以下是一些VC下的强制类型转换的函数
一、字符串转换
1.CString 转化为整形Int
2.将一个CString转到一个char的数组(char*)中
3.int 转 cstring
4.char * 转 CString
5.Float 转 CString
6.CString 转 Float
7.string 转 CString
8.char* 转 int
9.CString 转 string
10.int 转 char *
11.string 转 char *
12、CString to LPCSTR
13、CString to LPSTR
14、Char[] to int
15、Char[] to float
16、Char* to int
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);
二、从其它包含字符串的变量中获取指向该字符串的指针
CString变量
str = "2008北京奥运";
buf = (LPSTR)(LPCTSTR)str;
BSTR类型的_variant_t变量
v1 = (_bstr_t)"程序员";
buf = _com_util::ConvertBSTRToString((_bstr_t)v1);
三、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);
四、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;
五、BSTR、_bstr_t与CComBSTR
CComBSTR、_bstr_t是对BSTR的封装,BSTR是指向字符串的32位指针。
char *转换到BSTR可以这样: BSTR b=_com_util::ConvertStringToBSTR("数据");///使用前需要加上头文件comutil.h
反之可以使用char *p=_com_util::ConvertBSTRToString(b);
六、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
对于不马上赋值的VARIANT,最好先用Void VariantInit(VARIANTARG FAR* pvarg);进行初始化,其本质是将vt设置为VT_EMPTY,下表我们列举vt与常用数据的对应关系:
unsigned char bVal; VT_UI1
short iVal; VT_I2
long lVal; VT_I4
float fltVal; VT_R4
double dblVal; VT_R8
VARIANT_BOOL boolVal; VT_BOOL
SCODE scode; VT_ERROR
CY cyVal; VT_CY
DATE date; VT_DATE
BSTR bstrVal; VT_BSTR
IUnknown FAR* punkVal; VT_UNKNOWN
IDispatch FAR* pdispVal; VT_DISPATCH
SAFEARRAY FAR* parray; VT_ARRAY|*
unsigned char FAR* pbVal; VT_BYREF|VT_UI1
short FAR* piVal; VT_BYREF|VT_I2
long FAR* plVal; VT_BYREF|VT_I4
float FAR* pfltVal; VT_BYREF|VT_R4
double FAR* pdblVal; VT_BYREF|VT_R8
VARIANT_BOOL FAR* pboolVal; VT_BYREF|VT_BOOL
SCODE FAR* pscode; VT_BYREF|VT_ERROR
CY FAR* pcyVal; VT_BYREF|VT_CY
DATE FAR* pdate; VT_BYREF|VT_DATE
BSTR FAR* pbstrVal; VT_BYREF|VT_BSTR
IUnknown FAR* FAR* ppunkVal; VT_BYREF|VT_UNKNOWN
IDispatch FAR* FAR* ppdispVal; VT_BYREF|VT_DISPATCH
SAFEARRAY FAR* FAR* pparray; VT_ARRAY|*
VARIANT FAR* pvarVal; VT_BYREF|VT_VARIANT
void FAR* byref; VT_BYREF
_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。
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;
七、其它
对消息的处理中我们经常需要将WPARAM或LPARAM等32位数据(DWORD)分解成两个16位数据(WORD),例如:
LPARAM lParam;
WORD loValue = LOWORD(lParam);///取低16位
WORD hiValue = HIWORD(lParam);///取高16位
对于16位的数据(WORD)我们可以用同样的方法分解成高低两个8位数据(BYTE),例如:
WORD wValue;
BYTE loValue = LOBYTE(wValue);///取低8位
BYTE hiValue = HIBYTE(wValue);///取高8位
后记:本文匆匆写成,错误之处在所难免,欢迎来信指正。
int ->str itoa,atoi
double- str ftoa,atof
_bstr_t,_variant_t,CString,long 等等看看下面:
我给你点详细的例子,看下面
先看懂_variant_t与_bstr_t这两个类的构造函数和 operator=
里面有重载了很多情况,
其他类型向_variant_t 赋值:
_variant_t( ) throw( );
_variant_t( const VARIANT& varSrc ) throw( _com_error );
_variant_t( const VARIANT* pVarSrc ) throw( _com_error );
_variant_t( const _variant_t& var_t_Src ) throw( _com_error );
_variant_t( VARIANT& varSrc, bool fCopy ) throw( _com_error );
_variant_t( short sSrc, VARTYPE vtSrc = VT_I2 ) throw( _com_error );
_variant_t( long lSrc, VARTYPE vtSrc = VT_I4 ) throw( _com_error );
_variant_t( float fltSrc ) throw( );
_variant_t( double dblSrc, VARTYPE vtSrc = VT_R8 ) throw( _com_error );
_variant_t( const CY& cySrc ) throw( );
_variant_t( const _bstr_t& bstrSrc ) throw( _com_error );
_variant_t( const wchar_t *wstrSrc ) throw( _com_error );
_variant_t( const char* strSrc ) throw( _com_error );
_variant_t( bool bSrc ) throw( );
_variant_t( IUnknown* pIUknownSrc, bool fAddRef = true ) throw( );
_variant_t( IDispatch* pDispSrc, bool fAddRef = true ) throw( );
_variant_t( const DECIMAL& decSrc ) throw( );
_variant_t( BYTE bSrc ) throw( );
operator=的重载形式:
_variant_t& operator=( const VARIANT& varSrc ) throw( _com_error );
_variant_t& operator=( const VARIANT* pVarSrc ) throw( _com_error );
_variant_t& operator=( const _variant_t& var_t_Src ) throw( _com_error );
_variant_t& operator=( short sSrc ) throw( _com_error );
_variant_t& operator=( long lSrc ) throw( _com_error );
_variant_t& operator=( float fltSrc ) throw( _com_error );
_variant_t& operator=( double dblSrc ) throw( _com_error );
_variant_t& operator=( const CY& cySrc ) throw( _com_error );
_variant_t& operator=( const _bstr_t& bstrSrc ) throw( _com_error );
_variant_t& operator=( const wchar_t* wstrSrc ) throw( _com_error );
_variant_t& operator=( const char* strSrc ) throw( _com_error );
_variant_t& operator=( IDispatch* pDispSrc ) throw( _com_error );
_variant_t& operator=( bool bSrc ) throw( _com_error );
_variant_t& operator=( IUnknown* pSrc ) throw( _com_error );
_variant_t& operator=( const DECIMAL& decSrc ) throw( _com_error );
_variant_t& operator=( BYTE bSrc ) throw( _com_error );
有了以上两个函数,举个例子:
double f=1.0
_variant_t v;
v=f;
CString str="ddd"
_variant_t v;
v=str.AllocSysString() 或者v=(_bstr_t)(char*)str;
即可
_variant_t转换成别的形式
你首先必须确定你要转化成什么样的形式
double f;
_variant_t v
f=v.dblVal 即可或者f=(double)v;也可以
附:_variant_t的操作符
operator short( ) const throw( _com_error );
operator long( ) const throw( _com_error);
operator float( ) const throw( _com_error );
operator double( ) const throw( _com_error );
operator CY( ) const throw( _com_error );
operator bool( ) const throw( _com_error );
operator DECIMAL( ) const throw( _com_error );
operator BYTE( ) const throw( _com_error );
operator _bstr_t( ) const throw( _com_error );
operator IDispatch*( ) const throw( _com_error );
operator IUnknown*( ) const throw( _com_error );
1 string 2 CString
2 CString 2 string
string str(CString.GetBuffer(str.GetLength()));
3 string 2 char *
char *p=string.c_str();
4 char * 2 string
string str(char*);
5 CString 2 char *
strcpy(char,CString,sizeof(char));
6 char * 2 CString
CString.format("%s",char*);
CString的format方法是非常好用的。string的c_str()也是非常常用的,但要注意和char *转换时,要把char定义成为const char*,这样是最安全的。
************************************************************************************************
1. char* to string
string s(char *);
注:在不是初始化的地方最好用assign().
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
2. string to const char*
string a="strte";
const char* r=a.c_str();
注意是const的。还要转到char*:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
2.2. const char* to char*
const char* r="123";
char
strcpy(p1,r);
附:http://hi.baidu.com/cfans/blog/item/06970ef4b671f366dcc4745d
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3. cstring to string
vs2005 Unicode下:
非Unicode下:
CString cs("test");
std::string str=cs.getBuffer(0);
cs.ReleaseBuffer();
注:GetBuffer()后一定要ReleaseBuffer(),否则就没有释放缓冲区所占的空间.
++++++++++++++++++++++++++++++++++++++++++++++++++++
4. double ,int to string
#include <sstream>
using namespace std;
stringstream ss;
string result;
long n=11111;
stream << n; //从long型数据输入
stream >>result; //转换为 string
===================================================
5.char*
char *s; double x; int i; long l;
s = " -2309.12E-15";
x = atof( s );
printf( "atof test: ASCII string: %s\tfloat: %e\n", s, x );
s = "7.8912654773d210";
x = atof( s );
printf( "atof test: ASCII string: %s\tfloat: %e\n", s, x );
s = " -9885 pigs";
i = atoi( s );
printf( "atoi test: ASCII string: %s\t\tinteger: %d\n", s, i );
s = "98854 dollars";
l = atol( s );
printf( "atol test: ASCII string: %s\t\tlong: %ld\n", s, l );
------------------------------------------------------------------------------------------------
6. string to int ,long ,double
——————————————————————————————————————————
7. date to string
#include <time>
using namespace std;
char dateStr [9];
char timeStr [9];
printf( "The current date is %s \n", dateStr);
_strtime( timeStr );
printf( "The current time is %s \n", timeStr);
--------实践证明是正确的版本--------------------------------------------------------------
#include <iostream>
#include <ctime>
#include <cerrno>
int main()
{
}
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8.string to cstring
+++++++++++++++++++++++++++++++++++++++++++++++++++++
非Unicode下:
int 转 CString:
CString.Format("%d",int);
...............................
string 转 CString
CString.format("%s", string.c_str());
用c_str()确实比data()要好.
.......................................
char* 转 CString
CString.format("%s", char*);
.....................................................
CString 转 int
...................................................................................................................................
9.在Unicode下的CString to double
CSting sTemp("123.567");
double dTemp = _wtof(sTemp.GetString());
二、数值处理
1、浮点数取整方法