xref: /freebsd/contrib/sendmail/libsm/vfscanf.c (revision d056fa046c6a91b90cd98165face0e42a33a5173)
1 /*
2  * Copyright (c) 2000-2001, 2004 Sendmail, Inc. and its suppliers.
3  *      All rights reserved.
4  * Copyright (c) 1990, 1993
5  *	The Regents of the University of California.  All rights reserved.
6  *
7  * This code is derived from software contributed to Berkeley by
8  * Chris Torek.
9  *
10  * By using this file, you agree to the terms and conditions set
11  * forth in the LICENSE file which can be found at the top level of
12  * the sendmail distribution.
13  */
14 
15 #include <sm/gen.h>
16 SM_IDSTR(id, "@(#)$Id: vfscanf.c,v 1.53 2005/06/14 23:07:20 ca Exp $")
17 
18 #include <ctype.h>
19 #include <stdlib.h>
20 #include <errno.h>
21 #include <setjmp.h>
22 #include <sm/time.h>
23 #include <sm/varargs.h>
24 #include <sm/config.h>
25 #include <sm/io.h>
26 #include <sm/signal.h>
27 #include <sm/clock.h>
28 #include <sm/string.h>
29 #include "local.h"
30 
31 #define BUF		513	/* Maximum length of numeric string. */
32 
33 /* Flags used during conversion. */
34 #define LONG		0x01	/* l: long or double */
35 #define SHORT		0x04	/* h: short */
36 #define QUAD		0x08	/* q: quad (same as ll) */
37 #define SUPPRESS	0x10	/* suppress assignment */
38 #define POINTER		0x20	/* weird %p pointer (`fake hex') */
39 #define NOSKIP		0x40	/* do not skip blanks */
40 
41 /*
42 **  The following are used in numeric conversions only:
43 **  SIGNOK, NDIGITS, DPTOK, and EXPOK are for floating point;
44 **  SIGNOK, NDIGITS, PFXOK, and NZDIGITS are for integral.
45 */
46 
47 #define SIGNOK		0x080	/* +/- is (still) legal */
48 #define NDIGITS		0x100	/* no digits detected */
49 
50 #define DPTOK		0x200	/* (float) decimal point is still legal */
51 #define EXPOK		0x400	/* (float) exponent (e+3, etc) still legal */
52 
53 #define PFXOK		0x200	/* 0x prefix is (still) legal */
54 #define NZDIGITS	0x400	/* no zero digits detected */
55 
56 /* Conversion types. */
57 #define CT_CHAR		0	/* %c conversion */
58 #define CT_CCL		1	/* %[...] conversion */
59 #define CT_STRING	2	/* %s conversion */
60 #define CT_INT		3	/* integer, i.e., strtoll or strtoull */
61 #define CT_FLOAT	4	/* floating, i.e., strtod */
62 
63 static void		scanalrm __P((int));
64 static unsigned char	*sm_sccl __P((char *, unsigned char *));
65 static jmp_buf		ScanTimeOut;
66 
67 /*
68 **  SCANALRM -- handler when timeout activated for sm_io_vfscanf()
69 **
70 **  Returns flow of control to where setjmp(ScanTimeOut) was set.
71 **
72 **	Parameters:
73 **		sig -- unused
74 **
75 **	Returns:
76 **		does not return
77 **
78 **	Side Effects:
79 **		returns flow of control to setjmp(ScanTimeOut).
80 **
81 **	NOTE:	THIS CAN BE CALLED FROM A SIGNAL HANDLER.  DO NOT ADD
82 **		ANYTHING TO THIS ROUTINE UNLESS YOU KNOW WHAT YOU ARE
83 **		DOING.
84 */
85 
86 /* ARGSUSED0 */
87 static void
88 scanalrm(sig)
89 	int sig;
90 {
91 	longjmp(ScanTimeOut, 1);
92 }
93 
94 /*
95 **  SM_VFSCANF -- convert input into data units
96 **
97 **	Parameters:
98 **		fp -- file pointer for input data
99 **		timeout -- time intvl allowed to complete (milliseconds)
100 **		fmt0 -- format for finding data units
101 **		ap -- vectors for memory location for storing data units
102 **
103 **	Results:
104 **		Success: number of data units assigned
105 **		Failure: SM_IO_EOF
106 */
107 
108 int
109 sm_vfscanf(fp, timeout, fmt0, ap)
110 	register SM_FILE_T *fp;
111 	int SM_NONVOLATILE timeout;
112 	char const *fmt0;
113 	va_list SM_NONVOLATILE ap;
114 {
115 	register unsigned char *SM_NONVOLATILE fmt = (unsigned char *) fmt0;
116 	register int c;		/* character from format, or conversion */
117 	register size_t width;	/* field width, or 0 */
118 	register char *p;	/* points into all kinds of strings */
119 	register int n;		/* handy integer */
120 	register int flags;	/* flags as defined above */
121 	register char *p0;	/* saves original value of p when necessary */
122 	int nassigned;		/* number of fields assigned */
123 	int nread;		/* number of characters consumed from fp */
124 	int base;		/* base argument to strtoll/strtoull */
125 	ULONGLONG_T (*ccfn)();	/* conversion function (strtoll/strtoull) */
126 	char ccltab[256];	/* character class table for %[...] */
127 	char buf[BUF];		/* buffer for numeric conversions */
128 	SM_EVENT *evt = NULL;
129 
130 	/* `basefix' is used to avoid `if' tests in the integer scanner */
131 	static short basefix[17] =
132 		{ 10, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16 };
133 
134 	if (timeout == SM_TIME_DEFAULT)
135 		timeout = fp->f_timeout;
136 	if (timeout == SM_TIME_IMMEDIATE)
137 	{
138 		/*
139 		**  Filling the buffer will take time and we are wanted to
140 		**  return immediately. So...
141 		*/
142 
143 		errno = EAGAIN;
144 		return SM_IO_EOF;
145 	}
146 
147 	if (timeout != SM_TIME_FOREVER)
148 	{
149 		if (setjmp(ScanTimeOut) != 0)
150 		{
151 			errno = EAGAIN;
152 			return SM_IO_EOF;
153 		}
154 
155 		evt = sm_seteventm(timeout, scanalrm, 0);
156 	}
157 
158 	nassigned = 0;
159 	nread = 0;
160 	base = 0;		/* XXX just to keep gcc happy */
161 	ccfn = NULL;		/* XXX just to keep gcc happy */
162 	for (;;)
163 	{
164 		c = *fmt++;
165 		if (c == 0)
166 		{
167 			if (evt != NULL)
168 				sm_clrevent(evt); /*  undo our timeout */
169 			return nassigned;
170 		}
171 		if (isspace(c))
172 		{
173 			while ((fp->f_r > 0 || sm_refill(fp, SM_TIME_FOREVER)
174 						== 0) &&
175 			    isspace(*fp->f_p))
176 				nread++, fp->f_r--, fp->f_p++;
177 			continue;
178 		}
179 		if (c != '%')
180 			goto literal;
181 		width = 0;
182 		flags = 0;
183 
184 		/*
185 		**  switch on the format.  continue if done;
186 		**  break once format type is derived.
187 		*/
188 
189 again:		c = *fmt++;
190 		switch (c)
191 		{
192 		  case '%':
193 literal:
194 			if (fp->f_r <= 0 && sm_refill(fp, SM_TIME_FOREVER))
195 				goto input_failure;
196 			if (*fp->f_p != c)
197 				goto match_failure;
198 			fp->f_r--, fp->f_p++;
199 			nread++;
200 			continue;
201 
202 		  case '*':
203 			flags |= SUPPRESS;
204 			goto again;
205 		  case 'h':
206 			flags |= SHORT;
207 			goto again;
208 		  case 'l':
209 			if (*fmt == 'l')
210 			{
211 				fmt++;
212 				flags |= QUAD;
213 			}
214 			else
215 			{
216 				flags |= LONG;
217 			}
218 			goto again;
219 		  case 'q':
220 			flags |= QUAD;
221 			goto again;
222 
223 		  case '0': case '1': case '2': case '3': case '4':
224 		  case '5': case '6': case '7': case '8': case '9':
225 			width = width * 10 + c - '0';
226 			goto again;
227 
228 		/*
229 		**  Conversions.
230 		**  Those marked `compat' are for 4.[123]BSD compatibility.
231 		**
232 		**  (According to ANSI, E and X formats are supposed
233 		**  to the same as e and x.  Sorry about that.)
234 		*/
235 
236 		  case 'D':	/* compat */
237 			flags |= LONG;
238 			/* FALLTHROUGH */
239 		  case 'd':
240 			c = CT_INT;
241 			ccfn = (ULONGLONG_T (*)())sm_strtoll;
242 			base = 10;
243 			break;
244 
245 		  case 'i':
246 			c = CT_INT;
247 			ccfn = (ULONGLONG_T (*)())sm_strtoll;
248 			base = 0;
249 			break;
250 
251 		  case 'O':	/* compat */
252 			flags |= LONG;
253 			/* FALLTHROUGH */
254 		  case 'o':
255 			c = CT_INT;
256 			ccfn = sm_strtoull;
257 			base = 8;
258 			break;
259 
260 		  case 'u':
261 			c = CT_INT;
262 			ccfn = sm_strtoull;
263 			base = 10;
264 			break;
265 
266 		  case 'X':
267 		  case 'x':
268 			flags |= PFXOK;	/* enable 0x prefixing */
269 			c = CT_INT;
270 			ccfn = sm_strtoull;
271 			base = 16;
272 			break;
273 
274 		  case 'E':
275 		  case 'G':
276 		  case 'e':
277 		  case 'f':
278 		  case 'g':
279 			c = CT_FLOAT;
280 			break;
281 
282 		  case 's':
283 			c = CT_STRING;
284 			break;
285 
286 		  case '[':
287 			fmt = sm_sccl(ccltab, fmt);
288 			flags |= NOSKIP;
289 			c = CT_CCL;
290 			break;
291 
292 		  case 'c':
293 			flags |= NOSKIP;
294 			c = CT_CHAR;
295 			break;
296 
297 		  case 'p':	/* pointer format is like hex */
298 			flags |= POINTER | PFXOK;
299 			c = CT_INT;
300 			ccfn = sm_strtoull;
301 			base = 16;
302 			break;
303 
304 		  case 'n':
305 			if (flags & SUPPRESS)	/* ??? */
306 				continue;
307 			if (flags & SHORT)
308 				*SM_VA_ARG(ap, short *) = nread;
309 			else if (flags & LONG)
310 				*SM_VA_ARG(ap, long *) = nread;
311 			else
312 				*SM_VA_ARG(ap, int *) = nread;
313 			continue;
314 
315 		/* Disgusting backwards compatibility hacks.	XXX */
316 		  case '\0':	/* compat */
317 			if (evt != NULL)
318 				sm_clrevent(evt); /*  undo our timeout */
319 			return SM_IO_EOF;
320 
321 		  default:	/* compat */
322 			if (isupper(c))
323 				flags |= LONG;
324 			c = CT_INT;
325 			ccfn = (ULONGLONG_T (*)()) sm_strtoll;
326 			base = 10;
327 			break;
328 		}
329 
330 		/* We have a conversion that requires input. */
331 		if (fp->f_r <= 0 && sm_refill(fp, SM_TIME_FOREVER))
332 			goto input_failure;
333 
334 		/*
335 		**  Consume leading white space, except for formats
336 		**  that suppress this.
337 		*/
338 
339 		if ((flags & NOSKIP) == 0)
340 		{
341 			while (isspace(*fp->f_p))
342 			{
343 				nread++;
344 				if (--fp->f_r > 0)
345 					fp->f_p++;
346 				else if (sm_refill(fp, SM_TIME_FOREVER))
347 					goto input_failure;
348 			}
349 			/*
350 			**  Note that there is at least one character in
351 			**  the buffer, so conversions that do not set NOSKIP
352 			**  can no longer result in an input failure.
353 			*/
354 		}
355 
356 		/* Do the conversion. */
357 		switch (c)
358 		{
359 		  case CT_CHAR:
360 			/* scan arbitrary characters (sets NOSKIP) */
361 			if (width == 0)
362 				width = 1;
363 			if (flags & SUPPRESS)
364 			{
365 				size_t sum = 0;
366 				for (;;)
367 				{
368 					if ((size_t) (n = fp->f_r) < width)
369 					{
370 						sum += n;
371 						width -= n;
372 						fp->f_p += n;
373 						if (sm_refill(fp,
374 							      SM_TIME_FOREVER))
375 						{
376 							if (sum == 0)
377 								goto input_failure;
378 							break;
379 						}
380 					}
381 					else
382 					{
383 						sum += width;
384 						fp->f_r -= width;
385 						fp->f_p += width;
386 						break;
387 					}
388 				}
389 				nread += sum;
390 			}
391 			else
392 			{
393 				size_t r;
394 
395 				r = sm_io_read(fp, SM_TIME_FOREVER,
396 						(void *) SM_VA_ARG(ap, char *),
397 						width);
398 				if (r == 0)
399 					goto input_failure;
400 				nread += r;
401 				nassigned++;
402 			}
403 			break;
404 
405 		  case CT_CCL:
406 			/* scan a (nonempty) character class (sets NOSKIP) */
407 			if (width == 0)
408 				width = (size_t)~0;	/* `infinity' */
409 
410 			/* take only those things in the class */
411 			if (flags & SUPPRESS)
412 			{
413 				n = 0;
414 				while (ccltab[*fp->f_p] != '\0')
415 				{
416 					n++, fp->f_r--, fp->f_p++;
417 					if (--width == 0)
418 						break;
419 					if (fp->f_r <= 0 &&
420 					    sm_refill(fp, SM_TIME_FOREVER))
421 					{
422 						if (n == 0) /* XXX how? */
423 							goto input_failure;
424 						break;
425 					}
426 				}
427 				if (n == 0)
428 					goto match_failure;
429 			}
430 			else
431 			{
432 				p0 = p = SM_VA_ARG(ap, char *);
433 				while (ccltab[*fp->f_p] != '\0')
434 				{
435 					fp->f_r--;
436 					*p++ = *fp->f_p++;
437 					if (--width == 0)
438 						break;
439 					if (fp->f_r <= 0 &&
440 					    sm_refill(fp, SM_TIME_FOREVER))
441 					{
442 						if (p == p0)
443 							goto input_failure;
444 						break;
445 					}
446 				}
447 				n = p - p0;
448 				if (n == 0)
449 					goto match_failure;
450 				*p = 0;
451 				nassigned++;
452 			}
453 			nread += n;
454 			break;
455 
456 		  case CT_STRING:
457 			/* like CCL, but zero-length string OK, & no NOSKIP */
458 			if (width == 0)
459 				width = (size_t)~0;
460 			if (flags & SUPPRESS)
461 			{
462 				n = 0;
463 				while (!isspace(*fp->f_p))
464 				{
465 					n++, fp->f_r--, fp->f_p++;
466 					if (--width == 0)
467 						break;
468 					if (fp->f_r <= 0 &&
469 					    sm_refill(fp, SM_TIME_FOREVER))
470 						break;
471 				}
472 				nread += n;
473 			}
474 			else
475 			{
476 				p0 = p = SM_VA_ARG(ap, char *);
477 				while (!isspace(*fp->f_p))
478 				{
479 					fp->f_r--;
480 					*p++ = *fp->f_p++;
481 					if (--width == 0)
482 						break;
483 					if (fp->f_r <= 0 &&
484 					    sm_refill(fp, SM_TIME_FOREVER))
485 						break;
486 				}
487 				*p = 0;
488 				nread += p - p0;
489 				nassigned++;
490 			}
491 			continue;
492 
493 		  case CT_INT:
494 			/* scan an integer as if by strtoll/strtoull */
495 #if SM_CONF_BROKEN_SIZE_T
496 			if (width == 0 || width > sizeof(buf) - 1)
497 				width = sizeof(buf) - 1;
498 #else /* SM_CONF_BROKEN_SIZE_T */
499 			/* size_t is unsigned, hence this optimisation */
500 			if (--width > sizeof(buf) - 2)
501 				width = sizeof(buf) - 2;
502 			width++;
503 #endif /* SM_CONF_BROKEN_SIZE_T */
504 			flags |= SIGNOK | NDIGITS | NZDIGITS;
505 			for (p = buf; width > 0; width--)
506 			{
507 				c = *fp->f_p;
508 
509 				/*
510 				**  Switch on the character; `goto ok'
511 				**  if we accept it as a part of number.
512 				*/
513 
514 				switch (c)
515 				{
516 
517 				/*
518 				**  The digit 0 is always legal, but is
519 				**  special.  For %i conversions, if no
520 				**  digits (zero or nonzero) have been
521 				**  scanned (only signs), we will have
522 				**  base==0.  In that case, we should set
523 				**  it to 8 and enable 0x prefixing.
524 				**  Also, if we have not scanned zero digits
525 				**  before this, do not turn off prefixing
526 				**  (someone else will turn it off if we
527 				**  have scanned any nonzero digits).
528 				*/
529 
530 				  case '0':
531 					if (base == 0)
532 					{
533 						base = 8;
534 						flags |= PFXOK;
535 					}
536 					if (flags & NZDIGITS)
537 					    flags &= ~(SIGNOK|NZDIGITS|NDIGITS);
538 					else
539 					    flags &= ~(SIGNOK|PFXOK|NDIGITS);
540 					goto ok;
541 
542 				/* 1 through 7 always legal */
543 				  case '1': case '2': case '3':
544 				  case '4': case '5': case '6': case '7':
545 					base = basefix[base];
546 					flags &= ~(SIGNOK | PFXOK | NDIGITS);
547 					goto ok;
548 
549 				/* digits 8 and 9 ok iff decimal or hex */
550 				  case '8': case '9':
551 					base = basefix[base];
552 					if (base <= 8)
553 						break;	/* not legal here */
554 					flags &= ~(SIGNOK | PFXOK | NDIGITS);
555 					goto ok;
556 
557 				/* letters ok iff hex */
558 				  case 'A': case 'B': case 'C':
559 				  case 'D': case 'E': case 'F':
560 				  case 'a': case 'b': case 'c':
561 				  case 'd': case 'e': case 'f':
562 
563 					/* no need to fix base here */
564 					if (base <= 10)
565 						break;	/* not legal here */
566 					flags &= ~(SIGNOK | PFXOK | NDIGITS);
567 					goto ok;
568 
569 				/* sign ok only as first character */
570 				  case '+': case '-':
571 					if (flags & SIGNOK)
572 					{
573 						flags &= ~SIGNOK;
574 						goto ok;
575 					}
576 					break;
577 
578 				/* x ok iff flag still set & 2nd char */
579 				  case 'x': case 'X':
580 					if (flags & PFXOK && p == buf + 1)
581 					{
582 						base = 16;	/* if %i */
583 						flags &= ~PFXOK;
584 						goto ok;
585 					}
586 					break;
587 				}
588 
589 				/*
590 				**  If we got here, c is not a legal character
591 				**  for a number.  Stop accumulating digits.
592 				*/
593 
594 				break;
595 		ok:
596 				/* c is legal: store it and look at the next. */
597 				*p++ = c;
598 				if (--fp->f_r > 0)
599 					fp->f_p++;
600 				else if (sm_refill(fp, SM_TIME_FOREVER))
601 					break;		/* SM_IO_EOF */
602 			}
603 
604 			/*
605 			**  If we had only a sign, it is no good; push
606 			**  back the sign.  If the number ends in `x',
607 			**  it was [sign] '0' 'x', so push back the x
608 			**  and treat it as [sign] '0'.
609 			*/
610 
611 			if (flags & NDIGITS)
612 			{
613 				if (p > buf)
614 					(void) sm_io_ungetc(fp, SM_TIME_DEFAULT,
615 							    *(unsigned char *)--p);
616 				goto match_failure;
617 			}
618 			c = ((unsigned char *)p)[-1];
619 			if (c == 'x' || c == 'X')
620 			{
621 				--p;
622 				(void) sm_io_ungetc(fp, SM_TIME_DEFAULT, c);
623 			}
624 			if ((flags & SUPPRESS) == 0)
625 			{
626 				ULONGLONG_T res;
627 
628 				*p = 0;
629 				res = (*ccfn)(buf, (char **)NULL, base);
630 				if (flags & POINTER)
631 					*SM_VA_ARG(ap, void **) =
632 					    (void *)(long) res;
633 				else if (flags & QUAD)
634 					*SM_VA_ARG(ap, LONGLONG_T *) = res;
635 				else if (flags & LONG)
636 					*SM_VA_ARG(ap, long *) = res;
637 				else if (flags & SHORT)
638 					*SM_VA_ARG(ap, short *) = res;
639 				else
640 					*SM_VA_ARG(ap, int *) = res;
641 				nassigned++;
642 			}
643 			nread += p - buf;
644 			break;
645 
646 		  case CT_FLOAT:
647 			/* scan a floating point number as if by strtod */
648 			if (width == 0 || width > sizeof(buf) - 1)
649 				width = sizeof(buf) - 1;
650 			flags |= SIGNOK | NDIGITS | DPTOK | EXPOK;
651 			for (p = buf; width; width--)
652 			{
653 				c = *fp->f_p;
654 
655 				/*
656 				**  This code mimicks the integer conversion
657 				**  code, but is much simpler.
658 				*/
659 
660 				switch (c)
661 				{
662 
663 				  case '0': case '1': case '2': case '3':
664 				  case '4': case '5': case '6': case '7':
665 				  case '8': case '9':
666 					flags &= ~(SIGNOK | NDIGITS);
667 					goto fok;
668 
669 				  case '+': case '-':
670 					if (flags & SIGNOK)
671 					{
672 						flags &= ~SIGNOK;
673 						goto fok;
674 					}
675 					break;
676 				  case '.':
677 					if (flags & DPTOK)
678 					{
679 						flags &= ~(SIGNOK | DPTOK);
680 						goto fok;
681 					}
682 					break;
683 				  case 'e': case 'E':
684 
685 					/* no exponent without some digits */
686 					if ((flags&(NDIGITS|EXPOK)) == EXPOK)
687 					{
688 						flags =
689 						    (flags & ~(EXPOK|DPTOK)) |
690 						    SIGNOK | NDIGITS;
691 						goto fok;
692 					}
693 					break;
694 				}
695 				break;
696 		fok:
697 				*p++ = c;
698 				if (--fp->f_r > 0)
699 					fp->f_p++;
700 				else if (sm_refill(fp, SM_TIME_FOREVER))
701 					break;	/* SM_IO_EOF */
702 			}
703 
704 			/*
705 			**  If no digits, might be missing exponent digits
706 			**  (just give back the exponent) or might be missing
707 			**  regular digits, but had sign and/or decimal point.
708 			*/
709 
710 			if (flags & NDIGITS)
711 			{
712 				if (flags & EXPOK)
713 				{
714 					/* no digits at all */
715 					while (p > buf)
716 						(void) sm_io_ungetc(fp,
717 							     SM_TIME_DEFAULT,
718 							     *(unsigned char *)--p);
719 					goto match_failure;
720 				}
721 
722 				/* just a bad exponent (e and maybe sign) */
723 				c = *(unsigned char *) --p;
724 				if (c != 'e' && c != 'E')
725 				{
726 					(void) sm_io_ungetc(fp, SM_TIME_DEFAULT,
727 							    c); /* sign */
728 					c = *(unsigned char *)--p;
729 				}
730 				(void) sm_io_ungetc(fp, SM_TIME_DEFAULT, c);
731 			}
732 			if ((flags & SUPPRESS) == 0)
733 			{
734 				double res;
735 
736 				*p = 0;
737 				res = strtod(buf, (char **) NULL);
738 				if (flags & LONG)
739 					*SM_VA_ARG(ap, double *) = res;
740 				else
741 					*SM_VA_ARG(ap, float *) = res;
742 				nassigned++;
743 			}
744 			nread += p - buf;
745 			break;
746 		}
747 	}
748 input_failure:
749 	if (evt != NULL)
750 		sm_clrevent(evt); /*  undo our timeout */
751 	return nassigned ? nassigned : -1;
752 match_failure:
753 	if (evt != NULL)
754 		sm_clrevent(evt); /*  undo our timeout */
755 	return nassigned;
756 }
757 
758 /*
759 **  SM_SCCL -- sequenced character comparison list
760 **
761 **  Fill in the given table from the scanset at the given format
762 **  (just after `[').  Return a pointer to the character past the
763 **  closing `]'.  The table has a 1 wherever characters should be
764 **  considered part of the scanset.
765 **
766 **	Parameters:
767 **		tab -- array flagging "active" char's to match (returned)
768 **		fmt -- character list (within "[]")
769 **
770 **	Results:
771 */
772 
773 static unsigned char *
774 sm_sccl(tab, fmt)
775 	register char *tab;
776 	register unsigned char *fmt;
777 {
778 	register int c, n, v;
779 
780 	/* first `clear' the whole table */
781 	c = *fmt++;		/* first char hat => negated scanset */
782 	if (c == '^')
783 	{
784 		v = 1;		/* default => accept */
785 		c = *fmt++;	/* get new first char */
786 	}
787 	else
788 		v = 0;		/* default => reject */
789 
790 	/* should probably use memset here */
791 	for (n = 0; n < 256; n++)
792 		tab[n] = v;
793 	if (c == 0)
794 		return fmt - 1;	/* format ended before closing ] */
795 
796 	/*
797 	**  Now set the entries corresponding to the actual scanset
798 	**  to the opposite of the above.
799 	**
800 	**  The first character may be ']' (or '-') without being special;
801 	**  the last character may be '-'.
802 	*/
803 
804 	v = 1 - v;
805 	for (;;)
806 	{
807 		tab[c] = v;		/* take character c */
808 doswitch:
809 		n = *fmt++;		/* and examine the next */
810 		switch (n)
811 		{
812 
813 		  case 0:			/* format ended too soon */
814 			return fmt - 1;
815 
816 		  case '-':
817 			/*
818 			**  A scanset of the form
819 			**	[01+-]
820 			**  is defined as `the digit 0, the digit 1,
821 			**  the character +, the character -', but
822 			**  the effect of a scanset such as
823 			**	[a-zA-Z0-9]
824 			**  is implementation defined.  The V7 Unix
825 			**  scanf treats `a-z' as `the letters a through
826 			**  z', but treats `a-a' as `the letter a, the
827 			**  character -, and the letter a'.
828 			**
829 			**  For compatibility, the `-' is not considerd
830 			**  to define a range if the character following
831 			**  it is either a close bracket (required by ANSI)
832 			**  or is not numerically greater than the character
833 			**  we just stored in the table (c).
834 			*/
835 
836 			n = *fmt;
837 			if (n == ']' || n < c)
838 			{
839 				c = '-';
840 				break;	/* resume the for(;;) */
841 			}
842 			fmt++;
843 			do
844 			{
845 				/* fill in the range */
846 				tab[++c] = v;
847 			} while (c < n);
848 #if 1	/* XXX another disgusting compatibility hack */
849 
850 			/*
851 			**  Alas, the V7 Unix scanf also treats formats
852 			**  such as [a-c-e] as `the letters a through e'.
853 			**  This too is permitted by the standard....
854 			*/
855 
856 			goto doswitch;
857 #else
858 			c = *fmt++;
859 			if (c == 0)
860 				return fmt - 1;
861 			if (c == ']')
862 				return fmt;
863 			break;
864 #endif
865 
866 		  case ']':		/* end of scanset */
867 			return fmt;
868 
869 		  default:		/* just another character */
870 			c = n;
871 			break;
872 		}
873 	}
874 	/* NOTREACHED */
875 }
876