xref: /minix3/lib/libc/stdio/vfwscanf.c (revision 0a6a1f1d05b60e214de2f05a7310ddd1f0e590e7)

/*	$NetBSD: vfwscanf.c,v 1.12 2014/06/12 22:21:20 justin Exp $	*/

/*-
 * Copyright (c) 1990, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Chris Torek.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the University of
 *	California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/cdefs.h>
#if defined(LIBC_SCCS) && !defined(lint)
#if 0
static char sccsid[] = "@(#)ftell.c	8.2 (Berkeley) 5/4/95";
__FBSDID("$FreeBSD: src/lib/libc/stdio/vfwscanf.c,v 1.12 2004/05/02 20:13:29 obrien Exp $");
#else
__RCSID("$NetBSD: vfwscanf.c,v 1.12 2014/06/12 22:21:20 justin Exp $");
#endif
#endif /* LIBC_SCCS and not lint */

#include "namespace.h"
#include <ctype.h>
#include <inttypes.h>
#include <assert.h>
#include <stdio.h>
#include <stdlib.h>
#include <stddef.h>
#include <stdarg.h>
#include <string.h>
#include <limits.h>
#include <wchar.h>
#include <wctype.h>

#include "reentrant.h"
#include "local.h"

#include <locale.h>
#include "setlocale_local.h"

#define	BUF		513	/* Maximum length of numeric string. */

/*
 * Flags used during conversion.
 */
#define	LONG		0x01	/* l: long or double */
#define	LONGDBL		0x02	/* L: long double */
#define	SHORT		0x04	/* h: short */
#define	SUPPRESS	0x08	/* *: suppress assignment */
#define	POINTER		0x10	/* p: void * (as hex) */
#define	NOSKIP		0x20	/* [ or c: do not skip blanks */
#define	LONGLONG	0x400	/* ll: quad_t (+ deprecated q: quad) */
#define	INTMAXT		0x800	/* j: intmax_t */
#define	PTRDIFFT	0x1000	/* t: ptrdiff_t */
#define	SIZET		0x2000	/* z: size_t */
#define	SHORTSHORT	0x4000	/* hh: char */
#define	UNSIGNED	0x8000	/* %[oupxX] conversions */

/*
 * The following are used in integral conversions only:
 * SIGNOK, NDIGITS, PFXOK, and NZDIGITS
 */
#define	SIGNOK		0x40	/* +/- is (still) legal */
#define	NDIGITS		0x80	/* no digits detected */
#define	PFXOK		0x100	/* 0x prefix is (still) legal */
#define	NZDIGITS	0x200	/* no zero digits detected */
#define	HAVESIGN	0x10000	/* sign detected */

/*
 * Conversion types.
 */
#define	CT_CHAR		0	/* %c conversion */
#define	CT_CCL		1	/* %[...] conversion */
#define	CT_STRING	2	/* %s conversion */
#define	CT_INT		3	/* %[dioupxX] conversion */
#define	CT_FLOAT	4	/* %[efgEFG] conversion */

#ifndef NO_FLOATING_POINT
static int parsefloat(FILE *, wchar_t *, wchar_t *, locale_t);
#endif

#define	INCCL(_c)	\
	(cclcompl ? (wmemchr(ccls, (_c), (size_t)(ccle - ccls)) == NULL) : \
	(wmemchr(ccls, (_c), (size_t)(ccle - ccls)) != NULL))

/*
 * MT-safe version.
 */
int
vfwscanf(FILE * __restrict fp, const wchar_t * __restrict fmt, va_list ap)
{
	return vfwscanf_l(fp, _current_locale(), fmt, ap);
}

int
vfwscanf_l(FILE * __restrict fp, locale_t loc, const wchar_t * __restrict fmt,
    va_list ap)
{
	int ret;

	FLOCKFILE(fp);
	_SET_ORIENTATION(fp, 1);
	ret = __vfwscanf_unlocked_l(fp, loc, fmt, ap);
	FUNLOCKFILE(fp);
	return ret;
}

#define SCANF_SKIP_SPACE() \
do { \
	wint_t tc; \
 \
	while ((tc = __fgetwc_unlock(fp)) != WEOF && iswspace_l(tc, loc)) \
		continue; \
	if (tc != WEOF) \
		ungetwc(tc, fp); \
} while (/*CONSTCOND*/ 0)

/*
 * Non-MT-safe version.
 */
int
__vfwscanf_unlocked_l(FILE * __restrict fp, locale_t loc,
    const wchar_t * __restrict fmt, va_list ap)
{
	wint_t c;		/* character from format, or conversion */
	size_t width;		/* field width, or 0 */
	wchar_t *p;		/* points into all kinds of strings */
	int n;			/* handy integer */
	int flags;		/* flags as defined above */
	wchar_t *p0;		/* saves original value of p when necessary */
	int nassigned;		/* number of fields assigned */
	int nconversions;	/* number of conversions */
	size_t nread;		/* number of characters consumed from fp */
	int base;		/* base argument to conversion function */
	wchar_t buf[BUF];	/* buffer for numeric conversions */
	const wchar_t *ccls;	/* character class start */
	const wchar_t *ccle;	/* character class end */
	int cclcompl;		/* ccl is complemented? */
	wint_t wi;		/* handy wint_t */
	char *mbp;		/* multibyte string pointer for %c %s %[ */
	size_t nconv;		/* number of bytes in mb. conversion */
	static const mbstate_t initial;
	mbstate_t mbs;
	char mbbuf[MB_LEN_MAX];	/* temporary mb. character buffer */
	/* `basefix' is used to avoid `if' tests in the integer scanner */
	static short basefix[17] =
		{ 10, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16 };

	nassigned = 0;
	nconversions = 0;
	nread = 0;
	ccls = ccle = NULL;
	base = 0;
	cclcompl = 0;
	mbp = NULL;
	p = NULL; /* XXXgcc */
	for (;;) {
		c = *fmt++;
		if (c == 0)
			return nassigned;
		if (iswspace_l(c, loc)) {
			while ((c = __fgetwc_unlock(fp)) != WEOF &&
			    iswspace_l(c, loc))
				;
			if (c != WEOF)
				ungetwc(c, fp);
			continue;
		}
		if (c != '%')
			goto literal;
		width = 0;
		flags = 0;
		/*
		 * switch on the format.  continue if done;
		 * break once format type is derived.
		 */
again:		c = *fmt++;
		switch (c) {
		case '%':
			SCANF_SKIP_SPACE();
literal:
			if ((wi = __fgetwc_unlock(fp)) == WEOF)
				goto input_failure;
			if (wi != c) {
				ungetwc(wi, fp);
				goto input_failure;
			}
			nread++;
			continue;

		case '*':
			flags |= SUPPRESS;
			goto again;
		case 'j':
			flags |= INTMAXT;
			goto again;
		case 'l':
			if (flags & LONG) {
				flags &= ~LONG;
				flags |= LONGLONG;
			} else
				flags |= LONG;
			goto again;
		case 'q':
			flags |= LONGLONG;	/* not quite */
			goto again;
		case 't':
			flags |= PTRDIFFT;
			goto again;
		case 'z':
			flags |= SIZET;
			goto again;
		case 'L':
			flags |= LONGDBL;
			goto again;
		case 'h':
			if (flags & SHORT) {
				flags &= ~SHORT;
				flags |= SHORTSHORT;
			} else
				flags |= SHORT;
			goto again;

		case '0': case '1': case '2': case '3': case '4':
		case '5': case '6': case '7': case '8': case '9':
			width = width * 10 + c - '0';
			goto again;

		/*
		 * Conversions.
		 */
		case 'd':
			c = CT_INT;
			base = 10;
			break;

		case 'i':
			c = CT_INT;
			base = 0;
			break;

		case 'o':
			c = CT_INT;
			flags |= UNSIGNED;
			base = 8;
			break;

		case 'u':
			c = CT_INT;
			flags |= UNSIGNED;
			base = 10;
			break;

		case 'X':
		case 'x':
			flags |= PFXOK;	/* enable 0x prefixing */
			c = CT_INT;
			flags |= UNSIGNED;
			base = 16;
			break;

#ifndef NO_FLOATING_POINT
		case 'A': case 'E': case 'F': case 'G':
		case 'a': case 'e': case 'f': case 'g':
			c = CT_FLOAT;
			break;
#endif

		case 'S':
			flags |= LONG;
			/* FALLTHROUGH */
		case 's':
			c = CT_STRING;
			break;

		case '[':
			ccls = fmt;
			if (*fmt == '^') {
				cclcompl = 1;
				fmt++;
			} else
				cclcompl = 0;
			if (*fmt == ']')
				fmt++;
			while (*fmt != '\0' && *fmt != ']')
				fmt++;
			ccle = fmt;
			fmt++;
			flags |= NOSKIP;
			c = CT_CCL;
			break;

		case 'C':
			flags |= LONG;
			/* FALLTHROUGH */
		case 'c':
			flags |= NOSKIP;
			c = CT_CHAR;
			break;

		case 'p':	/* pointer format is like hex */
			flags |= POINTER | PFXOK;
			c = CT_INT;		/* assumes sizeof(uintmax_t) */
			flags |= UNSIGNED;	/*      >= sizeof(uintptr_t) */
			base = 16;
			break;

		case 'n':
			nconversions++;
			if (flags & SUPPRESS)	/* ??? */
				continue;
			if (flags & SHORTSHORT)
				*va_arg(ap, char *) = (char)nread;
			else if (flags & SHORT)
				*va_arg(ap, short *) = (short)nread;
			else if (flags & LONG)
				*va_arg(ap, long *) = nread;
			else if (flags & LONGLONG)
				*va_arg(ap, quad_t *) = nread;
			else if (flags & INTMAXT)
				*va_arg(ap, intmax_t *) = nread;
			else if (flags & SIZET)
				*va_arg(ap, size_t *) = nread;
			else if (flags & PTRDIFFT)
				*va_arg(ap, ptrdiff_t *) = nread;
			else
				*va_arg(ap, int *) = (int)nread;
			continue;

		default:
			goto match_failure;

		/*
		 * Disgusting backwards compatibility hack.	XXX
		 */
		case '\0':	/* compat */
			return EOF;
		}

		/*
		 * Consume leading white space, except for formats
		 * that suppress this.
		 */
		if ((flags & NOSKIP) == 0) {
			while ((wi = __fgetwc_unlock(fp)) != WEOF &&
			       iswspace_l(wi, loc))
				nread++;
			if (wi == WEOF)
				goto input_failure;
			ungetwc(wi, fp);
		}

		/*
		 * Do the conversion.
		 */
		switch (c) {

		case CT_CHAR:
			/* scan arbitrary characters (sets NOSKIP) */
			if (width == 0)
				width = 1;
			if (flags & LONG) {
				if (!(flags & SUPPRESS))
					p = va_arg(ap, wchar_t *);
				n = 0;
				while (width-- != 0 &&
				    (wi = __fgetwc_unlock(fp)) != WEOF) {
					if (!(flags & SUPPRESS))
						*p++ = (wchar_t)wi;
					n++;
				}
				if (n == 0)
					goto input_failure;
				nread += n;
				if (!(flags & SUPPRESS))
					nassigned++;
			} else {
				if (!(flags & SUPPRESS))
					mbp = va_arg(ap, char *);
				n = 0;
				mbs = initial;
				while (width != 0 &&
				    (wi = __fgetwc_unlock(fp)) != WEOF) {
					if (width >= MB_CUR_MAX_L(loc) &&
					    !(flags & SUPPRESS)) {
						nconv = wcrtomb_l(mbp, wi,
						    &mbs, loc);
						if (nconv == (size_t)-1)
							goto input_failure;
					} else {
						nconv = wcrtomb_l(mbbuf, wi,
						    &mbs, loc);
						if (nconv == (size_t)-1)
							goto input_failure;
						if (nconv > width) {
							ungetwc(wi, fp);
							break;
						}
						if (!(flags & SUPPRESS))
							memcpy(mbp, mbbuf,
							    nconv);
					}
					if (!(flags & SUPPRESS))
						mbp += nconv;
					width -= nconv;
					n++;
				}
				if (n == 0)
					goto input_failure;
				nread += n;
				if (!(flags & SUPPRESS))
					nassigned++;
			}
			nconversions++;
			break;

		case CT_CCL:
			/* scan a (nonempty) character class (sets NOSKIP) */
			if (width == 0)
				width = (size_t)~0;	/* `infinity' */
			/* take only those things in the class */
			if ((flags & SUPPRESS) && (flags & LONG)) {
				n = 0;
				while ((wi = __fgetwc_unlock(fp)) != WEOF &&
				    width-- != 0 && INCCL(wi))
					n++;
				if (wi != WEOF)
					ungetwc(wi, fp);
				if (n == 0)
					goto match_failure;
			} else if (flags & LONG) {
				p0 = p = va_arg(ap, wchar_t *);
				while ((wi = __fgetwc_unlock(fp)) != WEOF &&
				    width-- != 0 && INCCL(wi))
					*p++ = (wchar_t)wi;
				if (wi != WEOF)
					ungetwc(wi, fp);
				_DIAGASSERT(__type_fit(int, p - p0));
				n = (int)(p - p0);
				if (n == 0)
					goto match_failure;
				*p = 0;
				nassigned++;
			} else {
				if (!(flags & SUPPRESS))
					mbp = va_arg(ap, char *);
				n = 0;
				mbs = initial;
				while ((wi = __fgetwc_unlock(fp)) != WEOF &&
				    width != 0 && INCCL(wi)) {
					if (width >= MB_CUR_MAX_L(loc) &&
					   !(flags & SUPPRESS)) {
						nconv = wcrtomb_l(mbp, wi,
						    &mbs, loc);
						if (nconv == (size_t)-1)
							goto input_failure;
					} else {
						nconv = wcrtomb_l(mbbuf, wi,
						    &mbs, loc);
						if (nconv == (size_t)-1)
							goto input_failure;
						if (nconv > width)
							break;
						if (!(flags & SUPPRESS))
							memcpy(mbp, mbbuf,
							    nconv);
					}
					if (!(flags & SUPPRESS))
						mbp += nconv;
					width -= nconv;
					n++;
				}
				if (wi != WEOF)
					ungetwc(wi, fp);
				if (!(flags & SUPPRESS)) {
					*mbp = 0;
					nassigned++;
				}
			}
			nread += n;
			nconversions++;
			break;

		case CT_STRING:
			/* like CCL, but zero-length string OK, & no NOSKIP */
			if (width == 0)
				width = (size_t)~0;
			if ((flags & SUPPRESS) && (flags & LONG)) {
				while ((wi = __fgetwc_unlock(fp)) != WEOF &&
				    width-- != 0 &&
				    !iswspace_l(wi, loc))
					nread++;
				if (wi != WEOF)
					ungetwc(wi, fp);
			} else if (flags & LONG) {
				p0 = p = va_arg(ap, wchar_t *);
				while ((wi = __fgetwc_unlock(fp)) != WEOF &&
				    width-- != 0 &&
				    !iswspace_l(wi, loc)) {
					*p++ = (wchar_t)wi;
					nread++;
				}
				if (wi != WEOF)
					ungetwc(wi, fp);
				*p = '\0';
				nassigned++;
			} else {
				if (!(flags & SUPPRESS))
					mbp = va_arg(ap, char *);
				mbs = initial;
				while ((wi = __fgetwc_unlock(fp)) != WEOF &&
				    width != 0 &&
				    !iswspace_l(wi, loc)) {
					if (width >= MB_CUR_MAX_L(loc) &&
					    !(flags & SUPPRESS)) {
						nconv = wcrtomb_l(mbp, wi,
						    &mbs, loc);
						if (nconv == (size_t)-1)
							goto input_failure;
					} else {
						nconv = wcrtomb_l(mbbuf, wi,
						    &mbs, loc);
						if (nconv == (size_t)-1)
							goto input_failure;
						if (nconv > width)
							break;
						if (!(flags & SUPPRESS))
							memcpy(mbp, mbbuf,
							    nconv);
					}
					if (!(flags & SUPPRESS))
						mbp += nconv;
					width -= nconv;
					nread++;
				}
				if (wi != WEOF)
					ungetwc(wi, fp);
				if (!(flags & SUPPRESS)) {
					*mbp = 0;
					nassigned++;
				}
			}
			nconversions++;
			continue;

		case CT_INT:
			/* scan an integer as if by the conversion function */
			if (width == 0 || width > sizeof(buf) /
			    sizeof(*buf) - 1)
				width = sizeof(buf) / sizeof(*buf) - 1;
			flags |= SIGNOK | NDIGITS | NZDIGITS;
			for (p = buf; width; width--) {
				c = __fgetwc_unlock(fp);
				/*
				 * Switch on the character; `goto ok'
				 * if we accept it as a part of number.
				 */
				switch (c) {

				/*
				 * The digit 0 is always legal, but is
				 * special.  For %i conversions, if no
				 * digits (zero or nonzero) have been
				 * scanned (only signs), we will have
				 * base==0.  In that case, we should set
				 * it to 8 and enable 0x prefixing.
				 * Also, if we have not scanned zero digits
				 * before this, do not turn off prefixing
				 * (someone else will turn it off if we
				 * have scanned any nonzero digits).
				 */
				case '0':
					if (base == 0) {
						base = 8;
						flags |= PFXOK;
					}
					if (flags & NZDIGITS)
					    flags &= ~(SIGNOK|NZDIGITS|NDIGITS);
					else
					    flags &= ~(SIGNOK|PFXOK|NDIGITS);
					goto ok;

				/* 1 through 7 always legal */
				case '1': case '2': case '3':
				case '4': case '5': case '6': case '7':
					base = basefix[base];
					flags &= ~(SIGNOK | PFXOK | NDIGITS);
					goto ok;

				/* digits 8 and 9 ok iff decimal or hex */
				case '8': case '9':
					base = basefix[base];
					if (base <= 8)
						break;	/* not legal here */
					flags &= ~(SIGNOK | PFXOK | NDIGITS);
					goto ok;

				/* letters ok iff hex */
				case 'A': case 'B': case 'C':
				case 'D': case 'E': case 'F':
				case 'a': case 'b': case 'c':
				case 'd': case 'e': case 'f':
					/* no need to fix base here */
					if (base <= 10)
						break;	/* not legal here */
					flags &= ~(SIGNOK | PFXOK | NDIGITS);
					goto ok;

				/* sign ok only as first character */
				case '+': case '-':
					if (flags & SIGNOK) {
						flags &= ~SIGNOK;
						flags |= HAVESIGN;
						goto ok;
					}
					break;

				/*
				 * x ok iff flag still set & 2nd char (or
				 * 3rd char if we have a sign).
				 */
				case 'x': case 'X':
					if (flags & PFXOK && p ==
					    buf + 1 + !!(flags & HAVESIGN)) {
						base = 16;	/* if %i */
						flags &= ~PFXOK;
						goto ok;
					}
					break;
				}

				/*
				 * If we got here, c is not a legal character
				 * for a number.  Stop accumulating digits.
				 */
				if (c != WEOF)
					ungetwc(c, fp);
				break;
		ok:
				/*
				 * c is legal: store it and look at the next.
				 */
				*p++ = (wchar_t)c;
			}
			/*
			 * If we had only a sign, it is no good; push
			 * back the sign.  If the number ends in `x',
			 * it was [sign] '0' 'x', so push back the x
			 * and treat it as [sign] '0'.
			 */
			if (flags & NDIGITS) {
				if (p > buf)
					ungetwc(*--p, fp);
				goto match_failure;
			}
			c = p[-1];
			if (c == 'x' || c == 'X') {
				--p;
				ungetwc(c, fp);
			}
			if ((flags & SUPPRESS) == 0) {
				uintmax_t res;

				*p = 0;
				if ((flags & UNSIGNED) == 0)
				    res = wcstoimax_l(buf, NULL, base, loc);
				else
				    res = wcstoumax_l(buf, NULL, base, loc);
				if (flags & POINTER)
					*va_arg(ap, void **) =
							(void *)(uintptr_t)res;
				else if (flags & SHORTSHORT)
					*va_arg(ap, char *) = (char)res;
				else if (flags & SHORT)
					*va_arg(ap, short *) = (short)res;
				else if (flags & LONG)
					*va_arg(ap, long *) = (long)res;
				else if (flags & LONGLONG)
					*va_arg(ap, quad_t *) = res;
				else if (flags & INTMAXT)
					*va_arg(ap, intmax_t *) = res;
				else if (flags & PTRDIFFT)
					*va_arg(ap, ptrdiff_t *) = (ptrdiff_t)res;
				else if (flags & SIZET)
					*va_arg(ap, size_t *) = (size_t)res;
				else
					*va_arg(ap, int *) = (int)res;
				nassigned++;
			}
			_DIAGASSERT(__type_fit(int, p - buf));
			nread += (int)(p - buf);
			nconversions++;
			break;

#ifndef NO_FLOATING_POINT
		case CT_FLOAT:
			/* scan a floating point number as if by strtod */
			if (width == 0 || width > sizeof(buf) /
			    sizeof(*buf) - 1)
				width = sizeof(buf) / sizeof(*buf) - 1;
			if ((width = parsefloat(fp, buf, buf + width, loc)) == 0)
				goto match_failure;
			if ((flags & SUPPRESS) == 0) {
				if (flags & LONGDBL) {
					long double res = wcstold_l(buf, &p,
					    loc);
					*va_arg(ap, long double *) = res;
				} else
				if (flags & LONG) {
					double res = wcstod_l(buf, &p, loc);
					*va_arg(ap, double *) = res;
				} else {
					float res = wcstof_l(buf, &p, loc);
					*va_arg(ap, float *) = res;
				}
#ifdef DEBUG
				if (p - buf != (ptrdiff_t)width)
					abort();
#endif
				nassigned++;
			}
			nread += width;
			nconversions++;
			break;
#endif /* !NO_FLOATING_POINT */
		}
	}
input_failure:
	return nconversions != 0 ? nassigned : EOF;
match_failure:
	return nassigned;
}

#ifndef NO_FLOATING_POINT
static int
parsefloat(FILE *fp, wchar_t *buf, wchar_t *end, locale_t loc)
{
	wchar_t *commit, *p;
	int infnanpos = 0;
	enum {
		S_START, S_GOTSIGN, S_INF, S_NAN, S_MAYBEHEX,
		S_DIGITS, S_FRAC, S_EXP, S_EXPDIGITS
	} state = S_START;
	wchar_t c;
	wchar_t decpt = (wchar_t)(unsigned char)*localeconv_l(loc)->decimal_point;
	int gotmantdig = 0, ishex = 0;

	/*
	 * We set commit = p whenever the string we have read so far
	 * constitutes a valid representation of a floating point
	 * number by itself.  At some point, the parse will complete
	 * or fail, and we will ungetc() back to the last commit point.
	 * To ensure that the file offset gets updated properly, it is
	 * always necessary to read at least one character that doesn't
	 * match; thus, we can't short-circuit "infinity" or "nan(...)".
	 */
	commit = buf - 1;
	c = WEOF;
	for (p = buf; p < end; ) {
		if ((c = __fgetwc_unlock(fp)) == WEOF)
			break;
reswitch:
		switch (state) {
		case S_START:
			state = S_GOTSIGN;
			if (c == '-' || c == '+')
				break;
			else
				goto reswitch;
		case S_GOTSIGN:
			switch (c) {
			case '0':
				state = S_MAYBEHEX;
				commit = p;
				break;
			case 'I':
			case 'i':
				state = S_INF;
				break;
			case 'N':
			case 'n':
				state = S_NAN;
				break;
			default:
				state = S_DIGITS;
				goto reswitch;
			}
			break;
		case S_INF:
			if (infnanpos > 6 ||
			    (c != "nfinity"[infnanpos] &&
			     c != "NFINITY"[infnanpos]))
				goto parsedone;
			if (infnanpos == 1 || infnanpos == 6)
				commit = p;	/* inf or infinity */
			infnanpos++;
			break;
		case S_NAN:
			switch (infnanpos) {
			case -1:	/* XXX kludge to deal with nan(...) */
				goto parsedone;
			case 0:
				if (c != 'A' && c != 'a')
					goto parsedone;
				break;
			case 1:
				if (c != 'N' && c != 'n')
					goto parsedone;
				else
					commit = p;
				break;
			case 2:
				if (c != '(')
					goto parsedone;
				break;
			default:
				if (c == ')') {
					commit = p;
					infnanpos = -2;
				} else if (!iswalnum_l(c, loc) && c != '_')
					goto parsedone;
				break;
			}
			infnanpos++;
			break;
		case S_MAYBEHEX:
			state = S_DIGITS;
			if (c == 'X' || c == 'x') {
				ishex = 1;
				break;
			} else {	/* we saw a '0', but no 'x' */
				gotmantdig = 1;
				goto reswitch;
			}
		case S_DIGITS:
			if ((ishex && iswxdigit_l(c, loc)) ||
			    iswdigit_l(c, loc))
				gotmantdig = 1;
			else {
				state = S_FRAC;
				if (c != decpt)
					goto reswitch;
			}
			if (gotmantdig)
				commit = p;
			break;
		case S_FRAC:
			if (((c == 'E' || c == 'e') && !ishex) ||
			    ((c == 'P' || c == 'p') && ishex)) {
				if (!gotmantdig)
					goto parsedone;
				else
					state = S_EXP;
			} else if ((ishex && iswxdigit_l(c, loc)) ||
			    iswdigit_l(c, loc)) {
				commit = p;
				gotmantdig = 1;
			} else
				goto parsedone;
			break;
		case S_EXP:
			state = S_EXPDIGITS;
			if (c == '-' || c == '+')
				break;
			else
				goto reswitch;
		case S_EXPDIGITS:
			if (iswdigit_l(c, loc))
				commit = p;
			else
				goto parsedone;
			break;
		default:
			abort();
		}
		*p++ = c;
		c = WEOF;
	}

parsedone:
	if (c != WEOF)
		ungetwc(c, fp);
	while (commit < --p)
		ungetwc(*p, fp);
	*++commit = '\0';
	_DIAGASSERT(__type_fit(int, commit - buf));
	return (int)(commit - buf);
}
#endif