C 標準

#include <stdlib.h>
mbstowcs 多位元組字串轉換為寬字串
wcstombs 寬字串轉換為多位元組字串

在呼叫 mbstowcs 之前，先用 setlocale 將全域性預設 locale 設為當前系統預設 locale
如果是在非中文系統上轉 GBK 編碼，就需要指定中文 locale ：

#include <locale.h>
setlocale(LC_ALL, "chs");

wcstombs例子：

#include <locale.h>
#include <stdio.h>
#include <stdlib.h>
 


#define BUFFER_SIZE 100

int main( void )
{
    size_t  count;
    char    *pMBBuffer = (char *)malloc(BUFFER_SIZE);
    wchar_t *pWCBuffer = L"Hello, world.你好，世界。";

    setlocale(LC_ALL, "chs");
    count = wcstombs(NULL, pWCBuffer, 0); // 只獲取多位元組字串的長度 
    count = wcstombs(pMBBuffer, pWCBuffer, BUFFER_SIZE); // 轉換並返回多位元組字串的長度
 

    printf(" Characters converted: %u\n", count);
    printf(" Multibyte character: %s\n\n", pMBBuffer);
    free(pMBBuffer);
}

輸出：

 Characters converted: 25
 Multibyte character: Hello, world.你好，世界。 

mbstowcs例子

#include <locale.h>
#include <stdio.h>
#include <stdlib.h>

#define BUFFER_SIZE 100
 


int main(void)
{
    size_t  count;
    char    *pMBBuffer = "Hello, world.你好，世界。";
    wchar_t *pWCBuffer = (wchar_t *)malloc(BUFFER_SIZE);

    setlocale(LC_ALL, "chs");
    count = mbstowcs(NULL, pMBBuffer, 0);
    count = mbstowcs(pWCBuffer, pMBBuffer, strlen(pMBBuffer));
    printf(" Characters converted: %u\n", count);
    wprintf(L" Widebyte character: %s\n\n", pWCBuffer);
    free(pWCBuffer);
}

輸出：

 Characters converted: 19
 Widebyte character: Hello, world.你好，世界。 

Windows API

#include <Windows.h>
MultiByteToWideChar 多位元組轉寬位元組，並且支援字元編碼相互轉換（gbk–utf8）
WideCharToMultiByte 寬位元組轉多位元組，並且支援字元編碼相互轉換（gbk–utf8）

WideCharToMultiByte例子：

#include <stdio.h>
#include <stdlib.h>
#include <Windows.h>

#define BUFFER_SIZE 100

int main( void )
{
    size_t  count;
    char    *pMBBuffer = (char *)malloc(BUFFER_SIZE);
    wchar_t *pWCBuffer = L"Hello, world.你好，世界。";

    count = WideCharToMultiByte(0, 0, pWCBuffer, wcslen(pWCBuffer)+1, pMBBuffer, BUFFER_SIZE, NULL, NULL); 

    printf(" Characters converted: %u\n",count );
    printf(" Multibyte character: %s\n\n",pMBBuffer );
    free(pMBBuffer);
}

結果：

 Characters converted: 26
 Multibyte character: Hello, world.你好，世界。 

MultiByteToWideChar例子：

#include <locale.h>
#include <stdio.h>
#include <stdlib.h>
#include <Windows.h>

#define BUFFER_SIZE 100

int main(void)
{
    size_t  count;
    char    *pMBBuffer = "Hello, world.你好，世界。";
    wchar_t *pWCBuffer = (wchar_t *)malloc(BUFFER_SIZE);

    count = MultiByteToWideChar(0, 0, pMBBuffer, strlen(pMBBuffer)+1, pWCBuffer, BUFFER_SIZE);

    setlocale(LC_ALL, "chs"); // 設定wprintf正常顯示中文
    printf(" Characters converted: %u\n", count);
    wprintf(L" Widebyte character: %s\n\n", pWCBuffer);
    free(pWCBuffer);
}

結果：

 Characters converted: 20
 Widebyte character: Hello, world.你好，世界。