C/C++教程
VC中BSTR、bstr_t、CComBSTR的定义
一、BSTR数据类型
1、BSTR的定义
参考C:\Program Files\Microsoft SDKs\v6.0A \Include\wtypes.h中BSTR的定义：
typedef OLECHAR __RPC_FAR *BSTR;
typedef WCHAR OLECHAR;
typedef wchar_t WCHAR;
再参考C:\Program Files\Microsoft SDKs\v5.0\Include\Basetyps.h 中wchar_t的定义：
typedef unsigned short wchar_t;
二、bstr_t类
1、_bstr_t类的定义
参考C:\Program Files\Microsoft Visual Studio 9.0 \VC\Include\comutil.h
class _bstr_t {
public:
// Constructors
_bstr_t() throw();
_bstr_t(const _bstr_t& s) throw();
_bstr_t(const char* s) ;
_bstr_t(const wchar_t* s) ;
_bstr_t(const _variant_t& var) ;
_bstr_t(BSTR bstr, bool fCopy) ;
// Destructor
~_bstr_t() throw();
// Assignment operators
_bstr_t& operator=(const _bstr_t& s) throw();
_bstr_t& operator=(const char* s) ;
_bstr_t& operator=(const wchar_t* s) ;
_bstr_t& operator=(const _variant_t& var) ;
// Operators
_bstr_t& operator+=(const _bstr_t& s) ;
_bstr_t operator+(const _bstr_t& s) const ;
// Friend operators
friend _bstr_t operator+(const char* s1, const _bstr_t& s2) ;
friend _bstr_t operator+(const wchar_t* s1, const _bstr_t& s2) ;
// Extractors
operator const wchar_t*() const throw();
operator wchar_t*() const throw();
operator const char*() const ;
operator char*() const ;
// Comparison operators
bool operator!() const throw();
bool operator==(const _bstr_t& str) const throw();
bool operator!=(const _bstr_t& str) const throw();
bool operator<(const _bstr_t& str) const throw();
bool operator>(const _bstr_t& str) const throw();
bool operator<=(const _bstr_t& str) const throw();
bool operator>=(const _bstr_t& str) const throw();
// Low-level helper functions
BSTR copy(bool fCopy = true) const ;
unsigned int length() const throw();
// Binary string assign
void Assign(BSTR s) ;
// Get the physical BSTR
BSTR& GetBSTR() ;
BSTR* GetAddress() ;
// Attach to the internal BSTR w/o copying
void Attach(BSTR s) ;
// Detach the internal BSTR
BSTR Detach() throw();
private:
// Referenced counted wrapper
class Data_t {
public:
// Constructors
Data_t(const char* s) ;
Data_t(const wchar_t* s) ;
Data_t(BSTR bstr, bool fCopy) ;
Data_t(const _bstr_t& s1, const _bstr_t& s2) ;
// Reference counting routines
unsigned long AddRef() throw();
unsigned long Release() throw();
unsigned long RefCount() const throw();
// Extractors
operator const wchar_t*() const throw();
operator const char*() const ;
// Low-level helper functions
const wchar_t* GetWString() const throw();
wchar_t*& GetWString() throw();
const char* GetString() const ;
BSTR Copy() const ;
void Assign(BSTR s) ;
void Attach(BSTR s) throw();
unsigned int Length() const throw();
int Compare(const Data_t& str) const throw();
// Exception agnostic wrapper for new
void* operator new(size_t sz);
private:
BSTR m_wstr;
mutable char* m_str;
unsigned long m_RefCount;
// Never allow default construction
Data_t() throw();
// Never allow copy
Data_t(const Data_t& s) throw();
// Prevent deletes from outside. Release() must be used.
~Data_t() throw();
void _Free() throw();
};
private:
// Reference counted representation
Data_t* m_Data;
private:
// Low-level utilities
void _AddRef() throw();
void _Free() throw();
int _Compare(const _bstr_t& str) const throw();
};
三、CComBSTR类
1、CComBSTR的定义
参考C:\Program Files\Microsoft Visual Studio 9.0 \VC \atlmfc\Include\atlcomcli.h
class CComBSTR
{
public:
BSTR m_str;
CComBSTR()
{
m_str = NULL;
}
CComBSTR(int nSize)
{
m_str = ::SysAllocStringLen(NULL, nSize);
}
CComBSTR(int nSize, LPCOLESTR sz)
{
m_str = ::SysAllocStringLen(sz, nSize);
}
CComBSTR(LPCOLESTR pSrc)
{
m_str = ::SysAllocString(pSrc);
}
CComBSTR(const CComBSTR& src)
{
m_str = src.Copy();
}
CComBSTR(REFGUID src)
{
LPOLESTR szGuid;
StringFromCLSID(src, &szGuid);
m_str = ::SysAllocString(szGuid);
CoTaskMemFree(szGuid);
}
CComBSTR& operator=(const CComBSTR& src)
{
if (m_str != src.m_str)
{
if (m_str)
::SysFreeString(m_str);
m_str = src.Copy();
}
return *this;
}
CComBSTR& operator=(LPCOLESTR pSrc)
{
::SysFreeString(m_str);
m_str = ::SysAllocString(pSrc);
return *this;
}
~CComBSTR()
{
::SysFreeString(m_str);
}
unsigned int Length() const
{
return (m_str == NULL)? 0 : SysStringLen(m_str);
}
operator BSTR() const
{
return m_str;
}
BSTR* operator&()
{
return &m_str;
}
BSTR Copy() const
{
return ::SysAllocStringLen(m_str, ::SysStringLen(m_str));
}
HRESULT CopyTo(BSTR* pbstr)
{
ATLASSERT(pbstr != NULL);
if (pbstr == NULL)
return E_POINTER;
*pbstr = ::SysAllocStringLen(m_str, ::SysStringLen(m_str));
if (*pbstr == NULL)
return E_OUTOFMEMORY;
return S_OK;
}
void Attach(BSTR src)
{
ATLASSERT(m_str == NULL);
m_str = src;
}
BSTR Detach()
{
BSTR s = m_str;
m_str = NULL;
return s;
}
void Empty()
{
::SysFreeString(m_str);
m_str = NULL;
}
bool operator!() const
{
return (m_str == NULL);
}
HRESULT Append(const CComBSTR& bstrSrc)
{
return Append(bstrSrc.m_str, SysStringLen(bstrSrc.m_str));
}
HRESULT Append(LPCOLESTR lpsz)
{
return Append(lpsz, ocslen(lpsz));
}
// a BSTR is just a LPCOLESTR so we need a special version to signify
// that we are appending a BSTR
HRESULT AppendBSTR(BSTR p)
{
return Append(p, SysStringLen(p));
}
HRESULT Append(LPCOLESTR lpsz, int nLen)
{
int n1 = Length();
BSTR b;
b = ::SysAllocStringLen(NULL, n1+nLen);
if (b == NULL)
return E_OUTOFMEMORY;
memcpy(b, m_str, n1*sizeof(OLECHAR));
memcpy(b+n1, lpsz, nLen*sizeof(OLECHAR));
b[n1+nLen] = NULL;
SysFreeString(m_str);
m_str = b;
return S_OK;
}
HRESULT ToLower()
{
USES_CONVERSION;
if (m_str != NULL)
{
LPTSTR psz = CharLower(OLE2T(m_str));
if (psz == NULL)
return E_OUTOFMEMORY;
BSTR b = T2BSTR(psz);
if (psz == NULL)
return E_OUTOFMEMORY;
SysFreeString(m_str);
m_str = b;
}
return S_OK;
}
HRESULT ToUpper()
{
USES_CONVERSION;
if (m_str != NULL)
{
LPTSTR psz = CharUpper(OLE2T(m_str));
if (psz == NULL)
return E_OUTOFMEMORY;
BSTR b = T2BSTR(psz);
if (psz == NULL)
return E_OUTOFMEMORY;
SysFreeString(m_str);
m_str = b;
}
return S_OK;
}
bool LoadString(HINSTANCE hInst, UINT nID)
{
USES_CONVERSION;
TCHAR sz[512];
UINT nLen = ::LoadString(hInst, nID, sz, 512);
ATLASSERT(nLen < 511);
SysFreeString(m_str);
m_str = (nLen != 0) ? SysAllocString(T2OLE(sz)) : NULL;
return (nLen != 0);
}
bool LoadString(UINT nID)
{
return LoadString(_pModule->m_hInstResource, nID);
}
CComBSTR& operator+=(const CComBSTR& bstrSrc)
{
AppendBSTR(bstrSrc.m_str);
return *this;
}
bool operator<(BSTR bstrSrc) const
{
if (bstrSrc == NULL && m_str == NULL)
return false;
if (bstrSrc != NULL && m_str != NULL)
return wcscmp(m_str, bstrSrc) < 0;
return m_str == NULL;
}
bool operator==(BSTR bstrSrc) const
{
if (bstrSrc == NULL && m_str == NULL)
return true;
if (bstrSrc != NULL && m_str != NULL)
return wcscmp(m_str, bstrSrc) == 0;
return false;
}
bool operator<(LPCSTR pszSrc) const
{
if (pszSrc == NULL && m_str == NULL)
return false;
USES_CONVERSION;
if (pszSrc != NULL && m_str != NULL)
return wcscmp(m_str, A2W(pszSrc)) < 0;
return m_str == NULL;
}
bool operator==(LPCSTR pszSrc) const
{
if (pszSrc == NULL && m_str == NULL)
return true;
USES_CONVERSION;
if (pszSrc != NULL && m_str != NULL)
return wcscmp(m_str, A2W(pszSrc)) == 0;
return false;
}
#ifndef OLE2ANSI
CComBSTR(LPCSTR pSrc)
{
m_str = A2WBSTR(pSrc);
}
CComBSTR(int nSize, LPCSTR sz)
{
m_str = A2WBSTR(sz, nSize);
}
void Append(LPCSTR lpsz)
{
USES_CONVERSION;
LPCOLESTR lpo = A2COLE(lpsz);
Append(lpo, ocslen(lpo));
}
CComBSTR& operator=(LPCSTR pSrc)
{
::SysFreeString(m_str);
m_str = A2WBSTR(pSrc);
return *this;
}
#endif
HRESULT WriteToStream(IStream* pStream)
{
ATLASSERT(pStream != NULL);
ULONG cb;
ULONG cbStrLen = m_str ? SysStringByteLen(m_str)+sizeof(OLECHAR) : 0;
HRESULT hr = pStream->Write((void*) &cbStrLen, sizeof(cbStrLen), &cb);
if (FAILED(hr))
return hr;
return cbStrLen ? pStream->Write((void*) m_str, cbStrLen, &cb) : S_OK;
}
HRESULT ReadFromStream(IStream* pStream)
{
ATLASSERT(pStream != NULL);
ATLASSERT(m_str == NULL); // should be empty
ULONG cbStrLen = 0;
HRESULT hr = pStream->Read((void*) &cbStrLen, sizeof(cbStrLen), NULL);
if ((hr == S_OK) && (cbStrLen != 0))
{
//subtract size for terminating NULL which we wrote out
//since SysAllocStringByteLen overallocates for the NULL
m_str = SysAllocStringByteLen(NULL, cbStrLen-sizeof(OLECHAR));
if (m_str == NULL)
hr = E_OUTOFMEMORY;
else
hr = pStream->Read((void*) m_str, cbStrLen, NULL);
}
if (hr == S_FALSE)
hr = E_FAIL;
return hr;
}
};
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