125 lines
2.9 KiB
C++
125 lines
2.9 KiB
C++
/*
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* BSTRING.H
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*
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* Defines a BSTRING C++ class that allows us to wrap the OLE BSTR (Basic
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* String) type, primarily to simplify the creation and freeing of these
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* objects. This is intended to be a lightweight wrapper with minimal
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* overhead.
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*
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* If no input string is specified to the constructor or if the allocation
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* of the BSTR fails, then the <m_bstr> member is set to NULL.
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*
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* Note: The BSTRING class is not intended to allow managing multiple BSTR
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* strings with a single object.
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*
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* Usage scenarios:
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*
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* 1) Create a BSTR from an existing string, have it automatically freed
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* when done.
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*
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* // Allocate BSTR using SysAllocString()
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* BSTRING bstrComputerName(lpstrComputerName);
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*
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* ...
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*
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* // Automatic, lightweight cast to BSTR
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* SomeFunctionThatTakesABSTR(bstrComputerName);
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*
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* ...
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*
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* // SysFreeString() gets called automatically when the scope of
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* // bstrComputerName ends.
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*
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* 2) Create a null BSTRING object, pass it to a function that returns an
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* allocated BSTR, then have it automatically freed when done.
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*
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* // Create null BSTRING
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* BSTRING bstrReturnedComputerName;
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*
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* ...
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*
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* // Call a function that returns an allocated BSTR.
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* SomeFunctionThatReturnsABSTR(bstrReturnedComputerName.GetLPBSTR());
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*
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* ...
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*
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* // SysFreeString() gets called automatically when the scope of
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* // bstrReturnedComputerName ends.
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*
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* Author:
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* dannygl, 29 Oct 96
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*/
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#if !defined(_BSTRING_H_)
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#define _BSTRING_H_
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#include <oleauto.h>
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#include <confdbg.h>
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class BSTRING
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{
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private:
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BSTR m_bstr;
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public:
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// Constructors
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BSTRING() {m_bstr = NULL;}
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inline BSTRING(LPCWSTR lpcwString);
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#if !defined(UNICODE)
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// We don't support construction from an ANSI string in the Unicode build.
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BSTRING(LPCSTR lpcString);
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#endif // !defined(UNICODE)
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// Destructor
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inline ~BSTRING();
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// Cast to BSTR
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operator BSTR() {return m_bstr;}
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// Get a BSTR pointer.
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//
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// This member function is intended for passing this object to
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// functions that allocate a BSTR, return a pointer to this BSTR,
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// and expect the caller to free the BSTR when done. The BSTR is
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// freed when the BSTRING destructor gets called.
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inline LPBSTR GetLPBSTR(void);
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};
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BSTRING::BSTRING(LPCWSTR lpcwString)
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{
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if (NULL != lpcwString)
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{
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// SysAllocString returns NULL on failure
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m_bstr = SysAllocString(lpcwString);
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ASSERT(NULL != m_bstr);
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}
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else
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{
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m_bstr = NULL;
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}
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}
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BSTRING::~BSTRING()
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{
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if (NULL != m_bstr)
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{
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SysFreeString(m_bstr);
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}
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}
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inline LPBSTR BSTRING::GetLPBSTR(void)
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{
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// This function is intended to be used to set the BSTR value for
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// objects that are initialized to NULL. It should not be called
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// on objects which already have a non-NULL BSTR.
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ASSERT(NULL == m_bstr);
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return &m_bstr;
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}
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#endif // !defined(_BSTRING_H_)
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