MFC string char cstring 类型转换

在Unicode环境下用以下转换：

CString z_strCurtTime = _T("");

// 获取当前时间
CTime z_tCurTime = CTime::GetCurrentTime();
z_strCurtTime = z_tCurTime.Format("%Y-%m-%d %H:%M:%S");
int z_len =WideCharToMultiByte(CP_ACP,0,z_strCurtTime,-1,NULL,0,NULL,NULL);
char *z_cCurTime =new char[z_len +1];
WideCharToMultiByte(CP_ACP,0,z_strCurtTime,-1,z_cCurTime,z_len,NULL,NULL );

1 前言

今天在网上看论坛,发现大家对CString与Char *互转各说一词,其实我发现提问者所说的情况与回答问题的人完全不是同一情况,这里做一总结.

首先大家得清楚一件事,一般在网上提出问题的人大部分使用的都是VC,那么你就应该知道,在VC下编程,工程属性中有一属性Charecter Set属性,其值可以设置为Use Multi-Byte Charecter Set 和 Use Unicode Charecter Set 这两种选择,具默认情况下工程是采用了Use Unicode Charecter Set选项.如我使用的VS2010的工程属性中如下:

VC在处理CString类型字符时,在这两种不种选择的处理结果也是完全不一样的,而网上那么答复大都是针对假设提问者是使用了Use Mult-Byte Chracter Set的前提下,但大多提这个问题的人都是使用了后者的情况的人.

暂且将Use Mult-Byte Chracter Set称之为宽字节字符模式,而Use Unicode Charecter Set称之为Unicode编码模式.

2 宽字节字符模式

首先讨论一下宽字符字符模式下的CStirng与Char *之间的互转,在这种情况下互换很简单:

2.1 CString -->char *

如下:

CString str1 ="123";
char *p =(LPSTR)(LPCSTR)str1;

但好像官方并不建议这么做,而建议采用下面这种方式:

CString str1 ="123";
char *t1 =str1.GetBuffer(str1.GetLength());
str1.ReleaseBuffer();
//do something with t1

网上也有人说是这样t1 =str1.GetBuffer(0);但其实我在实测时并没发现str1.GetBuffer(str1.GetLenth())与str.GetBuffer(0)返回值有啥区别,MSDN中相应说明如下:

CString::GetBuffer
LPTSTR GetBuffer( int nMinBufLength );
throw( CMemoryException );
Return Value
An LPTSTR pointer to the object’s (null-terminated) character buffer.
Parameters
nMinBufLength
The minimum size of the character buffer in characters. This value does not include space for a null terminator.
Remarks
Returns a pointer to the internal character buffer for the CString object. The returned LPTSTR is not const and thus allows direct modification of CString contents.
If you use the pointer returned by GetBuffer to change the string contents, you must call ReleaseBuffer before using any other CString member functions.
The address returned by GetBuffer may not be valid after the call to ReleaseBuffer since additional CString operations may cause the CString buffer to be reallocated. The buffer will not be reallocated if you do not change the length of the CString.
The buffer memory will be freed automatically when the CString object is destroyed.
Note that if you keep track of the string length yourself, you should not append the terminating null character. You must, however, specify the final string length when you release the buffer with ReleaseBuffer. If you do append a terminating null character, you should pass –1 for the length to ReleaseBuffer and ReleaseBuffer will perform a strlen on the buffer to determine its length.

由上可知,GetBuffer的参数nMinBufLength为最小缓冲区长度,但实际结果没啥区别...

2.2 char * -->CString

char *str ="aaaa"
CString str1(str);
//...

2.3 CString -->int

在宽字符字符模式下,这个非常简单:

CString str1 ="123";
int i =atoi(str1);
//do something with i

2.4 int -->CString

int i =100;
CString str;
str.Format("%d",i);
//...

3 Unicode编码模式

3.1 CString -->char *

在这种情况下,上述所说的转化全是浮云,目前只发现可以用WideCharToMultiByte函数来实现.

如下 :

CString str1 =_T("123");
int len =WideCharToMultiByte(CP_ACP,0,str1,-1,NULL,0,NULL,NULL);
char *ptxtTemp =new char[len +1];
WideCharToMultiByte(CP_ACP,0,str1,-1,ptxtTemp,len,NULL,NULL );
//...
delete[] ptxtTemp;

3.2 char * -->CString

还是可以如下:

char *p ="test";
CString str(p);
//...

3.3 CString -->int

在这种情况下atoi不再适用,其实可以用swscanf,如下:

CString str2 =_T("100");
int i;
swscanf(str2,_T("%d"),&i);

3.4 int -->CString

这个其实最简单了,如下:

int j =100;
CString str3;
str3.Format(_T("%d"),j);

CString转std::wstring

std::wstring str = filename.GetString();

std::wstring转CString

CString str( filename.c_str() );

4 结束

另外,有关ANSI与Unicode之间的转换及UTF-8与Unicode之间的转换可以参与下面这个链接:

http://www.cnblogs.com/gakusei/articles/1585211.html