wcstol.c

C语言库函数的原型,有用的拿去

/***
*wcstol.c - Contains C runtimes wcstol and wcstoul
*
*       Copyright (c) Microsoft Corporation. All rights reserved.
*
*Purpose:
*       wcstol - convert wchar_t string to long signed integer
*       wcstoul - convert wchar_t string to long unsigned integer
*
*******************************************************************************/

#include <cruntime.h>
#include <stdlib.h>
#include <limits.h>
#include <errno.h>
#include <ctype.h>
#include <internal.h>
#include <locale.h>
#include <mtdll.h>
#include <setlocal.h>

extern "C" int _wchartodigit(wchar_t);

/***
*wcstol, wcstoul(nptr,endptr,ibase) - Convert ascii string to long un/signed
*       int.
*
*Purpose:
*       Convert an ascii string to a long 32-bit value.  The base
*       used for the caculations is supplied by the caller.  The base
*       must be in the range 0, 2-36.  If a base of 0 is supplied, the
*       ascii string must be examined to determine the base of the
*       number:
*           (a) First char = '0', second char = 'x' or 'X',
*               use base 16.
*           (b) First char = '0', use base 8
*           (c) First char in range '1' - '9', use base 10.
*
*       If the 'endptr' value is non-NULL, then wcstol/wcstoul places
*       a pointer to the terminating character in this value.
*       See ANSI standard for details
*
*Entry:
*       nptr == NEAR/FAR pointer to the start of string.
*       endptr == NEAR/FAR pointer to the end of the string.
*       ibase == integer base to use for the calculations.
*
*       string format: [whitespace] [sign] [0] [x] [digits/letters]
*
*Exit:
*       Good return:
*           result
*
*       Overflow return:
*           wcstol -- LONG_MAX or LONG_MIN
*           wcstoul -- ULONG_MAX
*           wcstol/wcstoul -- errno == ERANGE
*
*       No digits or bad base return:
*           0
*           endptr = nptr*
*
*Exceptions:
*       Input parameters are validated. Refer to the validation section of the function.
*
*******************************************************************************/

/* flag values */
#define FL_UNSIGNED   1       /* wcstoul called */
#define FL_NEG        2       /* negative sign found */
#define FL_OVERFLOW   4       /* overflow occured */
#define FL_READDIGIT  8       /* we've read at least one correct digit */


static unsigned long __cdecl wcstoxl (
        const wchar_t *nptr,
        const wchar_t **endptr,
        int ibase,
        int flags
        )
{
    const wchar_t *p;
    wchar_t c;
    unsigned long number;
    unsigned digval;
    unsigned long maxval;

    /* validation section */
    if (endptr != NULL)
    {
        /* store beginning of string in endptr */
        *endptr = nptr;
    }
    _VALIDATE_RETURN(nptr != NULL, EINVAL, 0L);
    _VALIDATE_RETURN(ibase == 0 || (2 <= ibase && ibase <= 36), EINVAL, 0L);

    p = nptr;           /* p is our scanning pointer */
    number = 0;         /* start with zero */

    c = *p++;           /* read char */

    while ( iswspace(c) )
        c = *p++;       /* skip whitespace */

    if (c == '-') {
        flags |= FL_NEG;    /* remember minus sign */
        c = *p++;
    }
    else if (c == '+')
        c = *p++;       /* skip sign */

    if (ibase == 0) {
        /* determine base free-lance, based on first two chars of
           string */
        if (_wchartodigit(c) != 0)
            ibase = 10;
        else if (*p == L'x' || *p == L'X')
            ibase = 16;
        else
            ibase = 8;
    }

    if (ibase == 16) {
        /* we might have 0x in front of number; remove if there */
        if (_wchartodigit(c) == 0 && (*p == L'x' || *p == L'X')) {
            ++p;
            c = *p++;   /* advance past prefix */
        }
    }

    /* if our number exceeds this, we will overflow on multiply */
    maxval = ULONG_MAX / ibase;


    for (;;) {  /* exit in middle of loop */

        /* convert c to value */
        if ( (digval = _wchartodigit(c)) != -1 )
            ;
        else if ( __ascii_iswalpha(c))
            digval = __ascii_towupper(c) - L'A' + 10;
        else
            break;

        if (digval >= (unsigned)ibase)
            break;      /* exit loop if bad digit found */

        /* record the fact we have read one digit */
        flags |= FL_READDIGIT;

        /* we now need to compute number = number * base + digval,
           but we need to know if overflow occured.  This requires
           a tricky pre-check. */

        if (number < maxval || (number == maxval &&
        (unsigned long)digval <= ULONG_MAX % ibase)) {
            /* we won't overflow, go ahead and multiply */
            number = number * ibase + digval;
        }
        else {
            /* we would have overflowed -- set the overflow flag */
            flags |= FL_OVERFLOW;
            if (endptr == NULL) {
                /* no need to keep on parsing if we
                   don't have to return the endptr. */
                break;
            }
        }

        c = *p++;       /* read next digit */
    }

    --p;                /* point to place that stopped scan */

    if (!(flags & FL_READDIGIT)) {
        /* no number there; return 0 and point to beginning of
           string */
        if (endptr)
            /* store beginning of string in endptr later on */
            p = nptr;
        number = 0L;        /* return 0 */
    }
    else if ( (flags & FL_OVERFLOW) ||
          ( !(flags & FL_UNSIGNED) &&
            ( ( (flags & FL_NEG) && (number > -LONG_MIN) ) ||
              ( !(flags & FL_NEG) && (number > LONG_MAX) ) ) ) )
    {
        /* overflow or signed overflow occurred */
        errno = ERANGE;
        if ( flags & FL_UNSIGNED )
            number = ULONG_MAX;
        else if ( flags & FL_NEG )
            number = (unsigned long)(-LONG_MIN);
        else
            number = LONG_MAX;
    }

    if (endptr != NULL)
        /* store pointer to char that stopped the scan */
        *endptr = p;

    if (flags & FL_NEG)
        /* negate result if there was a neg sign */
        number = (unsigned long)(-(long)number);

    return number;          /* done. */
}

extern "C" long __cdecl wcstol (
        const wchar_t *nptr,
        wchar_t **endptr,
        int ibase
        )
{
    return (long) wcstoxl(nptr, (const wchar_t **)endptr, ibase, 0);
}

extern "C" long __cdecl _wcstol_l (
        const wchar_t *nptr,
        wchar_t **endptr,
        int ibase,
        _locale_t plocinfo
        )
{
    return (long) wcstoxl(nptr, (const wchar_t **)endptr, ibase, 0);
}

extern "C" unsigned long __cdecl wcstoul (
        const wchar_t *nptr,
        wchar_t **endptr,
        int ibase
        )
{
    return wcstoxl(nptr, (const wchar_t **)endptr, ibase, FL_UNSIGNED);
}

extern "C" unsigned long __cdecl _wcstoul_l (
        const wchar_t *nptr,
        wchar_t **endptr,
        int ibase,
        _locale_t plocinfo
        )
{
    return wcstoxl(nptr, (const wchar_t **)endptr, ibase, FL_UNSIGNED);
}