Data Conversion
http://msdn.microsoft.com/en-us/library/0heszx3w.aspx
Convert a string to integer
int atoi(
const char *str
);
int _wtoi(
const wchar_t *str
);
Each function returns the int value produced by interpreting the input characters as a number. The return value is 0 for atoi and _wtoi, if the input cannot be converted to a value of that type.
Required header
Header file: stdlib.h
ATL and MFC String Conversion Macros
1 //Example 1
2 // Convert LPCWSTR to LPCSTR.
3 void ExampleFunction1(LPCWSTR pszW)
4 {
5 // Create an instance of CW2A, called pszA,
6 // and initialize it with pszW.
7 CW2A pszA(pszW);
8 // pszA works like an LPCSTR, and can be used thus:
9 ExampleFunctionA(pszA);
10 // Note: pszA will become invalid when it goes out of scope.
11 }
12
13 // Example 2
14 // Use a temporary instance of CW2A.
15 void ExampleFunction2(LPCWSTR pszW)
16 {
17 // Create a temporary instance of CW2A,
18 // and initialize it with pszW.
19 ExampleFunctionA(CW2A(pszW));
20 // Note: the temporary instance becomes invalid
21 // after the execution of the statement above.
22 }
23
24 // Example 3
25 // Incorrect use of conversion macros.
26 void ExampleFunction3(LPCWSTR pszW)
27 {
28 // Create a temporary instance of CW2A,
29 // save a pointer to it and then delete
30 // the temportary instance.
31 LPCSTR pszA = CW2A(pszW);
32 // The pszA in the following line is an invalid pointer,
33 // as the instance of CW2A has gone out of scope.
34 ExampleFunctionA(pszA);
35 }
The recommended way of converting to and from BSTR strings is to use the CComBSTR class. To convert to a BSTR, pass the existing string to the constructor of CComBSTR. To convert from a BSTR, use COLE2[C]DestinationType[EX], such as COLE2T.
Requirements
Header file: AtlBase.h, AtlConv.h (declared in AtlConv.h)
http://msdn.microsoft.com/en-us/library/87zae4a3(v=VS.100).aspx
Programming with CComBSTR
1 // Declare a CComBSTR object. Although the argument is ANSI,
2 // the constructor converts it into UNICODE.
3 CComBSTR bstrMyString("Hello World");
4 // Convert the string into an ANSI string
5 CW2A szMyString(bstrMyString);
6 // Display the ANSI string
7 MessageBoxA(NULL, szMyString, "String Test", MB_OK);
If you are using a string literal to modify a CComBSTR object, use wide character strings. This will reduce unnecessary conversions.
As the CComBSTR class allocates a buffer to perform certain operations, such as the += operator or Append method, it is not recommended that you perform string manipulation inside a tight loop. In these situations, CStringT provides better performance.
Requirements
Header: atlbase.h
http://msdn.microsoft.com/en-us/library/bdyd6xz6.aspx
MultiByteToWideChar function
int MultiByteToWideChar(
__in UINT CodePage,
__in DWORD dwFlags,
__in LPCSTR lpMultiByteStr,
__in int cbMultiByte,
__out LPWSTR lpWideCharStr,
__in int cchWideChar
);
例：
1 char sText[20] = "多字节字符串!OK!";
2 DWORD dwNum = MultiByteToWideChar(CP_ACP, 0, sText, -1, NULL, 0);
3 wchar_t *pwText = NULL;
4 pwText = new wchar_t[dwNum];
5 memset(pwText, 0, (dwNum+1) * sizeof(wchar_t));
6 MultiByteToWideChar(CP_ACP, 0, sText, -1, pwText, dwNum);
7 if(!pwText)
8 {
9 delete []pwText;
10 pwText = NULL;
11 }
Requirements
Header: Winnls.h (include Windows.h)
http://msdn.microsoft.com/en-us/library/dd319072(v=VS.85).aspx
WideCharToMultiByte function
int WideCharToMultiByte(
__in UINT CodePage,
__in DWORD dwFlags,
__in LPCWSTR lpWideCharStr,
__in int cchWideChar,
__out LPSTR lpMultiByteStr,
__in int cbMultiByte,
__in LPCSTR lpDefaultChar,
__out LPBOOL lpUsedDefaultChar
);
例：
1 wchar_t wText[20] = {L"宽字符转换实例!OK!"};
2 DWORD dwNum = WideCharToMultiByte(CP_OEMCP, NULL, wText, -1, NULL, 0, NULL, FALSE);
3 char *psText = NULL;
4 psText = new char[dwNum];
5 memset(psText, 0, (dwNum+1) * sizeof(char));
6 WideCharToMultiByte(CP_OEMCP, NULL, wText, -1, psText, dwNum, NULL, FALSE);
7 if(!psText)
8 {
9 delete []psText;
10 psText = NULL;
11 }
Requirements
Header: Winnls.h (include Windows.h)