     ((list-ref)
	      (require 'rev4-optional-procedures)
	      `(lambda (,v) (set-car! (list-tail ,@(cdr sexp)) ,v) #t))
	     ((car) `(lambda (,v) (set-car! ,@(cdr sexp) ,v) #t))
	     ((cdr) `(lambda (,v) (set-cdr! ,@(cdr sexp) ,v) #t))
	     (else (slib:error 'scanf "setter not known" sexp)))))))

(defmacro scanf (format-string . args)
  `(stdio:scan-and-set ,format-string (current-input-port)
		       ,@(map stdio:setter-procedure args)))

(defmacro sscanf (str format-string . args)
  `(call-with-input-string
    ,str (lambda (input-port)
	   (stdio:scan-and-set ,format-string input-port
			       ,@(map stdio:setter-procedure args)))))

(defmacro fscanf (input-port format-string . args)
  `(stdio:scan-and-set ,format-string ,input-port
		       ,@(map stdio:setter-procedure args)))