OLE字符串
作者：冯明德
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:
typedef unsigned short wchar_t; (unsigned short为两字节)
typedef wchar_t WCHAR;
typedef WCHAR OLECHAR;(Win32)
typedef OLECHAR* BSTR;
typedef /* [string] */ OLECHAR __RPC_FAR *LPOLESTR;
三、使用
1.分配
// Create BSTR containing "Text"
bs = SysAllocString(L"Text")
// Create BSTR containing "Te"
bs = SysAllocStringLen(L"Text", 2)
// Create BSTR containing "Text" followed by \0 and a junk character
bs = SysAllocStringLen(L"Text", 6)
// Reallocate BSTR bs as "NewText" 重新赋值
f = SysReAllocString(&bs, "NewText");
2.长度
// Get character length of string.
cch = SysStringLen(bs);
3.释放
// Deallocate a string.
SysFreeString(bs);
四、转换问题
1 使用_bstr_t
BSTR tmpBStr;
m_pObject1->get_ObjectString(&tmpBStr);
_bstr_t tmpbstr(tmpBStr, FALSE); //将得到的BSTR作为构造函数参数
SetDlgItemText(IDC_CURPROPVAL, tmpbstr);
注意: 直接赋值转换，会引发内存泄漏
BSTR tmpBStr;
m_pObject1->get_ObjectString(&tmpBStr);
_bstr_t tmpbstr;
tmpbstr= tmpBStr; //Caution: 内存泄漏参数
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
#define T2COLE(lpa) A2CW(lpa)
#define T2OLE(lpa) A2W(lpa)
#define OLE2CT(lpo) W2CA(lpo)
#define OLE2T(lpo) W2A(lpo)
#define A2CW(lpa) ((LPCWSTR)A2W(lpa))
#define W2CA(lpw) ((LPCSTR)W2A(lpw))
#define A2W(lpa) (((_lpa = lpa) == NULL) ? NULL : (_convert = (lstrlenA(_lpa)+1),ATLA2WHELPER((LPWSTR) alloca(_convert*2), _lpa, _convert)))
#define W2A(lpw) (((_lpw = lpw) == NULL) ? NULL : (_convert = (lstrlenW(_lpw)+1)*2,ATLW2AHELPER((LPSTR) alloca(_convert), _lpw, _convert)))
LPSTR AFXAPI AfxW2AHelper(LPSTR lpa, LPCWSTR lpw, int nChars)
{
if (lpw == NULL)
return NULL;
ASSERT(lpa != NULL);
// verify that no illegal character present
// since lpa was allocated based on the size of lpw
// don''t worry about the number of chars
lpa[0] = ''\0'';
VERIFY(WideCharToMultiByte(CP_ACP, 0, lpw, -1, lpa, nChars, NULL, NULL));
return lpa;
}
LPWSTR AFXAPI AfxA2WHelper(LPWSTR lpw, LPCSTR lpa, int nChars)
{
if (lpa == NULL)
return NULL;
ASSERT(lpw != NULL);
// verify that no illegal character present
// since lpw was allocated based on the size of lpa
// don''t worry about the number of chars
lpw[0] = ''\0'';
VERIFY(MultiByteToWideChar(CP_ACP, 0, lpa, -1, lpw, nChars));
return lpw;
}
3 .CString 对转化的支持
//m_cstrCaption是一个CString 对象。
BSTR bstrCaption =m_cstrCaption.AllocSysString();
FireChange(&bstrCaption,&m_lAlignment);
::SysFreeString(bstrCaption);
(全文完)