Visual C++ 如何：在各种字符串类型之间进行转换
本主题演示如何将各种 C++ 字符串类型转换为其他字符串。可以转换的字符串类型包括 char *、wchar_t*、_bstr_t、CComBSTR、CString、basic_string 和 System.String。在所有情况下，在将字符串转换为新类型时，都会创建字符串的副本。对新字符串进行的任何更改都不会影响原始字符串，反之亦然。
从 char * 转换
// convert_from_char.cpp
// compile with /clr /link comsuppw.lib
#include <iostream>
#include <stdlib.h>
#include <string>
#include "atlbase.h"
#include "atlstr.h"
#include "comutil.h"
using namespace std;
using namespace System;
int main()
{
char *orig = "Hello, World!";
cout << orig << " (char *)" << endl;
// Convert to a wchar_t*
size_t origsize = strlen(orig) + 1;
const size_t newsize = 100;
size_t convertedChars = 0;
wchar_t wcstring[newsize];
mbstowcs_s(&convertedChars, wcstring, origsize, orig, _TRUNCATE);
wcscat_s(wcstring, L" (wchar_t *)");
wcout << wcstring << endl;
// Convert to a _bstr_t
_bstr_t bstrt(orig);
bstrt += " (_bstr_t)";
cout << bstrt << endl;
// Convert to a CComBSTR
CComBSTR ccombstr(orig);
if (ccombstr.Append(L" (CComBSTR)") == S_OK)
{
CW2A printstr(ccombstr);
cout << printstr << endl;
}
// Convert to a CString
CString cstring(orig);
cstring += " (CString)";
cout << cstring << endl;
// Convert to a basic_string
string basicstring(orig);
basicstring += " (basic_string)";
cout << basicstring << endl;
// Convert to a System::String
String ^systemstring = gcnew String(orig);
systemstring += " (System::String)";
Console::WriteLine("{0}", systemstring);
delete systemstring;
}
从 wchar_t * 转换
// convert_from_wchar_t.cpp
// compile with /clr /link comsuppw.lib
#include <iostream>
#include <stdlib.h>
#include <string>
#include "atlbase.h"
#include "atlstr.h"
#include "comutil.h"
using namespace std;
using namespace System;
int main()
{
wchar_t *orig = L"Hello, World!";
wcout << orig << L" (wchar_t *)" << endl;
// Convert to a char*
size_t origsize = wcslen(orig) + 1;
const size_t newsize = 100;
size_t convertedChars = 0;
char nstring[newsize];
wcstombs_s(&convertedChars, nstring, origsize, orig, _TRUNCATE);
strcat_s(nstring, " (char *)");
cout << nstring << endl;
// Convert to a _bstr_t
_bstr_t bstrt(orig);
bstrt += " (_bstr_t)";
cout << bstrt << endl;
// Convert to a CComBSTR
CComBSTR ccombstr(orig);
if (ccombstr.Append(L" (CComBSTR)") == S_OK)
{
CW2A printstr(ccombstr);
cout << printstr << endl;
}
// Convert to a CString
CString cstring(orig);
cstring += " (CString)";
cout << cstring << endl;
// Convert to a basic_string
wstring basicstring(orig);
basicstring += L" (basic_string)";
wcout << basicstring << endl;
// Convert to a System::String
String ^systemstring = gcnew String(orig);
systemstring += " (System::String)";
Console::WriteLine("{0}", systemstring);
delete systemstring;
}
从 _bstr_t 转换
// convert_from_bstr_t.cpp
// compile with /clr /link comsuppw.lib
#include <iostream>
#include <stdlib.h>
#include <string>
#include "atlbase.h"
#include "atlstr.h"
#include "comutil.h"
using namespace std;
using namespace System;
int main()
{
_bstr_t orig("Hello, World!");
wcout << orig << " (_bstr_t)" << endl;
// Convert to a char*
const size_t newsize = 100;
char nstring[newsize];
strcpy_s(nstring, (char *)orig);
strcat_s(nstring, " (char *)");
cout << nstring << endl;
// Convert to a wchar_t*
wchar_t wcstring[newsize];
wcscpy_s(wcstring, (wchar_t *)orig);
wcscat_s(wcstring, L" (wchar_t *)");
wcout << wcstring << endl;
// Convert to a CComBSTR
CComBSTR ccombstr((char *)orig);
if (ccombstr.Append(L" (CComBSTR)") == S_OK)
{
CW2A printstr(ccombstr);
cout << printstr << endl;
}
// Convert to a CString
CString cstring((char *)orig);
cstring += " (CString)";
cout << cstring << endl;
// Convert to a basic_string
string basicstring((char *)orig);
basicstring += " (basic_string)";
cout << basicstring << endl;
// Convert to a System::String
String ^systemstring = gcnew String((char *)orig);
systemstring += " (System::String)";
Console::WriteLine("{0}", systemstring);
delete systemstring;
}
从 CString 转换
// convert_from_cstring.cpp
// compile with /clr /link comsuppw.lib
#include <iostream>
#include <stdlib.h>
#include <string>
#include "atlbase.h"
#include "atlstr.h"
#include "comutil.h"
using namespace std;
using namespace System;
int main()
{
CString orig("Hello, World!");
wcout << orig << " (CString)" << endl;
// Convert to a char*
const size_t newsize = 100;
char nstring[newsize];
strcpy_s(nstring, orig);
strcat_s(nstring, " (char *)");
cout << nstring << endl;
// Convert to a wchar_t*
// You must first convert to a char * for this to work.
size_t origsize = strlen(orig) + 1;
size_t convertedChars = 0;
wchar_t wcstring[newsize];
mbstowcs_s(&convertedChars, wcstring, origsize, orig, _TRUNCATE);
wcscat_s(wcstring, L" (wchar_t *)");
wcout << wcstring << endl;
// Convert to a _bstr_t
_bstr_t bstrt(orig);
bstrt += " (_bstr_t)";
cout << bstrt << endl;
// Convert to a CComBSTR
CComBSTR ccombstr(orig);
if (ccombstr.Append(L" (CComBSTR)") == S_OK)
{
CW2A printstr(ccombstr);
cout << printstr << endl;
}
// Convert to a basic_string
string basicstring(orig);
basicstring += " (basic_string)";
cout << basicstring << endl;
// Convert to a System::String
String ^systemstring = gcnew String(orig);
systemstring += " (System::String)";
Console::WriteLine("{0}", systemstring);
delete systemstring;
}
关于函数：wcstombs_s, _wcstombs_s_l
函数描述：Converts a sequence of wide characters to a corresponding sequence of multibyte characters.
errno_t wcstombs_s( size_t *pReturnValue, char *mbstr, size_t sizeInBytes, const wchar_t *wcstr, size_t count ); errno_t _wcstombs_s_l( size_t *pReturnValue, char *mbstr, size_t sizeInBytes, const wchar_t *wcstr, size_t count, _locale_t locale );
Parameters
[out] pReturnValue The number of characters converted. [out] mbstr The address of a buffer for the resulting converted multibyte character string. [in] sizeInBytes The size in bytes of the mbstr buffer. [in] wcstr Points to the wide character string to be converted. [in] count The maximum number of bytes to be stored in the mbstr buffer, or _TRUNCATE. [in] locale The locale to use.