OLE字符串

一、概述

32位寬字符串，前面32位為長度,尾部以0結束

二、相關定義

BSTR (又稱Basic 類型字符串)

LPOLESTR

相關宏定義:

typedef unsigned short wchar_t; (unsigned short為兩字節)
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"　重新賦值
f = SysReAllocString(&bs, "NewText");

2.長度

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

3.釋放

// Deallocate a string.
SysFreeString(bs);

四、轉換問題

1 使用_bstr_t

BSTR tmpBStr;
m_pObject1->get_ObjectString(&tmpBStr);
_bstr_t tmpbstr(tmpBStr, FALSE); //將得到的BSTR作為構造函數參數
SetDlgItemText(IDC_CURPROPVAL, tmpbstr);

注意: 直接賦值轉換，會引發內存洩漏

BSTR tmpBStr;
m_pObject1->get_ObjectString(&tmpBStr);
_bstr_t tmpbstr;
tmpbstr= tmpBStr; //Caution: 內存洩漏參數
SetDlgItemText(IDC_CURPROPVAL, tmpbstr);

2 使用T2COLE、T2OLE等

#include<afxpriv.h>

在轉換前需要添加宏

USES_CONVERSION

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

這個宏提供了一些臨時變量供轉化用

看一下其在單字節字符集時的宏定義

#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 對轉化的支持

//m_cstrCaption是一個CString 對象。
BSTR bstrCaption =m_cstrCaption.AllocSysString();
FireChange(&bstrCaption,&m_lAlignment);
::SysFreeString(bstrCaption);

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