xref: /titanic_41/usr/src/cmd/sendmail/libsm/vfscanf.c (revision ea394cb00fd96864e34d2841b4a22357b621c78f)
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 #pragma ident	"%Z%%M%	%I%	%E% SMI"
16 
17 #include <sm/gen.h>
18 SM_IDSTR(id, "@(#)$Id: vfscanf.c,v 1.54 2006/10/12 22:03:52 ca Exp $")
19 
20 #include <ctype.h>
21 #include <stdlib.h>
22 #include <errno.h>
23 #include <setjmp.h>
24 #include <sm/time.h>
25 #include <sm/varargs.h>
26 #include <sm/config.h>
27 #include <sm/io.h>
28 #include <sm/signal.h>
29 #include <sm/clock.h>
30 #include <sm/string.h>
31 #include "local.h"
32 
33 #define BUF		513	/* Maximum length of numeric string. */
34 
35 /* Flags used during conversion. */
36 #define LONG		0x01	/* l: long or double */
37 #define SHORT		0x04	/* h: short */
38 #define QUAD		0x08	/* q: quad (same as ll) */
39 #define SUPPRESS	0x10	/* suppress assignment */
40 #define POINTER		0x20	/* weird %p pointer (`fake hex') */
41 #define NOSKIP		0x40	/* do not skip blanks */
42 
43 /*
44 **  The following are used in numeric conversions only:
45 **  SIGNOK, NDIGITS, DPTOK, and EXPOK are for floating point;
46 **  SIGNOK, NDIGITS, PFXOK, and NZDIGITS are for integral.
47 */
48 
49 #define SIGNOK		0x080	/* +/- is (still) legal */
50 #define NDIGITS		0x100	/* no digits detected */
51 
52 #define DPTOK		0x200	/* (float) decimal point is still legal */
53 #define EXPOK		0x400	/* (float) exponent (e+3, etc) still legal */
54 
55 #define PFXOK		0x200	/* 0x prefix is (still) legal */
56 #define NZDIGITS	0x400	/* no zero digits detected */
57 
58 /* Conversion types. */
59 #define CT_CHAR		0	/* %c conversion */
60 #define CT_CCL		1	/* %[...] conversion */
61 #define CT_STRING	2	/* %s conversion */
62 #define CT_INT		3	/* integer, i.e., strtoll or strtoull */
63 #define CT_FLOAT	4	/* floating, i.e., strtod */
64 
65 static void		scanalrm __P((int));
66 static unsigned char	*sm_sccl __P((char *, unsigned char *));
67 static jmp_buf		ScanTimeOut;
68 
69 /*
70 **  SCANALRM -- handler when timeout activated for sm_io_vfscanf()
71 **
72 **  Returns flow of control to where setjmp(ScanTimeOut) was set.
73 **
74 **	Parameters:
75 **		sig -- unused
76 **
77 **	Returns:
78 **		does not return
79 **
80 **	Side Effects:
81 **		returns flow of control to setjmp(ScanTimeOut).
82 **
83 **	NOTE:	THIS CAN BE CALLED FROM A SIGNAL HANDLER.  DO NOT ADD
84 **		ANYTHING TO THIS ROUTINE UNLESS YOU KNOW WHAT YOU ARE
85 **		DOING.
86 */
87 
88 /* ARGSUSED0 */
89 static void
90 scanalrm(sig)
91 	int sig;
92 {
93 	longjmp(ScanTimeOut, 1);
94 }
95 
96 /*
97 **  SM_VFSCANF -- convert input into data units
98 **
99 **	Parameters:
100 **		fp -- file pointer for input data
101 **		timeout -- time intvl allowed to complete (milliseconds)
102 **		fmt0 -- format for finding data units
103 **		ap -- vectors for memory location for storing data units
104 **
105 **	Results:
106 **		Success: number of data units assigned
107 **		Failure: SM_IO_EOF
108 */
109 
110 int
111 sm_vfscanf(fp, timeout, fmt0, ap)
112 	register SM_FILE_T *fp;
113 	int SM_NONVOLATILE timeout;
114 	char const *fmt0;
115 	va_list SM_NONVOLATILE ap;
116 {
117 	register unsigned char *SM_NONVOLATILE fmt = (unsigned char *) fmt0;
118 	register int c;		/* character from format, or conversion */
119 	register size_t width;	/* field width, or 0 */
120 	register char *p;	/* points into all kinds of strings */
121 	register int n;		/* handy integer */
122 	register int flags;	/* flags as defined above */
123 	register char *p0;	/* saves original value of p when necessary */
124 	int nassigned;		/* number of fields assigned */
125 	int nread;		/* number of characters consumed from fp */
126 	int base;		/* base argument to strtoll/strtoull */
127 
128 	/* conversion function (strtoll/strtoull) */
129 	ULONGLONG_T (*ccfn) __P((const char *, char **, int));
130 	char ccltab[256];	/* character class table for %[...] */
131 	char buf[BUF];		/* buffer for numeric conversions */
132 	SM_EVENT *evt = NULL;
133 
134 	/* `basefix' is used to avoid `if' tests in the integer scanner */
135 	static short basefix[17] =
136 		{ 10, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16 };
137 
138 	if (timeout == SM_TIME_DEFAULT)
139 		timeout = fp->f_timeout;
140 	if (timeout == SM_TIME_IMMEDIATE)
141 	{
142 		/*
143 		**  Filling the buffer will take time and we are wanted to
144 		**  return immediately. So...
145 		*/
146 
147 		errno = EAGAIN;
148 		return SM_IO_EOF;
149 	}
150 
151 	if (timeout != SM_TIME_FOREVER)
152 	{
153 		if (setjmp(ScanTimeOut) != 0)
154 		{
155 			errno = EAGAIN;
156 			return SM_IO_EOF;
157 		}
158 
159 		evt = sm_seteventm(timeout, scanalrm, 0);
160 	}
161 
162 	nassigned = 0;
163 	nread = 0;
164 	base = 0;		/* XXX just to keep gcc happy */
165 	ccfn = NULL;		/* XXX just to keep gcc happy */
166 	for (;;)
167 	{
168 		c = *fmt++;
169 		if (c == 0)
170 		{
171 			if (evt != NULL)
172 				sm_clrevent(evt); /*  undo our timeout */
173 			return nassigned;
174 		}
175 		if (isspace(c))
176 		{
177 			while ((fp->f_r > 0 || sm_refill(fp, SM_TIME_FOREVER)
178 						== 0) &&
179 			    isspace(*fp->f_p))
180 				nread++, fp->f_r--, fp->f_p++;
181 			continue;
182 		}
183 		if (c != '%')
184 			goto literal;
185 		width = 0;
186 		flags = 0;
187 
188 		/*
189 		**  switch on the format.  continue if done;
190 		**  break once format type is derived.
191 		*/
192 
193 again:		c = *fmt++;
194 		switch (c)
195 		{
196 		  case '%':
197 literal:
198 			if (fp->f_r <= 0 && sm_refill(fp, SM_TIME_FOREVER))
199 				goto input_failure;
200 			if (*fp->f_p != c)
201 				goto match_failure;
202 			fp->f_r--, fp->f_p++;
203 			nread++;
204 			continue;
205 
206 		  case '*':
207 			flags |= SUPPRESS;
208 			goto again;
209 		  case 'h':
210 			flags |= SHORT;
211 			goto again;
212 		  case 'l':
213 			if (*fmt == 'l')
214 			{
215 				fmt++;
216 				flags |= QUAD;
217 			}
218 			else
219 			{
220 				flags |= LONG;
221 			}
222 			goto again;
223 		  case 'q':
224 			flags |= QUAD;
225 			goto again;
226 
227 		  case '0': case '1': case '2': case '3': case '4':
228 		  case '5': case '6': case '7': case '8': case '9':
229 			width = width * 10 + c - '0';
230 			goto again;
231 
232 		/*
233 		**  Conversions.
234 		**  Those marked `compat' are for 4.[123]BSD compatibility.
235 		**
236 		**  (According to ANSI, E and X formats are supposed
237 		**  to the same as e and x.  Sorry about that.)
238 		*/
239 
240 		  case 'D':	/* compat */
241 			flags |= LONG;
242 			/* FALLTHROUGH */
243 		  case 'd':
244 			c = CT_INT;
245 			ccfn = (ULONGLONG_T (*)())sm_strtoll;
246 			base = 10;
247 			break;
248 
249 		  case 'i':
250 			c = CT_INT;
251 			ccfn = (ULONGLONG_T (*)())sm_strtoll;
252 			base = 0;
253 			break;
254 
255 		  case 'O':	/* compat */
256 			flags |= LONG;
257 			/* FALLTHROUGH */
258 		  case 'o':
259 			c = CT_INT;
260 			ccfn = sm_strtoull;
261 			base = 8;
262 			break;
263 
264 		  case 'u':
265 			c = CT_INT;
266 			ccfn = sm_strtoull;
267 			base = 10;
268 			break;
269 
270 		  case 'X':
271 		  case 'x':
272 			flags |= PFXOK;	/* enable 0x prefixing */
273 			c = CT_INT;
274 			ccfn = sm_strtoull;
275 			base = 16;
276 			break;
277 
278 		  case 'E':
279 		  case 'G':
280 		  case 'e':
281 		  case 'f':
282 		  case 'g':
283 			c = CT_FLOAT;
284 			break;
285 
286 		  case 's':
287 			c = CT_STRING;
288 			break;
289 
290 		  case '[':
291 			fmt = sm_sccl(ccltab, fmt);
292 			flags |= NOSKIP;
293 			c = CT_CCL;
294 			break;
295 
296 		  case 'c':
297 			flags |= NOSKIP;
298 			c = CT_CHAR;
299 			break;
300 
301 		  case 'p':	/* pointer format is like hex */
302 			flags |= POINTER | PFXOK;
303 			c = CT_INT;
304 			ccfn = sm_strtoull;
305 			base = 16;
306 			break;
307 
308 		  case 'n':
309 			if (flags & SUPPRESS)	/* ??? */
310 				continue;
311 			if (flags & SHORT)
312 				*SM_VA_ARG(ap, short *) = nread;
313 			else if (flags & LONG)
314 				*SM_VA_ARG(ap, long *) = nread;
315 			else
316 				*SM_VA_ARG(ap, int *) = nread;
317 			continue;
318 
319 		/* Disgusting backwards compatibility hacks.	XXX */
320 		  case '\0':	/* compat */
321 			if (evt != NULL)
322 				sm_clrevent(evt); /*  undo our timeout */
323 			return SM_IO_EOF;
324 
325 		  default:	/* compat */
326 			if (isupper(c))
327 				flags |= LONG;
328 			c = CT_INT;
329 			ccfn = (ULONGLONG_T (*)()) sm_strtoll;
330 			base = 10;
331 			break;
332 		}
333 
334 		/* We have a conversion that requires input. */
335 		if (fp->f_r <= 0 && sm_refill(fp, SM_TIME_FOREVER))
336 			goto input_failure;
337 
338 		/*
339 		**  Consume leading white space, except for formats
340 		**  that suppress this.
341 		*/
342 
343 		if ((flags & NOSKIP) == 0)
344 		{
345 			while (isspace(*fp->f_p))
346 			{
347 				nread++;
348 				if (--fp->f_r > 0)
349 					fp->f_p++;
350 				else if (sm_refill(fp, SM_TIME_FOREVER))
351 					goto input_failure;
352 			}
353 			/*
354 			**  Note that there is at least one character in
355 			**  the buffer, so conversions that do not set NOSKIP
356 			**  can no longer result in an input failure.
357 			*/
358 		}
359 
360 		/* Do the conversion. */
361 		switch (c)
362 		{
363 		  case CT_CHAR:
364 			/* scan arbitrary characters (sets NOSKIP) */
365 			if (width == 0)
366 				width = 1;
367 			if (flags & SUPPRESS)
368 			{
369 				size_t sum = 0;
370 				for (;;)
371 				{
372 					if ((size_t) (n = fp->f_r) < width)
373 					{
374 						sum += n;
375 						width -= n;
376 						fp->f_p += n;
377 						if (sm_refill(fp,
378 							      SM_TIME_FOREVER))
379 						{
380 							if (sum == 0)
381 								goto input_failure;
382 							break;
383 						}
384 					}
385 					else
386 					{
387 						sum += width;
388 						fp->f_r -= width;
389 						fp->f_p += width;
390 						break;
391 					}
392 				}
393 				nread += sum;
394 			}
395 			else
396 			{
397 				size_t r;
398 
399 				r = sm_io_read(fp, SM_TIME_FOREVER,
400 						(void *) SM_VA_ARG(ap, char *),
401 						width);
402 				if (r == 0)
403 					goto input_failure;
404 				nread += r;
405 				nassigned++;
406 			}
407 			break;
408 
409 		  case CT_CCL:
410 			/* scan a (nonempty) character class (sets NOSKIP) */
411 			if (width == 0)
412 				width = (size_t)~0;	/* `infinity' */
413 
414 			/* take only those things in the class */
415 			if (flags & SUPPRESS)
416 			{
417 				n = 0;
418 				while (ccltab[*fp->f_p] != '\0')
419 				{
420 					n++, fp->f_r--, fp->f_p++;
421 					if (--width == 0)
422 						break;
423 					if (fp->f_r <= 0 &&
424 					    sm_refill(fp, SM_TIME_FOREVER))
425 					{
426 						if (n == 0) /* XXX how? */
427 							goto input_failure;
428 						break;
429 					}
430 				}
431 				if (n == 0)
432 					goto match_failure;
433 			}
434 			else
435 			{
436 				p0 = p = SM_VA_ARG(ap, char *);
437 				while (ccltab[*fp->f_p] != '\0')
438 				{
439 					fp->f_r--;
440 					*p++ = *fp->f_p++;
441 					if (--width == 0)
442 						break;
443 					if (fp->f_r <= 0 &&
444 					    sm_refill(fp, SM_TIME_FOREVER))
445 					{
446 						if (p == p0)
447 							goto input_failure;
448 						break;
449 					}
450 				}
451 				n = p - p0;
452 				if (n == 0)
453 					goto match_failure;
454 				*p = 0;
455 				nassigned++;
456 			}
457 			nread += n;
458 			break;
459 
460 		  case CT_STRING:
461 			/* like CCL, but zero-length string OK, & no NOSKIP */
462 			if (width == 0)
463 				width = (size_t)~0;
464 			if (flags & SUPPRESS)
465 			{
466 				n = 0;
467 				while (!isspace(*fp->f_p))
468 				{
469 					n++, fp->f_r--, fp->f_p++;
470 					if (--width == 0)
471 						break;
472 					if (fp->f_r <= 0 &&
473 					    sm_refill(fp, SM_TIME_FOREVER))
474 						break;
475 				}
476 				nread += n;
477 			}
478 			else
479 			{
480 				p0 = p = SM_VA_ARG(ap, char *);
481 				while (!isspace(*fp->f_p))
482 				{
483 					fp->f_r--;
484 					*p++ = *fp->f_p++;
485 					if (--width == 0)
486 						break;
487 					if (fp->f_r <= 0 &&
488 					    sm_refill(fp, SM_TIME_FOREVER))
489 						break;
490 				}
491 				*p = 0;
492 				nread += p - p0;
493 				nassigned++;
494 			}
495 			continue;
496 
497 		  case CT_INT:
498 			/* scan an integer as if by strtoll/strtoull */
499 #if SM_CONF_BROKEN_SIZE_T
500 			if (width == 0 || width > sizeof(buf) - 1)
501 				width = sizeof(buf) - 1;
502 #else /* SM_CONF_BROKEN_SIZE_T */
503 			/* size_t is unsigned, hence this optimisation */
504 			if (--width > sizeof(buf) - 2)
505 				width = sizeof(buf) - 2;
506 			width++;
507 #endif /* SM_CONF_BROKEN_SIZE_T */
508 			flags |= SIGNOK | NDIGITS | NZDIGITS;
509 			for (p = buf; width > 0; width--)
510 			{
511 				c = *fp->f_p;
512 
513 				/*
514 				**  Switch on the character; `goto ok'
515 				**  if we accept it as a part of number.
516 				*/
517 
518 				switch (c)
519 				{
520 
521 				/*
522 				**  The digit 0 is always legal, but is
523 				**  special.  For %i conversions, if no
524 				**  digits (zero or nonzero) have been
525 				**  scanned (only signs), we will have
526 				**  base==0.  In that case, we should set
527 				**  it to 8 and enable 0x prefixing.
528 				**  Also, if we have not scanned zero digits
529 				**  before this, do not turn off prefixing
530 				**  (someone else will turn it off if we
531 				**  have scanned any nonzero digits).
532 				*/
533 
534 				  case '0':
535 					if (base == 0)
536 					{
537 						base = 8;
538 						flags |= PFXOK;
539 					}
540 					if (flags & NZDIGITS)
541 					    flags &= ~(SIGNOK|NZDIGITS|NDIGITS);
542 					else
543 					    flags &= ~(SIGNOK|PFXOK|NDIGITS);
544 					goto ok;
545 
546 				/* 1 through 7 always legal */
547 				  case '1': case '2': case '3':
548 				  case '4': case '5': case '6': case '7':
549 					base = basefix[base];
550 					flags &= ~(SIGNOK | PFXOK | NDIGITS);
551 					goto ok;
552 
553 				/* digits 8 and 9 ok iff decimal or hex */
554 				  case '8': case '9':
555 					base = basefix[base];
556 					if (base <= 8)
557 						break;	/* not legal here */
558 					flags &= ~(SIGNOK | PFXOK | NDIGITS);
559 					goto ok;
560 
561 				/* letters ok iff hex */
562 				  case 'A': case 'B': case 'C':
563 				  case 'D': case 'E': case 'F':
564 				  case 'a': case 'b': case 'c':
565 				  case 'd': case 'e': case 'f':
566 
567 					/* no need to fix base here */
568 					if (base <= 10)
569 						break;	/* not legal here */
570 					flags &= ~(SIGNOK | PFXOK | NDIGITS);
571 					goto ok;
572 
573 				/* sign ok only as first character */
574 				  case '+': case '-':
575 					if (flags & SIGNOK)
576 					{
577 						flags &= ~SIGNOK;
578 						goto ok;
579 					}
580 					break;
581 
582 				/* x ok iff flag still set & 2nd char */
583 				  case 'x': case 'X':
584 					if (flags & PFXOK && p == buf + 1)
585 					{
586 						base = 16;	/* if %i */
587 						flags &= ~PFXOK;
588 						goto ok;
589 					}
590 					break;
591 				}
592 
593 				/*
594 				**  If we got here, c is not a legal character
595 				**  for a number.  Stop accumulating digits.
596 				*/
597 
598 				break;
599 		ok:
600 				/* c is legal: store it and look at the next. */
601 				*p++ = c;
602 				if (--fp->f_r > 0)
603 					fp->f_p++;
604 				else if (sm_refill(fp, SM_TIME_FOREVER))
605 					break;		/* SM_IO_EOF */
606 			}
607 
608 			/*
609 			**  If we had only a sign, it is no good; push
610 			**  back the sign.  If the number ends in `x',
611 			**  it was [sign] '0' 'x', so push back the x
612 			**  and treat it as [sign] '0'.
613 			*/
614 
615 			if (flags & NDIGITS)
616 			{
617 				if (p > buf)
618 					(void) sm_io_ungetc(fp, SM_TIME_DEFAULT,
619 							    *(unsigned char *)--p);
620 				goto match_failure;
621 			}
622 			c = ((unsigned char *)p)[-1];
623 			if (c == 'x' || c == 'X')
624 			{
625 				--p;
626 				(void) sm_io_ungetc(fp, SM_TIME_DEFAULT, c);
627 			}
628 			if ((flags & SUPPRESS) == 0)
629 			{
630 				ULONGLONG_T res;
631 
632 				*p = 0;
633 				res = (*ccfn)(buf, (char **)NULL, base);
634 				if (flags & POINTER)
635 					*SM_VA_ARG(ap, void **) =
636 					    (void *)(long) res;
637 				else if (flags & QUAD)
638 					*SM_VA_ARG(ap, LONGLONG_T *) = res;
639 				else if (flags & LONG)
640 					*SM_VA_ARG(ap, long *) = res;
641 				else if (flags & SHORT)
642 					*SM_VA_ARG(ap, short *) = res;
643 				else
644 					*SM_VA_ARG(ap, int *) = res;
645 				nassigned++;
646 			}
647 			nread += p - buf;
648 			break;
649 
650 		  case CT_FLOAT:
651 			/* scan a floating point number as if by strtod */
652 			if (width == 0 || width > sizeof(buf) - 1)
653 				width = sizeof(buf) - 1;
654 			flags |= SIGNOK | NDIGITS | DPTOK | EXPOK;
655 			for (p = buf; width; width--)
656 			{
657 				c = *fp->f_p;
658 
659 				/*
660 				**  This code mimicks the integer conversion
661 				**  code, but is much simpler.
662 				*/
663 
664 				switch (c)
665 				{
666 
667 				  case '0': case '1': case '2': case '3':
668 				  case '4': case '5': case '6': case '7':
669 				  case '8': case '9':
670 					flags &= ~(SIGNOK | NDIGITS);
671 					goto fok;
672 
673 				  case '+': case '-':
674 					if (flags & SIGNOK)
675 					{
676 						flags &= ~SIGNOK;
677 						goto fok;
678 					}
679 					break;
680 				  case '.':
681 					if (flags & DPTOK)
682 					{
683 						flags &= ~(SIGNOK | DPTOK);
684 						goto fok;
685 					}
686 					break;
687 				  case 'e': case 'E':
688 
689 					/* no exponent without some digits */
690 					if ((flags&(NDIGITS|EXPOK)) == EXPOK)
691 					{
692 						flags =
693 						    (flags & ~(EXPOK|DPTOK)) |
694 						    SIGNOK | NDIGITS;
695 						goto fok;
696 					}
697 					break;
698 				}
699 				break;
700 		fok:
701 				*p++ = c;
702 				if (--fp->f_r > 0)
703 					fp->f_p++;
704 				else if (sm_refill(fp, SM_TIME_FOREVER))
705 					break;	/* SM_IO_EOF */
706 			}
707 
708 			/*
709 			**  If no digits, might be missing exponent digits
710 			**  (just give back the exponent) or might be missing
711 			**  regular digits, but had sign and/or decimal point.
712 			*/
713 
714 			if (flags & NDIGITS)
715 			{
716 				if (flags & EXPOK)
717 				{
718 					/* no digits at all */
719 					while (p > buf)
720 						(void) sm_io_ungetc(fp,
721 							     SM_TIME_DEFAULT,
722 							     *(unsigned char *)--p);
723 					goto match_failure;
724 				}
725 
726 				/* just a bad exponent (e and maybe sign) */
727 				c = *(unsigned char *) --p;
728 				if (c != 'e' && c != 'E')
729 				{
730 					(void) sm_io_ungetc(fp, SM_TIME_DEFAULT,
731 							    c); /* sign */
732 					c = *(unsigned char *)--p;
733 				}
734 				(void) sm_io_ungetc(fp, SM_TIME_DEFAULT, c);
735 			}
736 			if ((flags & SUPPRESS) == 0)
737 			{
738 				double res;
739 
740 				*p = 0;
741 				res = strtod(buf, (char **) NULL);
742 				if (flags & LONG)
743 					*SM_VA_ARG(ap, double *) = res;
744 				else
745 					*SM_VA_ARG(ap, float *) = res;
746 				nassigned++;
747 			}
748 			nread += p - buf;
749 			break;
750 		}
751 	}
752 input_failure:
753 	if (evt != NULL)
754 		sm_clrevent(evt); /*  undo our timeout */
755 	return nassigned ? nassigned : -1;
756 match_failure:
757 	if (evt != NULL)
758 		sm_clrevent(evt); /*  undo our timeout */
759 	return nassigned;
760 }
761 
762 /*
763 **  SM_SCCL -- sequenced character comparison list
764 **
765 **  Fill in the given table from the scanset at the given format
766 **  (just after `[').  Return a pointer to the character past the
767 **  closing `]'.  The table has a 1 wherever characters should be
768 **  considered part of the scanset.
769 **
770 **	Parameters:
771 **		tab -- array flagging "active" char's to match (returned)
772 **		fmt -- character list (within "[]")
773 **
774 **	Results:
775 */
776 
777 static unsigned char *
778 sm_sccl(tab, fmt)
779 	register char *tab;
780 	register unsigned char *fmt;
781 {
782 	register int c, n, v;
783 
784 	/* first `clear' the whole table */
785 	c = *fmt++;		/* first char hat => negated scanset */
786 	if (c == '^')
787 	{
788 		v = 1;		/* default => accept */
789 		c = *fmt++;	/* get new first char */
790 	}
791 	else
792 		v = 0;		/* default => reject */
793 
794 	/* should probably use memset here */
795 	for (n = 0; n < 256; n++)
796 		tab[n] = v;
797 	if (c == 0)
798 		return fmt - 1;	/* format ended before closing ] */
799 
800 	/*
801 	**  Now set the entries corresponding to the actual scanset
802 	**  to the opposite of the above.
803 	**
804 	**  The first character may be ']' (or '-') without being special;
805 	**  the last character may be '-'.
806 	*/
807 
808 	v = 1 - v;
809 	for (;;)
810 	{
811 		tab[c] = v;		/* take character c */
812 doswitch:
813 		n = *fmt++;		/* and examine the next */
814 		switch (n)
815 		{
816 
817 		  case 0:			/* format ended too soon */
818 			return fmt - 1;
819 
820 		  case '-':
821 			/*
822 			**  A scanset of the form
823 			**	[01+-]
824 			**  is defined as `the digit 0, the digit 1,
825 			**  the character +, the character -', but
826 			**  the effect of a scanset such as
827 			**	[a-zA-Z0-9]
828 			**  is implementation defined.  The V7 Unix
829 			**  scanf treats `a-z' as `the letters a through
830 			**  z', but treats `a-a' as `the letter a, the
831 			**  character -, and the letter a'.
832 			**
833 			**  For compatibility, the `-' is not considerd
834 			**  to define a range if the character following
835 			**  it is either a close bracket (required by ANSI)
836 			**  or is not numerically greater than the character
837 			**  we just stored in the table (c).
838 			*/
839 
840 			n = *fmt;
841 			if (n == ']' || n < c)
842 			{
843 				c = '-';
844 				break;	/* resume the for(;;) */
845 			}
846 			fmt++;
847 			do
848 			{
849 				/* fill in the range */
850 				tab[++c] = v;
851 			} while (c < n);
852 #if 1	/* XXX another disgusting compatibility hack */
853 
854 			/*
855 			**  Alas, the V7 Unix scanf also treats formats
856 			**  such as [a-c-e] as `the letters a through e'.
857 			**  This too is permitted by the standard....
858 			*/
859 
860 			goto doswitch;
861 #else
862 			c = *fmt++;
863 			if (c == 0)
864 				return fmt - 1;
865 			if (c == ']')
866 				return fmt;
867 			break;
868 #endif
869 
870 		  case ']':		/* end of scanset */
871 			return fmt;
872 
873 		  default:		/* just another character */
874 			c = n;
875 			break;
876 		}
877 	}
878 	/* NOTREACHED */
879 }
880