mbsnset.c

C标准库源代码

/***
*mbsnset.c - Sets first n charcaters of string to given character (MBCS)
*
*       Copyright (c) 1985-1997, Microsoft Corporation.  All rights reserved.
*
*Purpose:
*       Sets first n charcaters of string to given character (MBCS)
*
*******************************************************************************/

#ifdef _MBCS

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


/***
* _mbsnset - Sets first n charcaters of string to given character (MBCS)
*
*Purpose:
*       Sets the first n characters of string to the supplied
*       character value.  If the length of string is less than n,
*       the length of string is used in place of n.  Handles
*       MBCS chars correctly.
*
*       There are several factors that make this routine complicated:
*               (1) The fill value may be 1 or 2 bytes long.
*               (2) The fill operation may end by hitting the count value
*               or by hitting the end of the string.
*               (3) A null terminating char is NOT placed at the end of
*               the string.
*
*       Cases to be careful of (both of these can occur at once):
*               (1) Leaving an "orphaned" trail byte in the string (e.g.,
*               overwriting a lead byte but not the corresponding trail byte).
*               (2) Writing only the 1st byte of a 2-byte fill value because the
*               end of string was encountered.
*
*Entry:
*       unsigned char *string = string to modify
*       unsigned int val = value to fill string with
*       size_t count = count of characters to fill
*
*
*Exit:
*       Returns string = now filled with char val
*
*Uses:
*
*Exceptions:
*
*******************************************************************************/

unsigned char * __cdecl _mbsnset(
        unsigned char *string,
        unsigned int val,
        size_t count
        )
{
        unsigned char  *start = string;
        unsigned int leadbyte = 0;
        unsigned char highval, lowval;

        /*
         * leadbyte flag indicates if the last byte we overwrote was
         * a lead byte or not.
         */

        if ( _ISNOTMBCP )
                return _strnset(string, val, count);

        _mlock(_MB_CP_LOCK);

        if (highval = (unsigned char)(val>>8)) {

                /* double byte value */

                lowval = (unsigned char)(val & 0x00ff);

                while (count-- && *string) {

                        leadbyte = _ismbbtruelead(leadbyte, *string);
                        *string++ = highval;

                        if (*string) {
                                leadbyte = _ismbbtruelead(leadbyte, *string);
                                *string++ = lowval;
                        }
                        else
                                /* overwrite orphaned highval byte */
                                *(string-1) = ' ';
                }
        }

        else {
                /* single byte value */

                while (count-- && *string) {
                        leadbyte = _ismbbtruelead(leadbyte, *string);
                        *string++ = (unsigned char)val;
                }

        }

        /* overwrite orphaned trailing byte, if necessary */
        if(leadbyte && *string)
                *string = ' ';

        _munlock(_MB_CP_LOCK);
        return( start );
}

#endif  /* _MBCS */