OLE字符串

 

一、概述

32位宽字符串，前面32位为长度,尾部以0结束

二、相关定义 
BSTR (又称Basic 类型字符串) 
LPOLESTR 
相关宏定义:

1 typedef unsigned short wchar_t; (unsigned short为两字节)
2 typedef wchar_t WCHAR;
3 typedef WCHAR OLECHAR;    (Win32)
4 typedef OLECHAR* BSTR;
5 typedef /* [string] */ OLECHAR __RPC_FAR *LPOLESTR;

三、使用

1.分配

 1 // Create BSTR containing "Text"
 2 bs = SysAllocString(L"Text")
 3 
 4 // Create BSTR containing "Te"
 5 bs = SysAllocStringLen(L"Text", 2)
 6 // Create BSTR containing "Text" followed by \0 and a junk character
 7 bs = SysAllocStringLen(L"Text", 6)
 8 
 9 // Reallocate BSTR bs as "NewText"  重新赋值
10 f = SysReAllocString(&bs, "NewText");

2.长度

1 // Get character length of string.
2 cch = SysStringLen(bs);

3.释放

1 // Deallocate a string.
2 SysFreeString(bs);

四、转换问题

1 使用_bstr_t

1 BSTR tmpBStr;
2 m_pObject1->get_ObjectString(&tmpBStr);
3 _bstr_t tmpbstr(tmpBStr, FALSE); //将得到的BSTR作为构造函数参数
4 SetDlgItemText(IDC_CURPROPVAL, tmpbstr);

注意: 直接赋值转换，会引发内存泄漏

1 BSTR tmpBStr;
2 m_pObject1->get_ObjectString(&tmpBStr);
3 _bstr_t tmpbstr;
4 tmpbstr= tmpBStr; //Caution: 内存泄漏参数
5 SetDlgItemText(IDC_CURPROPVAL, tmpbstr);

2 使用T2COLE、T2OLE等

#include <afxpriv.h>

在转换前需要添加宏

USES_CONVERSION

#define USES_CONVERSION int _convert = 0; \
    _convert;\
     UINT _acp = GetACP();\
     _acp;\
     LPCWSTR _lpw = NULL;\
     _lpw;\
     LPCSTR _lpa = NULL;\
     _lpa

这个宏提供了一些临时变量供转化用

看一下其在单字节字符集时的宏定义

 1 #define T2COLE(lpa) A2CW(lpa)
 2 #define T2OLE(lpa) A2W(lpa)
 3 #define OLE2CT(lpo) W2CA(lpo)
 4 #define OLE2T(lpo) W2A(lpo)
 5   
 6 #define A2CW(lpa) ((LPCWSTR)A2W(lpa))
 7 #define W2CA(lpw) ((LPCSTR)W2A(lpw))
 8 
 9 #define A2W(lpa) (\
10     ((_lpa = lpa) == NULL) ? NULL : (\
11         _convert = (lstrlenA(_lpa)+1),\
12         ATLA2WHELPER((LPWSTR) alloca(_convert*2), _lpa, _convert)))
13 
14 #define W2A(lpw) (\
15     ((_lpw = lpw) == NULL) ? NULL : (\
16         _convert = (lstrlenW(_lpw)+1)*2,\
17         ATLW2AHELPER((LPSTR) alloca(_convert), _lpw, _convert)))
18 
19 LPSTR AFXAPI AfxW2AHelper(LPSTR lpa, LPCWSTR lpw, int nChars)
20 {
21     if (lpw == NULL)
22         return NULL;
23     ASSERT(lpa != NULL);
24     // verify that no illegal character present
25     // since lpa was allocated based on the size of lpw
26     // don''t worry about the number of chars
27     lpa[0] = ''\0'';
28     VERIFY(WideCharToMultiByte(CP_ACP, 0, lpw, -1, lpa, nChars, NULL, NULL));
29     return lpa;
30 }
31 
32 LPWSTR AFXAPI AfxA2WHelper(LPWSTR lpw, LPCSTR lpa, int nChars)
33 {
34     if (lpa == NULL)
35         return NULL;
36     ASSERT(lpw != NULL);
37     // verify that no illegal character present
38     // since lpw was allocated based on the size of lpa
39     // don''t worry about the number of chars
40     lpw[0] = ''\0'';
41     VERIFY(MultiByteToWideChar(CP_ACP, 0, lpa, -1, lpw, nChars));
42     return lpw;
43 }

3 .CString 对转化的支持

1 //m_cstrCaption是一个CString 对象。
2 
3 BSTR bstrCaption =m_cstrCaption.AllocSysString();
4 FireChange(&bstrCaption,&m_lAlignment);
5 ::SysFreeString(bstrCaption);

本文转载自：http://www.vckbase.com/document/viewdoc/?id=617

posted on 2012-04-20 15:16  Joshua Leung  阅读(502)  评论(0)  编辑  收藏  举报

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