windows-server-2003/base/crts/crtw32/mbstring/mbsrev.c

/***
*mbsrev.c - Reverse a string in place (MBCS)
*
*       Copyright (c) 1985-2001, Microsoft Corporation.  All rights reserved.
*
*Purpose:
*       Reverse a string in place (MBCS)
*
*Revision History:
*       11-19-92  KRS   Ported from 16-bit sources.
*       10-05-93  GJF   Replaced _CRTAPI1 with __cdecl.
*       04-15-93  CFW   Add _MB_CP_LOCK.
*       05-09-94  CFW   Optimize for SBCS.
*       05-19-94  CFW   Enable non-Win32.
*       09-11-97  GJF   Replaced __mbcodepage == 0 with _ISNOTMBCP.
*       04-17-98  GJF   Revised multithread support based on threadmbcinfo
*                       structs
*
*******************************************************************************/

#ifdef  _MBCS

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


/***
* _mbsrev - Reverse a string in place (MBCS)
*
*Purpose:
*       Reverses the order of characters in the string.  The terminating
*       null character remains in place.  The order of MBCS characters
*       is not changed.
*
*Entry:
*       unsigned char *string = string to reverse
*
*Exit:
*       returns string - now with reversed characters
*
*Exceptions:
*
*******************************************************************************/

unsigned char * __cdecl _mbsrev(
        unsigned char *string
        )
{

        unsigned char *start = string;
        unsigned char *left  = string;
        unsigned char c;
#ifdef  _MT
        pthreadmbcinfo ptmbci = _getptd()->ptmbcinfo;

        if ( ptmbci != __ptmbcinfo )
            ptmbci = __updatetmbcinfo();

        if ( _ISNOTMBCP_MT(ptmbci) )
#else
        if ( _ISNOTMBCP )
#endif
            return _strrev(string);


        /* first go through and reverse the bytes in MBCS chars */
        while ( *string ) {
#ifdef  _MT
            if ( __ismbblead_mt(ptmbci, *string++) ) {
#else
            if ( _ismbblead(*string++) ) {
#endif
                if ( *string ) {
                    c = *string;
                    *string = *(string - 1);
                    *(string - 1) = c;
                    string++;
                }
                else /* second byte is EOS */
                    break;
            }
        }

        /* now reverse the whole string */
        string--;
        while ( left < string ) {
            c = *left;
            *left++ = *string;
            *string-- = c;
        }

        return ( start );
}

#endif  /* _MBCS */