USES_CONVERSION

宽窄字符的转换对于C++专业户来说是经常的动作。一般两种比较方便的方法：

1. C++:WideCharToMultiByte  MultiByteToWideChar; C语言提供的转换函数为mbstowcs()/wcstombs()

2. C++:A2W W2A (USES_CONVERSION)

3. (追加)CStringA CStringW 之间仅用一个"="就完成了转换 神奇的很！！Love CString, Love Programming!

 

Method 1: #include <windows.h> 

Method 2: #include <atlconv.h>  且使用A2W/W2A前一定要写USES_CONVERSION

Test Func:

void Func17()
{
    //测试W2A时是否需要一倍的空间
    cout<<"------------------------testing _W2A_------------------------"<<endl;
    CStringW cW = "nVIDIA";
    int nLenW = cW.GetLength();
    cout<<"W length:  "<<nLenW<<endl;
    wcout<<L"W string:   "<<cW.GetBuffer()<<endl;

    int nLenA = nLenW*2+1;

    char* szA = new char[nLenA];
    memset(szA, 0, nLenA);
    
    cout<<"A length before translating:  "<<nLenA<<endl;

    WideCharToMultiByte(CP_ACP, 0, cW.GetBuffer(), -1, szA, nLenA, NULL, NULL);  //CP_ACP when to use other ?

    cout<<"A length after translated:  "<<strlen(szA)<<endl;
    cout<<"A string:  "<<szA<<endl;

    free(szA);
    szA = NULL;


    cout<<"--------------------------testing _A2W_----------------------------------"<<endl;
    CStringA cA = "Intel Chipset";
    int nLenA2 = cA.GetLength();
    cout<<"A length:  "<<nLenA2<<endl;
    cout<<"A string:   "<<cA.GetBuffer()<<endl;

    cout<<endl;

    int nLenW2 = nLenA2 + 1;     //  '\0' plus
    wchar_t* szW = new wchar_t[nLenW2];
    memset(szW, 0, nLenW2);
    cout<<"W length b4 translating:   "<<nLenW2<<endl;
    MultiByteToWideChar(CP_ACP, 0, cA.GetBuffer(), -1, szW, nLenW2);
    cout<<"W length a4 translated:    "<<wcslen(szW)<<endl;
    wcout<<"W string:    "<<szW<<endl;

    free(szW);
    szW = NULL;

    cout<<"----------------------testing   USES_CONVERSION----------------"<<endl;
    CStringA cA3 = "Grok those URLs";
    cout<<"cA3 b4:  "<<cA3.GetBuffer()<<endl;

    USES_CONVERSION;
    CStringW cW3 = A2W(cA3.GetBuffer());
    wcout<<cW3.GetBuffer()<<endl;

    cA3 = W2A(cW3.GetBuffer());
    cout<<"cA3 a4:   "<<cA3.GetBuffer()<<endl;  //yeah~

}

 

 但要注意：使用USES_CONVERSION是从堆栈上分配的内存，如果这么写：

void fn()
{
    while(true)
    {
        {
            USES_CONVERSION;
            DoSomething(A2W("SomeString"));
        }
    }
}

很可能导致stack overflow.

参考：http://www.cnblogs.com/carekee/articles/1935789.html

 （追加）

    cout<<"----------------------CStringA  <--> CStringW can translated automatically----------------"<<endl;
    CStringW cW4= "Love CString, Love Programming";
    CStringA cA4 = cW4;
    wcout<<"W string:  "<<cW4.GetBuffer()<<endl;
    cout<<"A string:     "<<cA4.GetBuffer()<<endl;

    cout<<endl<<endl;

    cW4 = cA4;
    wcout<<"W string :    "<<cW4.GetBuffer()<<endl;