xref: /dflybsd-src/lib/libc/stdio/vfscanf.c (revision 53e987cee557d989dbf172d8a3c2ade9ea6fc46f)
1 /*-
2  * Copyright (c) 1990, 1993
3  *	The Regents of the University of California.  All rights reserved.
4  *
5  * This code is derived from software contributed to Berkeley by
6  * Chris Torek.
7  *
8  * Redistribution and use in source and binary forms, with or without
9  * modification, are permitted provided that the following conditions
10  * are met:
11  * 1. Redistributions of source code must retain the above copyright
12  *    notice, this list of conditions and the following disclaimer.
13  * 2. Redistributions in binary form must reproduce the above copyright
14  *    notice, this list of conditions and the following disclaimer in the
15  *    documentation and/or other materials provided with the distribution.
16  * 3. All advertising materials mentioning features or use of this software
17  *    must display the following acknowledgement:
18  *	This product includes software developed by the University of
19  *	California, Berkeley and its contributors.
20  * 4. Neither the name of the University nor the names of its contributors
21  *    may be used to endorse or promote products derived from this software
22  *    without specific prior written permission.
23  *
24  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
25  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
26  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
27  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
28  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
29  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
30  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
31  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
32  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
33  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
34  * SUCH DAMAGE.
35  *
36  * @(#)vfscanf.c	8.1 (Berkeley) 6/4/93
37  * $FreeBSD: /repoman/r/ncvs/src/lib/libc/stdio/vfscanf.c,v 1.35 2004/01/31 23:16:09 das Exp $
38  * $DragonFly: src/lib/libc/stdio/vfscanf.c,v 1.7 2005/04/21 16:36:35 joerg Exp $
39  */
40 
41 #include "namespace.h"
42 #include <sys/types.h>
43 #include <stdio.h>
44 #include <stdlib.h>
45 #include <ctype.h>
46 #include <stdarg.h>
47 #include <string.h>
48 #include "un-namespace.h"
49 
50 #include "collate.h"
51 #include "libc_private.h"
52 #include "local.h"
53 
54 #define FLOATING_POINT
55 
56 #ifdef FLOATING_POINT
57 #include <locale.h>
58 #include "floatio.h"
59 #endif
60 
61 #define	BUF		513	/* Maximum length of numeric string. */
62 
63 /*
64  * Flags used during conversion.
65  */
66 #define	LONG		0x01	/* l: long or double */
67 #define	LONGDBL		0x02	/* L: long double */
68 #define	SHORT		0x04	/* h: short */
69 #define	SUPPRESS	0x08	/* suppress assignment */
70 #define	POINTER		0x10	/* weird %p pointer (`fake hex') */
71 #define	NOSKIP		0x20	/* do not skip blanks */
72 #define	QUAD		0x400
73 
74 /*
75  * The following are used in numeric conversions only:
76  * SIGNOK, NDIGITS, DPTOK, and EXPOK are for floating point;
77  * SIGNOK, NDIGITS, PFXOK, and NZDIGITS are for integral.
78  */
79 #define	SIGNOK		0x40	/* +/- is (still) legal */
80 #define	NDIGITS		0x80	/* no digits detected */
81 
82 #define	DPTOK		0x100	/* (float) decimal point is still legal */
83 #define	EXPOK		0x200	/* (float) exponent (e+3, etc) still legal */
84 
85 #define	PFXOK		0x100	/* 0x prefix is (still) legal */
86 #define	NZDIGITS	0x200	/* no zero digits detected */
87 #define	HAVESIGN	0x10000	/* sign detected */
88 
89 /*
90  * Conversion types.
91  */
92 #define	CT_CHAR		0	/* %c conversion */
93 #define	CT_CCL		1	/* %[...] conversion */
94 #define	CT_STRING	2	/* %s conversion */
95 #define	CT_INT		3	/* integer, i.e., strtoq or strtouq */
96 #define	CT_FLOAT	4	/* floating, i.e., strtod */
97 
98 #define u_char unsigned char
99 #define u_long unsigned long
100 
101 static u_char *__sccl(char *, u_char *);
102 
103 /*
104  * __vfscanf MT-safe version
105  */
106 int
107 __vfscanf(FILE *fp, char const *fmt0, va_list ap)
108 {
109 	int ret;
110 
111 	FLOCKFILE(fp);
112 	ret = __svfscanf(fp, fmt0, ap);
113 	FUNLOCKFILE(fp);
114 	return (ret);
115 }
116 
117 /*
118  * __svfscanf - non-MT-safe version of __vfscanf
119  */
120 int
121 __svfscanf(FILE *fp, char const *fmt0, va_list ap)
122 {
123 	u_char *fmt = (u_char *)fmt0;
124 	int c;			/* character from format, or conversion */
125 	size_t width;		/* field width, or 0 */
126 	char *p;		/* points into all kinds of strings */
127 	int n;			/* handy integer */
128 	int flags;		/* flags as defined above */
129 	char *p0;		/* saves original value of p when necessary */
130 	int nassigned;		/* number of fields assigned */
131 	int nconversions;	/* number of conversions */
132 	int nread;		/* number of characters consumed from fp */
133 	int base;		/* base argument to strtoq/strtouq */
134 	u_quad_t(*ccfn)();	/* conversion function (strtoq/strtouq) */
135 	char ccltab[256];	/* character class table for %[...] */
136 	char buf[BUF];		/* buffer for numeric conversions */
137 
138 	/* `basefix' is used to avoid `if' tests in the integer scanner */
139 	static short basefix[17] =
140 		{ 10, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16 };
141 #ifdef FLOATING_POINT
142 	char decimal_point = localeconv()->decimal_point[0];
143 #endif
144 
145 	nassigned = 0;
146 	nconversions = 0;
147 	nread = 0;
148 	base = 0;		/* XXX just to keep gcc happy */
149 	ccfn = NULL;		/* XXX just to keep gcc happy */
150 	for (;;) {
151 		c = *fmt++;
152 		if (c == 0)
153 			return (nassigned);
154 		if (isspace(c)) {
155 			while ((fp->_r > 0 || __srefill(fp) == 0) && isspace(*fp->_p))
156 				nread++, fp->_r--, fp->_p++;
157 			continue;
158 		}
159 		if (c != '%')
160 			goto literal;
161 		width = 0;
162 		flags = 0;
163 		/*
164 		 * switch on the format.  continue if done;
165 		 * break once format type is derived.
166 		 */
167 again:		c = *fmt++;
168 		switch (c) {
169 		case '%':
170 literal:
171 			if (fp->_r <= 0 && __srefill(fp))
172 				goto input_failure;
173 			if (*fp->_p != c)
174 				goto match_failure;
175 			fp->_r--, fp->_p++;
176 			nread++;
177 			continue;
178 
179 		case '*':
180 			flags |= SUPPRESS;
181 			goto again;
182 		case 'l':
183 			flags |= LONG;
184 			goto again;
185 		case 'q':
186 			flags |= QUAD;
187 			goto again;
188 		case 'L':
189 			flags |= LONGDBL;
190 			goto again;
191 		case 'h':
192 			flags |= SHORT;
193 			goto again;
194 
195 		case '0': case '1': case '2': case '3': case '4':
196 		case '5': case '6': case '7': case '8': case '9':
197 			width = width * 10 + c - '0';
198 			goto again;
199 
200 		/*
201 		 * Conversions.
202 		 * Those marked `compat' are for 4.[123]BSD compatibility.
203 		 *
204 		 * (According to ANSI, E and X formats are supposed
205 		 * to the same as e and x.  Sorry about that.)
206 		 */
207 		case 'D':	/* compat */
208 			flags |= LONG;
209 			/* FALLTHROUGH */
210 		case 'd':
211 			c = CT_INT;
212 			ccfn = (u_quad_t (*)())strtoq;
213 			base = 10;
214 			break;
215 
216 		case 'i':
217 			c = CT_INT;
218 			ccfn = (u_quad_t (*)())strtoq;
219 			base = 0;
220 			break;
221 
222 		case 'O':	/* compat */
223 			flags |= LONG;
224 			/* FALLTHROUGH */
225 		case 'o':
226 			c = CT_INT;
227 			ccfn = strtouq;
228 			base = 8;
229 			break;
230 
231 		case 'u':
232 			c = CT_INT;
233 			ccfn = strtouq;
234 			base = 10;
235 			break;
236 
237 		case 'X':	/* compat   XXX */
238 			flags |= LONG;
239 			/* FALLTHROUGH */
240 		case 'x':
241 			flags |= PFXOK;	/* enable 0x prefixing */
242 			c = CT_INT;
243 			ccfn = strtouq;
244 			base = 16;
245 			break;
246 
247 #ifdef FLOATING_POINT
248 		case 'E':	/* compat   XXX */
249 		case 'F':	/* compat */
250 			flags |= LONG;
251 			/* FALLTHROUGH */
252 		case 'e': case 'f': case 'g':
253 			c = CT_FLOAT;
254 			break;
255 #endif
256 
257 		case 's':
258 			c = CT_STRING;
259 			break;
260 
261 		case '[':
262 			fmt = __sccl(ccltab, fmt);
263 			flags |= NOSKIP;
264 			c = CT_CCL;
265 			break;
266 
267 		case 'c':
268 			flags |= NOSKIP;
269 			c = CT_CHAR;
270 			break;
271 
272 		case 'p':	/* pointer format is like hex */
273 			flags |= POINTER | PFXOK;
274 			c = CT_INT;
275 			ccfn = strtouq;
276 			base = 16;
277 			break;
278 
279 		case 'n':
280 			nconversions++;
281 			if (flags & SUPPRESS)	/* ??? */
282 				continue;
283 			if (flags & SHORT)
284 				*va_arg(ap, short *) = nread;
285 			else if (flags & LONG)
286 				*va_arg(ap, long *) = nread;
287 			else if (flags & QUAD)
288 				*va_arg(ap, quad_t *) = nread;
289 			else
290 				*va_arg(ap, int *) = nread;
291 			continue;
292 
293 		/*
294 		 * Disgusting backwards compatibility hacks.	XXX
295 		 */
296 		case '\0':	/* compat */
297 			return (EOF);
298 
299 		default:	/* compat */
300 			if (isupper(c))
301 				flags |= LONG;
302 			c = CT_INT;
303 			ccfn = (u_quad_t (*)())strtoq;
304 			base = 10;
305 			break;
306 		}
307 
308 		/*
309 		 * We have a conversion that requires input.
310 		 */
311 		if (fp->_r <= 0 && __srefill(fp))
312 			goto input_failure;
313 
314 		/*
315 		 * Consume leading white space, except for formats
316 		 * that suppress this.
317 		 */
318 		if ((flags & NOSKIP) == 0) {
319 			while (isspace(*fp->_p)) {
320 				nread++;
321 				if (--fp->_r > 0)
322 					fp->_p++;
323 				else if (__srefill(fp))
324 					goto input_failure;
325 			}
326 			/*
327 			 * Note that there is at least one character in
328 			 * the buffer, so conversions that do not set NOSKIP
329 			 * ca no longer result in an input failure.
330 			 */
331 		}
332 
333 		/*
334 		 * Do the conversion.
335 		 */
336 		switch (c) {
337 
338 		case CT_CHAR:
339 			/* scan arbitrary characters (sets NOSKIP) */
340 			if (width == 0)
341 				width = 1;
342 			if (flags & SUPPRESS) {
343 				size_t sum = 0;
344 				for (;;) {
345 					if ((n = fp->_r) < width) {
346 						sum += n;
347 						width -= n;
348 						fp->_p += n;
349 						if (__srefill(fp)) {
350 							if (sum == 0)
351 							    goto input_failure;
352 							break;
353 						}
354 					} else {
355 						sum += width;
356 						fp->_r -= width;
357 						fp->_p += width;
358 						break;
359 					}
360 				}
361 				nread += sum;
362 			} else {
363 				size_t r = fread((void *)va_arg(ap, char *), 1,
364 				    width, fp);
365 
366 				if (r == 0)
367 					goto input_failure;
368 				nread += r;
369 				nassigned++;
370 			}
371 			nconversions++;
372 			break;
373 
374 		case CT_CCL:
375 			/* scan a (nonempty) character class (sets NOSKIP) */
376 			if (width == 0)
377 				width = (size_t)~0;	/* `infinity' */
378 			/* take only those things in the class */
379 			if (flags & SUPPRESS) {
380 				n = 0;
381 				while (ccltab[*fp->_p]) {
382 					n++, fp->_r--, fp->_p++;
383 					if (--width == 0)
384 						break;
385 					if (fp->_r <= 0 && __srefill(fp)) {
386 						if (n == 0)
387 							goto input_failure;
388 						break;
389 					}
390 				}
391 				if (n == 0)
392 					goto match_failure;
393 			} else {
394 				p0 = p = va_arg(ap, char *);
395 				while (ccltab[*fp->_p]) {
396 					fp->_r--;
397 					*p++ = *fp->_p++;
398 					if (--width == 0)
399 						break;
400 					if (fp->_r <= 0 && __srefill(fp)) {
401 						if (p == p0)
402 							goto input_failure;
403 						break;
404 					}
405 				}
406 				n = p - p0;
407 				if (n == 0)
408 					goto match_failure;
409 				*p = 0;
410 				nassigned++;
411 			}
412 			nread += n;
413 			nconversions++;
414 			break;
415 
416 		case CT_STRING:
417 			/* like CCL, but zero-length string OK, & no NOSKIP */
418 			if (width == 0)
419 				width = (size_t)~0;
420 			if (flags & SUPPRESS) {
421 				n = 0;
422 				while (!isspace(*fp->_p)) {
423 					n++, fp->_r--, fp->_p++;
424 					if (--width == 0)
425 						break;
426 					if (fp->_r <= 0 && __srefill(fp))
427 						break;
428 				}
429 				nread += n;
430 			} else {
431 				p0 = p = va_arg(ap, char *);
432 				while (!isspace(*fp->_p)) {
433 					fp->_r--;
434 					*p++ = *fp->_p++;
435 					if (--width == 0)
436 						break;
437 					if (fp->_r <= 0 && __srefill(fp))
438 						break;
439 				}
440 				*p = 0;
441 				nread += p - p0;
442 				nassigned++;
443 			}
444 			nconversions++;
445 			continue;
446 
447 		case CT_INT:
448 			/* scan an integer as if by strtoq/strtouq */
449 #ifdef hardway
450 			if (width == 0 || width > sizeof(buf) - 1)
451 				width = sizeof(buf) - 1;
452 #else
453 			/* size_t is unsigned, hence this optimisation */
454 			if (--width > sizeof(buf) - 2)
455 				width = sizeof(buf) - 2;
456 			width++;
457 #endif
458 			flags |= SIGNOK | NDIGITS | NZDIGITS;
459 			for (p = buf; width; width--) {
460 				c = *fp->_p;
461 				/*
462 				 * Switch on the character; `goto ok'
463 				 * if we accept it as a part of number.
464 				 */
465 				switch (c) {
466 
467 				/*
468 				 * The digit 0 is always legal, but is
469 				 * special.  For %i conversions, if no
470 				 * digits (zero or nonzero) have been
471 				 * scanned (only signs), we will have
472 				 * base==0.  In that case, we should set
473 				 * it to 8 and enable 0x prefixing.
474 				 * Also, if we have not scanned zero digits
475 				 * before this, do not turn off prefixing
476 				 * (someone else will turn it off if we
477 				 * have scanned any nonzero digits).
478 				 */
479 				case '0':
480 					if (base == 0) {
481 						base = 8;
482 						flags |= PFXOK;
483 					}
484 					if (flags & NZDIGITS)
485 					    flags &= ~(SIGNOK|NZDIGITS|NDIGITS);
486 					else
487 					    flags &= ~(SIGNOK|PFXOK|NDIGITS);
488 					goto ok;
489 
490 				/* 1 through 7 always legal */
491 				case '1': case '2': case '3':
492 				case '4': case '5': case '6': case '7':
493 					base = basefix[base];
494 					flags &= ~(SIGNOK | PFXOK | NDIGITS);
495 					goto ok;
496 
497 				/* digits 8 and 9 ok iff decimal or hex */
498 				case '8': case '9':
499 					base = basefix[base];
500 					if (base <= 8)
501 						break;	/* not legal here */
502 					flags &= ~(SIGNOK | PFXOK | NDIGITS);
503 					goto ok;
504 
505 				/* letters ok iff hex */
506 				case 'A': case 'B': case 'C':
507 				case 'D': case 'E': case 'F':
508 				case 'a': case 'b': case 'c':
509 				case 'd': case 'e': case 'f':
510 					/* no need to fix base here */
511 					if (base <= 10)
512 						break;	/* not legal here */
513 					flags &= ~(SIGNOK | PFXOK | NDIGITS);
514 					goto ok;
515 
516 				/* sign ok only as first character */
517 				case '+': case '-':
518 					if (flags & SIGNOK) {
519 						flags &= ~SIGNOK;
520 						flags |= HAVESIGN;
521 						goto ok;
522 					}
523 					break;
524 
525 				/*
526 				 * x ok iff flag still set & 2nd char (or
527 				 * 3rd char if we have a sign).
528 				 */
529 				case 'x': case 'X':
530 					if (flags & PFXOK && p ==
531 					    buf + 1 + !!(flags & HAVESIGN)) {
532 						base = 16;	/* if %i */
533 						flags &= ~PFXOK;
534 						goto ok;
535 					}
536 					break;
537 				}
538 
539 				/*
540 				 * If we got here, c is not a legal character
541 				 * for a number.  Stop accumulating digits.
542 				 */
543 				break;
544 		ok:
545 				/*
546 				 * c is legal: store it and look at the next.
547 				 */
548 				*p++ = c;
549 				if (--fp->_r > 0)
550 					fp->_p++;
551 				else if (__srefill(fp))
552 					break;		/* EOF */
553 			}
554 			/*
555 			 * If we had only a sign, it is no good; push
556 			 * back the sign.  If the number ends in `x',
557 			 * it was [sign] '0' 'x', so push back the x
558 			 * and treat it as [sign] '0'.
559 			 */
560 			if (flags & NDIGITS) {
561 				if (p > buf)
562 					(void)__ungetc(*(u_char *)--p, fp);
563 				goto match_failure;
564 			}
565 			c = ((u_char *)p)[-1];
566 			if (c == 'x' || c == 'X') {
567 				--p;
568 				(void)__ungetc(c, fp);
569 			}
570 			if ((flags & SUPPRESS) == 0) {
571 				u_quad_t res;
572 
573 				*p = 0;
574 				res = (*ccfn)(buf, (char **)NULL, base);
575 				if (flags & POINTER)
576 					*va_arg(ap, void **) =
577 						(void *)(u_long)res;
578 				else if (flags & SHORT)
579 					*va_arg(ap, short *) = res;
580 				else if (flags & LONG)
581 					*va_arg(ap, long *) = res;
582 				else if (flags & QUAD)
583 					*va_arg(ap, quad_t *) = res;
584 				else
585 					*va_arg(ap, int *) = res;
586 				nassigned++;
587 			}
588 			nread += p - buf;
589 			nconversions++;
590 			break;
591 
592 #ifdef FLOATING_POINT
593 		case CT_FLOAT:
594 			/* scan a floating point number as if by strtod */
595 #ifdef hardway
596 			if (width == 0 || width > sizeof(buf) - 1)
597 				width = sizeof(buf) - 1;
598 #else
599 			/* size_t is unsigned, hence this optimisation */
600 			if (--width > sizeof(buf) - 2)
601 				width = sizeof(buf) - 2;
602 			width++;
603 #endif
604 			flags |= SIGNOK | NDIGITS | DPTOK | EXPOK;
605 			for (p = buf; width; width--) {
606 				c = *fp->_p;
607 				/*
608 				 * This code mimicks the integer conversion
609 				 * code, but is much simpler.
610 				 */
611 				switch (c) {
612 
613 				case '0': case '1': case '2': case '3':
614 				case '4': case '5': case '6': case '7':
615 				case '8': case '9':
616 					flags &= ~(SIGNOK | NDIGITS);
617 					goto fok;
618 
619 				case '+': case '-':
620 					if (flags & SIGNOK) {
621 						flags &= ~SIGNOK;
622 						goto fok;
623 					}
624 					break;
625 				case 'e': case 'E':
626 					/* no exponent without some digits */
627 					if ((flags&(NDIGITS|EXPOK)) == EXPOK) {
628 						flags =
629 						    (flags & ~(EXPOK|DPTOK)) |
630 						    SIGNOK | NDIGITS;
631 						goto fok;
632 					}
633 					break;
634 				default:
635 					if ((char)c == decimal_point &&
636 					    (flags & DPTOK)) {
637 						flags &= ~(SIGNOK | DPTOK);
638 						goto fok;
639 					}
640 					break;
641 				}
642 				break;
643 		fok:
644 				*p++ = c;
645 				if (--fp->_r > 0)
646 					fp->_p++;
647 				else if (__srefill(fp))
648 					break;	/* EOF */
649 			}
650 			/*
651 			 * If no digits, might be missing exponent digits
652 			 * (just give back the exponent) or might be missing
653 			 * regular digits, but had sign and/or decimal point.
654 			 */
655 			if (flags & NDIGITS) {
656 				if (flags & EXPOK) {
657 					/* no digits at all */
658 					while (p > buf)
659 						__ungetc(*(u_char *)--p, fp);
660 					goto match_failure;
661 				}
662 				/* just a bad exponent (e and maybe sign) */
663 				c = *(u_char *)--p;
664 				if (c != 'e' && c != 'E') {
665 					(void)__ungetc(c, fp);/* sign */
666 					c = *(u_char *)--p;
667 				}
668 				(void)__ungetc(c, fp);
669 			}
670 			if ((flags & SUPPRESS) == 0) {
671 				double res;
672 
673 				*p = 0;
674 				/* XXX this loses precision for long doubles. */
675 				res = strtod(buf, (char **) NULL);
676 				if (flags & LONGDBL)
677 					*va_arg(ap, long double *) = res;
678 				else if (flags & LONG)
679 					*va_arg(ap, double *) = res;
680 				else
681 					*va_arg(ap, float *) = res;
682 				nassigned++;
683 			}
684 			nread += p - buf;
685 			nconversions++;
686 			break;
687 #endif /* FLOATING_POINT */
688 		}
689 	}
690 input_failure:
691 	return (nconversions != 0 ? nassigned : EOF);
692 match_failure:
693 	return (nassigned);
694 }
695 
696 /*
697  * Fill in the given table from the scanset at the given format
698  * (just after `[').  Return a pointer to the character past the
699  * closing `]'.  The table has a 1 wherever characters should be
700  * considered part of the scanset.
701  */
702 static u_char *
703 __sccl(tab, fmt)
704 	char *tab;
705 	u_char *fmt;
706 {
707 	int c, n, v, i;
708 
709 	/* first `clear' the whole table */
710 	c = *fmt++;		/* first char hat => negated scanset */
711 	if (c == '^') {
712 		v = 1;		/* default => accept */
713 		c = *fmt++;	/* get new first char */
714 	} else
715 		v = 0;		/* default => reject */
716 
717 	/* XXX: Will not work if sizeof(tab*) > sizeof(char) */
718 	(void) memset(tab, v, 256);
719 
720 	if (c == 0)
721 		return (fmt - 1);/* format ended before closing ] */
722 
723 	/*
724 	 * Now set the entries corresponding to the actual scanset
725 	 * to the opposite of the above.
726 	 *
727 	 * The first character may be ']' (or '-') without being special;
728 	 * the last character may be '-'.
729 	 */
730 	v = 1 - v;
731 	for (;;) {
732 		tab[c] = v;		/* take character c */
733 doswitch:
734 		n = *fmt++;		/* and examine the next */
735 		switch (n) {
736 
737 		case 0:			/* format ended too soon */
738 			return (fmt - 1);
739 
740 		case '-':
741 			/*
742 			 * A scanset of the form
743 			 *	[01+-]
744 			 * is defined as `the digit 0, the digit 1,
745 			 * the character +, the character -', but
746 			 * the effect of a scanset such as
747 			 *	[a-zA-Z0-9]
748 			 * is implementation defined.  The V7 Unix
749 			 * scanf treats `a-z' as `the letters a through
750 			 * z', but treats `a-a' as `the letter a, the
751 			 * character -, and the letter a'.
752 			 *
753 			 * For compatibility, the `-' is not considerd
754 			 * to define a range if the character following
755 			 * it is either a close bracket (required by ANSI)
756 			 * or is not numerically greater than the character
757 			 * we just stored in the table (c).
758 			 */
759 			n = *fmt;
760 			if (n == ']'
761 			    || (__collate_load_error ? n < c :
762 				__collate_range_cmp (n, c) < 0
763 			       )
764 			   ) {
765 				c = '-';
766 				break;	/* resume the for(;;) */
767 			}
768 			fmt++;
769 			/* fill in the range */
770 			if (__collate_load_error) {
771 				do {
772 					tab[++c] = v;
773 				} while (c < n);
774 			} else {
775 				for (i = 0; i < 256; i ++)
776 					if (   __collate_range_cmp (c, i) < 0
777 					    && __collate_range_cmp (i, n) <= 0
778 					   )
779 						tab[i] = v;
780 			}
781 #if 1	/* XXX another disgusting compatibility hack */
782 			c = n;
783 			/*
784 			 * Alas, the V7 Unix scanf also treats formats
785 			 * such as [a-c-e] as `the letters a through e'.
786 			 * This too is permitted by the standard....
787 			 */
788 			goto doswitch;
789 #else
790 			c = *fmt++;
791 			if (c == 0)
792 				return (fmt - 1);
793 			if (c == ']')
794 				return (fmt);
795 #endif
796 			break;
797 
798 		case ']':		/* end of scanset */
799 			return (fmt);
800 
801 		default:		/* just another character */
802 			c = n;
803 			break;
804 		}
805 	}
806 	/* NOTREACHED */
807 }
808