字符转换

说明

此示例演示如何从 char * 转换为上面列出的其他字符串类型。 char * 字符串（也称为 C 样式字符串）使用 null 字符指示字符串的末尾。 C 样式字符串通常每个字符需要一个字节，但也可以使用两个字节。 在下面的示例中，char * 字符串有时称为多字节字符字符串，因为该字符串数据是从 Unicode 字符串转换得到的。 可对 char * 字符串执行单字节和多字节字符 (MBCS) 函数运算

// 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()
{
    // Create and display a C style string, and then use it 
    // to create different kinds of strings.
    char *orig = "Hello, World!";
    cout << orig << " (char *)" << endl;

    // newsize describes the length of the 
    // wchar_t string called wcstring in terms of the number 
    // of wide characters, not the number of bytes.
    size_t newsize = strlen(orig) + 1;

    // The following creates a buffer large enough to contain 
    // the exact number of characters in the original string
    // in the new format. If you want to add more characters
    // to the end of the string, increase the value of newsize
    // to increase the size of the buffer.
    wchar_t * wcstring = new wchar_t[newsize];

    // Convert char* string to a wchar_t* string.
    size_t convertedChars = 0;
    mbstowcs_s(&convertedChars, wcstring, newsize, orig, _TRUNCATE);
    // Display the result and indicate the type of string that it is.
    wcout << wcstring << _T(" (wchar_t *)") << endl;

    // Convert the C style string to a _bstr_t string.
    _bstr_t bstrt(orig);
    // Append the type of string to the new string
    // and then display the result.
    bstrt += " (_bstr_t)";
    cout << bstrt << endl;

    // Convert the C style string to a CComBSTR string.
    CComBSTR ccombstr(orig);
    if (ccombstr.Append(_T(" (CComBSTR)")) == S_OK)
    {
        CW2A printstr(ccombstr);
        cout << printstr << endl;
    }

    // Convert the C style string to a CstringA and display it.
    CStringA cstringa(orig);
    cstringa += " (CStringA)";
    cout << cstringa << endl;

    // Convert the C style string to a CStringW and display it.
    CStringW cstring(orig);
    cstring += " (CStringW)";
    // To display a CStringW correctly, use wcout and cast cstring
    // to (LPCTSTR).
    wcout << (LPCTSTR)cstring << endl;

    // Convert the C style string to a basic_string and display it.
    string basicstring(orig);
    basicstring += " (basic_string)";
    cout << basicstring << endl;

    // Convert the C style string to a System::String and display it.
    String ^systemstring = gcnew String(orig);
    systemstring += " (System::String)";
    Console::WriteLine("{0}", systemstring);
    delete systemstring;
}

Output

Hello, World! (char *)
Hello, World! (wchar_t *)
Hello, World! (_bstr_t)
Hello, World! (CComBSTR)
Hello, World! (CStringA)
Hello, World! (CStringW)
Hello, World! (basic_string)
Hello, World! (System::String)

说明

此示例演示如何从 wchar_t * 转换为上面列出的其他字符串类型。 包括 wchar_t * 在内的一些字符串类型可实现宽字符格式。 若要在多字节和宽字符格式之间转换字符串，则可以使用单个函数调用（如 mbstowcs_s），也可以使用针对类的构造函数调用（如 CStringA）。

// 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()
{
    // Create a string of wide characters, display it, and then
    // use this string to create other types of strings.
    wchar_t *orig = _T("Hello, World!");
    wcout << orig << _T(" (wchar_t *)") << endl;

    // Convert the wchar_t string to a char* string. Record 
    //.the length of the original string and add 1 to it to
    //.account for the terminating null character.
    size_t origsize = wcslen(orig) + 1;
    size_t convertedChars = 0;

    // Use a multibyte string to append the type of string
    // to the new string before displaying the result.
    char strConcat[] = " (char *)";
    size_t strConcatsize = (strlen( strConcat ) + 1)*2;

    // Allocate two bytes in the multibyte output string for every wide
    // character in the input string (including a wide character
    // null). Because a multibyte character can be one or two bytes,
    // you should allot two bytes for each character. Having extra
    // space for the new string is not an error, but having
    // insufficient space is a potential security problem.
    const size_t newsize = origsize*2;
    // The new string will contain a converted copy of the original
    // string plus the type of string appended to it.
    char *nstring = new char[newsize+strConcatsize];

    // Put a copy of the converted string into nstring
    wcstombs_s(&convertedChars, nstring, newsize, orig, _TRUNCATE);
    // append the type of string to the new string.
    _mbscat_s((unsigned char*)nstring, newsize+strConcatsize, (unsigned char*)strConcat);
    // Display the result.
    cout << nstring << endl;

    // Convert a wchar_t to a _bstr_t string and display it.
    _bstr_t bstrt(orig);
    bstrt += " (_bstr_t)";
    cout << bstrt << endl;

    // Convert the wchar_t string to a BSTR wide character string 
    // by using the ATL CComBSTR wrapper class for BSTR strings.
    // Then display the result.

    CComBSTR ccombstr(orig);
    if (ccombstr.Append(_T(" (CComBSTR)")) == S_OK)
    {
        // CW2A converts the string in ccombstr to a multibyte 
        // string in printstr, used here for display output.
        CW2A printstr(ccombstr);
        cout << printstr << endl;
        // The following line of code is an easier way to
        // display wide character strings:
        // wcout << (LPCTSTR) ccombstr << endl;
    }

    // Convert a wide wchar_t string to a multibyte CStringA,
    // append the type of string to it, and display the result.
    CStringA cstringa(orig);
    cstringa += " (CStringA)";
    cout << cstringa << endl;

    // Convert a wide character wchar_t string to a wide
    // character CStringW string and append the type of string to it
    CStringW cstring(orig);
    cstring += " (CStringW)";
    // To display a CStringW correctly, use wcout and cast cstring
    // to (LPCTSTR).
    wcout << (LPCTSTR)cstring << endl;

    // Convert the wide character wchar_t string to a
    // basic_string, append the type of string to it, and
    // display the result.
    wstring basicstring(orig);
    basicstring += _T(" (basic_string)");
    wcout << basicstring << endl;

    // Convert a wide character wchar_t string to a 
    // System::String string, append the type of string to it,
    // and display the result.
    String ^systemstring = gcnew String(orig);
    systemstring += " (System::String)";
    Console::WriteLine("{0}", systemstring);
    delete systemstring;
}

Output

Hello, World! (wchar_t *)
Hello, World! (char *)
Hello, World! (_bstr_t)
Hello, World! (CComBSTR)
Hello, World! (CStringA)
Hello, World! (CStringW)
Hello, World! (basic_string)
Hello, World! (System::String)

说明

此示例演示如何从 _bstr_t 转换为上面列出的其他字符串类型。 _bstr_t 对象是一种封装宽字符 BSTR 字符串的方法。 BSTR 字符串具有长度值且不使用 null 字符终止字符串，但所要转换到的目标字符串类型可能需要终止 null。

代码

// 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()
{
    // Create a _bstr_t string, display the result, and indicate the
    // type of string that it is.
    _bstr_t orig("Hello, World!");
    wcout << orig << " (_bstr_t)" << endl;

    // Convert the wide character _bstr_t string to a C style
    // string. To be safe, allocate two bytes for each character
    // in the char* string, including the terminating null.
    const size_t newsize = (orig.length()+1)*2;
    char *nstring = new char[newsize];

    // Uses the _bstr_t operator (char *) to obtain a null 
    // terminated string from the _bstr_t object for
    // nstring.
    strcpy_s(nstring, newsize, (char *)orig);
    strcat_s(nstring, newsize, " (char *)");
    cout << nstring << endl;

    // Prepare the type of string to append to the result.
    wchar_t strConcat[] = _T(" (wchar_t *)");
    size_t strConcatLen = wcslen(strConcat) + 1;

    // Convert a _bstr_t to a wchar_t* string.
    const size_t widesize = orig.length()+ strConcatLen;
    wchar_t *wcstring = new wchar_t[newsize];
    wcscpy_s(wcstring, widesize, (wchar_t *)orig);
    wcscat_s(wcstring, widesize, strConcat);
    wcout << wcstring << endl;

    // Convert a _bstr_t string to a CComBSTR string.
    CComBSTR ccombstr((char *)orig);
    if (ccombstr.Append(_T(" (CComBSTR)")) == S_OK)
    {
        CW2A printstr(ccombstr);
        cout << printstr << endl;
    }

    // Convert a _bstr_t to a CStringA string.
    CStringA cstringa(orig.GetBSTR());
    cstringa += " (CStringA)";
    cout << cstringa << endl;

    // Convert a _bstr_t to a CStringW string.
    CStringW cstring(orig.GetBSTR());
    cstring += " (CStringW)";
    // To display a cstring correctly, use wcout and
    // "cast" the cstring to (LPCTSTR).
    wcout << (LPCTSTR)cstring << endl;

    // Convert the _bstr_t to a basic_string.
    string basicstring((char *)orig);
    basicstring += " (basic_string)";
    cout << basicstring << endl;

    // Convert the _bstr_t to a System::String.
    String ^systemstring = gcnew String((char *)orig);
    systemstring += " (System::String)";
    Console::WriteLine("{0}", systemstring);
    delete systemstring;
}

Output
Hello, World! (_bstr_t)
Hello, World! (char *)
Hello, World! (wchar_t *)
Hello, World! (CComBSTR)
Hello, World! (CStringA)
Hello, World! (CStringW)
Hello, World! (basic_string)
Hello, World! (System::String)
说明
  
  
  
  

   
   
   
   
此示例演示如何从 CComBSTR 转换为上面列出的其他字符串类型。 与 _bstr_t 一样，CComBSTR 对象是一种封装宽字符 BSTR 字符串的方法。 BSTR 字符串具有长度值且不使用 null 字符终止字符串，但所要转换到的目标字符串类型可能需要终止 null。
  
  
  
  
代码
// convert_from_ccombstr.cpp
// compile with: /clr /link comsuppw.lib

#include <iostream>
#include <stdlib.h>
#include <string>

#include "atlbase.h"
#include "atlstr.h"
#include "comutil.h"
#include "vcclr.h"

using namespace std;
using namespace System;
using namespace System::Runtime::InteropServices;

int main()
{
    // Create and initialize a BSTR string by using a CComBSTR object.
    CComBSTR orig("Hello, World!");
    // Convert the BSTR into a multibyte string, display the result,
    // and indicate the type of string that it is.
    CW2A printstr(orig);
    cout << printstr << " (CComBSTR)" << endl;

    // Convert a wide character CComBSTR string to a
    // regular multibyte char* string. Allocate enough space
    // in the new string for the largest possible result,
    // including space for a terminating null.
    const size_t newsize = (orig.Length()+1)*2;
    char *nstring = new char[newsize];

    // Create a string conversion object, copy the result to
    // the new char* string, and display the result.
    CW2A tmpstr1(orig);
    strcpy_s(nstring, newsize, tmpstr1);
    cout << nstring << " (char *)" << endl;

    // Prepare the type of string to append to the result.
    wchar_t strConcat[] = _T(" (wchar_t *)");
    size_t strConcatLen = wcslen(strConcat) + 1;

    // Convert a wide character CComBSTR string to a wchar_t*.
    // The code first determines the length of the converted string
    // plus the length of the appended type of string, then
    // prepares the final wchar_t string for display.
    const size_t widesize = orig.Length()+ strConcatLen;
    wchar_t *wcstring = new wchar_t[widesize];
    wcscpy_s(wcstring, widesize, orig);
    wcscat_s(wcstring, widesize, strConcat);

    // Display the result. Unlike CStringW, a wchar_t does not need
    // a cast to (LPCTSTR) with wcout.
    wcout << wcstring << endl;

    // Convert a wide character CComBSTR to a wide character _bstr_t,
    // append the type of string to it, and display the result.
    _bstr_t bstrt(orig);
    bstrt += " (_bstr_t)";
    cout << bstrt << endl;

    // Convert a wide character CComBSTR to a multibyte CStringA,
    // append the type of string to it, and display the result.
    CStringA cstringa(orig);
    cstringa += " (CStringA)";
    cout << cstringa << endl;

    // Convert a wide character CComBSTR to a wide character CStringW.
    CStringW cstring(orig);
    cstring += " (CStringW)";
    // To display a cstring correctly, use wcout and cast cstring
    // to (LPCTSTR).
    wcout << (LPCTSTR)cstring << endl;

    // Convert a wide character CComBSTR to a wide character 
    // basic_string.
    wstring basicstring(orig);
    basicstring += _T(" (basic_string)");
    wcout << basicstring << endl;

    // Convert a wide character CComBSTR to a System::String.
    String ^systemstring = gcnew String(orig);
    systemstring += " (System::String)";
    Console::WriteLine("{0}", systemstring);
    delete systemstring;
}
Output
Hello, World! (CComBSTR)
Hello, World! (char *)
Hello, World! (wchar_t *)
Hello, World! (_bstr_t)
Hello, World! (CStringA)
Hello, World! (CStringW)
Hello, World! (basic_string)
Hello, World! (System::String)
说明
  
  
  
  

   
   
   
   
此示例演示如何从 CString 转换为上面列出的其他字符串类型。 CString 基于 TCHAR 数据类型，而后者又依赖于是否定义了 _UNICODE 符号。 如果未定义 _UNICODE，则TCHAR 定义为 char 且 CString 包含一个多字节字符字符串；如果定义了 _UNICODE，则 TCHAR 定义为 wchar_t 且 CString 包含一个宽字符字符串。
   
   
   
   
CStringA 是 CString 的多字节字符串的始终版本；CStringW 是宽字符字符串的唯一版本。 CStringA 和 CStringW 都不使用 _UNICODE 确定它们应采用的编译方式。 此示例使用 CStringA 和 CStringW 明确指定缓冲区大小分配和输出处理中的一些细微差异。
  
  
  
  
代码
// 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()
{
    // Set up a multibyte CStringA string.
    CStringA origa("Hello, World!");
    cout << origa << " (CStringA)" << endl;
    // Set up a wide character CStringW string.
    CStringW origw("Hello, World!");
    wcout << (LPCTSTR)origw << _T(" (CStringW)") << endl;

    // Convert to a char* string from CStringA string 
    // and display the result.
    const size_t newsizea = (origa.GetLength() + 1);
    char *nstringa = new char[newsizea];
    strcpy_s(nstringa, newsizea, origa);
    cout << nstringa << " (char *)" << endl;

    // Convert to a char* string from a wide character 
    // CStringW string. To be safe, we allocate two bytes for each
    // character in the original string, including the terminating
    // null.
    const size_t newsizew = (origw.GetLength() + 1)*2;
    char *nstringw = new char[newsizew];
    size_t convertedCharsw = 0;
    wcstombs_s(&convertedCharsw, nstringw, newsizew, origw, _TRUNCATE );
    cout << nstringw << " (char *)" << endl;

    // Convert to a wchar_t* from CStringA
    size_t convertedCharsa = 0;
    wchar_t *wcstring = new wchar_t[newsizea];
    mbstowcs_s(&convertedCharsa, wcstring, newsizea, origa, _TRUNCATE);
    wcout << wcstring << _T(" (wchar_t *)") << endl;

    // Convert to a wide character wchar_t* string from 
    // a wide character CStringW string. 
    wchar_t *n2stringw = new wchar_t[newsizew];
    wcscpy_s( n2stringw, newsizew, origw );
    wcout << n2stringw << _T(" (wchar_t *)") << endl;

    // Convert to a wide character _bstr_t string from 
    // a multibyte CStringA string.
    _bstr_t bstrt(origa);
    bstrt += _T(" (_bstr_t)");
    wcout << bstrt << endl;

    // Convert to a wide character_bstr_t string from 
    // a wide character CStringW string.
    bstr_t bstrtw(origw);
    bstrtw += " (_bstr_t)";
    wcout << bstrtw << endl;

    // Convert to a wide character CComBSTR string from 
    // a multibyte character CStringA string.
    CComBSTR ccombstr(origa);
    if (ccombstr.Append(_T(" (CComBSTR)")) == S_OK)
    {
        // Convert the wide character string to multibyte
        // for printing.
        CW2A printstr(ccombstr);
        cout << printstr << endl;
    }

    // Convert to a wide character CComBSTR string from 
    // a wide character CStringW string.
    CComBSTR ccombstrw(origw);
    // Append the type of string to it, and display the result.

    if (ccombstrw.Append(_T(" (CComBSTR)")) == S_OK)
    {
        CW2A printstrw(ccombstrw);
        wcout << printstrw << endl;
    }

    // Convert a multibyte character CStringA to a 
    // multibyte version of a basic_string string.
    string basicstring(origa);
    basicstring += " (basic_string)";
    cout << basicstring << endl;

    // Convert a wide character CStringW to a 
    // wide character version of a basic_string 
    // string.
    wstring basicstringw(origw);
    basicstringw += _T(" (basic_string)");
    wcout << basicstringw << endl;

    // Convert a multibyte character CStringA to a 
    // System::String.
    String ^systemstring = gcnew String(origa);
    systemstring += " (System::String)";
    Console::WriteLine("{0}", systemstring);
    delete systemstring;
说明
  
  
  
  

   
   
   
   
此示例演示如何从宽字符 (Unicode) [System::String] 转换为上面列出的其他字符串类型。
  
  
  
  
// convert_from_system_string.cpp
// compile with: /clr /link comsuppw.lib

#include <iostream>
#include <stdlib.h>
#include <string>

#include "atlbase.h"
#include "atlstr.h"
#include "comutil.h"
#include "vcclr.h"

using namespace std;
using namespace System;
using namespace System::Runtime::InteropServices;

int main()
{
    // Set up a System::String and display the result.
    String ^orig = gcnew String("Hello, World!");
    Console::WriteLine("{0} (System::String)", orig);
  
    // Obtain a pointer to the System::String in order to
    // first lock memory into place, so that the
    // Garbage Collector (GC) cannot move that object
    // while we call native functions.
    pin_ptr<const wchar_t> wch = PtrToStringChars(orig);

    // Make a copy of the system string as a multibyte
    // char* string. Allocate two bytes in the multibyte
    // output string for every wide character in the input
    // string, including space for a terminating null.
    size_t origsize = wcslen(wch) + 1;
    const size_t newsize = origsize*2;
    size_t convertedChars = 0;
    char *nstring = new char[newsize];
    wcstombs_s(&convertedChars, nstring, newsize, wch, _TRUNCATE);
    cout << nstring << " (char *)" << endl;

    // Convert a wide character system string to a 
    // wide character wchar_t* string.
    const size_t newsizew = origsize;
    wchar_t *wcstring = new wchar_t[newsizew];
    wcscpy_s(wcstring, newsizew, wch);
    wcout << wcstring << _T(" (wchar_t *)") << endl;

    // Convert a wide character system string to a
    // wide character _bstr_t string.
    _bstr_t bstrt(wch);
    bstrt += " (_bstr_t)";
    cout << bstrt << endl;

    // Convert a wide character system string 
    // to a wide character CComBSTR string.
    CComBSTR ccombstr(wch);
    if (ccombstr.Append(_T(" (CComBSTR)")) == S_OK)
    {
        // Make a multibyte copy of the CComBSTR string
        // and display the result.
        CW2A printstr(ccombstr);
        cout << printstr << endl;
    }

    // Convert a wide character System::String to
    // a multibyte CStringA string.
    CStringA cstring(wch);
    cstring += " (CStringA)";
    cout << cstring << endl;

    // Convert a wide character System::String to
    // a wide character CStringW string.
    CStringW cstringw(wch);
    cstringw += " (CStringW)";
    wcout << (LPCTSTR)cstringw << endl;

    // Convert a wide character System::String to 
    // a wide character basic_string.
    wstring basicstring(wch);
    basicstring += _T(" (basic_string)");
    wcout << basicstring << endl;

    delete orig;
}
Output
Hello, World! (System::String)
Hello, World! (char *)
Hello, World! (wchar_t *)
Hello, World! (_bstr_t)
Hello, World! (CComBSTR)
Hello, World! (CStringA)
Hello, World! (CStringW)
Hello, World! (basic_string)