/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * 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.
 *
 * Copyright (c) 2011 The FreeBSD Foundation
 *
 * Copyright (c) 2023 Dag-Erling Smørgrav
 *
 * Portions of this software were developed by David Chisnall
 * under sponsorship from the FreeBSD Foundation.
 *
 * 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. 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 "namespace.h"
#include <ctype.h>
#include <inttypes.h>
#include <limits.h>
#include <stdio.h>
#include <stdlib.h>
#include <stddef.h>
#include <stdarg.h>
#include <string.h>
#include <wchar.h>
#include <wctype.h>
#include "un-namespace.h"

#include "libc_private.h"
#include "local.h"
#include "xlocale_private.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 FASTINT         0x200   /* wfN: int_fastN_t */
#define LONGLONG        0x400   /* ll: long long (+ 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 */

/*
 * 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 */

static int parsefloat(FILE *, wchar_t *, wchar_t *, locale_t);

struct ccl {
        const wchar_t *start;   /* character class start */
        const wchar_t *end;     /* character class end */
        int compl;              /* ccl is complemented? */
};

static __inline int
inccl(const struct ccl *ccl, wint_t wi)
{

        if (ccl->compl) {
                return (wmemchr(ccl->start, wi, ccl->end - ccl->start)
                    == NULL);
        } else {
                return (wmemchr(ccl->start, wi, ccl->end - ccl->start) != NULL);
        }
}

/*
 * Conversion functions are passed a pointer to this object instead of
 * a real parameter to indicate that the assignment-suppression (*)
 * flag was specified.  We could use a NULL pointer to indicate this,
 * but that would mask bugs in applications that call scanf() with a
 * NULL pointer.
 */
static const int suppress;
#define SUPPRESS_PTR    ((void *)&suppress)

static const mbstate_t initial_mbs;

/*
 * The following conversion functions return the number of characters consumed,
 * or -1 on input failure.  Character class conversion returns 0 on match
 * failure.
 */

static __inline int
convert_char(FILE *fp, char * mbp, int width, locale_t locale)
{
        mbstate_t mbs;
        size_t nconv;
        wint_t wi;
        int n;

        n = 0;
        mbs = initial_mbs;
        while (width-- != 0 && (wi = __fgetwc(fp, locale)) != WEOF) {
                if (mbp != SUPPRESS_PTR) {
                        nconv = wcrtomb(mbp, wi, &mbs);
                        if (nconv == (size_t)-1)
                                return (-1);
                        mbp += nconv;
                }
                n++;
        }
        if (n == 0)
                return (-1);
        return (n);
}

static __inline int
convert_wchar(FILE *fp, wchar_t *wcp, int width, locale_t locale)
{
        wint_t wi;
        int n;

        n = 0;
        while (width-- != 0 && (wi = __fgetwc(fp, locale)) != WEOF) {
                if (wcp != SUPPRESS_PTR)
                        *wcp++ = (wchar_t)wi;
                n++;
        }
        if (n == 0)
                return (-1);
        return (n);
}

static __inline int
convert_ccl(FILE *fp, char * mbp, int width, const struct ccl *ccl,
    locale_t locale)
{
        mbstate_t mbs;
        size_t nconv;
        wint_t wi;
        int n;

        n = 0;
        mbs = initial_mbs;
        while ((wi = __fgetwc(fp, locale)) != WEOF &&
            width-- != 0 && inccl(ccl, wi)) {
                if (mbp != SUPPRESS_PTR) {
                        nconv = wcrtomb(mbp, wi, &mbs);
                        if (nconv == (size_t)-1)
                                return (-1);
                        mbp += nconv;
                }
                n++;
        }
        if (wi != WEOF)
                __ungetwc(wi, fp, locale);
        if (mbp != SUPPRESS_PTR)
                *mbp = 0;
        return (n);
}

static __inline int
convert_wccl(FILE *fp, wchar_t *wcp, int width, const struct ccl *ccl,
    locale_t locale)
{
        wchar_t *wcp0;
        wint_t wi;
        int n;

        if (wcp == SUPPRESS_PTR) {
                n = 0;
                while ((wi = __fgetwc(fp, locale)) != WEOF &&
                    width-- != 0 && inccl(ccl, wi))
                        n++;
                if (wi != WEOF)
                        __ungetwc(wi, fp, locale);
        } else {
                wcp0 = wcp;
                while ((wi = __fgetwc(fp, locale)) != WEOF &&
                    width-- != 0 && inccl(ccl, wi))
                        *wcp++ = (wchar_t)wi;
                if (wi != WEOF)
                        __ungetwc(wi, fp, locale);
                n = wcp - wcp0;
                if (n == 0)
                        return (0);
                *wcp = 0;
        }
        return (n);
}

static __inline int
convert_string(FILE *fp, char * mbp, int width, locale_t locale)
{
        mbstate_t mbs;
        size_t nconv;
        wint_t wi;
        int nread;

        mbs = initial_mbs;
        nread = 0;
        while ((wi = __fgetwc(fp, locale)) != WEOF && width-- != 0 &&
            !iswspace(wi)) {
                if (mbp != SUPPRESS_PTR) {
                        nconv = wcrtomb(mbp, wi, &mbs);
                        if (nconv == (size_t)-1)
                                return (-1);
                        mbp += nconv;
                }
                nread++;
        }
        if (wi != WEOF)
                __ungetwc(wi, fp, locale);
        if (mbp != SUPPRESS_PTR)
                *mbp = 0;
        return (nread);
}

static __inline int
convert_wstring(FILE *fp, wchar_t *wcp, int width, locale_t locale)
{
        wint_t wi;
        int nread;

        nread = 0;
        if (wcp == SUPPRESS_PTR) {
                while ((wi = __fgetwc(fp, locale)) != WEOF &&
                    width-- != 0 && !iswspace(wi))
                        nread++;
                if (wi != WEOF)
                        __ungetwc(wi, fp, locale);
        } else {
                while ((wi = __fgetwc(fp, locale)) != WEOF &&
                    width-- != 0 && !iswspace(wi)) {
                        *wcp++ = (wchar_t)wi;
                        nread++;
                }
                if (wi != WEOF)
                        __ungetwc(wi, fp, locale);
                *wcp = '\0';
        }
        return (nread);
}

enum parseint_state {
        begin,
        havesign,
        havezero,
        haveprefix,
        any,
};

static __inline int
parseint_fsm(wchar_t c, enum parseint_state *state, int *base)
{
        switch (c) {
        case '+':
        case '-':
                if (*state == begin) {
                        *state = havesign;
                        return 1;
                }
                break;
        case '0':
                if (*state == begin || *state == havesign) {
                        *state = havezero;
                        return 1;
                }
                /* FALL THROUGH */
        case '1':
        case '2':
        case '3':
        case '4':
        case '5':
        case '6':
        case '7':
                if (*state == havezero && *base == 0) {
                        *base = 8;
                }
                /* FALL THROUGH */
        case '8':
        case '9':
                if (*state == begin ||
                    *state == havesign) {
                        if (*base == 0) {
                                *base = 10;
                        }
                }
                if (*state == begin ||
                    *state == havesign ||
                    *state == havezero ||
                    *state == haveprefix ||
                    *state == any) {
                        if (*base > c - '0') {
                                *state = any;
                                return 1;
                        }
                }
                break;
        case 'b':
                if (*state == havezero) {
                        if (*base == 0 || *base == 2) {
                                *state = haveprefix;
                                *base = 2;
                                return 1;
                        }
                }
                /* FALL THROUGH */
        case 'a':
        case 'c':
        case 'd':
        case 'e':
        case 'f':
                if (*state == begin ||
                    *state == havesign ||
                    *state == havezero ||
                    *state == haveprefix ||
                    *state == any) {
                        if (*base > c - 'a' + 10) {
                                *state = any;
                                return 1;
                        }
                }
                break;
        case 'B':
                if (*state == havezero) {
                        if (*base == 0 || *base == 2) {
                                *state = haveprefix;
                                *base = 2;
                                return 1;
                        }
                }
                /* FALL THROUGH */
        case 'A':
        case 'C':
        case 'D':
        case 'E':
        case 'F':
                if (*state == begin ||
                    *state == havesign ||
                    *state == havezero ||
                    *state == haveprefix ||
                    *state == any) {
                        if (*base > c - 'A' + 10) {
                                *state = any;
                                return 1;
                        }
                }
                break;
        case 'x':
        case 'X':
                if (*state == havezero) {
                        if (*base == 0 || *base == 16) {
                                *state = haveprefix;
                                *base = 16;
                                return 1;
                        }
                }
                break;
        }
        return 0;
}

/*
 * Read an integer, storing it in buf.
 *
 * Return 0 on a match failure, and the number of characters read
 * otherwise.
 */
static __inline int
parseint(FILE *fp, wchar_t * __restrict buf, int width, int base,
    locale_t locale)
{
        enum parseint_state state = begin;
        wchar_t *wcp;
        int c;

        for (wcp = buf; width; width--) {
                c = __fgetwc(fp, locale);
                if (c == WEOF)
                        break;
                if (!parseint_fsm(c, &state, &base))
                        break;
                *wcp++ = (wchar_t)c;
        }
        /*
         * If we only had a sign, push it back.  If we only had a 0b or 0x
         * prefix (possibly preceded by a sign), we view it as "0" and
         * push back the letter.  In all other cases, if we stopped
         * because we read a non-number character, push it back.
         */
        if (state == havesign) {
                wcp--;
                __ungetwc(*wcp, fp, locale);
        } else if (state == haveprefix) {
                wcp--;
                __ungetwc(c, fp, locale);
        } else if (width && c != WEOF) {
                __ungetwc(c, fp, locale);
        }
        return (wcp - buf);
}

/*
 * MT-safe version.
 */
int
vfwscanf_l(FILE * __restrict fp, locale_t locale,
                const wchar_t * __restrict fmt, va_list ap)
{
        int ret;
        FIX_LOCALE(locale);

        FLOCKFILE_CANCELSAFE(fp);
        ORIENT(fp, 1);
        ret = __vfwscanf(fp, locale, fmt, ap);
        FUNLOCKFILE_CANCELSAFE();
        return (ret);
}
int
vfwscanf(FILE * __restrict fp, const wchar_t * __restrict fmt, va_list ap)
{
        return vfwscanf_l(fp, __get_locale(), fmt, ap);
}

/*
 * Non-MT-safe version.
 */
int
__vfwscanf(FILE * __restrict fp, locale_t locale,
                const wchar_t * __restrict fmt, va_list ap)
{
#define GETARG(type)    ((flags & SUPPRESS) ? SUPPRESS_PTR : va_arg(ap, type))
        wint_t c;               /* character from format, or conversion */
        size_t width;           /* field width, or 0 */
        int flags;              /* flags as defined above */
        int nassigned;          /* number of fields assigned */
        int nconversions;       /* number of conversions */
        int nr;                 /* characters read by the current conversion */
        int nread;              /* number of characters consumed from fp */
        int base;               /* base argument to conversion function */
        struct ccl ccl;         /* character class info */
        wchar_t buf[BUF];       /* buffer for numeric conversions */
        wint_t wi;              /* handy wint_t */

        nassigned = 0;
        nconversions = 0;
        nread = 0;
        ccl.start = ccl.end = NULL;
        for (;;) {
                c = *fmt++;
                if (c == 0)
                        return (nassigned);
                if (iswspace(c)) {
                        while ((c = __fgetwc(fp, locale)) != WEOF &&
                            iswspace_l(c, locale))
                                nread++;
                        if (c != WEOF)
                                __ungetwc(c, fp, locale);
                        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 '%':
literal:
                        if ((wi = __fgetwc(fp, locale)) == WEOF)
                                goto input_failure;
                        if (wi != c) {
                                __ungetwc(wi, fp, locale);
                                goto match_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 'w':
                        /*
                         * Fixed-width integer types.  On all platforms we
                         * support, int8_t is equivalent to char, int16_t
                         * is equivalent to short, int32_t is equivalent
                         * to int, int64_t is equivalent to long long int.
                         * Furthermore, int_fast8_t, int_fast16_t and
                         * int_fast32_t are equivalent to int, and
                         * int_fast64_t is equivalent to long long int.
                         */
                        flags &= ~(SHORTSHORT|SHORT|LONG|LONGLONG|SIZET|INTMAXT|PTRDIFFT);
                        if (fmt[0] == 'f') {
                                flags |= FASTINT;
                                fmt++;
                        } else {
                                flags &= ~FASTINT;
                        }
                        if (fmt[0] == '8') {
                                if (!(flags & FASTINT))
                                        flags |= SHORTSHORT;
                                else
                                        /* no flag set = 32 */ ;
                                fmt += 1;
                        } else if (fmt[0] == '1' && fmt[1] == '6') {
                                if (!(flags & FASTINT))
                                        flags |= SHORT;
                                else
                                        /* no flag set = 32 */ ;
                                fmt += 2;
                        } else if (fmt[0] == '3' && fmt[1] == '2') {
                                /* no flag set = 32 */ ;
                                fmt += 2;
                        } else if (fmt[0] == '6' && fmt[1] == '4') {
                                flags |= LONGLONG;
                                fmt += 2;
                        } else {
                                goto match_failure;
                        }
                        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 'B':
                case 'b':
                        c = CT_INT;
                        flags |= UNSIGNED;
                        base = 2;
                        break;

                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':
                        c = CT_INT;
                        flags |= UNSIGNED;
                        base = 16;
                        break;

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

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

                case '[':
                        ccl.start = fmt;
                        if (*fmt == '^') {
                                ccl.compl = 1;
                                fmt++;
                        } else
                                ccl.compl = 0;
                        if (*fmt == ']')
                                fmt++;
                        while (*fmt != '\0' && *fmt != ']')
                                fmt++;
                        ccl.end = 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;
                        c = CT_INT;             /* assumes sizeof(uintmax_t) */
                        flags |= UNSIGNED;      /*      >= sizeof(uintptr_t) */
                        base = 16;
                        break;

                case 'n':
                        if (flags & SUPPRESS)   /* ??? */
                                continue;
                        if (flags & SHORTSHORT)
                                *va_arg(ap, char *) = nread;
                        else if (flags & SHORT)
                                *va_arg(ap, short *) = nread;
                        else if (flags & LONG)
                                *va_arg(ap, long *) = nread;
                        else if (flags & LONGLONG)
                                *va_arg(ap, long long *) = 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 *) = 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(fp, locale)) != WEOF && iswspace(wi))
                                nread++;
                        if (wi == WEOF)
                                goto input_failure;
                        __ungetwc(wi, fp, locale);
                }

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

                case CT_CHAR:
                        /* scan arbitrary characters (sets NOSKIP) */
                        if (width == 0)
                                width = 1;
                        if (flags & LONG) {
                                nr = convert_wchar(fp, GETARG(wchar_t *), width,
                                    locale);
                        } else {
                                nr = convert_char(fp, GETARG(char *), width,
                                    locale);
                        }
                        if (nr < 0)
                                goto input_failure;
                        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 & LONG) {
                                nr = convert_wccl(fp, GETARG(wchar_t *), width,
                                    &ccl, locale);
                        } else {
                                nr = convert_ccl(fp, GETARG(char *), width,
                                    &ccl, locale);
                        }
                        if (nr <= 0) {
                                if (nr < 0)
                                        goto input_failure;
                                else /* nr == 0 */
                                        goto match_failure;
                        }
                        break;

                case CT_STRING:
                        /* like CCL, but zero-length string OK, & no NOSKIP */
                        if (width == 0)
                                width = (size_t)~0;
                        if (flags & LONG) {
                                nr = convert_wstring(fp, GETARG(wchar_t *),
                                    width, locale);
                        } else {
                                nr = convert_string(fp, GETARG(char *), width,
                                    locale);
                        }
                        if (nr < 0)
                                goto input_failure;
                        break;

                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;

                        nr = parseint(fp, buf, width, base, locale);
                        if (nr == 0)
                                goto match_failure;
                        if ((flags & SUPPRESS) == 0) {
                                uintmax_t res;

                                buf[nr] = L'\0';
                                if ((flags & UNSIGNED) == 0)
                                    res = wcstoimax(buf, NULL, base);
                                else
                                    res = wcstoumax(buf, NULL, base);
                                if (flags & POINTER)
                                        *va_arg(ap, void **) =
                                                        (void *)(uintptr_t)res;
                                else if (flags & SHORTSHORT)
                                        *va_arg(ap, char *) = res;
                                else if (flags & SHORT)
                                        *va_arg(ap, short *) = res;
                                else if (flags & LONG)
                                        *va_arg(ap, long *) = res;
                                else if (flags & LONGLONG)
                                        *va_arg(ap, long long *) = res;
                                else if (flags & INTMAXT)
                                        *va_arg(ap, intmax_t *) = res;
                                else if (flags & PTRDIFFT)
                                        *va_arg(ap, ptrdiff_t *) = res;
                                else if (flags & SIZET)
                                        *va_arg(ap, size_t *) = res;
                                else
                                        *va_arg(ap, int *) = res;
                        }
                        break;

                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;
                        nr = parsefloat(fp, buf, buf + width, locale);
                        if (nr == 0)
                                goto match_failure;
                        if ((flags & SUPPRESS) == 0) {
                                if (flags & LONGDBL) {
                                        long double res = wcstold(buf, NULL);
                                        *va_arg(ap, long double *) = res;
                                } else if (flags & LONG) {
                                        double res = wcstod(buf, NULL);
                                        *va_arg(ap, double *) = res;
                                } else {
                                        float res = wcstof(buf, NULL);
                                        *va_arg(ap, float *) = res;
                                }
                        }
                        break;
                }
                if (!(flags & SUPPRESS))
                        nassigned++;
                nread += nr;
                nconversions++;
        }
input_failure:
        return (nconversions != 0 ? nassigned : EOF);
match_failure:
        return (nassigned);
}

static int
parsefloat(FILE *fp, wchar_t *buf, wchar_t *end, locale_t locale)
{
        mbstate_t mbs;
        size_t nconv;
        wchar_t *commit, *p;
        int infnanpos = 0;
        enum {
                S_START, S_GOTSIGN, S_INF, S_NAN, S_DONE, S_MAYBEHEX,
                S_DIGITS, S_FRAC, S_EXP, S_EXPDIGITS
        } state = S_START;
        wchar_t c;
        wchar_t decpt;
        _Bool gotmantdig = 0, ishex = 0;

        mbs = initial_mbs;
        nconv = mbrtowc(&decpt, localeconv()->decimal_point, MB_CUR_MAX, &mbs);
        if (nconv == (size_t)-1 || nconv == (size_t)-2)
                decpt = '.';    /* failsafe */

        /*
         * 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(fp, locale)) == 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 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;
                                        state = S_DONE;
                                } else if (!iswalnum(c) && c != '_')
                                        goto parsedone;
                                break;
                        }
                        infnanpos++;
                        break;
                case S_DONE:
                        goto parsedone;
                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(c)) || iswdigit(c))
                                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(c)) || iswdigit(c)) {
                                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(c))
                                commit = p;
                        else
                                goto parsedone;
                        break;
                default:
                        abort();
                }
                *p++ = c;
                c = WEOF;
        }

parsedone:
        if (c != WEOF)
                __ungetwc(c, fp, locale);
        while (commit < --p)
                __ungetwc(*p, fp, locale);
        *++commit = '\0';
        return (commit - buf);
}