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其它数据类型转换为字符串

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 on 2009-01-03 14:31 doing5552 阅读(515) 评论(0) 编辑收藏引用

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doing5552

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留言簿(24)

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随笔档案(73)

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搜索

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最新随笔

最新评论

阅读排行榜

评论排行榜

输出

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

doing5552

公告

常用链接

留言簿(24)

我参与的团队

随笔分类(2)

随笔档案(73)

news

最新随笔

搜索

积分与排名

最新随笔

最新评论

阅读排行榜

评论排行榜

输出

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

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