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72 lines
2.4 KiB
72 lines
2.4 KiB
/*++
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Copyright (C) 1992-2001 Microsoft Corporation
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Module Name:
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ELEMENTS.H
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Abstract:
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History:
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--*/
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// This is a part of the Microsoft Foundation Classes C++ library.
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// Copyright (C) 1992-1993 Microsoft Corporation
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// All rights reserved.
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//
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// This source code is only intended as a supplement to the
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// Microsoft Foundation Classes Reference and Microsoft
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// QuickHelp documentation provided with the library.
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// See these sources for detailed information regarding the
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// Microsoft Foundation Classes product.
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// Collection implementation helpers
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/*
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* The short story:
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* this file contains inline functions that make up the building blocks
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* for implementing the string versions of standard parameterized
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* collection shapes
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*
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* The long story:
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* Because the implementation of collection classes moves objects around
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* in various ways, it is very inefficient to use only generic C++ constructs.
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* For example, in order to grow an array of FOO objects by one element,
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* you would be forced to allocate a new array of appropriate size, calling
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* the FOO constructor on every element. Then copy the original array, element
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* by element using a possibly overloaded assignment operator. Finally destroy
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* the original array element by element.
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* For built-in data types (WORD, DWORD, pointer types), this is complete
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* overkill. For non-trivial classes (eg: CString in particular) this is
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* a terrible implementation.
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*
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* The bottom line: we have to special routines for doing construction
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* and destruction of arrays of special elements - in particular CStrings.
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* The standard templates are parameterized on 'HAS_CREATE' which is
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* non-zero if the collection implementation requires a special
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* construct and destruct function.
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*
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* Please note that these are inline overloaded operators, and do not have
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* any form of runtime polymorphism (i.e. nothing is 'virtual').
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*/
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/////////////////////////////////////////////////////////////////////////////
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// Special implementations for CStrings
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// it is faster to bit-wise copy a CString than to call an official
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// constructor - since an empty CString can be bit-wise copied
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extern const CString afxEmptyString;
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static inline void ConstructElement(CString* pNewData)
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{
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memcpy(pNewData, &afxEmptyString, sizeof(CString));
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}
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static inline void DestructElement(CString* pOldData)
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{
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pOldData->Empty();
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}
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/////////////////////////////////////////////////////////////////////////////
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