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The latest version of this topic can be found at mbsinit.

Tracks the state of a multibyte character conversion.

      int mbsinit(  
   const mbstate_t* ps  


A pointer to an mbstate_t variable.

Nonzero if ps is NULL or if not in the middle of a conversion.

When using one of the ANSI functions that takes an mbstate_t pointer, passing the address of your mbstate_t will return information about whether the last byte in the buffer was converted.

The appropriate code page needs to be installed to support your multibyte characters.

// crt_mbsinit.cpp  
#include <stdio.h>  
#include <mbctype.h>  
#include <string.h>  
#include <locale.h>  
#include <cwchar>  
#include <xlocinfo.h>  
#define   BUF_SIZE   0x40  
wchar_t      g_wcBuf[BUF_SIZE] = L"This a wc buffer that will be over written...";  
char      g_mbBuf[BUF_SIZE] = "AaBbCc\x9A\x8B\xE0\xEF\xF0xXyYzZ";  
int      g_nInit = strlen(g_mbBuf);  
int MbsinitSample(char* szIn, wchar_t* wcOut, int nMax)  
   mbstate_t   state = {0};  
   size_t      nConvResult, nmbLen = 0, nwcLen = 0;  
   wchar_t*   wcCur = wcOut;  
   wchar_t*   wcEnd = wcCur + nMax;  
   const char*   mbCur = szIn;  
   const char*   mbEnd = mbCur + strlen(mbCur) + 1;  
   char*      szLocal = setlocale(LC_ALL, "japanese");  
   printf("Locale set to: \"%s\"\n", szLocal);  
   if   (_setmbcp(_MB_CP_LOCALE) != -1)  
      while   ((mbCur < mbEnd) && (wcCur < wcEnd))  
         nConvResult = mbrtowc(wcCur, mbCur, 1, &state);   
         switch   (nConvResult)  
            case 0:  
            {   // done  
               printf("Conversion succeeded!\nMB String: ");  
               printf("\nWC String: ");  
               mbCur = mbEnd;  
            case -1:  
            {   // encoding error  
               printf("ERROR: The call to mbrtowc has detected an encoding error.\n");  
               mbCur = mbEnd;  
            case -2:  
            {   // incomplete character  
               if   (!mbsinit(&state))  
                  printf("Currently in middle of mb conversion, state = %x\n", state);  
                  // state will contain data regarding lead byte of mb character  
               if   (nConvResult > 2)   // Microsoft mb should never be larger than 2  
                  printf("ERROR: nConvResult = %d\n", nConvResult);  
      printf("ERROR: _setmbcp(932) failed!");  
   return 0;  
int main(int argc, char* argv[])  
   return MbsinitSample(g_mbBuf, g_wcBuf, BUF_SIZE);  

Locale set to: "Japanese_Japan.932"  
Currently in middle of mb conversion, state = 9a  
Currently in middle of mb conversion, state = e0  
Currently in middle of mb conversion, state = f0  
Conversion succeeded!  
MB String: AaBbCcxXyYzZ  
WC String: AaBbCcxXyYzZ  

Byte Classification