常用字符串转换

一、其它数据类型转换为字符串

  • 短整型(int)
    itoa(i,temp,10);///将i转换为字符串放入temp中,最后一个数字表示十进制
    itoa(i,temp,2); ///按二进制方式转换
  • 长整型(long)
    ltoa(l,temp,10);
  • 浮点数(float,double)
    用fcvt可以完成转换,这是MSDN中的例子:
    int decimal, sign;
    char *buffer;
    double source = 3.1415926535;
    buffer = _fcvt( source, 7, &decimal, &sign );
    运行结果:source: 3.1415926535 buffer: '31415927' decimal: 1 sign: 0
    decimal表示小数点的位置,sign表示符号:0为正数,1为负数
  • CString变量
    str = "2008北京奥运";
    buf = (LPSTR)(LPCTSTR)str;
  • BSTR变量
    BSTR bstrValue = ::SysAllocString(L"程序员");
    char * buf = _com_util::ConvertBSTRToString(bstrValue);
    SysFreeString(bstrValue);
    AfxMessageBox(buf);
    delete(buf);
  • CComBSTR变量
    CComBSTR bstrVar("test");
    char *buf = _com_util::ConvertBSTRToString(bstrVar.m_str);
    AfxMessageBox(buf);
    delete(buf);
  • _bstr_t变量
    _bstr_t类型是对BSTR的封装,因为已经重载了=操作符,所以很容易使用
    _bstr_t bstrVar("test");
    const char *buf = bstrVar;///不要修改buf中的内容
    AfxMessageBox(buf);
  • 通用方法(针对非COM数据类型)
    用sprintf完成转换
    char buffer[200]; char c = '1'; int i = 35; long j = 1000; float f = 1.7320534f; sprintf( buffer, "%c",c); sprintf( buffer, "%d",i); sprintf( buffer, "%d",j); sprintf( buffer, "%f",f);
    二、字符串转换为其它数据类型
    strcpy(temp,"123");
  • 短整型(int)
    i = atoi(temp);
  • 长整型(long)l = atol(temp);
  • 浮点(double)   d = atof(temp);
  • CString变量CString name = temp;
  • BSTR变量BSTR bstrValue = ::SysAllocString(L"程序员");

         ...///完成对bstrValue的使用          SysFreeString(bstrValue);

  • CComBSTR变量CComBSTR类型变量可以直接赋值 CComBSTR bstrVar1("test"); CComBSTR bstrVar2(temp);
  • _bstr_t变量_bstr_t类型的变量可以直接赋值 _bstr_t bstrVar1("test");
    _bstr_t bstrVar2(temp);

三、其它数据类型转换到CString使用CString的成员函数Format来转换,例如:

  • 整数(int) str.Format("%d",i);
  • 浮点数(float) str.Format("%f",i);
  • 字符串指针(char *)等已经被CString构造函数支持的数据类型可以直接赋值 str = username;
  • 对于Format所不支持的数据类型,可以通过上面所说的关于其它数据类型转化到char *的方法先转到char *,然后赋值给CString变量。

四、BSTR、_bstr_t与CComBSTR

  • CComBSTR 是ATL对BSTR的封装,_bstr_t是C++对BSTR的封装,BSTR是32位指针,但并不直直指向字串的缓冲区。 char *转换到BSTR可以这样: BSTR b=_com_util::ConvertStringToBSTR("数据");///使用前需要加上comutil.h和comsupp.lib SysFreeString(bstrValue); 反之可以使用 char *p=_com_util::ConvertBSTRToString(b); delete p; 具体可以参考一,二段落里的具体说明。
    CComBSTR与_bstr_t对大量的操作符进行了重载,可以直接进行=,!=,==等操作,所以使用非常方便。
    特别是_bstr_t,建议大家使用它。

五、VARIANT 、_variant_t 与 COleVariant

VARIANT的结构可以参考头文件VC98\Include\OAIDL.H中关于结构体tagVARIANT的定义。
对于VARIANT变量的赋值:首先给vt成员赋值,指明数据类型,再对联合结构中相同数据类型的变量赋值,举个例子:
VARIANT va;
int a=2001;
va.vt=VT_I4;///指明整型数据
va.lVal=a; ///赋值
_variant_t是VARIANT的封装类,其赋值可以使用强制类型转换,其构造函数会自动处理这些数据类型。
使用时需加上#include <comdef.h>
例如:
long l=222;
ing i=100;
_variant_t lVal(l);
lVal = (long)i;

  • COleVariant的使用与_variant_t的方法基本一样,请参考如下例子:
    COleVariant v3 = "字符串", v4 = (long)1999;
    CString str =(BSTR)v3.pbstrVal;
    long i = v4.lVal;

  • ////////////////////////////////////////////////////////////////////////////////////
    本主题演示如何将各种 C++ 字符串类型转换为其他字符串。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 rigsize = 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;
    }

  • 输出
    Hello, World! (char *)
    Hello, World! (wchar_t *)
    Hello, World! (_bstr_t)
    Hello, World! (CComBSTR)
    Hello, World! (CString)
    Hello, World! (basic_string)
    Hello, World! (System::String)

  • 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 rigsize = 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;
    }

  • 输出
    Hello, World! (wchar_t *)
    Hello, World! (char *)
    Hello, World! (_bstr_t)
    Hello, World! (CComBSTR)
    Hello, World! (CString)
    Hello, World! (basic_string)
    Hello, World! (System::String)

    • 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;
      }

      输出
      Hello, World! (_bstr_t)
      Hello, World! (char *)
      Hello, World! (wchar_t *)
      Hello, World! (CComBSTR)
      Hello, World! (CString)
      Hello, World! (basic_string)
      Hello, World! (System::String)

      从 CComBSTR 转换

      // 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()
      {
          CComBSTR orig("Hello, World!");
          CW2A printstr(orig);
          cout << printstr << " (CComBSTR)" << endl;

          // Convert to a char*
          const size_t newsize = 100;
          char nstring[newsize];
          CW2A tmpstr1(orig);
          strcpy_s(nstring, tmpstr1);
          strcat_s(nstring, " (char *)");
          cout << nstring << endl;

          // Convert to a wchar_t*
          wchar_t wcstring[newsize];
          wcscpy_s(wcstring, orig);
          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 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;
      }

    输出

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

     

    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 rigsize = 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;
    }
    输出

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

         从basic_string 转换

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

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

    using namespace std;
    using namespace System;

    int main()
    {
        string orig("Hello, World!");
        cout << orig << " (basic_string)" << endl;

        // Convert to a char*
        const size_t newsize = 100;
        char nstring[newsize];
        strcpy_s(nstring, orig.c_str());
        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 rigsize = strlen(orig.c_str()) + 1;
        size_t convertedChars = 0;
        wchar_t wcstring[newsize];
        mbstowcs_s(&convertedChars, wcstring, origsize, orig.c_str(), _TRUNCATE);
        wcscat_s(wcstring, L" (wchar_t *)");
        wcout << wcstring << endl;

        // Convert to a _bstr_t
        _bstr_t bstrt(orig.c_str());
        bstrt += " (_bstr_t)";
        cout << bstrt << endl;

        // Convert to a CComBSTR
        CComBSTR ccombstr(orig.c_str());
        if (ccombstr.Append(L" (CComBSTR)") == S_OK)
        {
            CW2A printstr(ccombstr);
            cout << printstr << endl;
        }

        // Convert to a CString
        CString cstring(orig.c_str());
        cstring += " (CString)";
        cout << cstring << endl;

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

    输出
    Hello, World! (basic_string)
    Hello, World! (char *)
    Hello, World! (wchar_t *)
    Hello, World! (_bstr_t)
    Hello, World! (CComBSTR)
    Hello, World! (CString)
    Hello, World! (System::String)

       
    从 System::String 转换

    // 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()
    {
        String ^orig = gcnew String("Hello, World!");
        Console::WriteLine("{0} (System::String)", orig);

        pin_ptr<const wchar_t> wch = PtrToStringChars(orig);

        // Convert to a char*
        size_t rigsize = wcslen(wch) + 1;
        const size_t newsize = 100;
        size_t convertedChars = 0;
        char nstring[newsize];
        wcstombs_s(&convertedChars, nstring, origsize, wch, _TRUNCATE);
        strcat_s(nstring, " (char *)");
        cout << nstring << endl;

        // Convert to a wchar_t*
        wchar_t wcstring[newsize];
        wcscpy_s(wcstring, wch);
        wcscat_s(wcstring, L" (wchar_t *)");
        wcout << wcstring << endl;

        // Convert to a _bstr_t
        _bstr_t bstrt(wch);
        bstrt += " (_bstr_t)";
        cout << bstrt << endl;

        // Convert to a CComBSTR
        CComBSTR ccombstr(wch);
        if (ccombstr.Append(L" (CComBSTR)") == S_OK)
        {
            CW2A printstr(ccombstr);
            cout << printstr << endl;
        }

        // Convert to a CString
        CString cstring(wch);
        cstring += " (CString)";
        cout << cstring << endl;

        // Convert to a basic_string
        wstring basicstring(wch);
        basicstring += L" (basic_string)";
        wcout << basicstring << endl;

        delete orig;
    }

  • posted @ 2009-04-24 13:01 郭涛 阅读(...) 评论(...) 编辑 收藏