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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
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