mbsnbcnt.c

C标准库源代码

/***
*mbsnbcnt.c - Returns byte count of MBCS string
*
*       Copyright (c) 1985-1997, Microsoft Corporation.  All rights reserved.
*
*Purpose:
*       Returns byte count of MBCS string
*
*******************************************************************************/

#ifdef _MBCS

#include <mtdll.h>
#include <cruntime.h>
#include <mbdata.h>
#include <mbctype.h>
#include <mbstring.h>


/***
* _mbsnbcnt - Returns byte count of MBCS string
*
*Purpose:
*       Returns the number of bytes between the start of the supplied
*       string and the char count supplied.  That is, this routine
*       indicates how many bytes are in the first "ccnt" characters
*       of the string.
*
*Entry:
*       unsigned char *string = pointer to string
*       unsigned int ccnt = number of characters to scan
*
*Exit:
*       Returns number of bytes between string and ccnt.
*
*       If the end of the string is encountered before ccnt chars were
*       scanned, then the length of the string in bytes is returned.
*
*Exceptions:
*
*******************************************************************************/

size_t __cdecl _mbsnbcnt(
    const unsigned char *string,
    size_t ccnt
    )
{
        unsigned char *p;

        _mlock(_MB_CP_LOCK);

        for (p = (char *)string; (ccnt-- && *p); p++) {

                if (_ISLEADBYTE(*p)) {
                        if (*++p == '\0') {
                                --p;
                                break;
                        }
                }
        }

        _munlock(_MB_CP_LOCK);
        return ((size_t) ((char *)p - (char *)string));
}

#endif  /* _MBCS */