• VC 中类型转换(转)


    CString->TCHAR*的转化可以用函数GetBuff()

    函数原型为:LPTSTR GetBuffer( int nMinBufLength );
    CString str("CString");
    TCHAR* szMsg = new TCHAR[100];
    //其参数为CString字符串的长度
    szMsg = str.GetBuffer(str.GetLength());
    str.ReleaseBuffer();
    delete []szMsg;
    szMsg = NULL;

    TCHAR*->CString的转化

    TCHAR szTchar[18] = L"TCHAR";
    CString str;
    str.Format(_T("%s"),szTchar);

    CString和string的互相转换

    CString->std::string 例子:
    CString strMfc="test";
    std::string strStl;
    strStl=strMfc.GetBuffer(0);
    std::string->CString 例子:
    CString strMfc;
    std::string strStl="test";
    strMfc=strStl.c_str();

    对有关数据类型转换的整理

    int i = 100;
    long l = 2001;
    float f=300.2;
    double d=12345.119;
    char username[]="程佩君";
    char temp[200];
    char *buf;
    CString str;
    _variant_t v1;
    _bstr_t v2;
    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,但并不直接指向字串的缓冲区。
      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。可以转换的字符串类型包括 char *wchar_t*_bstr_tCComBSTRCStringbasic_stringSystem.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

      示例

      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。

      // 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;
      }
      
      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

      示例

      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。

      // 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;
      }
      
      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

      示例

      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。

      // 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

      示例

      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。

      // 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

      示例

      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。

      // 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;
      }
      
      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

      示例

      说明

      此示例演示如何从 basic_string 转换为上面列出的其他字符串类型。

      // convert_from_basic_string.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()
      {
          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 origsize = 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

      示例

      说明

      此示例演示如何从 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()
      {
          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 origsize = 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;
      }
      
      输出
      Hello, World! (System::String)
      Hello, World! (char *)
      Hello, World! (wchar_t *)
      Hello, World! (_bstr_t)
      Hello, World! (CComBSTR)
      Hello, World! (CString)
      Hello, World! (basic_string)
      
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  • 原文地址:https://www.cnblogs.com/mazhenyu/p/1846652.html
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